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To maintain performance of an aqueous-based drilling muds (ABDMs), it was imperative to understand the decay mechanism of the incorporated synthetic polymers, when exposed to the elevated temperatures. The understanding of the decay mechanism could provide a polymer replenishment strategy for the fluid to retain a specific rheology and filtrate control performance. In this context, thermal-degradation of various acrylamide co-polymers was investigated in different monovalent brines. The acrylamide co-polymers were custom synthesized, and their molecular weight and % sulfonic substitution was verified using the capillary viscometer and nuclear magnetic resonance spectroscopy techniques respectively. The co-polymer thermal degradation mechanism (i.e., polymer hydrolysis) in various monovalent brines (KCl, NaCl and NaBr) was quantified by novel titration for temperature range {121 °C, 177 °C}. The degradation response of the co-polymers was then correlated with their rheology and HPHT (high-pressure-high-temperature) filtrate performance; for instance, the titration studies showed that co-polymer degradation was 12–15% and 44–47% after sixteen hours aging at 121 °C and 177 °C respectively; correspondingly the co-polymer performance in ABDM, exhibited HPHT filtrate of 12–18 mL and 38–40 mL at those respective temperatures after sixteen hours of aging. The quantified understanding of the co-polymer thermal degradation was used to device a new approach for co-polymer replenishment strategy; it was illustrated that a 7% replenishment of the co-polymer for every eight hours, at 121 °C, enabled sustained HPHT filtrate of 12–18 mL for the studied evaluation period of thirty-two hours. The replenishment approach presented in the study would provide a valuable tool for drilling automation to ensure sustained fluid performance.

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, and K. 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.

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.

The revolutionized field of nanotechnology emerged in the oil and gas sector to enhance drilling fluid performance. This technology increases the success rate of drilling operations in different environments. However, their performance in presence of various salts has not been entirely discovered up till now. In this research, three different salt mud systems that include KCl, NaCl and MgCl2were prepared and coated with silica iron oxide nanoparticles. The rheological and filtration characteristics of all the samples with the joint interaction of salt and nanoparticles were analyzed. Additionally, the stability of the mud samples after the interaction between the two entities was investigated using a visualization tool. This unique application will be useful in observing the changes in the mud system during nonproductive time events (NPT). The result of the study reveals that all the fluids in the presence of these entities showed shear thinning behavior with flow index <1. Reduction in shear stresses in the salt systems was observed mainly because of the neutralization of the negative charges associated with the base mud system. However, this behavior was weaker in monovalent cations as compared with divalent. KCL/(Si/Fe3O4) demonstrates the most stable mud system when investigated through intensity profile plots. Minimum segregation and maximum dispersion were the key parameters that demonstrated its stability. Moreover, all three cations in the presence of Si/Fe3O4nanoparticles reduce the filtrate loss volume and provide a thin and smooth mud cake. The Si/Fe3O4because of its spherical bead shape plugs the pore spacing of the filter paper while blocking of microsize spacing was done with the help of cations.

Hydration and dispersion are the two most common problems encounter in shale formation. These problems eventually give rise to some serious wellbore instability issues, which are difficult to handle through conventional mud systems. The application of nanotechnology has now provided some inimitable solution to those integrity issues. In the current study, for the first time comparison between activated carbon and silica coated iron oxide nanoparticles in terms of filtration and shale stability is reported. Limited literature is available for both these entities; therefore focus was primarily on these particles. Both the particles were added in water-base mud system in two different concentrations of (0.25–0.50) wt% that are equivalent to 0.875–1.75 g respectively. Result reveals that the effect of high concentration of activated carbon was effective in terms of reducing the loss of filtrate volume from the mud system. Furthermore, thin and smooth filter cake was obtained for both samples of nanoparticles and high weight percent samples of activated carbon. Moreover, both the samples of activated carbon demonstrate better shale inhibition characteristics. After an immersion test, the recovered shale sample from activated carbon exhibits less erosion and cracks on its outer surface. On the contrary, a larger quantity of salt deposition on the shale surface was witnessed in the nanoparticle sample. In addition, shale samples behave more hydrophobic under the influence of activated carbon. This hydrophobicity increases as the concentration of activated carbon increases in the mud system. The results of filtration and immersion tests were also modeled using the image processing technique in order to validate all the findings of this study.

