Deep Drilling Research Articles

E&P Notes (November 2022)

E&P Notes (November 2022)

Wellbore multiphase flow behaviors of gas kick in deep water horizontal drilling

During the deepwater drilling, the complicated gas-liquid-solid multiphase flow will occur if the formation gas enters and migrates in the wellbore. Through understanding of the wellbore flow behaviors is of great importance for the blowout prevention and well control. Considering the dynamic mass and heat transfer process in wellbore caused by alternating ambient temperature field, a multiphase flow model of multicomponent fluid in wellbore is deduced and developed, including the continuity equation, momentum conservation equation and energy conservation equation. Furthermore, the corresponding initial and boundary conditions are proposed for different working conditions in deepwater drilling, and an efficient numerical solution method is established, including dynamic mesh generation method and discrete solution method of partial differential equations. Applied in a deep-water kicking well, the proposed model is used to analyze the multiphase flow rules in the wellbore. The results show that in the process of annular fluid returning from the bottomhole, the pressure generally decreases linearly, while the temperature change is nonlinear. The temperature first rises and then falls at the formation section, and first falls and then rises at the seawater section. Furthermore, the pit gain increases approximately in a quadratic polynomial relationship, caused by the rise and expansion of gas in the wellbore, and the pressure drop and gas influx rate increase at the bottomhole. In the process of kick evolution, the standpipe pressure and bottomhole pressure gradually decrease, which can be an important sign for kick detection.

PROSPECTS OF OIL AND GAS POTENTIAL OF THE JUNCTION ZONE OF THE NORTH-EAST OF THE PRECASPIAN BASIN AND THE SOUTHERN SEGMENT OF THE URAL FOLD SYSTEM (AKTOBE URALIAN FOREDEEP)

The identification of promising areas of exploration to develop the resource base of the Aktobe region is an urgent issue due to the gradual depletion of proven hydrocarbon reserves. The subsalt complex of the Aktobe Uralian Foreland is a prospective object, where prospecting and exploration work was carried out unevenly in the 1950s and 1980s, and most of the seismic survey data of 2004-2008 are low-informative. The subsalt complex of the studied area has been poorly studied by high resolution seismic studies and deep exploration drilling and previously belonged to the territories with low hydrocarbon potential. On the basis of the conducted research, data on the structural and tectonic zoning of the junction zone of the Precaspian basin and the southern segment of the Urals Foredeep are summarized, the geological structure of the Aktobe Uralian Foreland area is substantiated, favorable geochemical criteria of oil and gas potential are revealed.

Birth of the Pearl River at 30 Ma: Evidence from sedimentary records in the northern South China Sea

The Pearl River drains the South China Block and delivers large amounts of sediments to the northern South China Sea, and its development can be closely linked to the regional paleoenvironmental changes. However, the evolutionary history of the Pearl River has been poorly understood, mainly because of the lack of continuous and high-resolution sedimentary records over a long geological time. In this study, we present multiple new analytical results, including clay mineral assemblages and Sr-Nd isotopic compositions of the <2 μm siliciclastic sediments, from the latest deep sea drilling core in the northern South China Sea from International Ocean Discovery Program (IODP) Site U1501. We aim to reconstruct the evolutionary history of the Pearl River by tracing changes in clay mineral assemblages and Sr-Nd isotopic compositions. Provenance analysis indicates that the sediment source experienced a significant change between 32 and 30 Ma. Specifically, sediments prior to 32 Ma were derived from the southeastern Cathaysia coast, whereas sediments post to 30 Ma were mainly supplied by a proto-Pearl River. This provenance transition indicates that the modern-scale Pearl River has fully developed at least ∼30 Ma and began to contribute sediments to the northern South China Sea. We additionally compared the timings of major climatic and tectonic events in this region, and suggest that the topographic uplift of the SE Tibetan Plateau most likely drove the large-scale westward expansion of rivers drainage from the coast located in the Cathaysia Block to the interior of Yangtze Block. As a result of this fluvial drainage evolution followed by the development of Pearl River, geochemical and clay mineralogical characteristics of the deposits in the northern South China Sea correspondingly changed.

