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Oil and gas industry continues to the increasing demand of more cost-effective well design and operations. Thus, team successfully eliminated intermediate casing string from the design thereby achieving not only a 33% reduction in dry hole cost/meter, but also delivering wells and producing oil 25% faster than before. Removing an intermediate casing string resulted in a longer open hole (more than 2000 mMD) which by default created new challenges which had to be dealt with and solved without compromising the targeted cost saving. The challenges can be summarized as follow: • Combining loss of circulation zone with unstable shale formations in one section. • PPFG uncertainties. • Bit selection and design optimization. • BHA selection and drive optimization. • Running wireline logging through a long open hole. • Running casing and having good quality cement. • Hole cleaning and displacement efficiency when changing mud systems. • Proper contingencies in place to meet the required completion strategy. Risk assessment, feasibility studies, workshops, and co-operation among all involved personnel has been conducted to ensure that this design optimization would result in positive outcome. Since the first implementation in 2019, more than 17 wells have been successfully delivered and completed in Best in Class performance based on latest update of Rushmore data tracking. The longest open hole section of 2790 m measured depth (MD) with total depth (TD) of 3910 mMD has been achieved generating above 800 Kusd saving per well, thus setting new benchmarks for the field and opening up new opportunities for the future. All this ensure Process Safety and compliance with Well Delivery process. This paper not only describes how two string design was successfully engineered and executed but also serves as a guide for selecting proper candidates for this design and an operational guide for two section wells design to ensure that these challenging long open hole will be successfully drilled while minimizing risks.

Nanomaterials have gained a wide interest in the oil and gas industry due to their immense applicability. Nanomaterials are being used to formulate a new generation of drilling mud known as Nanomud or Smart mud, where it has the ability to improve mud properties and eliminate borehole problems. Using nanoparticles as an additive agent in conventional drilling mud can lead to a more efficient drilling process in troublesome formations. In this study, several conventional water-based muds from a selected well drilled in the Kurdistan/Iraq oil field have been prepared. Then, nanodrilling muds were formulated by dispersing SiO2 and ZnO nanoparticles in concentrations ranging from 0.25 to 1 wt.% to conventional water-based mud (WBM). This study aims to evaluate and compare the performance of conventional water-based muds after adding SiO2 and ZnO nanoparticles. This evaluation was performed by carrying out a series of laboratory experiments to determine the rheological and mud filtrate properties. The results demonstrated that nanomuds improved the rheological behaviors and provided better filtration control compared to conventional drilling muds. However, there was little or no impact of the nanomaterials on the mud density for all mud systems.

A significant parameter in the drilling of a petroleum wellbore is to design a drilling fluid with good control on its rheology and fluid loss characteristics. The present study aims at designing a drilling mud with improved properties in terms of rheology and filtration loss. Effect of laboratory synthesized α-MnO2 nanoparticles (MNPs) on the properties of drilling fluid is evaluated by comparing the properties of base fluid with that of nano-enhanced fluids. First, a base mud comprising of polyanionic cellulose (PAC), xanthan gum (XG) and bentonite was prepared and analysed for its properties, such as rheology and filtration characteristics, and heat tolerance. The properties of base mud were then compared with those of nanoparticles containing muds, prepared by adding different concentrations of MNPs into the base mud. The drilling fluid formulations were also subjected to high temperature rolling condition at 100 °C and 30 rpm for 16 h with the objective of replicating the wellbore environment with the help of roller oven. It was observed that the incorporation of nanoparticles into base fluid diminishes the tendency of thermal degradation of drilling fluid properties. Presence of nanoparticles even at low concentration significantly improved rheological parameters of mud and reduced filtration loss. Therefore, it can be concluded that the incorporation of α-MnO2 nanoparticles synthesized via green route into the base mud along with the conventional additives (added to reduce the fluid loss) enhances the mud performance. It improves the efficiency of additives by imparting thermal stability to the rheological and filtration properties of mud systems along with minimizing the filtration loss.

Oil and Gas drilling is not a simple fundamental procedure, never the less it accounts many subsurface uncertainties to deal with. The primary objective of an efficient and optimized drilling program is to analyze the formation uncertainties and chose a systematic logical approach for pursue drilling operations to overcome any problem encountered. Wellbore stability is the most important and cardinal part of drilling i.e. 1. Maintaining wellbore stability limits the Non Productive Time (NPT) for a well and 2. Analyzing the GTO to select a logical and effective approach for drilling saves time and allows remedial measures to get prepared for instability if encountered. During the process of drilling, the stability of wellbore is achieved by minimizing the fractures across the wellbore, which will occur mainly due to imbalanced mechanical forces. If the stresses acting on the wellbore surfaces increases then there will be a chance of pipe stuck due to formation collapse, which makes the wellbore cleaning difficult. The present paper deals in accordance with developing an understanding of the problems associated with wellbore instabilities and focuses on designing of proper drilling fluids formulations to counter these problems. The major experiments conducted are for analysis of formulating mud, namely: a. KCL-Polymer mud system b. Salt saturated mud system. Designing of drilling fluid done for Water Based Mud Systems only using additives in different proportions to maximize control and ensure cost effectiveness of the mud. Apart from the above oil well cleaning has been approached by the Navier stoke’s equation, power model, continuity equation to develop a mathematical model to help us understand the lifting of the cuttings as a function of fluid viscosity, density, fluid velocity. This in turn helps us to generate the flow regimes near the wellbore around the tubing while transporting the cuttings. The phase of CFD analyses has initiated with the motto of understanding the flow models and verifying the graphs generated from the simulation on the conventional Software’s.

Gas hydrate sediments are known as future energy source and potential technique for the storage CO2. However, the drilling of hydrate sediments are challenged with inappropriate drilling mud systems. Ionic liquids are introduced as novel drilling mud agents that can enhance the rheology of water-based mud and at the same time manage hydrate formation risk during hydrate sediments drilling. However, the disturbances of ionic liquid water-based mud filtrate on hydrate in-situ rocks is not well understood. To achieve this, the phase behaviour of methane hydrates in 1-Ethyl-3-methy-limidazolium chloride (EMIM-Cl) water-based mud at different EMIM-Cl concentrations were measured using the isochoric T-cycle technique in a high-pressure hydrate cell within the temperatures and pressures and ranges from 273.68 – 286.10 K and 3.60 – 9.70 MPa, respectively. The rheological properties of the EMIM-Cl mud systems were tested using a TA rheometer at 271.15 K – 313.15 K. The presence of EMIM-Cl had very minimal disturbances (less than 0.5 K shift) on methane hydrate at the studied concentrations. The disturbance of EMIM-Cl of methane hydrates in pure water system is reduced by 74% in drilling mud systems. The use of EMIM-Cl at 3 wt.% could reduce the methane hydrate disturbance effect 2 times as methanol. EMIM-Cl reduced the thermal degradation of the mud by 55% at 1 wt.% with very low viscosity. The viscosity reduction of the mud occurs at lower EMIM-Cl concentrations. Suggesting that, using ionic liquids water-based mud to drill hydrate sediments will reduce the risk of releasing compacted methane gas into the borehole while drilling. In addition, an attempt is made to predict the methane hydrate equilibrium curve in the presence of the EMIM-Cl using the Dickens and Quinby-Hunt, (1997) model.

