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After several years of gas production, a black solid hydrocarbon material began to be produced along with the gas stream from the Risha gas field, in the northeastern part of Jordan. The main reason for the formation of this material is still unknown until this time, so knowing the source of this material is this study's main goal. Organic geochemical studies for black solid material and effective source rocks (Lower Silurian shales) are used to determine the physical and organic components of the produced black solid material (heavy oil) and attempt to identify its source. The black solid material demonstrates high organic carbon (TOC = 12% by leco instrument) and a high calorific value, like those of oils, asphalts, and shale oils with moderate sulfur content. The gross composition of the black solid material sample is dominated by saturates and asphaltene but contains very low aromatic hydrocarbons reflecting the naphthenic oil type. Meanwhile, the Silurian extracts range between paraffinic and paraffinic-naphthenic organic matters. The biomarker indicators related depositional environment and carbon isotopic composition for the black solid material sample and Silurian extracts, show that they were relatively deposited in a reducing marine environment. The black material reveals lower maturity level than the Silurian extracts. Oil/source rock correlation study for the studied samples suggests strong affinity between the black material and Lower Silurian source rock in their source characteristics, suggesting that the black hydrocarbon material was expelled from the Silurian source rocks at low maturity stage as normal oil. This normal oil is subjected to secondary alteration process (evaporative fractionation) and was stored in the reservoir. It contaminated with some inorganic material that was introduced into the well as a component of a drilling mud additive or drill string lubricant or, potentially, in part, a corrosion product of wellbore tubulars, since significant iron was present in the sample. [ABSTRACT FROM AUTHOR]

DDWC (Directional Drilling with Casing) is an effective wellbore construction technique, particularly suitable for soft marine formations. In DDWC, the casing replaces the drill pipe for sliding drilling operations, and the passability of the drill string through the casing has become one of the primary challenges in applying DDWC. This study uses ANSYS Workbench to simulate the strain and bending behavior of the casing under various geological conditions. Simulations were conducted for different wellbore trajectories, casing specifications, and materials to evaluate the feasibility of the drill string passing through the casing under different conditions. The results show that, when the dogleg severity reaches 18°/30 m and the casing's inner diameter is 315 mm, the maximum radial strain of the casing is 4.2 mm, which cannot guarantee the successful passage of a drill string assembly with a 311 mm outer diameter. For other casing specifications, with a minimum inner diameter of 317 mm, the drill string can pass through under the maximum dogleg severity. Additionally, since the elastic modulus and Poisson's ratio of the casing materials are identical, the strain behavior is consistent across different materials, meaning that the material does not affect the passability of the casing. Moreover, the study optimized the selection of casing specifications and materials. From the perspective of ensuring drill string passability and resource conservation, a casing with an inner diameter of 319.4 mm was chosen. To ensure the longevity of the casing and the stability of the wellbore, N80 steel was selected as the material. A sensitivity analysis was conducted on the factors affecting casing strain, and the results aligned with the simulation findings, showing that wellbore trajectory and casing specifications have a significant impact on casing strain. Verifying the passability of the drill string through the casing is critical for the development and application of DDWC technology. [ABSTRACT FROM AUTHOR]

During the operation of the drill string, it displays a degree of flexibility. Simultaneously, its dynamic properties, influenced by complex stress conditions, manifest nonlinearity and uncertainty. A comprehensive investigation into the dynamics of flexible drill strings is imperative for deep well drilling. This paper presents a model that simulates random interactions between a flexible drill string and the borehole wall, simplifying the actual drill string model using analogous principles. Dynamic simulation software is utilized for analysis, and an indoor experimental setup has been established. The results reveal that with a constant weight on bit (WOB), higher drill string rotational speeds correlate with increased susceptibility to buckling deformation. Additionally, the critical time for deformation onset exhibits a nearly linear relationship with rotational speed. Maintaining a constant rotational speed, an increase in WOB enhances the likelihood of buckling deformation. The experimental findings suggest a correlation between the drill string's rotation frequency and the WOB. [ABSTRACT FROM AUTHOR]

This study presents the findings of a comprehensive geotechnical and seismic site investigation conducted at Otuasega Town located in Bayelsa State within the Niger Delta region of Nigeria. Subsurface exploration involved advancing 10 boreholes to 30 m depth using hollow stem auger drilling. Continuous disturbed and undisturbed soil sampling was performed at 1.5 m intervals for detailed geotechnical testing. Laboratory tests on the recovered soil samples established the index properties, classification, densities and consistency limits of the stratified deposits. The subsurface profile comprised alternating layers of clay, silt and sand typical of deltaic sediments, with the clay fractions exhibiting medium to high plasticity. Shear wave velocity (Vs) profiling using Multichannel Analysis of Surface Waves (WASW) techniques categorised the site predominantly as Site Class C and D based on international standards. The Standard Penetration Test (SPT) N-values ranged from 5 to 10, indicating soft normally consolidated clay conditions typical of the Niger Delta region. Predictive empirical models developed from the field and lab data showed strong correlations for estimating key geotechnical parameters such as SPT blow count, Vs and liquefaction resistance. Ground response analyses using the Vs and SPT data indicated significant site amplification potential, with peak ground accelerations up to 1.5 times the bedrock motion. Liquefaction analysis based on the empirical SPT-based methods revealed a high potential for liquefaction in the sandy layers, especially under strong earthquake shaking. The study characterized the complex sedimentology and provided baseline information for seismic microzonation and site-specific ground response analyses to advance understanding of geohazards in this delta environment. [ABSTRACT FROM AUTHOR]