Study of a High-Temperature and High-Density Water-Based Drilling Fluid System Based on Non-sulfonated Plant Polymers.

The environment-friendly water-based drilling fluid system developed for the petroleum development industry cannot successfully withstand temperatures up to 180 °C, and most high temperature-resistant additives with sulfonic acid groups that have been successfully applied to water-based drilling fluid are not good for environmental protection. In order to solve the above technical problems, a non-sulfonated filtrate reducer and viscosity reducer with resistance to high temperature were prepared by using humic acid, lignin and a multifunctional monomer as raw materials. In laboratory experiments, the molecular weights of the FLO-H filtrate reducer and the VR-H viscosity reducer were 5.45 × 105 g/mol and 8.51 × 103 g/mol, respectively, and all of them showed good high-temperature resistance. The API filtration loss of the bentonite-base slurry with 3.0 wt% FLO-H was only 6.2 mL, which indicated that FLO-H had a prominent reduction in filtration loss after aging at high temperature. When the dosage of VR-H was 1.0 wt%, the plastic viscosity of the water-based drilling fluid after aging at 200 °C decreased from 71 mPa·s to 55 mPa·s, which provided excellent dispersion and dilution. The high-temperature and high-density water-based drilling fluid containing the FLO-H filtrate reducer and the VR-H viscosity reducer had good suspension stability and low filtration performance at the high temperature of 200 °C, which can meet the requirements of high-temperature deep well drilling.

Wire Arc Additive Manufactured Mild Steel and Austenitic Stainless Steel Components: Microstructure, Mechanical Properties and Residual Stresses.

Wire arc additive manufacturing (WAAM) is an additive manufacturing process based on the arc welding process in which wire is melted by an electric arc and deposited layer by layer. Due to the cost and rate benefits over powder-based additive manufacturing technologies and other alternative heat sources such as laser and electron beams, the process is currently receiving much attention in the industrial production sector. The gas metal arc welded (GMAW) based WAAM process provides a higher deposition rate than other methods, making it suitable for additive manufacturing. The fabrication of mild steel (G3Si1), austenitic stainless steel (SS304), and a bimetallic sample of both materials were completed successfully using the GMAW based WAAM process. The microstructure characterization of the developed sample was conducted using optical and scanning electron microscopes. The interface reveals two discrete zones of mild steel and SS304 deposits without any weld defects. The hardness profile indicates a drastic increase in hardness near the interface, which is attributed to chromium migration from the SS304. The toughness of the sample was tested based on the Charpy Impact (ASTM D6110) test. The test reveals isotropy in both directions. The tensile strength of samples deposited by the WAAM technique measured slightly higher than the standard values of weld filament. The deep hole drilling (DHD) method was used to measure the residual stresses, and it was determined that the stresses are compressive in the mild steel portion and tensile in austenitic stainless steel portion, and that they vary throughout the thickness due to variation in the cooling rate at the inner and outer surfaces.

Laponite-polymer composite as a rheology modifier and filtration loss reducer for water-based drilling fluids at high temperature

In the process of deep oil and gas drilling, high temperature and high amounts of salt will greatly deteriorate the rheological properties of water-based drilling fluids (WBDFs), increase the fluid loss of drilling fluids, and seriously threaten the safety of operations. It is urgent to develop new high-temperature and salt-resistant drilling fluid additives. In this study, a novel organic-inorganic polymer nanocomposite (P-RD') was synthesized by combining laponite and polymer, and its chemical structure and properties were characterized and evaluated by various experimental methods. The results show that P-RD' forms a spatial network structure in aqueous solution, and has good clay adsorption capacity and pore and crack sealing ability. At 180 °C and 15 wt% NaCl, it has good rheological stability to WBDFs, the American Petroleum Institute (API) filtration loss is only 7.1 mL, and the high temperature and high pressure (HTHP) filtration loss is controlled at 29.2 mL. P-RD' has dual functions, which can effectively strengthen the temperature and salt resistance of WBDFs, and is expected to be used as a rheology modifier and filtration loss reducer in high-temperature deep well drilling.