Decades of innovation, research and improvements have left drilling fluid vastly different from a mixture of water and clay but are now referred to as non-Newtonian fluids. For optimum well performance for new wells, drillers are to make a choice between drilling with pseudo oil based mud to achieve stability in difficult trajectories and risk permeability impairment; or drill with water based drilling fluid and risk possible drilling instability. Reversible emulsion based muds which can be converted using an acid-base chemical switch from water-in-oil (W/O) to oil-in-water (O/W) emulsion have been suggested as solution in literature. The effect of this acid-base chemical-switch reaction with drilling equipment and personnel prompted this study. Silicon Ethoxide was identified and applied in this study because it has the properties of a reversible surfactant and can be used to formulate a reversible mud that will not react with the drilling equipment nor the formation. Different measurements of Silicon Ethoxide were used, ranging from 5 ml to 45 ml, but we achieved reversibility from 30 ml. Three different base oils (EDC-99, Palm Kernel Oil and Polytriethanolamine) were also used. With the reversed emulsion mud systems, reduction in permeability within the range of 16–19 mD which is minimal was recorded. Thus, this mud system can be used close to the reservoir during drilling operation without encountering significant permeability impairment.

During drilling, different problems are encountered that can interfere with smooth drilling processes, including the accumulation of cuttings, reduced penetration rates, pipe sticking, loss of wellbore stability, and loss of circulation. These problems are generally encountered with conventional drilling mud, such as the bentonite–barite mud system. Formation damage is the most common problem encountered in bentonite mud systems with high solid content. In this work, we aimed to formulate two low-solid nondispersed (LSND) muds: carboxymethyl cellulose (CMC)–LSND mud and partially hydrolyzed polyacrylamide (PHPA)–LSND mud. A comparative analysis was performed to evaluate their property enhancements. LSND muds aid in maintaining hole stability and proper cutting removal. The results of this work show that the addition of both CMC and PHPA helps to improve drilling fluid properties; however, the PHPA–LSND mud was found to be superior. Shale swelling is a major concern in the petroleum industry, as it causes various other problems, such as pipe sticking, low penetration rates, and bit wear. The effect of these two LSND polymer muds in inhibiting shale swelling was analyzed using shale collected from the Champhai district of Mizoram, India.

Xanthan gum is commonly used in drilling fluids to provide viscosity, solid suspension, and fluid-loss control. However, it is sensitive to high temperatures and not tolerant of field contaminants. This paper presents an experimental study on the effects of an eco-friendly biopolymer (diutan gum) on xanthan gum (XC) in a water-based bentonite mud. Laboratory experiments were carried out for different compositions of the biopolymers in water-based bentonite muds formulated without salt and in water-based bentonite muds containing sodium chloride (NaCl). The rheological properties of the water-based bentonite muds formulated with XC (2 Ibm) and those of the water-based bentonite muds prepared using XC (1Ibm) and diutan gum (1Ibm) were measured using Model 1100 viscometer after aging at 25 °C, 100 °C, and 120 °C for 16 h. The API fluid loss and filter cake of the mud formulations were measured using HTHP filter press. The properties of the water-based bentonite muds containing only XC were compared with those of the water-based bentonite muds containing XC and diutan gum. Presented results show that combining diutan gum and xanthan gum in a ratio of 1:1 in a water-based bentonite mud enhances its performance with respect to fluid properties—apparent viscosity, gel strength, yield points, YP/PV ratio, LSRV,n, andK. The fluid formulations also showed favorable mud cake building characteristics. Experimental data also indicate a 16%, 19%, and 34% reduction in API fluid loss values for the water-based benitoite muds containing XC in the presence of diutan gum after aging at 25 °C, 100 °C, and 120 °C for 16 h, respectively. Experimental results also show that the water-based benitoite mud containing XC and diutan gum would cause less formation damage and was tolerant of contamination with a monovalent cation (Na+). The synergy of xanthan gum and diutan gum can, therefore, improve the performance of water-based drilling fluids.

Drilling muds with less environmental impact are highly desired over conventional diesel-based mud systems, especially in light of the emerging strict environmental laws. In this article, a novel oil-in-water (O/W) emulsion drilling fluid formulated with a methyl ester extracted from Indian mango seed oil was evaluated. The effect of the weight percent of different constituents of the emulsion/suspension including the oil phase, bentonite, and polyanionic cellulose polymer on the rheology and the fluid loss was examined. The methyl ester oil phase/mud system displayed superior physical, chemical, rheological and filtration properties relative to the diesel and the mango seed oil. Eco-toxicity of the methyl ester and diesel (O/W) emulsion mud systems was assessed using the acute lethal concentration test. The Indian mango methyl ester (O/W) emulsion mud displayed much less impact on fish population. Flow characteristics collected from the flow model at 85 °C suggested excellent shear thinning behavior of the Indian mango methyl ester (IMME) (O/W) emulsion mud. Moreover, the IMME (O/W) emulsion displayed strong pseudoplastic behavior, an attractive feature in a drilling mud, with increasing clay content and polymer concentration. The methyl ester mud was thermally stable over a wide range of the constituent concentrations. Furthermore, a particle size analysis revealed that engineered drilling muds targeting suspension of particles with certain size range can be formulated by changing the volume fraction of the methyl ester in the mud system.

Oil-based mud (OBM), a non-Newtonian fluid, is known for its superior performance in drilling complex wells as well as combating potential drilling complications. However, the good performance may degrade under certain circumstances especially because of the impact of chemical instability at an elevated temperature. The same phenomenon occurs for water-based mud (WBM) when it is used in drilling under high temperature conditions. To prevent this degradation from occurring, numerous studies on utilizing nanoparticles to formulate smart fluids for drilling operations are being conducted worldwide. Hence, this study aims to evaluate the performance of nanosilica (NS) as a fluid loss reducer and a rheological property improver in both OBM and WBM systems at high temperature conditions. This study focuses on the impacts of different nanosilica concentrations, varying from 0.5 ppb to 1.5 ppb, and different mud weights of 9 ppg and 12 pg as well as different aging temperatures, ranging from ambient temperature to 300 °F, on the rheological performance of OBM and WBM. All the rheological properties are measured at ambient temperature, and additionally tests, including lubricity, electrical stability, and high-pressure high-temperature filtration measurements, are conducted, and rheological models are obtained. The performance of nanosilica is then studied by comparing each of the nanosilica-enhanced mud systems with the corresponding basic mud system, taking the fluid loss and rheological properties as the benchmark parameters. Nanosilica shows a positive impact on OBM and WBM, as the presence of nanosilica in the mud systems can effectively improve almost all their rheological properties.

In a bid to combat fluid loss in muds where the effects of high downhole temperatures have pronounced effects on conventional fluid loss additives, several materials have over time been evaluated. One of such materials is the multiwalled carbon nanotubes (MWCNTs). Most studies in the literature limit the scope of their investigation to how the MWCNT affects mud rheology when added in minute concentrations (0.01–1 ppb). In this study, however, the performance of high concentrations (0.5–3 ppb) of multiwall carbon nanotubes as fluid loss control additives in field-applicable mud systems was put to the test. The essence was to establish an optimal concentration useful for field applications. The degree to which the introduction of varying concentrations of the MWCNT altered the muds capacity to control filter loss was the cardinal areas evaluated. The following are the major outcomes of the experimental study: The plastic viscosity, the yield point and the gel strengths showed a progressive increase as the concentration of the MWCNT in the mud increased for both the water- and oil-based muds. However, an optimum concentration of 2 ppb was observed for the water-based mud. For the filter loss tests on the oil-based mud, the results indicate that low concentrations (0.5 ppb) of the MWCNT led to high filter loss volumes (15 ml), but an increase up to 2.5 ppb reduced the margin of the filter loss volume by 52% (7 ml) from the initial value and a 50% decrease for the standard case. In the case of the water-based mud, equivalent amounts of MWCNT recorded less fluid loss than the standard. A moderately hard and firm cake was reported for all concentrations of the standard and MWCNT for the water- and oil-based muds; however, their cake thickness values were 2 mm and 1 mm for the water- and the oil-based muds, respectively.