The safety and efficiency of drilling engineering are greatly impeded by destructive vibrations of drill string in air drilling, such as stick-slip, bit-bounce and their coupled vibrations. To avoid or suppress these vibrations improving the stability of drilling operations, revealing the occurrence mechanisms of abovementioned harmful vibrations are indispensable by investigating dynamics characteristics of drill string system. In this paper, an axial-torsional coupled dynamics model that can capture the motion behaviors of bottom hole assembly (BHA) is established adopting the lumped parameter method. Subsequently, a rate of penetration (ROP) model appropriating for air drilling is obtained firstly by linear fitting means. Meanwhile, a novel discontinuous support model is established to describe the bit-formation interactions. Then, BHA dynamics are discussed using numerical simulations under different vibration scenarios: normal operation; stick-slip; bit-bounce; bit-bounce and stick-slip combination. Subsequently, in two drilling modes: the continuous and intermittent drilling, the vibration mitigation strategies and dynamics sensibility study of BHA are carried out based on the parametric analysis. The results show that increasing torsional stiffness of drill-pipes, appropriately adjusting rotation speed of top driven system and dynamic weight on bit (WOB) are deemed as an effective strategy suppressing or eliminating stick-slip and bit-bounce vibrations of BHA. Suggest that the rotation speed of top driven system and dynamic WOB are 5 rad/s and 3.5 kN, respectively. Finally, the constructed probability maps allow to driller to choose reasonable mechanical parameters, thereby realizing smooth drilling operation in the air drilling. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of rapidly and accurately predicting the production of test wells in offshore tight oil reservoirs, specifically within the L Formation of the Beibu Basin. This challenge is particularly pronounced in situations where drill stem tests are limited and evaluating each untested well layer is difficult. To achieve this objective, we analyzed fifteen typical test wells in the L Formation, taking into account both geological and engineering factors. Initially, Pearson correlation analysis, partial correlation analysis, and grey relational analysis were used to identify the main production factors. Based on these analyses, two types of production prediction models were developed: one employing the comprehensive production index method and the other utilizing the production coefficient method. The research identified effective permeability, porosity, oil saturation, and shale content as the main production factors for the test wells in the study area. The model verification results showed that the comprehensive production index model performs effectively for the L Formation, with an average prediction error of 20.40% compared to the actual production values. This research is significant for optimizing and stabilizing production in tight oil reservoirs. [ABSTRACT FROM AUTHOR]

AbstractActive cooling is a technique for expanding the upper temperature limit of drilling measurement instruments. An innovative active cooling system, where a cooling device and a circuit compartment that requires cooling are located at the drill string central water eye, is proposed in this paper. The structure of three types thermal conductors that quickly transfers the heat of the chip to the refrigerator, is designed. The thermal conductivity of different structures is studied using numerical simulation methods. The research results indicate that the point-point cooling scheme that uses four small heat transfer arms to transfer heat separately is more optimal. The overall temperature inside the cabin increases, except for the chip. The environmental heat leakage is reduced by 1.2W, the cold end temperature is reduced by 23.4K, compared to the other two solutions. When the total thickness of the four heat transfer arms remains unchanged, increasing the thickness of the long heat transfer arm and decreasing the thickness of the short heat transfer arm slightly reduces the heat load of the refrigeration machine, but the temperature on the cold end of the refrigeration machine increases by 5K, and the temperature difference on the four chips narrows by 8.5K. Therefore, the use of a four claw heat transfer structure with variable thickness is the optimal choice. [ABSTRACT FROM AUTHOR]

A finite element model for analysing the sealing performance of three types of wellhead rotary blowout preventer rubber ring structures in use on site was established. By using this model, the stress, deformation and contact pressure distribution of the passive rubber ring during pre-tightening conditions were calculated when the inner annulus of the passive rubber ring passed through the 5-inch drill pipe body and the 7-inch joint. The distribution position, length, and magnitude of contact pressure on the contact surface between the three types of rubber rings and the outer wall of the drill string under different pressure penetration loads under rated working conditions were calculated. Overall, the sealing performance of the active rubber ring is the best while the sealing performance of the passive rubber ring is the worst. However, the passive rubber ring has a simple structure and does not require a hydraulic system, which makes it impossible to adjust the sealing strength of the rubber ring in real time based on the actual fluid pressure on site. On the other hand, the I-type rubber ring uses part of the rotating blowout preventer structure as the hydraulic chamber wall, which can thicken the rubber layer in contact with drill pipe. Therefore, passive rubber rings are more suitable for low fluid pressure drilling operations. When the fluid pressure at the lower part of the rubber ring exceeds the rated maximum fluid pressure, it will lead to a sharp decrease in the sealing performance of the rubber ring. Therefore, stricter control of the use of the rubber ring is needed during on-site use, especially in drilling conditions with wellhead fluid pressure. The research methods and achievements in the article provide theoretical guidance for the safety evaluation of rotary blowout preventers used in ultra deep wells unbalanced drilling. [ABSTRACT FROM AUTHOR]

The reservoir in the Shunbei field is characterized by ultra-deep, ultra-high temperature, and ultra-high pressure. During the drilling process, the circulating temperature at the bottom of the well is higher than the temperature resistance of downhole instruments, which leads to frequent problems of device burnout and no signal. Therefore, it is of great significance to accurately predict the wellbore temperature field of ultra-deep directional wells. In this paper, the influence of the drilling string assembly, the flow channel structure and the flow pattern on the convective heat exchange coefficient is considered. Based on the energy conservation equation, a numerical model of wellbore-formation transient heat transfer is developed. Then, the model was verified by the real data of two ultra-deep wells in Shunbei block, China, and the results showed that the prediction errors of bottom-hole temperature were all within 2%. Finally, the key factors and rules of the wellbore annulus temperature are analyzed. The results show that the bottom-hole temperature decreases with the decrease of inlet temperature, the thermal conductivity of drilling fluid, and the thermal conductivity of drill pipe, and increases with the decrease of flow rate, the density of drilling fluid, viscosity of drilling fluid, and specific heat capacity of drilling fluid. The inlet temperature has the greatest influence on the outlet temperature, and the specific heat of the pipe string has a minor influence on the wellbore annulus temperature. The research results of this paper provide an accurate wellbore temperature field prediction method for ultra-deep directional wells in the Shunbei block, China, which is of great significance for temperature-controlled drilling. [ABSTRACT FROM AUTHOR]

Deep and ultra-deep reservoirs are characterized by low porosity and permeability, pronounced heterogeneity, and complex pore structures, complicating permeability evaluations. Permeability, directly influencing the fluid production capacity of reservoirs, is a key parameter in comprehensive reservoir assessments. In the X Depression, low-porosity and low-permeability formations present highly discrete and variable core data points for porosity and permeability, rendering single-variable regression models ineffective. Consequently, accurately representing permeability in heterogeneous reservoirs proves challenging. In the following study, lithological and physical property data are integrated with mercury injection data to analyze pore structure types. The formation flow zone index (FZI) is utilized to differentiate reservoir types, and permeability is calculated based on core porosity–permeability relationships from logging data for each flow unit. Subsequently, the average permeability for each flow unit is computed according to reservoir classification, followed by a weighted average according to effective thickness. This approach transforms logging permeability into drill stem test permeability. Unlike traditional point-by-point averaging methods, this approach incorporates reservoir thickness and heterogeneity, making it more suitable for complex reservoir environments and resulting in more reasonable conversion outcomes. [ABSTRACT FROM AUTHOR]