Application of titanium dioxide nanomaterial having different crystal forms has been extensively studied in various fields. However, as a drilling fluid additive it is still an unexplored area. Changing the composition of TiO2morphology, leads to substantial improvements in the environmental and energy sector. These enhancements are based on the chemical and physical interaction of the crystal structure. In the current work, the carbon supported anatase TiO2particles are used as a drilling fluid additive to improve the efficiency of water-based mud systems. For the first time, the effect of the crystal system is considered on the drilling fluid performance. Three carbon supported particles in the form of MWCNT/TiO2, GO/TiO2and activated carbon/TiO2are used in drilling fluid. Each particle was added in the mud system with concentration ranging from (0.35 g, 0.875 g, 1.75 g, 2.625 g, 3.5 g,) respectively. The rheology, filtration, stability, and shale inhibition characteristics of the samples was performed. Improvement in electrochemical characteristics of the mud system was recorded after the incorporation of carbonaceous TiO2particles. Moreover, the gelation and filtration characteristics of the muds were also enhanced after the synergy of carbonaceous material with TiO2.This interaction leads to better cutting suspension and provides smooth and compacted mud cake. In addition, all the mud samples interacted with Ranikot formation to observe its stability behavior. Substantial improvement in hydrophobic nature of the shale sample was recorded after interacting with the carbon supported TiO2nanoparticles. These carbon supported particles are extremely potential in plugging the nano-pores of Ranikot shale and are responsible for maintaining the shale integrity.

One of the leading problems in the oil and gas sector is the swelling of shale formation after the adsorption of water during drilling activity. This mechanism has some intense effects on wellbore integrity. Experimentally, the swelling characteristics of a shale formation can be best evaluated by the linear dynamic swell-meter (LDSM). In this study, modeling the diffusion of water in the shale formation is done using the three diffusion models proposed by Higuchi model, Peppas model, and Peppas and Sahlin model, and the best model is selected. During this article, swelling characteristics of Khadro formation obtained from the Lower Indus Basin of Pakistan were examined using three above-mentioned models. Experimentally, the swelling behavior of Khadro formation was investigated in salt polymer and silicate mud systems. For the first time, the effect of changing the mud type on the performances of the models is evaluated. The experimental swelling curves obtained from LDSM are divided into two separate segments that indicate transient and steady state zones, respectively. During the transient state, water molecules diffuse into the nano-platelets of shale formation. For this region, the Higuchi model is best in modeling the swelling results with near to 100% accuracy. However, the model performance substantially overestimates the swelling rate during the steady state condition. Moreover, maximum relative error of 120% and MAE > 50% in both muds is inadequacies associated with this model. On the contrary, the remaining two models exhibit a completely different behavior in the steady state region. Both the models estimate the swelling percentages with MAE values below 5%. Additionally, the performance of the models substantially improves as the quantity of the water in the formulation of the mud system reduces. The silicate mud system having low volume of water exhibits three times reduction in MAE values in Peppas model and Peppas and Sahlin model  respectively as compared with salt polymer mud system.

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 esculentusas 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.

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 carambolaL.) has the characteristic of being a substitute for PAC R when beneficiated for water-based drilling fluids.