Water-based drilling muds, a more environment-friendly candidate than oil-based drilling muds, are wildly used for drilling oil and gas wells. When water-based drilling mud is used for drilling formations with shale containing active clay constituents, it is challenging to preserve stability of the borehole due to clay swelling unless proper inhibition mechanisms are foreseen. In the current study, the feasibility of using Korean red Ginseng root extract was assessed as a clay swelling inhibitor. This root extract is rich in non-ionic surfactants such as Ginsenosides Rg3, Rg5, and RK1, and is referred to as “biosurfactant” throughout this manuscript. After preparation of mud systems containing problematic clay particles, the clay-swelling inhibition performance of the biosurfactant was systematically investigated through a series of tests, including mud formation, filtration, immersion, sedimentation assisted with optical microscopy, wettability by sessile drop technique, use of thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR), and shale cuttings recovery. The clay-swelling inhibition performance of the biosurfactant was then compared against two clay swelling inhibitors namely CTAB (Cetrimonium bromide, a known cationic surfactant) and potassium chloride. There are some properties associated with the mud systems prepared with biosurfactant solution which makes this product unique. These properties include: remarkable loading capacity of sodium montmorillonite (Mt) which in turn resulted in low rheological profile, poor fluid loss control, creation of stable Mt pellets, creation of larger size and aggregated Mt particles with less hydrophilicity, creation of fully unstable dispersed Mt particles that resulted in good sedimentation over time, less mass loss, and higher shale cuttings recovery, all compared to the baseline fluid made without the presence of biosurfactant. The results of this study indicate that the biosurfactant provides excellent clay swelling inhibition properties, comparable to known inhibitors. The biosurfactant's compatibility with other drilling mud components was also checked, and it was found that the fluid properties are independent of the biosurfactant. The wettability and FTIR analyses were also performed to investigate the mechanisms involved in clay swelling inhibition of the biosurfactant, which are believed to be as a result of coating the clay active surfaces with a hydrophobic layer, hence repelling the water phase. This hydrophobic layer is probably formed by interactions of the hydrophilic group of the Ginsenosides and the oxygen atoms available on the Mt surfaces, when the hydrophobic tail is oriented toward the aqueous phase.

A common issue encountered by drilling engineers during drilling operation in oil and gas industries is that simple water-based muds are not suitable for deeper depth and certain clay-swelling formations. Another option as to increasing the density of the drilling mud which brings about an increase in filtration loss, additives may be added to improve the fluid properties. This paper aims on determining the effectiveness of common salts, sodium chloride (NaCl) and potassium chloride (KCl), and haematite on the rheological properties of optimized carboxymethyl cellulose (CMC)–bentonite and partially hydrolyzed polyacrylamide (PHPA)–bentonite muds. Both CMC and PHPA polymer act as fluid loss-reducing agents and viscosifiers for normal bentonite water-based mud. The mud is further enhanced to counter certain swelling formations such as shale through the addition of NaCl and KCl. These salts inhibit the shale formation from swelling through its ions by entering the lattice of the drilling mud or formation instead of the water ions. Haematite, on the other hand, basically functions to increase mud density and acts as a substitute for barite. The effect of haematite on drilling fluid was studied because it gives higher degree of rheological parameters and increases density as compared to barite. So, an optimized concentration of additives was determined for both CMC–bentonite and PHPA–bentonite mud systems, respectively. Three grams of KCl and 3 g haematite were used for CMC–bentonite mud, while 3 g KCl and 1 g haematite were added into PHPA–bentonite mud. Both these muds have shown swelling reduction as compared to those without the use of additives. Moreover, they exhibited Herschel–Bulkley fluid behaviour according to the power law model where their ‘n’ value was less than 1, while their yield points were more than zero. Since shale sloughing is a major problem faced during drilling operation, it leads to major complications in drilling. So, finally, both the formulated drilling fluids are tested to analyse their effect in shale formations by static immersion test. The shale rock was collected from Champhai District of Mizoram. Both the formulated muds exhibited great results as swelling in shale rock was reduced for both muds and optimum rheological values were maintained.

Most oil and gas wellbores are drilled using water based mud (WBM), but this is the case when drilling through non-reactive formations that does not contain swelling shale. In reactive shale formation, KCl Polymer additive should be added to the mud. It will provide a source of potassium ions which will help stabilizing the reactive shale. So that the swelling process is minimized. The basis of the KCL polymer mud system is the polymer used as a wrapper for rock pieces during borehole cleaning process . In the wells in the POK Field , the use of polymer KCL mud i s evaluated on trajectori es of 1 7½ ", 1 2¼ ", and 8½ ". The evaluation process uses parameters that aim to find the suitable mud properties that result in the best drilling performance in each trajectory in the POK Field well. The determination of the best drilling performance is based on drilling time. The parameters used in this research are: r ate of p enetration , t rip t ime, yield point (YP), K+ content, mud weight (MW), viscosity ( m ), plastic viscosity (PV), and gel strength (GS), mud cake, pH, and additional parameter (e xcess c ement ) . Based on analysis and investigation, the best drilling performance for trajectory of 1 7½ " occured in POK 1075 well, while the best performance for the trajectories 12¼” and 8½” occured in POK 1058 well. Therefore the KCl polymer mud properties used in these wells can be used as a reference and basis for planning mud systems for the next well s .

Lost circulation is one of the most common problems in the drilling of oil and gas wells where mud escapes through natural or induced fractures. Lost circulation can have severe consequences from increasing the operational cost to compromising the stability of wells. Recently, polymeric formulations have been introduced for wellbore strengthening purposes where it can serve as Loss Circulation Materials (LCMs) simultaneously. Polymeric LCMs have the potential to be mixed with drilling fluids during the operation without stopping to avoid non-productive time. In this study, the significance of most common conventional mud additives and their impact on the gelation performance of Polyacrylamide (PAM) / Polyethyleneimine (PEI) has been investigated. This work helps in better understanding the process of using polymeric formulations in drilling activities. It provides insights to integrate gelling systems that are conventionally used for water shut-off during the drilling operation to replace the conventional loss circulation materials to provide a higher success rate. The authors would like to acknowledge the support of Qatar National Research Fund (a member of Qatar Foundation) through Grant # NPRP10-0125-170240. The findings achieved herein are solely the responsibility of the authors. Special thanks with gratitude to SNF Company for supplying the polymers used in this study. Scopus

Experimental tests were carried to control lost circulation in the Khabaz oil field using different types of LCMs including Nano-materials. A closed-loop circulation system was built to simulate the process of lost circulation into formations. Two dolomite plugs were used from different depths of the formation of Azkand in Khabaz oil field. The experimentations were carried out to study the effect of different types of LCMs, cross-linked copolymer (FLOSORB CE 300 S), SiO2 NP, and Fe2O3 NP, on mud volume losses as a function of time. The rheological measurements of the nanoparticles-reference mud system showed that both of the SiO2 NP and Fe2O3 NP worked best at 1.2 g/l. and the closed-loop circulation system showed that SiO2 NP cured losses by 48.3% and 37.5% for core plugs 5C1 and 1C2 respectively which is better than Fe2O3 NP loss curing which was 37.9% and 31.3% for core plugs 5C1 and 1C2 respectively. On the other hand, FLOSORB CE 300 S- Fe2O3 NP-reference mud systems cured losses up to 69% with 0.25g/l FLOSORB CE 300 S and 79.3% with 0.5 g/l FLOSORB CE 300 S which is better than the FLOSORB CE 300 S- SiO2 NP-reference mud systems results.