Stick–slip vibration (SV) of drill string systems is the main cause of fatigue failure of PDC bits under complex drilling conditions. Exploring its mechanism is helpful for identifying the causes of bit failure and developing preventive measures to prolong bit service life. In this study, the influence of various factors on torque characteristics is tested by drilling rock breaking with various PDC bits and the variations in torsion variables and torsion speed of drill string systems under different torque loading conditions of drill bits are ascertained. Through a finite element simulation of the drill string–bit system, the influence of the PDC bit on the torsional deformation with variable torque is determined, and the influence mechanisms of bit size, tooth structure, invasion depth, rock strength, and other factors on the SV induced by a PDC bit are established. The results show that the change in the reaction resistance moment of the formation rock leads to variation in the driving speed of the drill string system, which is one of the main reasons for the SV. Even if the torque change in the bit is minor, SV will occur if the drill string is too long. [ABSTRACT FROM AUTHOR]

Modulated pressure waves propagating in the drilling fluids inside the drill string are a reliable real-time communication technology that transmit data from downhole to the surface during oil and gas drilling. In the analysis of pressure waves' propagation characteristics, the modeling of transient friction in non-Newtonian fluids remains a great challenge. This paper establishes a numerical model for transient pipe flow of power-law non-Newtonian fluids by using the weighted residual collocation method. Then, the Newton–Raphson method is applied to solve the nonlinear equations. The numerical method is validated by using the theoretical solution of Newtonian fluids and is proven to converge reliably with larger time steps. Finally, the influencing factors of the wall shear stress are analyzed using this numerical method. For shear-thinning fluids, the friction loss of periodic flow decreases with the increase in flow rate, which is opposite to the variation law of friction with the flow rate for stable pipe flow. Keeping the amplitude of pressure pulsation unchanged, an increase in frequency leads to a decrease in velocity fluctuations; therefore, the friction loss decreases with the increase in frequency. [ABSTRACT FROM AUTHOR]

In the environment of oil and gas wells, the shielding effect of metal casing increases the difficulty of applying wireless electromagnetic wave transmission technology in such wells. This paper constructs a theoretical model of downhole electromagnetic helical loop transmission based on the finite element method. The magnetic loop is equated with the helical loop antenna in the model. By means of simulation calculations, this study deeply investigates the impact of various factors, such as working frequency within the cased well, drilling fluid resistivity, formation resistivity, drill string dimensions, and electrical conductivity, on the attenuation pattern of the helical loop antenna. The results show that low-frequency signals experience relatively less attenuation underground, while high-frequency signals demonstrate better transmission effects over shorter distances. Moreover, drilling fluids with low resistivity are more suitable for short-distance transmission, whereas high resistivity can effectively reduce signal attenuation and improve transmission distance. The variation in formation resistivity has a relatively small impact on signal transmission and can be considered negligible. In terms of drill string characteristics, as the electrical conductivity of the drill collars increases, signal attenuation gradually decreases, and the amplitude of the received signal is enhanced. With the inner and outer diameters of the drill collars remaining the same, a finer inner diameter of the casing aids electromagnetic wave short-distance transmission, whereas a thicker casing can reduce electromagnetic wave attenuation. Theoretical and practical results are in good agreement through field trial comparative analysis. [ABSTRACT FROM AUTHOR]

Silicate drilling fluids have strong inhibitive capacity and good environment protection property, but their poor lubricity limits their application. In screening good lubricating agents for silicate drilling fluids, extreme pressure (EP) lubrication tester is used to measure the coefficient of friction of silicate drilling fluid samples containing amphiphilic carbon dots and polyoxyethylene surfactant. The best lubricating agent selected is then tested with total organic carbon analyzer, dynamic light scattering tester and contact angle tester to analyze its mechanisms of lubrication. The test results show that the amphiphilic cardon dots have excellent lubricity and high temperature stability. A 5% sodium silicate (Na2SiO3 ) water solution treated has EP coefficient of friction of around 0.500. The solution is then treated with 0.3% amphiphilic carbon dots (C12-CDs), and the EP coefficient of friction is reduced to 0.065. After hot rolling the C12-CDs treated Na2SiO3 solution at 110 ℃ for 16 h, the EP coefficient of friction of the solution is further reduced to 0.063, that is, the EP coefficient of friction of the Na2SiO3 solution is reduced by 87.52%. On the other hand, the polyoxyethylene surfactant shows no effect on the lubricity of the Na2SiO3 solution. Further study shows that C12-CDs has excellent adsorption performance on the surface of the quartz sands, the surface tension of a C12-CDs solution (c = 100 mg/L) increases from 44.81 mN/m before the adsorption process to 64.03 mN/m after the adsorption process, the adsorption capacity is 89.23 mg/L. Particle size analysis shows that the C12-CDs can effectively reduce the particle sizes of the Na2SiO3 solution; the average particle size of the Na2SiO3 solution is reduced from 514 nm to 63.2 nm. The multi-hydroxy structure and the long hydrophobic chain on the surface of the carbon nuclei can improve the adsorption of the amphiphilic carbon dots on the surfaces of the drill string, the borehole walls and the silicate aggregates. The amphiphilic carbon dots as a good lubricating agent have good compatibility with silicate drilling fluids. Field application shows that C12-CDs can reduce the coefficient of friction of silicate drilling fluids by 86.34%, and are thus a good lubricating agent for silicate drilling fluids. [ABSTRACT FROM AUTHOR]

In 2019, the authors analyzed supply chains and noted the complete dependence of Russian manufacturers of bottom-hole assemblies of drilling strings on the supply* of nonmagnetic types of steel from other countries. Industry's technical requirements for nonmagnetic types of steel were developed and approved, considering the operating conditions of drilling equipment. An audit of foundries in the Russian Federation was conducted. In 2020, by order of Proizvodstvennaya Kommercheskaya Firma (PKF) Gazneftemash, a pilot batch of rods made of austenitic nonmagnetic steel was produced at Ruspolimet facilities. Laboratory tests confirmed compliance to industry technical requirements, namely a yield strength of 1093 MPa, tensile strength of 1155 MPa, and impact work of 242 J. The authors analyzed the leading global practices in conducting field tests of products made of nonmagnetic types of steel, based on which a field industrial testing methodology was developed and approved. This article presents the results of the trial operation of products and proves the serial use of equipment made from nonmagnetic rods with a diameter of up to 95 mm. A defect analysis performed during trial field operations is presented, and opportunities for adapting the technological process for manufacturing rods of a diameter greater than 95 mm are identified. [ABSTRACT FROM AUTHOR]