For a successful drilling operation, rheological and filtration properties are the most essential parameters to monitor. Rheological properties in desire operating range help the drilling fluid system to suspend and carry the cutting up to the surface. On the other hand, prevention of the filtrate volume loss is crucial particularly in formations that are hydrophilic in nature and has tendency to swell. The main purpose of this study is to investigate experimentally, the combine influence of graphene oxide (GO), pure-bore (PB) and sodium alginate on rheological and filtration properties of water-based drilling fluid (WBDF). A total of eight samples were prepared excluding the based mud system. Particles of GO and PB were divided into two concentrations of 0.35 g and 1.75 g, while for sodium alginate 0.25 g and 2.25 g concentration was used. Laboratory measurements on viscometer for rheological properties, and API filter press for filtration loss were conducted. The results obtained reveal that all the samples demonstrated shear thinning behavior. This behavior was also validated by the dynamic viscosity results, where decrease in viscosity was observed with increase in shear rate. Out of all the samples, Sample 5 shows maximum dynamic viscosity as this sample comprises of maximum concentration of the particles. Rheological properties particularly yield point and apparent viscosity for Samples 1 and 5 were not in the desired operating range. Both of these samples comprise of maximum weight percent of pure-bore and sodium alginate. In addition, Samples 2, 4 and 6 demonstrate a weaker mud system with normalized cutting carrying index values below 1. Sample 6 comprises of smaller concentrations of all the three particles while Samples 2 and 4 consist of maximum concentration of graphene oxide, which results in agglomeration of this particle and decreases the efficacy of these mud systems. The result indicates that for a successful drilling fluid system, the concentration of these particles should be the prime concern. Failure to do so will result in degradation in the performance of the fluid system.

Maintaining the rheology and filtration properties of a drilling fluid plays a vital role during a drilling operation. With the current challenges of high pressure and high temperature environments, there is an urgent need to design thermally stable water-based mud systems (WBM) which are environmentally clean and economically cheap.

This study aims to understand the interactions among SiO2nanoparticles (NPs) and the main chemical constituents of bentonite-free water-based mud, including CaCO3and xanthan gum. To this end, both theoretical and experimental protocols are developed coupling molecular dynamics simulations with filtration and rheological property measurements of mud systems having different NP contents. The resultant filter cakes are inspected to capture the role of interactions among the deposited components. Static filtration tests at high pressure–temperature are carried out on a standard filter paper as well as an in-house prepared sandstone disk. The filtrate volume and filter cake thickness and permeability were reduced by 56, 36, and 72%, respectively, at an optimum NP content of 0.1 wt %. Using the sandstone disk, the mud with the optimum NP content showed a 72 and 59% reduction in spurt loss and total filtrate volume, respectively. Scanning electron microscopy images showed that the NPs improved the morphology of the filter cake. The higher NP–sandstone interaction was successfully described by molecular dynamics simulations, which showed the highest interaction between sandstone and NPs followed by CaCO3and then the system xanthan gum and water polymer solution. Moreover, the theoretical analysis showed that SiO2NPs reduced the repulsion energy among the CaCO3surfaces, promoting a tighter filter cake and subsequently less mud filtrate, as evident experimentally.

The mud-to-cement conversion or 'slag-mix' technology displays several advantages when compared to conventional well cementing operations. This alternative method means to combine drilling fluids, accelerators, and finely granulated slag as the hydraulic material. Steam injection is commonly used to improve crude oil production in the Lagunillas field (state of Zulia, NW Venezuela). This work compares the use of two slag-mix systems containing two polymer-based drilling muds during cementing of injection wells: an aqueous drilling fluid and an oil-in-water emulsion mud. After comparing the use of the two study drilling mud systems with a typical lignosulfonate slag-mix system, it can be stated that both systems may be suitable to be used in the application of the mentioned-above technology in steam stimulated wells. The aqueous formulations under study and a typical slag-mud slurry containing lignosulfonate show relatively similar values for most physic-mechanical properties. In contrast, the slag-mix emulsion system under consideration shows distinctive rheological and filtration behaviours compared to the other study polymer-based slag-mud slurry, but similar mechanical properties. [Received: April 26, 2019; Accepted: August 1, 2019]