Efficient cement bonding in wellbores provides better zonal insulation, containment of gas migration, prevention of excessive water production, besides affecting their economical performances. Carrying out a properly sized and formulated cleanup process (or pre-flush) is one of the most costly tasks in wellbore preparation. Different chemicals are commonly used both to remove filter cakes and enhance surface water-wetting, such as solvents and surfactants. The search for environmentally-friendly cleanup fluids, in particular, with acceptable wetting properties, has been challenging. This paper describes an experimental study to characterize and prepare a vegetable oil-based microemulsion to work as pre-flush fluid in wellbores. Results obtained from cleaning assays (removal test), wettability testings and fluid compatibility analyses have exhibited excellent performances in filter cake removal. Enhanced water-wetting and suitable rheological compatibility of cement/cleanup fluid/mud systems and good compressive strength were also achieved.

The design and formulation of drilling fluids require additives that are cost-effective and environmental friendly in line with international best practices. This study was conducted to investigate the potentials and effects of Cyperus esculentus (Tiger Nut) as a filtrate loss modifier in field applicable aqueous and non-aqueous drilling fluids. Sixteen (eight aqueous and eight non-aqueous) drilling fluid systems were formulated, four aqueous and non-aqueous had Cyperus esculentus as a filtration additive, while the others do not contain the additive. The rheological properties, as well as the fluid filtration properties of the drilling muds, were investigated and compared with standard drilling mud. To ascertain validity, the results obtained were validated with the classic filtration model to ensure fit. Results obtained showed that the formulated mud systems had rheological properties that favored the suspension and transportation of drill cuttings, as well as the prevention of flocculation and clogging of drill strings. The rheological properties also showed a progressive trend as the concentrations of the additive were increased from 2 to 8 ppb. It was also further observed from the API and HPHT filter press test that the increase in the concentration of the additive exhibits a progressive trend that can be compared with the standard. In addition, it was observed from the classic filtration model that the experimental results from both mud systems were fit for the adopted model.

The focus of this research was to present a data article for analyzing the cost of displacing a drilling fluid during the drilling operation. The cost of conventional Spud, KCl and Pseudo Oil base (POBM) muds used in drilling oil and gas wells are compared with that of a Reversible Invert Emulsion Mud. The cost analysis is limited to three sections for optimum and effective Comparison. To optimize drilling operations, it is important that we specify the yardstick by which drilling performance is measured. The most relevant yardstick is the cost per foot drilled. The data have shown that the prices for drilling mud systems are a function of the mud system formulation cost for that particular mud weight and maintenance per day. These costs for different mud systems and depend on the base fluid. The Reversible invert emulsion drilling fluid, eliminates the cost acquired in displacing Pseudo Oil Based mud (POBM) from the well, possible formation damage (permeability impairment) resulting from the use of viscous pill in displacing the POBM from the wellbore, and also eliminates the risk of taking a kick during mud change-over. With this reversible mud system, the costs of special fluids that are rarely applied for the well-completion purpose (cleaning of thick mud filter cake) may be reduced to the barest minimum.

Non-governmental and governmental agencies are demanding for environmentally friendly mud systems. This increase in environmental awareness has made the drilling mud service companies to re-evaluate some of the chemicals and materials used as additives for mud systems. In this study, some green materials were considered as possible substitutes for PAC R in water-based drilling fluid systems. The rheological properties of four water-based mud systems with typical compositions were studied at 80 and 150 °F. These two temperature ranges were necessary so as to evaluate the effect of temperature on the viscosity, plastic viscosity and yield point properties of these mud systems formulated with these green materials as viscosifier. These green materials were processed to powder form and sieved to their finest particle sizes to reduce amount of solute that will be present in the water-based drilling fluid formed with the materials. The properties of the formulated mud systems were analyzed using API standard. These green materials behaved optimally as viscosifiers for the formulated water-based mud systems under ambient temperature. Also the mud systems behaviour at 150 °F showed a reduction in the flow properties at this high temperature as recorded in the literatures. From the results of the experiment, we can say that Kian (Averrhoa carambola L.) has the characteristic of being a substitute for PAC R when beneficiated for water-based drilling fluids.

The hydrate inhibitors played a significant role in preventing hydrate formation in the drilling fluid systems. However, the disposal of these inhibitors was the primary concern for the drilling industries, as Thermodynamic Hydrate Inhibitors (THIs) are not eco-friendly, and Kinetic Hydrate Inhibitors (KHIs) are troublesome to dispose of due to their long polymeric structures. Hence, an attempt had been made to evaluate the Sarcosine, an amino acid, as a biodegradable, green hydrate inhibitor for water-based drilling fluid systems. Initial screening of Sarcosine in the THF-water hydrate (structure-II) system showed that it behaved as a zwitterionic, dual-function inhibitor. It had better inhibition characteristics in delaying induction time and improving rheological and filtration properties than PVCap and PVP while used in formulated mud compositions. The water-based mud used in this work was prepared by mixing carboxymethyl cellulose (CMC), polyanionic cellulose (PAC), xanthan gum (XG), and potassium chloride (KCl) with distilled water. For Sarcosine content water-based mud systems, coefficients of determination (R2) values were dependable, while low-temperature (2 C) rheological values were fitted in Herschel-Bulkley model. These experimental investigations showed that the Sarcosine might be used for the drilling of gas hydrate-bearing formations.

Most important aspect of drilling clay-rich formations is preventing the hydration and dispersion. Oil based drilling muds (OBM) have historically been the first choice for drilling these kinds of formations, however the usage of the OBM is currently forbidden in drilling operation due to environmental issues. As an alternative, many inhibitive water-based muds were proposed. This paper describes the experimental work carried out on ten shale samples to evaluate stabilization of shale and clay-fluid interactions. After mineralogical analysis of shale samples, swelling and hot-rolling dispersion test were conducted using fresh water, polyamine, sodium silicate and oil base mud. Mineralogical analysis results showed that the cutting samples of 3, 4, 5, 6 and 7 have the highest clay content. Cation exchange capacity (CEC) results indicated that the shale sample with high concentration of smectite recorded the highest CEC value as it has the ability to absorb water into its inter-layers and exchange cations. When shale samples were tested in linear Swell meter, it is expressed the lower swelling percentage for oil base mud and maximum for fresh water. However, it was found out that both sodium silicate and polyamine mud systems yield the same performances. Furthermore, dispersion results showed that the shale recovery percentage increased from 16.3% to 56.2% when sodium silicate mud was used instead of polyamine mud. For the fresh water and oil base mud, results confirmed findings of linear swelling meter test, which is the lowest recovery for the fresh water (6.7%), and maximum recovery for the OBM (109.9%). The improved swelling inhibition suggested that sodium silicate mud could be effectively used to control wellbore instability while drilling through the Kolosh Formation .