The application of hydraulic oscillator can solve the problems of large friction and serious pressure support in the drilling process of extended reach well and long horizontal well, but the conventional hydraulic oscillator parameter setting is not reasonable, high pressure consumption, easy to make the ground machine pump overload operation and failure. Therefore, based on the LuGre dynamic friction model theory, a calculation model for the friction between drill string and rock wall under the condition of longitudinal oscillation is established, and the influence law of hydraulic oscillator oscillation parameters on drag reduction efficiency is studied. The results show that the change of oscillation intensity, oscillation frequency and oscillation amplitude can improve the drag reduction efficiency, and the increase trend of drag reduction efficiency is first increased and then decreased. The selection of each parameter has the optimal value. According to the analysis of orthogonal test results, it is found that the reduction degree of friction between drill string and borehole wall rock by each parameter is in the order of oscillation intensity, oscillation frequency and oscillation amplitude from the largest to the smallest. [ABSTRACT FROM AUTHOR]

Buckling may cause drill string damage or even drilling failure. For the 3 000-m-long horizontal section drill string, a simplified analysis model of drill string in horizontal well is established, and the dynamic response results of axial displacement, angular displacement and contact force are obtained. When buckling, the closer the position of drill string is to the bottom, the later the buckling time, the smaller the buckling deformation degree, the slower the growth rate of axial displacement, and the smaller the attenuation degree of angular displacement and contact force amplitude. After buckling, drill string undergoes tensile deformation and eventually remains stable in the tensile state. After stabilization, from the top of drill string to the bottom of drill string, axial displacement increment increases first, then remains unchanged and then decreases, and the relative torsion angle between different positions gradually decreases. The drill string is always in horizontal contact with the wellbore, resulting in the same contact force values at different locations. The change of well inclination angle does not affect the change law of displacement and contact force. The absolute value of angular displacement is negatively correlated with the change of well inclination angle, and the value of axial displacement increment and contact force is positively correlated with the change of well deviation angle, but the value of contact force is quite close. The research results can provide reference for alleviating the buckling of drill string in horizontal wells. [ABSTRACT FROM AUTHOR]

Eliminating the excessive stick–slip torsional vibrations of drill strings by utilizing an effective controller can significantly increase penetration rates and reduce drilling operation costs. The present study aims to develop a fast and intelligent cascade control structure for a multi-degree-of-freedom drill string system under torsional vibrations. The proposed control configuration consists of two control loops in a cascade arrangement. The first controller estimates the top drive velocity reference from the actual drill bit velocity and its reference. The role of the second controller is to regulate the top drive velocity to its reference by generating the necessary torque for the drilling operation process to progress. Each control loop is designed based on a hybrid adaptive neuro-fuzzy PID and feedforward term. The latter assures fast regulation when there are sudden changes in operation. To evaluate the performance of the suggested cascade feedforward neuro-fuzzy PID (CFF-NFPID) control structure, extensive simulations were conducted using Matlab/Simulink. The simulation results clearly showed that the proposed CFF-NFPID controller provided high-performance control with variations in the weight on the bit and the desired drill bit rotary speed in comparison with that of cascade feedforward fuzzy PID, sliding-mode, cascade feedforward PID, cascade PID, and conventional PID controllers. Furthermore, the control robustness is very suitable despite the change in the system parameters. [ABSTRACT FROM AUTHOR]

The mechanical properties of the rotary drilling system are analyzed in depth and the complex mechanical behaviors of integral tubular strings and the effects of joints are studied. The results show that before the mechanical calculation of the drilling string, the inversion of the friction coefficient by the near-well data can improve the calculation accuracy of the friction and torque of the string. Rotating casing can ensure smooth running in the extended well. The injection of light medium can alleviate the axial force, but it is not enough to ensure safe running, which needs to be combined with the rotating casing method. By increasing the rotation per minute and reducing the weight on bit, the buckle of drill string can be avoided. [ABSTRACT FROM AUTHOR]

In order to select a better design trajectory, it needs to spend a lot of energy on parameter adjustment and calculation. Therefore, this paper establishes the intelligent optimization design model of horizontal well trajectory in with the target length and drilling string drag under rotary drilling conditions as the targets, and takes the target entry accuracy as the complex constraints. Meanwhile, multi-objective optimization algorithm and distributed calculation are used to realize the automatic optimization of the well trajectory. Under the given arithmetic conditions, compared with the original design trajectory, a horizontal well was designed with this method, the trajectory length is shortened by 92.1 m, and the maximum build-up rate is changed from 5.50° per 30 m to 4.97° per 30 m, reducing by 9.6%. Under the same BHA and boundary conditions, the drag becomes 232.42 kN, which is 6.8% lower than that before optimization. [ABSTRACT FROM AUTHOR]

To address the two critical issues of evaluating the necessity of implementing cooling techniques and achieving real-time temperature control of drilling fluids underground in the current drilling fluid cooling technology, we first established a temperature and pressure coupled downhole heat transfer model, which can be used in both water-based and oil-based drilling fluid. Then, fourteen factors, which could affect wellbore temperature, were analyzed. Based on the standard deviation of the downhole temperature corresponding to each influencing factor, the influence of each factor was quantified. The influencing factors that can be used to guide the drilling fluid's cooling technology were drilling fluid thermal conductivity, drilling fluid heat capacity, drilling fluid density, drill strings rotation speed, pump rate, viscosity, ROP, and injection temperature. The nondominated sorting genetic algorithm was used to optimize these six parameters, but the optimization process took 182 min. Combining these eight parameters' influence rules with the nondominated sorting genetic algorithm can reduce the optimization time to 108 s. Theoretically, the downhole temperature has been demonstrated to increase with the inlet temperature increasing linearly under quasi-steady states. Combining this law and PID, the downhole temperature can be controlled, which can reduce the energy for cooling the surface drilling fluid and can ensure the downhole temperature reaches the set value as soon as possible. [ABSTRACT FROM AUTHOR]