Prediction method of solubility of carbon dioxide and methane during gas invasion in deep-water drilling

Gases that invade during deep-water oil and gas drilling may be concealed due to the gas dissolution effect, leading to increased well control risks. Accurate and rapid prediction of carbon dioxide and methane dissolution is of great significance for the prediction and control of wellbore pressure during gas invasion. In this study, 316 sets of carbon dioxide solubility data at 288.15 to 423.15 K and 0.1 to 100 MPa, and 266 sets of methane solubility data at 275.15 to 444.3 K and 0.1 to 68 MPa were used to train a machine learning algorithm. The machine learning prediction method for gas solubility was established with a support vector regression machine and a particle swarm optimisation algorithm. The kernel function and disciplinary parameters of the support vector regression machine were optimised using the experimental dataset. The solubility of CO2 and CH4 in water was measured using a gas solubility measurement device. The experimental and model analysis showed that the solubility of CO2 varied in different phase states. At a given pressure, the solubility of CO2 was highest in the liquid state, followed by the supercritical state, and then the gaseous state. The average absolute relative deviation percentages between the calculated values of the CO2 and CH4 solubility models and the experimental values were 2.57 and 8.20, respectively. The machine learning method is consistent with the high-precision Duan thermodynamic model for predicting the solubility of CO2 and CH4 in water and can be used to predict the gas solubility in deep water and deep oil and gas drilling.

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons

Natural Hydrogen: A New Source of Carbon-Free and Renewable Energy That Can Compete With Hydrocarbons

Paleozoic and Mesozoic hydrocarbon foci of generation and assessment of their role in formation oil deposits of the Pre-Jurassic complex of Western Siberia

The following problem is solved by the present research: the probable sources of Paleozoic hydrocarbon deposits are determined on the basis of modeling the hydrocarbon foci of generation Paleozoic-Mesozoic oil source formations (for example, the southeast of Western Siberia, Tomsk Region). The research area is the lands Ostanino field group: the Selveikin area of deep drilling, the Ostaninskoye and Gerasimovskoye oil and gas condensate fields. Pre-Jurassic strata with oil source potential, including the Paleozoic Larinskaya (S1lr), Mirnaya (D13mr), Chuzikskaya (D2cz), Chaginskaya (D3cg) and Kehoregskaya (C1kh) formations, as well as Jurassic Bazhenovskaya (J3bg) and Tyumenskaya (J1-2tm ) formations, and, accordingly, the reservoirs of the weathering crust and bed-rock Paleozoic reservoirs are the objects of study. The subject of analysis was selected in accordance with the concept of the geothermal regime of the subsoil, as a leading factor in the implementation of the generation potential of the parent sediments. The research methods are digital paleotemperature modeling and historical-geological analysis. The results and conclusions concerning the fundamental problems of “Paleozoic oil” are obtained. 1. Source of the Paleozoic oil deposits can be both the Domanic type rocks of the Paleozoic formations and the Jurassic oil source formations. Thus, both upward vertical interstratal HC migration and downward HC migration can take place. Therefore, the two concepts of “main source” are compatible and should not be considered, as often, orthodoxly alternative. 2. The domanicoid rocks of the Paleozoic formations are most likely the source for Paleozoic gas and gas condensate deposits. 3. Paleozoic formations the roof of the bed-rock Paleozoic (on the Ostankinskaya group of fields – C1kh and D3cg) can be only the source of the «Paleozoic oil» and gas deposits in the Pre-Jurassic oil and gas complex. 4. Bazhenov formation – J3bg may be the “Jurassic” source of oil deposits in the Pre-Jurassic oil and gas complex. The results were obtained and conclusions were drawn concerning the applied (search) aspects of the problem: 1. Results additionally substantiate the author’s search criterion for the oil and gas content of the Paleozoic – these are anomalous geophysical and petrophysical characteristics of the Jurassic section. 2. The absence of hydrocarbon deposits in the Jurassic section is most likely a negative sign of the Paleozoic oil and gas content. 4. The low density of the modern heat flow (less than 40 mW/m2) is most likely a negative sign of oil deposits in the Paleozoic. 3. High paleotemperatures in terms of VR (more than 175oC) are most likely a negative sign of oil and gas deposits in the Paleozoic. 4. Reasons have been obtained to state that oil deposits in the Paleozoic cannot be richer than oil deposits in the Jurassic.