The sediment composition of the seabed governs its mobility, hence determining sediment transport and morphological evolution of estuaries and tidal basins. Bed sediments often consist of mixtures of sand and mud, with spatial gradients in the sand/mud content. This study aims at increasing the understanding of processes driving the sediment composition in tidal basins, focusing on depositional processes. We show that bed sediments in the Wadden Sea tend to be either mud‐dominated or sand‐dominated, resulting in a bimodal distribution of the mud content where the two modes represent equilibrium conditions. The equilibria depend primarily on the sediment deposition fluxes, with bimodality originating from the dependence of suspended sand/mud concentrations on the local bed composition. Our analysis shows that bimodality is a phenomenon that is not only specific for the Wadden Sea; it can be expected for a wide range of suspended sediment concentrations and thus also in other systems worldwide. The bottom of coastal seas is often composed of two sediment types, namely sand and mud. The evolution of the seabed, and thus of our coasts, depends on how these sediment types move. A correct representation of the spatial sand‐mud patterns in the bed is therefore essential if we want to understand and predict coastal evolution. Studying a large data set we found that sediment beds tend to be either sandy or muddy, with lower chances of finding something in between (i.e., bimodality). Although segregation of sand and mud has often been attributed to erosion processes, we found that this is mainly the result of depositional processes, and especially of the suspended sediment concentrations. Sand concentrations largely depend on local conditions, while local mud concentrations are much more affected by conditions elsewhere and/or earlier. The difference in the suspended sand and mud concentrations leads to multiple equilibria in the bed composition—resulting in the previously mentioned bimodality—for a very wide range of conditions. Therefore, we also expect bimodality and sharp sand‐mud transitions in other systems worldwide. Mud contents in the sediment bed can be bimodally distributed, resembling preferential sand‐mud segregationBimodality represents the existence of two stable equilibrium conditions, which are a result of the deposition fluxes of sand and mudBimodality is expected for a large range of suspended sediment concentrations in sand‐mud systems Mud contents in the sediment bed can be bimodally distributed, resembling preferential sand‐mud segregation Bimodality represents the existence of two stable equilibrium conditions, which are a result of the deposition fluxes of sand and mud Bimodality is expected for a large range of suspended sediment concentrations in sand‐mud systems

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.

The calculation of torque and drag in horizontal wells and extended reach wells is an important element in drilling operations, but determining the value of the friction factor is difficult in the calculation of friction. Sichuan Basin constitutes a special gas reservoir system with high pressure and tight formations. They are favorable for gas production which can be accomplished economically only with horizontal drilling and hydraulic fracturing, and Xujiahe Formation is the focus of the exploration and development. In order to determine the reasonable friction factor for directional well and horizontal well in Xujiahe Formation and complete comprehensive evaluation method, both theoretical study on friction mechanism and experimental investigation on friction factor need to be carried out. A series of experiments are conducted for different lithology (sandstone, sand-mudstone, and mudstone), steel, and lubricants (mud systems). The test results are as follows: lubricants have the most obvious influence on the friction coefficient; the friction-reducing effect of the same lubricant on different friction pairs varies; and lubricants have very different effects on the same friction pair. Under the condition of lubrication with clear water, the friction coefficient of rock increases slightly as the normal load rises. Under lubrication with mud, the change range of the friction coefficient of rock with the increase of normal load is low. Rotation speed has limited impact on the friction coefficient. Under the same test condition, the friction coefficient of sandstone is a little higher in the three kinds of rocks. Through a large number of experimental studies, the value range of the friction coefficient of different kinds of rock in the fifth member in Xujiahe Formation is obtained, providing a scientific basis for the drilling design and the calculation of torque and drag in high pressure and tight formations in Sichuan.

An investigation of the behavior of clay systems in drilling fluids was begun in 1958 to determine the cause of gelation in lime-treated muds with increased temperatures incurred during drilling operations. Mud systems were evaluated by physical property measurements, cation exchange data, X-ray diffraction analysis, and electron microscopy before and after hydrothermal treatment. Selected samples were rerun after two years' storage at laboratory temperatures. High-temperature gelation of lime-caustic muds is caused by the synthesis of calcium silicate hydrates, hereafter referred to as CSH, in general and tobermorite (XCaO, SiO2, H2O) specifically. These materials are considered the principal cementing agents of Portland cement. Spheroidal poorly crystallized tobermorite was produced from interlayered illite-montmorillonite muds. Laths and needles of crystalline tobermorite (11.3–11.6 Å type) were synthesized from the pure montmorillonite systems. Zeolite minerals were synthesized concurrently and were the dominant alteration product when Ca(OH)2was not added to the system. Synthesized aged (2 years) mud systems were studied after 8 weeks of dialysis with distilled water. Corundum was observed in samples where tobermorite formed, and was the dominant insoluble residue after HCl treatment. Much sharper diffraction maxima were obtained of the CSH compounds after dialysis or glycerine washing. “Al-chlorite,” “Al-vermiculite,” and “Al-micas” were synthesized when treatments included aluminum ions. The products formed were of varying stabilities after washing with distilled water and HCl. Glycerol expanded the montmorillonite which had not reacted, but no expansion from the 10 Å or 14 Å d(001) spacing of the new product occurrred.