In recent years, the focus has shifted towards leveraging physics-based modelling and data-driven analysis to predict drilling incidents and anomalies in real time, with the goal of reducing non-productive periods. However, much of this attention has directed at specific drilling operations like drilling and tripping, leaving other vital processes, such as wellbore conditioning, comparatively overlooked. The primary objective of this study is to employ data-driven techniques for predicting the dynamic state of the wellbore by utilising sensor data, operating parameters, and surface measurements. Accurate predictions are pivotal for automating these processes, promising significant savings in both redundant time and associated costs, ultimately elevating operational efficiency. In this research, the surface drilling parameters such as flowrate, rotation speed, block position, and drill string length are incorporated with the surface measurements such as hookload, pressure, and torque during wellbore conditioning operation to predict further surface sensor measurements. Different parameter settings are evaluated to find the best approach. Six supervised learning algorithms are used to select the best prediction method. The findings reveal that considering all surface parameters and measurements yields the most accurate predictions. Among various single and multi-target regression methods, including deep learning approaches, the Gaussian process and random forest models exhibit the lowest prediction errors. By reliably predicting and understanding wellbore behaviour, this research paves the way for more efficient and autonomous drilling operations in the future, bridging a critical gap in the industry's automation capabilities. [ABSTRACT FROM AUTHOR]

Drilling fluids are crucial for the safe and effective extraction of hydrocarbons from deep petroleum reserves. Lubricating, suspending, and conveying drilled cuttings to the surface are some of the functions of drilling fluids. Their performance depends on lubricity, fluid loss (FL) control, and rheology. Nanoparticles (NPs) have emerged in the oil and gas industry as an efficient fluid additive to modify and stabilize the properties of drilling fluids. NPs are thermally, chemically, and physically stable in drilling fluids; however, field data show they are inefficient at reducing drill string wear. Graphene nanoplatelets (GNPs) are now a useful drilling fluid agent because of their small particles with high specific surface area, good dispersion, high thermal and electrical stability, and their ability to lower stress and wear on the drill string. Thus, this study examined GNPs in drilling fluids, including surface modification methods and their effects on rheology, FL management, and lubricity. The unique properties of GNPs that make them a potential game-changer in drilling fluid are highlighted. The techniques used to modify GNP surfaces to improve drilling fluid compatibility, stability, and dispersion were also addressed. The broad study of laboratory GNP-modified drilling fluids is the central focus of this review. A scrutiny of the mechanisms by which GNPs influence the rheological behavior of drilling fluids and their impact on drilling efficiency and wellbore stability was also highlighted. Beyond laboratory tests, GNP's real-world applications and commercialization possibilities were examined, taking economic and environmental considerations into account. Comparative examination of methods and results helps optimize GNP-enhanced drilling fluids. Small concentrations of GNPs (0.1–2.5 g) increased the base fluid lubricity and rheology. They also reduced the FL by 40–89%. Due to hydroxyl groups on clay surfaces, GNP has a strong affinity for organophilic clays. The challenges and limitations of GNP-modified drilling fluids were highlighted, along with future research directions. Finally, using GNPs as a fluid modification agent may improve drilling fluid lubricity, FL control, and rheology. These attributes will improve oil and gas drilling safety and efficiency. This review consolidates information and lays the groundwork for this growing field's study and innovation. [ABSTRACT FROM AUTHOR]

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Nowadays, the blasting volume and the corresponding explosive demand have been increasing more and more with the continuous growth of open-pit mining projects. There is a substantial waste of explosive energy due to fly-rock and vibration in the blasting process. In order to maximize the utilization of explosive energy, the air-deck stemming structure is generally adopted. However, punching mechanism of the air-deck stemming structure is not revealed yet. In this study, the solution equation of punching height is first obtained to theoretically analyze the movement mechanism of blasthole stemming. Then, the effects of different stemming structures (air-deck stemming and conventional stemming) on the punch height and rock fragmentation are investigated by conducting three field experiments. Finally, the meshless smoothed particle hydrodynamics (SPH) model in ANSYS/AUTODYN module is employed to analyze the velocity of the stemming, the blasting pressure near the hole wall, and the rock fragmentation. The results show that: (1) compared with the conventional stemming structure, the air-deck stemming structure reduces the average punching height by 48–66%, which can mitigate the environmental hazards due to the blasting dust. (2) The size of the rock fragments in the conventional stemming area is significantly higher than the ones in the air-deck stemming area. The volume of the rock fragments with sizes smaller than 100 mm is 60–81% in the air-deck stemming area but only 24–45% in the conventional stemming area. (3) Compared with the conventional stemming, the blasting pressure increases by 1–2 times at the stemming part and decreases by 1.25–2 times at the charging part by using the air-deck stemming. The results show that the explosive energy can be effectively utilized by using the air-deck stemming structure, which provides significant guidance for the drilling blasting in the increasing open-pit mining projects. Highlights: The solution equation of punching height can be deduced by Newton's law of inertia and the conservation of momentum principle through theoretical analysis. Three field experiments are conducted to study the effects of air-deck stemming and conventional stemming on the punching height and the rock fragmentation. The stemming velocity, the blasting pressure, and the rock fragmentation are analyzed using the meshless SPH model in AUTODYN module. [ABSTRACT FROM AUTHOR]

In high temperature extended reach well drilling, the water-based drilling fluids are generally treated with liquid lubricants to alleviate friction. In high density, high salinity and high temperature conditions, the lubricity of the liquid lubricants is not enough to reduce the friction to the required level, causing from time to time downhole troubles such as halting of drilling string, stuck pipe and wear and tear of drill tools. To solve these problems, a sulfurized fatty acid ester is synthesized in laboratory and is compounded with lubricants to obtain a compound lubricant QT311. Adding the lubricant QT311 into the HTFlow high temperature high pressure water-based drilling fluid greatly improves the lubricity of the drilling fluid. Testing the QT311 treated HTFlow drilling fluid on four-ball friction tester shows that treatment of 1%QT311 reduces the coefficient of friction by 64% and the diameter of the wear scars is reduced by 43%. These results indicate the QT311 as a lubricant is superior to several widely used commercial lubricants. Analysis of the surface of the friction pair with SEM shows that QT311 react chemically with iron during friction to form sulfur-iron extreme pressure membrane, thereby improving the friction-reducing performance of the drilling fluid. The laboratory experiments also show that QT311 has excellent compatibility with the HTFlow drilling fluid, anti-hydrolysis performance, salt resistance and high temperature resistance. The experimental results have provided a reference for further studies on drill-in fluid lubricants. [ABSTRACT FROM AUTHOR]