Wellbore instability is caused by the radical change in the mechanical strength as well as chemical and physical alterations when exposed to drilling fluids. Unscheduled events that are related to wellbore instability account for more than 10% of the drilling cost, which is estimated to one billion dollars per annual cost. Understanding shale-drilling fluid interaction plays a key role in minimizing drilling problems in unconventional resources. The need for providing a more suitable drilling fluid system for drilling operations in unconventional resources is growing. The major consequences of improper fluid selection include bit-balling, hole sloughing, and most importantly low drilling rates. This study will evaluate the effect of different inhibitive drilling fluid systems on shale drilling performance. The mud systems use in this study include cesium formate, KCl based mud systems, and a conventional water-based mud. The conventional water-based mud is used as reference fluid. An innovative HPHT drilling simulator is used to perform real-time drilling operations on cylindrical shale core samples obtained from the Tuscaloosa Marine Shale (TMS). The process involved simulating real-time drilling operation at downhole conditions where different fluids served as drilling fluid. A comparative analysis of the impact of each drilling fluid systems on the drilling performance as then performed. The analysis focused on drilling parameters such as rate of penetration, torque, and friction factor during drilling. This paper evaluates the compatibility between different fluid systems and shale formations. The paper also provides an overview of the effect of the inhibitive mud systems on drilling performance. The inhibitive muds systems (KCl based fluids and cesium formate) provided improved drilling performance compared to conventional water-based mud.

Drilling mud is the most important part in drilling activity. Drilling could work fluently, safely, and economically on fluency by system and condition of drilling mud. It means the mud system and the physical properties of the slurry conform to the required specifications. There are some kinds of drilling mud that can be used in oil and gas drilling operation, such as water base mud and oil base mud. In terms of economical objective, water base mud is usually used in drilling process.The purpose of this study is to conduct laboratory research of the effect of various temperatures on the characteristic of mud system of low solid mud by adding biopolymer and bentonite extender. This research uses roller oven method as a medium for simulation to condition the mud as close as possible to the condition in wellbore to see the change of physical properties of sludge at various temperatures.The result found is that the higher the temperature, the lower the drilling mud physical properties such as density, viscosity, plastic viscosity, yield point, dial reading 600 RPM, dial reading 300 RPM, and gel strength. However, it is found that not all the physical properties decrease.

In drilling operations, drilling mud plays a very important role because it is irreplaceable functions. Drilling activities relate to problems caused by complex conditions in formation due to changes in temperature, pressure, and contamination from formation fluids. Using Oil Base Mud (OBM) mud systems in the form of Saraline and Smooth Fluid 05 is tested for drilling fluid performance and the results can be a reference for drilling operation. This research consist of two parts, the first: determining the drilling mud rheology value in the form of (Plastic Viscosity, Yield Point and Gel Strength) in each drilling mud of Saraline and Smooth fluid 05 mud using various high temperature parameters of 350oF, 300oF, and 270oF. The results of the mud rheology tests show at the higher the temperature, the values of rheology decreases. The second experiment is to determine the level of electrical stability in the mud which functions of oil-wet content in oil sludge (Saraline and Smooth fluid 05). The electrical stability value has a minimum limit value in OBM, which is 500 volts. In this experiment showed that the higher the temperature value, the electrical stability value in the mud will decrease, but in this study the value of electrical stability in Saraline mud and Smooth fluid 05 has a value above 500 volts, the composition OBM of Saraline and Smooth Fluid 05 sludge has very good oilwet content.

Wellbore instability is caused by the radical change in the mechanical strength as well as chemical and physical alterations when exposed to drilling fluids. A set of unexpected events associated with wellbore instability in shales account for more than 10% of drilling cost, which is estimated to one billion dollars per annum. Understanding shale-drilling fluid interaction plays a key role in minimizing drilling problems in unconventional resources. The need for efficient inhibitive drilling fluid system for drilling operations in unconventional resources is growing. This study analyzes different drilling fluid systems and their compatibility in unconventional drilling to improve wellbore stability. A set of inhibitive drilling muds including cesium formate, potassium formate, and diesel-based mud were tested on shale samples with drilling concerns due to high-clay content. An innovative high-pressure high temperature (HPHT) drilling simulator set-up was used to test the mud systems. The results from the test provides reliable data that will be used to capture more effective drilling fluid systems for treating reactive shales and optimizing unconventional drilling. This paper describes the use of an innovative drilling simulator for testing inhibitive mud systems for reactive shale. The effectiveness of inhibitive muds in high-clay shale was investigated. Their impact on a combination of problems, such high torque and drag, high friction factor, and lubricity was also assessed. Finally, the paper evaluates the sealing ability of some designed lost circulation material (LCM) muds in a high pressure high temperature environment.

The drilling for hydrocarbons from oil and gas wells requires efficient drilling fluid and cutting-edge drilling technology. Furthermore, the removal of rock cuttings from oil and gas wells while drilling is a vital task of the drilling fluid, particularly in large-angle wells and long-range drillings. The rock cuttings if not transported to the surface effectively can result in severe costly drilling problems of drag and torque, pipe sticking, faster bit damage, etc. This research suggests a new method that applies polypropylene beads (PP) and silica nanoparticle (NS) treated by sodium carbonate (Na2CO3) to enhance the cuttings transport efficiency (CTE) of water-based mud (WBM). Tests were carried out in laboratory-scale cuttings lifting rig simulator equipped with a 20-ft. Long annulus, a 2.75-in. ID outer acrylic pipe, and an inner drill pipe of 1.05-in. OD. Six different 10 ppg weighted mud samples were formulated and coded mud nos. 1–6 using PP beads and Na2CO3 treated NS concentrations. Four cuttings sizes in the range between 0.4 and 4.0 mm at various hole angles (0°, 30°, 60°, and 90°) without pipe rotation were evaluated using a constant flow rate of 5.13 L/s. The results of rheological characterization using Herschel-Buckley model showed that all the mud systems are shear-thinning as the flow behaviour index ranged between 0.50 and 0.60. The fluid consistency parameter of the WBM indicates that the addition of PP beads and NS concentrations decreases the viscosity of the WBM. Also, the viscosity, yield point, gel strength, and filtration parameters of the WBM were decreased when the PP beads and NS concentrations were introduced before and after thermal aging experiments. This interprets the thinning nature of the mud systems. However, when these products were applied to lift cuttings to the surface, the lifted cuttings increased. The optimum mud system using Bingham plastic expression was found at mud no. 6 (BM-PP8-NS1) containing apparent viscosity of 30.5 cP at a shear rate of 1022 s⁻1, plastic viscosity of 13 cP and a yield point of 35 lb/100 ft2 at 78 °F. Cuttings size and hole angles seem to wield significant influence on CTE as the smallest cuttings (0.4–1.4 mm) were easier to be lifted in the vertical hole (0° angle), while the largest ones (2.8–4.0 mm) were the most lifted in the horizontal section (90° angle). The findings of this study can help for a better understanding of the mud performance of PP beads and Na2CO3 dispersed NS mixture for cuttings transport in a wellbore.