Heavy-weight materials such as barite (BaSO4) is used in mud formulations to increase density. In deeper formations where a higher hydrostatic pressure of the mud column is required to overcome the pore pressure, the use of heavy-weight mud systems is indispensable. Unfortunately, these heavy-weight particles tend to settle under both static and dynamic conditions, resulting in density variations, a phenomenon known as sagging or barite sagging due to the dependence on barite as a heavy-weight agent.

Reports on the use of diluted bentonite water-based mud systems to drill nonreservoir sections of the Dukhan oil field in Qatar. Improvements in penetration rates and costs; Effects of filtration on drilling permeable rocks; Modifications of mud systems; Effects of bentonite drilling mud on fluid loss and investion in formation rocks.

The accurate prediction of transient surge-swab pressure, during the tripping operation under a narrow pressure window, is an important premise to ensure the safety of tripping operation and drilling. Different rheological modes of drilling fluid will have a great influence on the surge-swab pressure in wellbore, while the Herschel–Bulkley mode can simulate the rheological characteristics of actual drilling fluid in a better way. Therefore, the influence of drilling fluid flow friction under different rheological modes was mainly considered according to the transient flow model. Meanwhile, the influence of pumpage on transient surge-swab pressure during tripping operation was also considered with Herschel–Bulkley fluid-based tripping operation bottomhole transient surge-swab pressure calculation model established and model verification carried out. The following research results were obtained. First, compared with the Herschel–Bulkley mode, the power-law mode and Bingham mode will overestimate the flow friction of drilling fluid. Second, the surge-swab pressure peak values of different mud systems are water-based mud > polymer mud > oil-based mud. Third, the peak value of bottomhole transient surge-swab pressure increases with the increase of drilling fluid yield value, consistency coefficient, and flow behavior index, and the influence law is similar. Fourth, the tripping velocity and pumpage will directly affect the peak value and variation rule of bottomhole transient surge-swab pressure. Herschel–Bulkley fluid-based tripping operation bottomhole transient surge-swab pressure study helps control the surge-swab pressure during tripping operations and it is of great significance for lean, safe, and efficient drilling in narrow pressure window formations.

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.

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.

Abstract: An investigation is conducted to understand hydraulic transport characteristics of a solid-liquid mixture flowing vertically upward. Namely, this is the instance that solid particles are carried by non-Newtonian fluids in a slim hole concentric annulus with rotating inner cylinder. In this study a clear acrylic pipe was used in order to observe the movement of solid particles. The bulk axial velocities varied from 0.4 m/s to 1.2 m/s. The mud systems which were utilized included aqueous solution of sodium carboxymethyl cellulose (0.2∼0.4%CMC) and 5% bentonite solutions. Solid volumetric concentration and pressure drops were measured for the various parameters such as inclined annulus, flow rate, and rotational speed of inner cylinder. For both CMC and bentonite solutions, the higher the concentration of the solid particles are, the larger the pressure drops become.