Slim hole drilling as an important technology is more and more used in developing deep oil and gas resources. In slim hole drilling, the much higher annular pressure losses impose a challenge to the annular pressure control. Accurate prediction of the annular pressure losses under the condition of eccentric rotation of drill string is an important theoretical and practical base for slim hole drilling. Conventional prediction models for this purpose have limited applicability and often omit the influences caused by the tool joints, thus cannot satisfy the requirements for accuracy in field operation. To solve this problem, a method of constructing empirical models with pressure loss correction factors is established based on the analyses of the effects of the tool joints on the flowfield and pressure losses in annular spaces using numerical simulation. The analyses show that the extra pressure losses produced by the tool joints are affected by the type of drilling fluid, rotary speed of drill pipe, eccentricity of drill pipe and annular flow velocity. Thus, when determining the pressure loss correction factor, the coupling of these effects should be taken into account. Using the result of numerical simulation of 152 sets of data, a model for predicting the annular pressure losses of the slim holes drilled in the Mahu oilfield in Xinjiang is established. The calculation using this model shows that there is a critical rotary speed at low drill pipe eccentricity, at which the annular pressure loss reaches maximum. At high drill pipe eccentricity, the annular pressure losses increase with rotary speed. The effects of the drill pipe eccentricity on the annular pressure losses will become complex because of the rotary speed. Using the annular pressure loss prediction model developed, the equivalent circulation density of the well MHHW-X in the Mahu oilfield was calculated and compared with the PWD data, the average error was only 1.18%, indicating that the model has high accuracy. The results of the study show that, the model established through numerical simulation for calculating annular pressure losses in slim holes, which takes into account the effects of tool joints, is able to satisfy the requirement of accuracy for field prediction of annular pressure losses, and to provide guidance to the annular pressure control in field operation. [ABSTRACT FROM AUTHOR]

This paper presents a coupled computational fluid dynamics–discrete element method (CFD–DEM) simulation to predict cuttings transport by the drilling fluid (mud) in different oil well drilling conditions. The mud rheology is expressed by the Herschel–Bulkley behaviour and modelled in a Eulerian framework (CFD), while the cuttings are modelled using the Lagrangian approach (DEM). In this work, the effects of drill string rotation, inclination angle, cutting size, mud rheology, and annular velocity on cleaning efficiency are investigated. It is found that increasing the well deviation from vertical to horizontal leads to a higher cuttings concentration. However, at low annular velocity, the cuttings concentration for the inclined (45-degree) annulus is found to be higher than the horizontal one due to the sliding motion of cuttings on the lower section of the annulus. Overall, the drill pipe rotation has little effect on decreasing the cuttings concentration, but the effect is more pronounced at low annular velocity. [ABSTRACT FROM AUTHOR]

Martian rocks contain crucial information about the genesis of Mars and the historical evolution of Martian climate change. Consequently, extracting and examining Martian rocks are pivotal in advancing our comprehensive understanding of the red planet. However, the current core drill string is prone to wear and tear, and the samples are susceptible to thermal denaturation. To address these challenges, we introduce two novel types of drill bits, the conical straight junk slot and the conical spiral junk slot, both employing impregnated diamond as the primary material. Comparative experiments were meticulously conducted to evaluate the influence of different junk configurations on drilling parameters, including speed, abrasion resistance, drilling force loading, and sample temperature rise. The findings unequivocally demonstrate the superior performance of the spiral junk slot. Furthermore, simulations were performed to examine the drilling process on basalt using a fixed configuration drill bit, validating the occurrence of the sample temperature rise. The research presented in this paper offers valuable programmatic references and essential data support for future Martian rock coring drilling missions. [ABSTRACT FROM AUTHOR]

The object of research is the dynamic processes that occur in the drill string during the deepening of the hole in deep wells. The work is aimed at solving the problem for an idealized system in the form of rod systems while preserving its main oscillatory properties. The nature of oscillatory processes that occur in the drill string during drilling with downhole motors is considered, in some cases it turns out to be very complicated. In the general case, the dynamic process changes according to an aperiodic law, which is superimposed by processes of an oscillating nature with an increasing (damping) nature of the amplitudes of different frequencies. The influence of the torque characteristics of the downhole motor and bit on the development of oscillatory processes in the drill string during well drilling has been theoretically determined. The results of theoretical and experimental studies of oscillatory processes and their interaction with the use of proposed models of hole deepening in the future make it possible to create a simulation model. This model would include taking into account the mode parameters of drilling, the mechanical properties of the rocks to be drilled and the layout of the drill string bottom (DSB). The obtained research results can be applied in practice in the process of designing the structure of the drill string bottom (DSB) with the use of downhole motors, in particular, screw motors, the use of which leads to energy stress, the complication of work processes and structural schemes. As a result, the nature of vibrations changes and the vibration loads on parts of the downhole motor, bits and elements of the drill string are reduced. In the future, it is necessary to take into account the hydrodynamics and the type, as well as the design and parameters of the applied downhole elements for the development of their dynamic models. [ABSTRACT FROM AUTHOR]

Accurately obtaining wellbore-formation temperature distribution during drilling in fractured carbonate formations is the basis for effectively solving the problem of the well kick and loss circulation coexisting (WK-LC). Therefore, based on the energy conservation law and considering the convective heat transfer and variable mass flow caused by well kick and loss circulation, this paper developed a full transient heat transfer model of wellbore-formation coupled system under the WK-LC. The reliability of model was verified by field measured temperature data. Based on field well, the thermal behavior of wellbore-formation coupled system under normal condition, well kick, loss circulation and WK-LC were compared and studied. The results showed that the bottom-hole temperature of well kick and Case1-2 is higher than that of normal condition, while the bottom-hole temperature of loss circulation and Case3-4 is lower than that of normal condition. The temperature difference between annulus and drill string (TD-AD) shows a "wavy line" trend of increasing-decreasing-increasing-decreasing along the well depth. The TD-AD of wellhead is about 6 °C in normal and WK-LC conditions. The traditional wellhead temperature monitoring method can only distinguish well kick and leakage, and it is difficult to judge whether WK-LC occur. In addition, the influence of the distance and well kick/leakage rate difference between the well kick region and the leakage region on thermal behavior of wellbore-formation coupled system was discussed. Finally, a new auxiliary method is proposed to identify the well kick, the loss circulation and the WK-LC. Which will have a significant implication for well killing and leaking stoppage operations. • A new auxiliary method was proposed to identify the well kick, the loss circulation and the WK-LC. • A full transient heat transfer model of wellbore-formation coupled system under the WK-LC was developed. • Considered the convective heat transfer and variable mass flow caused by well kick and loss circulation. • Thermal behavior of wellbore-formation coupled system under WK-LC were studied. [ABSTRACT FROM AUTHOR]