In this work six structurally related imidazoline oligomers based on the reaction of liner polyamine with saturated and unsaturated long alkyl chains (C18 oleic and stearic) fatty acids were prepared, followed by a quaternization reaction to produce new conventional and gemini imidazolinium quaternary salts. The chemical structures of prepared amphiphiles were confirmed via spectroscopic methods and elemental microanalysis, also, the prepared emulsifier’s characterization has been studied through static interfacial tension, visual and microscopic examination of prepared emulsification systems. The static interfacial tension measurements show a high ability to reduce interfacial tension values between diesel oil and water. The visual and microscopic examination gave evidence of a multilayer interface around emulsion particles and an increase of emulsion droplets size as a function of time with acceptable emulsion stability and phase separation. For both oil-based mud cost and diesel oil toxicity, this article brings to light many important aspects of designing new emulsifiers for low toxicity invert emulsion muds with lower diesel oil content. The prepared emulsifiers were mixed to be investigated and evaluated as primary emulsifiers package to formulate the invert emulsion oil-based muds (IEOBMs). The electrical stability, rheological properties, and filter loss were evaluated before and after hot roller aging and compared with the reference mud sample formulated from the commercial-grade emulsifiers. The experimental investigations conducted based on the Herschel-Bulkley rheological model showed good rheological behavior compared to the reference mud sample, high resistance to the deformation that occurred to prepared mud systems due to hot roller aging, good electrical stability, and high pressure-high temperature filtration loss values.

Design of drilling fluids is critical to the techno-economic success of drilling a petroleum well bore and the present study is a forward step in that direction. Effect of TiO2 nanoparticles on the thermal stability of drilling fluid properties is evaluated using two different mud systems based on polyanionic cellulose (PAC) and hydroxyethyl cellulose (HEC). Drilling fluids were subjected to high temperature rolling conditions at 110 °C and 30 rpm for 16 hours in order to simulate the wellbore environment using a roller oven. Due to 16 h long hot rolling, the API FL values for DFB (base mud), DFP3 (1.0 w/v% PAC) and DFH3 (1.0 w/v% HEC) increased by ~56%, ~18% and ~46% respectively; whereas in presence of 0.5 w/v% nanoparticles respective figures were ~28%, ~16% and ~25%. In case of DFP3, AV at 25 °C was reduced due to hot rolling by ~34% without nanoparticles and by only ~15% in presence of nanoparticles. For DFH3, the percentage reduction in AV at 25 °C due to ageing was ~24% which decreased to ~16% for DFHN (1.0 w/v% HEC and 0.5 w/v% TiO2). It was found that nanoparticles imparted resistance to thermal degradation in rheological and filtration characteristics of drilling fluids. Filter cakes were studied using scanning electron microscopy and showed nanoparticles scattered over the surface of filter cakes which were filling the micro and nano sized gaps in the porous structure of mud cake and reducing the filtration rate. This study shows that using TiO2 nanoparticles along with a conventional fluid loss reducer additive not only enhances the efficacy of that additive but also improves the thermal stability and rheological properties of mud systems.

Summary Core goniometry is an established technique. However, the explosion of borehole imaging that occurred in the 1990’s onwards corresponded somewhat with a decline in the acquisition of cores by operating companies. Borehole images were acquired over much longer intervals than cores, and provided cost effective high resolution oriented data-sets. However, an increasing shift to drilling wells with non-conductive mud systems over the last decade has countered this to a degree, and there appears to be increased or renewed interest in using cores to undertake core goniometry to derive high resolution oriented datasets. This has in part been driven by the limitations common in some earlier generations of imaging tools developed for use in non-conductive borehole environments. In such cases, core goniometry can provide very significant increases in data density compared to borehole images, enabling highly detailed sedimentological and structural interpretation. 10-fold increases in dip data density are possible. The paper will summarize some of the techniques that can be used for core goniometry, demonstrating the orientation principle using Task Fronterra’s attitude software, and outlining the types of “core versus log” data density variations, together with benefits and limitations that may be encountered.

The drilling technology is widely used in various fields. This technology has been developed explosively by large companies. However, most of the conventional drilling systems require large equipment such as rig and mud systems. This makes it difficult for drilling in polar or space environments where large equipment is hard to enter or carry. To solve this problem, we propose an embedded drilling system which does not requires the rig, mud system, and pipes. In this paper, the concept of embedded drilling system will be proposed and we introduce a locomotion and rotary-percussion drilling mechanism of this system. Two simulations were performed to show efficiency of the proposed system compared toss the conventional rotary drilling system.

In Hassi Messaoud’s oil industry, the systems which are water based (WBM) are generally used for drilling in the first phase. For the rest of the well, the oil mud systems are employed (OBM). In the field of oil exploration, panoply of chemical products is employed in the drilling fluid formulation. These components of different natures and whose toxicity and biodegradability are of ill-defined parameters are, however, thrown into nature. In addition to the hydrocarbon (HC, such as diesel) which is a major constituent of oil-based mud, we also can notice spills as well as a variety of other products and additives on the drilling sites. These wastes are usually stored in places called (crud wastes). These may cause major problems to the ecosystem. To treat these wastes, we have considered two methods which are solidification/stabilization (chemical) and thermal. So that we can evaluate the techniques of treatment, a series of analyses are performed on dozens of specimens of wastes before treatment. After that, on the basis of our analyses of wastes, we opted for diagnostic treatments of pollution before and after solidification and stabilization. Finally, we have done some analyses before and after the thermal treatment to check the efficiency of the methods followed in the study.

Results are presented for metallographic and x-ray structural analyses of wear and damage features of a geological exploration pump type Gr16/40 valve pair, plate, and seat.

Herein, 1-methyl-3-octylimidazolium tetrafluoroborate (OMIM-BF4) was tested as a potential additive to enhance the rheological and hydrate inhibition properties of polymer water-based muds (WBMs) for drilling natural gas hydrate sediments. API standards were adopted for the mud testing with and without OMIM-BF4, while the hydrate study was conducted using a high-pressure reactor at 8 MPa and −2 °C. The presence of OMIM-BF4 efficiently improved the rheological properties of the PAC and XGUM based muds by decreasing their flow behavior index by 4.97% and 47.77% and increasing their consistency index by 96.00% and 33.63%, respectively. The XGUM based mud system exhibited efficient rheological properties suitable for drilling hydrate reservoir compared with the PAC based mud system with and without OMIM-BF4. The Hershel-Bulkley model best predicted the rheological properties of all the mud systems by exhibiting less Mean Percentage Error (MPE) values in the range of 1.39% – 24.71%. Furthermore, the presence of OMIM-BF4 greatly inhibited methane hydrate formation in both PAC and XGUM water-based mud systems due to its kinetic inhibition efficiency mainly arising from its long alkyl chain hydrophobic adsorption activity on the hydrate crystals.

In case of foamed lightweight aggregates (LWAs), porosity is introduced by the addition of a foaming agent to the glassy matrix, which degasses at an elevated temperature, so that the resulting gases remain trapped inside the glassy structure. The efficiency of action of MnO2 as a foaming agent in waste glass and waste glass/silica mud systems was studied. Samples were fired at different temperatures and with different dwelling times at a certain temperature, and the development of porosity was investigated by means of X-ray micro-tomography. It was found that, with the prolongation in dwelling times, the number of pores decreased, while, on the other hand, the volume of these pores increased, and that the addition of silica mud increases the foaming temperature and slows down the foaming process.