Measurement-While-Milling (MWM): An innovative approach for increasing the casing milling efficiency in deep drilling operations

Deep boreholes are secured by steel tubes (casings) which are run in the hole and cemented in place. In most cases, these casings are considered a permanent installation. However, sometimes they have to be removed in order to repair or abandon the well. As the casing is cemented in place, it cannot be pulled, but needs to be milled to small chips which are flushed out of the borehole by the drilling mud. One of the main challenges in casing milling operations is continuous and complete chip removal. If the metal chips are too long, chip nests will grow around the milling string. As a result, this will restrict the annulus flow area and affect the chip removal in boreholes. The obvious solution in such condition is to do round tripping and clean the chip nest which is associated with the risk of injuries, as well as, increasing the none-productive time. In the worst case, the poor cleaning and circulation of chips can even end up with the milling string stucking problem in boreholes, consequently long-time fishing job. According to the available literatures, hardly any study for identifying the chip shapes and accordingly adapting the operation parameters to the casing milling process environment downhole to keep milling within desired generated chip shapes and sizes could be found. This paper presents an encouraging idea to monitor the milling process in real time by utilizing the acoustic emission signals (vibration modes) accompanied with the milling process to identify the desired chip shape and size range. Initial laboratory tests have been carried out to investigate and study the acoustic emission signals accompanying the casing milling process to identify the chip shapes and sizes. The preliminary test results show very good correlation and agreement between the chip length formed during those specific tests and the observed burst events in the measured signals. The study results have demonstrated the functionality of the new concept, and thus confirmed that it is a very promising idea towards developing a practical real time downhole monitoring system for milling operations. Adapting the milling operation parameters downhole in real time to keep the milling process within the desired generated chip shapes and sizes will offer better cleaning and removal of the chips and will prevent the development of chip nest around the drill string and its consequences such as round tripping, risk of drilling crew injury, none-productive time and even milling string stucking problems.

A drilling wellbore pressure calculation model considering the effect of gas dissolution and suspension

The complex formation pressure system and diverse formation fluid components during deepwater and deep drilling make it easy for gas intrusion accidents to occur. The dissolution and suspension of the intruded gas in the drilling fluid and the difference between the gas–liquid phase distribution characteristics and the gas–water two-phase flow characteristics in the wellbore lead to errors in the calculation of wellbore pressure and overflow assessment after gas intrusion. In this article, a wellbore multiphase flow model, considering gas dissolution and suspension is established, and the influence of gas dissolution and suspension in the drilling fluid on multiphase flow in the wellbore during overflow, well shutdown, and compression is analyzed with the model calculation results. The higher the drilling fluid density and yield stress are, the higher is the gas limit suspension concentration, when free gas is present in the wellbore. After the gas intrusion shutdown, when there are suspended and transported gases in the wellbore, the rate of pressure increase in the wellbore decreases after the shutdown, and the volume fraction of free gas decreases when the shutdown time is longer, and eventually all the gases will be suspended in the drilling fluid. During the pressure process, gas dissolution leads to an increase in the peak pressure in the wellbore and a delay in its occurrence; gas suspension leads to a decrease in the peak pressure in the wellbore and a delay in its occurrence. This article establishes a multiphase flow calculation model for the wellbore, considering both gas dissolution and suspension, which is a guideline for the calculation of wellbore pressure after gas intrusion.