A landing string is directly exposed to seawater and subjected to significant stresses and complex deformations due to environmental loads such as wind, waves, and ocean currents during the phase in which the drill string carries the casing to the wellhead. Meanwhile, as the water depth increases, the weight of the drill string increases, leading to an increase in the tensile loads borne by the drill string, which can easily cause a risk of failure. Therefore, a quasi-static load calculation model for the deepwater insertion of the pipe column was established. Using the Ansys platform, simulations were conducted for average wind, wave, and ocean current conditions during different months throughout the year. The ultimate loads and stress distributions of the string were derived from theoretical analyses and numerical simulations for different operational sea states, and the suggested safe operating window and desired BOP trolley restraining reaction force for landing strings' lowering are given according to the existing industry standards. The research findings can help in identifying the potential risks and failure modes of the deepwater landing string under different working conditions. [ABSTRACT FROM AUTHOR]

In this paper, based on the non-linear mechanics theory of the drill pipe, a mechanical model of stick-slip vibration of the drill pipe has been established by considering the torsional properties of the drill pipe, kinetic energy and the motion law of the bit. The example calculations and sensitivity analysis of the parameters are carried out. The results show that increasing the rotational speed, viscous damping, length of the drill collar and de-creasing the weight of bit have the effect of suppressing the stick-slip vibration. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Iraqi Journal of Chemical & Petroleum Engineering is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The application of high-frequency vibrations to a drill bit is a promising means of increasing rate of penetration in deep hard formations. The implementation of such drill bit high-frequency vibrations is possible by installing the cavitation hydraulic vibrator in the drill string in front of the rock-cutting tool. Purpose. Evaluation of resonant modes (frequencies of oscillations) for the dynamic interaction of the mud pressure in the drill string and the drill bit longitudinal vibrations in case of contact with the rock being destroyed while drilling using the cavitation hydraulic vibrator; comparative analysis of the effectiveness of using a high-frequency mechanical vibrator and a cavitation hydraulic vibrator in case of drilling in hard rocks. Methodology. The research is based on a comparative analysis of the amplitudes and power spectral density of mud pressure oscillations of the mud and vibration accelerations in the drill bit cross section of drill string. Findings. The results are presented in the form of amplitude spectra and power spectral densities of mud pressure and vibration acceleration, as well as the dependence of the increase in the rate of penetration on the frequency of forced oscillations of the drill bit. Originality. Taking into account the influence of the cavitation hydraulic vibrator on the drill rig ROP made it possible: - to determine the resonant frequencies of pressure oscillations of the mud of the drilling tool, for the effective removal of drilled rock at the point of its contact with the drilling tool, and the longitudinal vibration accelerations of the drilling tool, to speed up rate of penetration during the construction of a well; - to evaluate the effectiveness of using a cavitation hydraulic vibrator in comparison with a high-frequency mechanical vibrator. For the studied modes of operation of the hydraulic vibrator at values of the cavitation parameter τ = 0.19, the well rate of penetration increases by 40 % compared to the traditional rotary method and by 26 % compared to the vibratory hammer. For the cavitation operating mode of the hydraulic vibrator τ = 0.41, the increase in the rate of penetration is 62 and 37 %, respectively. At the same time, the operating efficiency of the hydraulic vibrator was ensured at the resonant frequencies of the mud pressure with a frequency of 1,580 Hz at τ = 0.19 and 1,980 Hz at τ = 0.41. Practical value. For a specific design of the cavitation hydraulic vibrator as part of a drill string, by changing the frequency of the drill bit vibration impact on the rock, resonant frequencies are established that ensure the high ROP of the well. [ABSTRACT FROM AUTHOR]

Aiming at the problems of large torque fluctuation of drill bit and low weight-on-bit(WOB) transmission efficiency during the drilling process, a novel drilling tool generating constant torque and reducing stick-slip is proposed. For investigating the further dynamics behavior of drill string system, the mathematic models are established based on the new tool output characteristics. Also, compared with field test and application, the drilling tool effects on increasing ROP (rate of penetration) and reducing drill bit wear are verified. The research results show that the peak value of drill bit angular velocity increases gradually with the bigger value of the pre-compression of disk spring system, so as the rotary table inputting speed, during drill bit downward movement. About the drill string influence, the larger the length of drill string, the longer response time is the rotating angular velocity of drill bit. Another one, the shorter the steady time of drill bit angular velocity, the bigger ratio is the stick-slip within one period. This new drilling tool can effectively improve the drill bit force conditions, and reduce the stick-slip stage, which can also profitably increase drilling efficiency and the service life of downhole tools, especially in ultra-deep or long distance horizontal wells. [ABSTRACT FROM AUTHOR]

The object of research is a drill string. The work is directed to the study of the drill string dynamics and its influence on the rock, which is drilled using probabilistic methods. It is shown that the nature of the vibrations of the top of the drill string and the downhole signals are different and have a stationary random character. It is proved that the process at the output of the drill string, taking into account random disturbances, is narrow-band (quasi-harmonic) or close to it. It is found that the energy composition of the spectrum sections and the appearance of resonance peaks and their displacement is directly determined by the physical and mechanical properties of the rocks being drilled, as one of the factors that determines the vibration state of the drill string. Graphs of the spectral density of the power of pitting vibrations are given, showing their amplification at frequencies of 30–40 Hz as the hardness of the rocks being drilled increases. The maximum of the power density bending curve shifts towards low frequencies. There is a «mutual convergence» of the maxima of the power spectral density of the oscillations of the top and bottom of the drill string. It is shown that an important feature of drill string vibrations in the process of drilling with ball bits is that the intensity of vibrations of the top of the drill string passes with frequencies close to low frequencies, and the vibrations of the bottom of the string – to high frequencies. It is determined that the process at the output of the drill string, taking into account random disturbances, is narrow-band (quasi-harmonic) or close to it. As a result, the assumption of a narrow band at the output of the system, which is the basis of theoretical research, is justified. It is proven that the drill string, as a system with liquid filling under pressure, is more stable compared to a hollow structure. The washing liquid, in this case, plays the role of a dynamic absorber. [ABSTRACT FROM AUTHOR]