This chapter covers a number of additives that have been published in the literature as available for controlling one or more drilling fluids’ characteristics—mud weight, viscosity, fluid loss, and physical–chemical reactivity. Many of the chemical additives in this chapter were found in patent publications as well as technical papers. Several mud systems are covered, including the mixed-metal hydroxide and aphrons.

Drilling mud plays a crucial role during drilling operation as they not only enhance efficient transport of drilled-cuttings from the drill bit to the surface, but also maintain their rheological properties especially in harsh environments to suspend drilled-cuttings when drilling operations stop. Although water-based muds are known to be environmentally friendly and less expensive as compared to oil-based and synthetic-based muds, they exhibit poor performance with less stability when circulating in high-temperature wells particularly with shale formations. Water-based mud systems with potassium brine have proven better results in shale formations; nonetheless, very little is known about their performances in high-temperature environments. This study examines the performance of water-based muds with synthetic polymers and potassium formate brine as additives in high-temperature conditions up to 300 ℉. The drilling muds were formulated using the Taguchi Design of Experiment (TDOE) approach. The muds were prepared and tested in laboratory conditions under the guidelines of safety and drilling fluid testing using the American Petroleum Institute (API) standard. The experimental data obtained showed that the combinations of synthetic polymers and potassium formate brine were able to stabilize the rheology of the water-based muds at elevated temperatures. The usage of potassium formate brine at concentrations of 3.2, 6.7, and 10% aided in stabilizing the drilling mud’s rheological properties after dynamic aging at 300 ℉. Rheological properties such as plastic viscosity and yield point were also found to be almost identical for both static and dynamic aging conditions. Therefore, this study serves as optimization guide to design water-based muds applicable to high-temperature formations.

Five different drilling mud systems namely potassium chloride (KCl) as a basic mud, KCl/partial hydrolytic polyacrylamide (PHPA), KCl/graphene nanoplatelet (GNP), KCl/nanosilica and KCl/multi-walled carbon nano tube (MWCNT) were prepared and investigated for enhancement of rheological properties and shale inhibition. Nanoparticles were characterized in drilling mud using transmission electron microscope (TEM) analysis. Mineralogical analysis of shale was examined by X-ray diffraction (XRD). Five shale plugs were prepared using compactor cell for the determination of shale swelling. Shale swelling was determined using the linear swell meter (LSM) for 20hours. Results revealed that basic mud and KCl/polymer mud systems shows 30% and 24% change in shale volume. MWCNT, nanosilica and GNP were added separately in the KCl mud system. 0.1ppb of each MWCNT and nanosilica showed 32% and 33% change in shale volume. However, when the shale was interacted with WBM containing 0.1ppb of GNP, it was found that only 10% change in shale volume occurred. The results showed that the addition of nanoparticles in the KCl mud system improved the shale inhibition. API, HPHT filtrate loss volume, plastic viscosity (PV) and yield point (YP) were improved using GNP. It is learned from the experimental work that small concentration of KCl with GNP can mitigate shale swelling compared to the mud contains higher concentration of KCl and PHPA in WBM. Thus, GNP can be a better choice for enhancement of WBM performance.

Core samples are still today considered as the standard measurement against all other measurements which must be compared. Core analysis usually focuses on the worse portion of the reservoir due to the fact that core recovery has rarely been well in a highly fractured zone; hence, permeability measured from core sample is often not representative. Core analysis is a common method to identify small-scale fractures of the well and permeability and porosity; however, there are some limitations in the core procedure such as it is highly expensive and unidirectional and has a low recovery coefficient in fractured zone. In contrast, there tends to be a mistrust and even a suspicion of those logging instruments that make measurements which threaten to replicate or even replace the “sacred core.” Thus, image logs are more useful to study the subsurface fractures in these such cases and the logs which come closest to achieving this are the high-resolution micro resistivity (OBMI) and acoustic geological imaging (UBI). The core and OBMI-UBI result was matched in order to verify the log measurements. Furthermore, FMI data were integrated with other open-hole logs to derive a permeability curve. As demonstrated in the case studies, it is believed that the permeability in the basement could be reasonably evaluated using this method. As a result, this exercise has proven to be very valuable, not only for demonstrating the value of the log data, but also it has also highlighted some significant limitations of the core in water-based mud and oil-based mud systems.

This paper presents an experimental analysis of drilling fluid at elevated temperatures with and without magnesium saltwater influx in order to determine how these fluids behave when encountering the influx of salinity formation water. Salt contamination can come from drilling salt beds, or from a formation water influx. Salt water which contains magnesium chloride was added systematically to the formulated mud systems in order to evaluate its effects on the drilling fluid at elevated temperature conditions. It was observed that rheological changes in drilling fluids due to influx of magnesium salts have many effects on the degree of efficiency at which the drilling fluid performs its primary functions. From the analysis, it was observed that small quantities of magnesium saltwater can be removed with caustic soda but the large quantities are detrimental to rheological properties of drilling muds used in Niger formation.

In most of the drilling operations it is obvious that a considerable amount of money is spent for drilling related problems, including stuck pipe, lost circulation, and excessive mud cost. In order to decrease the percentage of non-productive time caused by these kind of problems, the aim is to control annular frictional pressure losses especially in the fields where pore pressure and fracture pressure gradient is too close, which is called narrow drilling window If we can solve these problems, the budget spent for drilling the wells will fall, therefore, enabling the industry to be able to drill wells that were previously uneconomical. Managed pressure drilling is a new technology that allows us to overcome these kinds of drilling problems by controlling the annular frictional pressure losses. As the industry remains relatively unaware of the full spectrum of benefits, this thesis involves the techniques used in managed pressure drilling with an emphasis upon revealing several of its lesser known and, therefore, less appreciated applications.

For complex drilling operations with narrow geo-pressure windows, it is not uncommon to have problems with formation fracturing, due to erroneous mud pump management. To assist the driller in managing the circulation, it is possible to limit both the acceleration of the mud pumps whilst changing the flow-rate as well as the actual flow-rate, to avoid generating downhole pressure above the fracturing pressure gradient of the open hole section. Such mud pump operating limits are dependent on the operational parameters (e.g. drill-string axial and rotational velocities), and the in situ conditions downhole. The in situ conditions evolve with time due to the changes of bit and bottom hole depths as well as the variations in temperature, mud properties and cutting concentrations. When starting to condition mud after a long period of time without circulation, the changes in temperature can be very large. Furthermore, in the eventuality of barite sag, lifting up drilling fluids containing a large concentration of high gravity solid can cause much increase of the downhole pressure. This paper presents a methodology that is used in an automatic drilling control system to account for all those factors in order to have a safe mud pump management including circumstances where mud is being conditioned.

The Tuns and Opuks shales are essentially kaolinitic with subordinate amounts of quartz, illite, and mixed layer clays. The total clay content of the shales varies from 55 to 92% with an average of 76%. The degree of reactivity in terms of their CEC is low and about 12 m.eq/100 mg on the average. The number of samples was, however, too small to be more useful. The high temperature/pressure assessment of the mud systems has revealed that the barite weighted SynTeq mud is more stable thermally and of better viscosity, gel strength, and load-bearing capacity than the other mud systems investigated. The secondarily viscosified Petrofree has some potential but is of low thermal resistance. It is concluded that the SynTeq mud system is generally a better drilling fluid for rocks in the Niger Delta than either Petrofree or KCL Polymer. The SynTeq is, therefore, recommended for adoption in the oil production company drilling operations. It has been re-emphasized as part of our recommendations that new gu...