Drilling mud systems are used by the petroleum industry to facilitate and expedite the drilling of oil and natural gas wells. In western Canada, spent water‐based muds (WBM) are often applied to cropland and native prairie at low application rates as a disposal option. We speculate that application of drilling waste on native prairie in semiarid climates will alter the soil surface energy balance and adversely affect soil biophysical processes and subsequently ecosystem productivity. This study was initiated to examine the effect of application rate (0, 40, and 80 m3ha−1) of summer‐applied WBM on surface albedo (α), soil temperature, and soil heat flux at the 0.05‐m depth (G0.05) and at the surface (G) over 42 d following application. Our results provide evidence of a significant alteration of these micrometeorological parameters with WBM application. Surface albedo decreased by 15% (relative to the control) with the application of 40 m3ha−1mud and by an additional 3% when this mud rate was doubled. The lower α meant that a greater proportion of incoming shortwave solar radiation (Rsi) was available for partitioning into components of the surface energy balance, including GThis coincides with observed increases in G0.05, G, and soil temperature at the 0.025‐m depth, with higher WBM. By modifying heat flow and temperature in the root zone, WBM application may alter critical ecosystem biophysical and physiological processes, with important implications for overall biological productivity. The direction and magnitude of such changes, in conjunction with all the other ecological effects of WBM, will ultimately define the sustainability of the practice in this fragile ecosystem.

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 .

Focuses on low-head drilling which avoids differential sticking and reduces formation damage. Drilling fluid pressure just above the reservoir pressure; Mud systems; Drilling costs.

Discusses the use of ester-based mud systems in drilling difficult shales and high-angle well sections. Statoil's use of ester-based muds; Legislation regarding use of oil-based mud in the North Sea; Less expense of ester-based muds; Requirement for employers to provide a safe and healthy working environment; Marine toxicity of drilling muds; Statoil's plans to continue using pseudo oil-based muds; More.

Drilling high-pressure/high-temperature (HP/HT) exploration wells remains a challenge, despite years of experience acquired by the drilling/completion industry. Development wells have further expanded the envelope of performance of the technologies and procedures required to deliver production from HP/HT fields safely and economically. Now comes the time of drilling and completing infill wells, which paradoxically appear to be more difficult as depletion increases and the mud-weight window (MWW) diminishes. To overcome this problem, intense engineering work has been carried out to better understand the effect of the depletion on compaction and fracturing gradient, to design and qualify new drilling-mud systems combined with stress-caging techniques, and to prepare contingent solutions with the deployment of expandable- and drilling-liner technologies. Three infill wells have been drilled, completed, and put on production by Total in the Elgin/Franklin fields on the UK Continental Shelf. This success was achieved through severely depleted reservoirs--with depletion greater than 800 bar--and has enabled phased HP/HT developments and deep exploration beneath depleted horizons. [ABSTRACT FROM AUTHOR]

The article explores the process and challenges on the use of managed pressure drilling (MPD) in the Bullmoose field, British Columbia. Compared to low-fluid loss mud systems, MPD is said to increase the rate of penetration and offer cost and time savings. The common fluid systems used to drill the Jurassic formation known as Nikanassin include gel chemical mud, invert oil-based mud and air. Shell Canada conducted operations planning, risk assessment and operations review when it used MPD.

Enhanced genetic algorithms (GA) applied in space-time block coded (STBC) multiuser detection (MUD) systems in Rayleigh flat-fading channels are reported in this paper. Firstly, an improved objective function, which is designed to help speed up the search for the optimal solution, is introduced. Secondly, a decorrelating detector (DD) and a minimum mean square error (MMSE) detector have been added to the GA STBC MUD receiver to create the seed chromosome in the initial population. This operation has improved the receiver performance further because some signal information has been intentionally embedded in the initial population. Simulation results show that the receiver employing the improved objective function and the DD or MMSE detector can converge faster with the same bit error rate (BER) performance than the receiver with the initial population chosen randomly. The total signal-to-noise ratio (SNR) improvement contributed by these two modifications can reach 4 dB. Hence the proposed GA receiver is a promising solution of the STBC MUD problem.

Reports on Caterpillar Inc.'s joint venture with National Oilwell of Houston, Texas and Uralmashzavod of Russia to develop drilling rigs for the petroleum industry in the Commonwealth of Independent States (CIS). UNOC Equipment and Supply as name of venture; Use of local Russian content and major components from Western suppliers for power units, mud systems and rig controls.