Tight glutenite reservoirs characterization and effective hydrocarbon-bearing formation identification faced great challenge due to ultra-low porosity, ultra-low permeability and complicated pore structure. Fracturing fracture-building technique always needed to obtain deliverability because of poor natural productive capacity. Pore structure characterization and friability prediction were essential in improving such type of reservoir evaluation. In this study, fractured tight glutenite reservoirs in Permian Jiamuhe Formation that located in northwest margin of Junggar Basin, northwest China, were chosen as an example, and 25 typical core samples were drilled and simultaneously applied for mercury injection capillary pressure (MICP), nuclear magnetic resonance (NMR) and whole-rock mineral X-ray diffraction experiments. A novel method of synthetizing pseudo-pore-throat radius (Rc) distribution from porosity frequency spectra was established to characterize fractured formation pore structure. Quartz and calcite were considered as the fragile mineral, and rock mineral component ratio method was used to predict brittleness index. Meanwhile, the statistical model raised by Jin et al. (SPE J 20:518–526, 2015) was used to predict two types of fracture toughness. And then, brittleness index and fracture toughness were combined to characterize tight glutenite reservoirs friability. Combining with maximal pore-throat radius (Rmax, reflected rock pore structure) and friability, our target formations were classified into four clusters. In addition, relationships among pore structure, friability and daily hydrocarbon production per meter (DI) were analyzed, and a model to predict DI from well-logging data was established. Comparison of predicted DI with the extracted results from drill stem test (DST) data illustrated the reliability of our raised models. This would be valuable in determining optimal hydrocarbon production intervals and formulating reasonable developed plans. [ABSTRACT FROM AUTHOR]

The swing of the riser in deep-water drilling can significantly impact the drill string. In this study, we establish a riser model that considers the combined disturbance of periodic dynamic wind and wave loads. By coupling it with the drill string model, we develop a dynamic model for deep-water drilling systems. Through analyzing multiple sets of different drilling parameters, we examine displacements and impact forces at various positions along the drill string system. Specifically, our focus lies on velocity, acceleration, and rotational speed information of BHA. We investigate how WOB and rotational speed influence motion trajectory and vibration characteristics of the drill string within the dynamic model of deep-water drilling systems. Simulation results reveal slight differences in whirling trajectories between inside the riser and below mud line for the drill string. Rotational speed has a greater impact on the drill string compared to WOB; higher rotational speeds lead to increased collision forces between the drill string system and both riser and wellbore. Our findings identify specific combinations of WOB and rotational speed parameters that can stabilize drilling operations within dynamic models for deep-water drilling systems. These research results provide valuable insights for adjusting WOB and rotational speed parameters in deep-water drilling. [ABSTRACT FROM AUTHOR]

Purpose: The deep or hard formation is an important development direction of oil and gas energy resource exploration, and new equipment for accelerating rock breaking is urgently needed. Therefore, a new composite impact acceleration tool is proposed in this paper. Methods: Based on the tool, the dynamic theoretical model and differential equation of the drill string system are established. And simulate the rock breaking characteristics of PDC (Polycrystalline Diamond Compact) cutters under composite impact. Results: The new tool can change these results from periodic fluctuation to be stable such as the angular velocity of the drill bit, driving and friction torque. Simultaneously, the angular displacement changes from discontinuous to continuous increase. The increase of WOB (Weight on Bit) could enhance PDC invasion depth and improve rock breaking efficiency, but it may cause bouncing of drill bit. The rotational speed of 60 rpm (revolution per minute) is the critical point in the cases. When the rotational speed increases above 60 rpm, the specific energy of rock breaking reduces and the efficiency improves. However, it shows the opposite characteristics when the rotational speed increases below 60 rpm. Conclusions: The application of the composite impact acceleration tool can significantly suppress the stick–slip vibration and improves dynamics stability of drill string system. Also, appropriate selection of key parameters such as WOB or rotational speed can improve drilling efficiency. [ABSTRACT FROM AUTHOR]

Currently, drilling of directional oil and gas wells under complex technical-technological and mining-geological conditions requires the use of drill pipes made of various materials. In turn, to choose rational modes of strengthening drill pipes and drill string layouts, information on the contact forces and friction forces of the drill string pipes on boreholes is necessary. Drill pipe curved sections friction with boreholes and drill bit resistance moment changes are the main causes of uneven rotation of a drill string during rotary or combined drilling methods and the occurrence of parametric oscillations. To reduce the cost of mechanical energy for well wiring, it is necessary to take into account the "drill string–borehole rocks" force interaction to estimate the magnitude of the frictional forces and their influence on the technological parameters of the drilling process. To solve this problem, mathematical models of "conventionally vertical and inclined drill string sections–borehole" were built. Based on the industrial data, an analysis of the force interaction of a deformed drill string composed of pipes made of different materials (aluminum, titanium, steel) was carried out. Analytical dependences were obtained for determining the contact forces and friction of the pipes on boreholes. A numerical study of the change of these power factors depending on the depth of the well under conditions of intensive vibration loading was carried out. The amplitude values of these forces, the frequency of their change for good sections, as well as the places for the most rational installation of drill pipes in the layout of the drill string were estimated. It was established that the intensity of contact and friction forces for steel drill pipes is greater than for titanium or aluminum ones. It is shown that the greater impact of a solid steel string on contact forces and frictional forces compared to a layout with sections of titanium or aluminum pipes in the range of vibration frequencies of 8–22 Hz corresponds to a bit rotation frequency of 70–80 rpm. The practical application of the obtained research results will contribute to the improvement of technical and economic indicators of the well drilling process. [ABSTRACT FROM AUTHOR]

Reducing friction between drill string and wellbore wall is one of the key functions of drilling fluid which may result from tight holes, key seats, differential sticking, or cutting build up along the drill string. However due to growing environmental concerns, biodegradable lubricants which are also cost-efficient are appreciated and mandated in many countries. This study discusses the performance analysis of biodegradable biodiesel produced from pomelo peels and Petroleum-based lube oil as drilling fluid lubricants. The test samples comprise 700 mL of water + 10 % bentonite + 3 % barite + 0.25 % CaCO3 + 0.25 % KOH + 1 % CMC + lubricant. Two sets of lubricants were utilized to prepare 10 samples of drilling fluid, one set with petroleum-based lubricant and other with biodiesel. Essential oil was extracted from pomelo peel with the help of the Clevenger apparatus. The oil was then converted to biodiesel through the process of transesterification. Biodiesel properties were tested for the ASTM standards. Both sets of drilling fluid samples were tested for their rheological, filtration and lubricating properties and from the results obtained it can be concluded that both type of lubricating agents have almost negligible impact on rheological and filtration loss properties. However, the lubricity coefficient values drastically decreased as we increased the lubricant content, which is an indication that biodiesel extracted from pomelo peel acts as a better lubricant. The values of the lubricity coefficient for biodiesel based drilling fluid also fell well within the advised range (<0.30). We can therefore draw the conclusion that biodiesel made from pomelo peel can replace petroleum-based lubricants while also lowering the environmental concerns related to lubricants. [ABSTRACT FROM AUTHOR]