Drilling muds are complex fluids, generally used to clean the well, maintain hole integrity, transport the rock cuttings, lubricate the drill bit and control formation pressures. Two basic types of drilling fluids are used, water based muds (WBM) and oil based muds (OBM). OBM are very effective but polluting, and environmental regulations continue to restrict the use of oil based muds in many areas of the world. In order to reduce the mud toxicity, we developed water based mud systems using two biopolymers, which are xanthan gum and scleroglucan, generally proposed for high permeability reservoirs or for complex geometries such as horizontal wells. In this study, we evaluated the rheological behaviour of different samples and we determined the effect of components such as clay, calcium carbonate and potassium chloride. This formulations exhibit non-Newtonian rheological behaviour which can be described well by the tree parameter in Herschel–Bulkley rheological model.

The objective of this study was to evaluate a series of mud systems and additives typically used in coalbed methane drilling in terms of formation of an instantaneous filter cake, ability of the coal reservoir to rid itself of the filter cake during production, and overall impact on coal permeability. To achieve this, a series of laboratory tests were conducted initially using artificially cleated gypstone rock (to simulate coal). This was followed by the use of large-diameter coal cores, which, unfortunately, did not allow for the tests to be done under in-situ confining stress conditions. The three mud systems tested against coal (Xantham Gum, HEC and Na-CMC) did not have a negative impact on coal permeability, in contrast to previous laboratory data that showed large decreases. Two fluid loss control additives, which have been used successfully in drilling clastic and carbonate rocks, were also tested using a non-ionic polymer mud system. During simulated drilling, these additives (FLC 2000™ and Q-Stop) were very effective in building a thin filter cake on the coal surface almost instantaneously, to the point that no solids were detected in the downstream fluid accumulator. During simulated production, a small pressure drop was sufficient to remove the filter cake. Coal permeability (to water) returned to its original (pre-test) value, which suggested that there was no permanent permeability damage caused by the two additives. When coal-derived fines were added to the drilling mud in another experiment using the same coal, the near wellbore coal permeability was reduced by 87.5%, indicating severe damage to the cleat system and in agreement with previously reported laboratory data. Following the very good performance of FLC 2000™ and Q-Stop in the laboratory tests, these two additives were then used in field applications. Their presence in the drilling fluid resulted in the successful drilling of 953 m and 1400 m of total horizontal length in the deep Mannville coals in Alberta (at True Vertical Depth of 1400 m and 1150 m, respectively). No borehole instability problems were encountered during drilling of the two horizontal wellbores. The monitored mud losses were low in both cases, with the horizontal well #2 experiencing lower mud loss possibly as a result of the absence of large fractures encountered along the horizontal path. Horizontal well #1 remained stable, which allowed sufficient time to insert a production liner.

This paper will describe how Differential Scanning Calorimetry (DSC) may be used to characterize emulsions, especially the concentrated and opaque water-in-oil emulsions encountered in the oil industry. After a presentation of the technique, we will point out how it is possible, from a single test performed on an emulsion sample without dilution, to get information about the solidification and melting properties of these complex fluids, the emulsion type, the amount of water, the presence of solute, the stability and even the droplet size. Some examples of applications are given concerning oilfield emulsions and oil-based mud systems.

Experimental work was performed on drill cuttings sampled from off-shore drilling operations. The cuttings contained remnants of two different types of drilling muds: a water-ilmenite based mud and an olefin-barite based mud. In a pilot experiment, a gradient of up to 65 mm thick layers of water-ilmenite based cuttings were added to 78 cm2 core samples. In another set-up, 3 mm layers of water-ilmenite and olefin-barite based cuttings were added to replicate 1000 cm2 box-core samples with natural benthic communities transferred from the Oslofjord, S.E. Norway. Boxes with no addition and addition of 3 mm “clean” sediment were used for control. Increased consumption of oxygen and nitrate indicated the presence of degradable organic phases in both mud systems. The release of silicate showed a general decrease with increasing thickness of the cuttings layer, but maximum rates in the 3.1 mm treatment indicated increased bioturbation at low and moderate doses. The initial (field) composition of the macrobenthic communities was maintained throughout the 3 months experimental period, and at community level, no significant difference was observed between the four treatments at the end of the exposure period. However, after grouping the treatments into “clean” (untreated control and 3 mm clean sediment) and “cuttings” (3 mm water-ilmenite and 3 mm olefin-barite based cuttings), multivariate statistical analyses revealed a significant difference in community composition between clean and cuttings treatments, and three taxa showed significantly reduced abundances in the cuttings treatments. Chemical toxicity of mud components is assumed to be small, and the observed effect was more likely a result of physical properties such as the size or shape of cuttings particles.

Control losses in geological formations consider as an important issue in drilling operation. Lost of circulation can be one of the more serious problems that can arise during the drilling of an oil well or gas well. Loss of drilling fluid can result in increased cost, loss of time, plugging of potentially productive zones, blowouts from decreased hydrostatic pressure in formations other than the thief zone, excessive inflow of water, and excessive caving of the formation. Lost circulation occurs through existing high-permeability zones such as highly fractured, vuggy, or cavernous structures or induced fractures when the hydrostatic pressure of drilling fluid exceeds the breaking strength of the formation. Carbonates are good examples of the former case. The following preventive measures can be used however in other cases:1 a) set casing, b) maintain drilling fluid density, c) avoid excessive downhole pressures. d) using high energy ball milling to oil based mud to observe the reduction in fluid loss as a result of the nano-additive, the results were positive indicating up to 27.7% fluid loss reduction due to the ability of the suspended nano-material to form compact impermeable mud cake as a result of its physical properties and increased surface area and interaction potential. Core plugs with pre-determined properties were re-tested after the saturation test and showed encouraging results with up to 15% permeability reduction and 8% porosity reduction.

Drilling fluid plays a key role in an efficient drilling operation to minimize problems such as wellbore collapse, circulation losses and stuck pipe. Well instability problems are costly as they increase the non-productive time and the overall budget (1) (2). Well instability problems controlled by designing appropriate mud density and fluid properties that controls the well. The fracture sealing ability of a drilling fluid is one very important of the drilling mud. This paper presents design of water-based drilling fluids and results from laboratory experiments to quantify the loss circulation performance of drilling fluids. Because it is preferable to use oil-based muds in some well sections, the paper will also include a recent study on how to minimize losses when using oil based muds. Here uses of micro/nanoparticles have shown to reduce filtrate losses and to build barriers that are more efficient during circulation loss events. All the tests presented are at low temperature, which is suitable for Artic environments.

Drilling fluid is a relatively minor direct expense (< 7% of the total drilling costs), but it can significantly affect principal item in drilling expense (which is time ~ 37%) and other items of expense, such as drill pipe, casing, bits, formation logging/testing, cementing, etc. (probably ~ 26%). Any formation damage due to using improper drilling fluid could affect the produtivity of the pay zone and increase post treatment costs. In case of permanent formation damage, lost cannot be described by certain amount of money. Therefore, performance of the drilling fluid is more important than it’s cost, i. e., an optimal drilling fluid system must be targeted.