Initial Postcontact Behavior of an Axially Compressed Fiber Constrained Inside a Rigid Cylinder: Experimental, Analytical, and Numerical Investigation

Abstract The postbuckling behavior of a clamped-clamped elastic fiber constrained inside a rigid cylinder is analyzed theoretically, numerically, and experimentally. We concentrate on characterizing the contact configuration between the fiber and the cylinder wall during initial postcontact stages of the fiber deformation, in which only a small segment of the fiber length maintains contact with the cylinder wall. This is apparently the first study of that phenomenon presenting an in-depth investigation of the fiber deformation and contact stages in experiments, along with a detailed examination of the effect of fiber geometrical imperfection. The main experimental challenge was to identify regions of contact between the fiber and the cylinder wall and to distinguish them from segments of the fiber that are very close to the cylinder wall but make no contact with it. To this end, we employed a novel experimental setup consisting of a transparent rigid cylinder filled with an opaque milky fluid, combined with image processing, and synchronized force measurements. The results of the experiments are supported by finite-element analysis and are also compared to available theoretical predictions based on the elastica model of an initially perfectly straight fiber. A small strain analytical solution reveals the role of minor initial geometrical imperfections in deriving the force–displacement relation during fiber bending. This study provides new understanding of the influence of key parameters on the behavior of such systems and may have practical implications in the fields of stent procedures, medical endoscopy, deep drilling, and more.

Determining Young's modulus of granite using accurate grain-based modeling with microscale rock mechanical experiments

It is critical to rigorously determine the mechanical properties of granitic rocks to effectively analyze and manage subsurface engineering activities, such as geothermal energy exploitation and nuclear waste disposal. However, the required deep drilling and sampling for macroscale rock mechanics experiments (macro-RME) are challenging and expensive. In this study, we developed a novel accurate grain-based modeling (AGBM) using the results of microscale rock mechanics experiments (micro-RME) to determine the elastic properties of arbitrarily shaped granite . The microstructure of each sample and Young's modulus of rock-forming minerals were measured with a TESCAN Integrated Mineral Analyzer (TIMA) and nanoindentation test . The geometry and Young's modulus of interphases between different minerals were determined using an advanced algorithm with atomic force microscopy (AFM) test. With the microstructure and microscale mechanical properties obtained from the micro-RME, the AGBM was applied to derive the macroscale mechanical properties of the granite samples. This new methodology was demonstrated on small test specimens extracted from granite fragments. Because we can use test specimens from arbitrarily shaped and small rock fragments, this new methodology has been proven to be a breakthrough from the conventional technology of macro-RME. • Minerals and interphase in granites were measured by microscale mechanics experiments. • Accurate Grain-Based Modeling was developed to determine the macroscale property. • Specimens can be arbitrarily-shaped, avoiding the difficulty of drilling intact rock.

Hydrocarbon system of the South Caspian Depression

Actuality. The hydrocarbon generation sources in the South Caspian Basin (SCB) are located at the depth of nine or more kilometers, where the organic-rich Maikop sediments occur. The main oil-and-gas fields here are found in reservoirs of the Productive Strata (Lower Pliocene), bedding at a depth of one or more kilometers. At the same time, the significant role at the process of hydrocarbons migration from the source of their generation to the reservoirs belongs to the tectonic faults (fractures). However, the results of the research according to the latest seismic data carried out in recent years are indicated the unavailability of the tectonic faults in the SCB, which connected the hydrocarbon generation sources with the reservoirs in the Productive Strata.&#x0D; Target. The determination of the geological elements at the studied area that contributed the role of the hydrocarbon migration channels and connected generation source with reservoirs in the Productive Strata.&#x0D; Objects. The hydrocarbon generation source, hydrocarbon migration channel, tectonic faults and fractures, Productive Strata reservoirs, eruptive channels of the mud volcanoes.&#x0D; Approach. The collaboration interpretation results of the deep drilling and the seismic data by using the common depth point method.&#x0D; Results. Based on the structural interpretation results of the seismic data with high-resolution parameters, are indicated the lack of the tectonic faults which connecting the hydrocarbon generation source with reservoirs of the Productive Strata in the SCB.&#x0D; In addition, the hydrocarbons that generated in the Maikop sediments are transported to the Productive Strata reservoirs by the eruptive channels of mud volcanoes. The opinion that the process of hydrocarbon generation in the Maikop clay deposits continues to the present time and the mud volcanoes eruptive channels provide feeding of the deposits with the continuous supply of oil-and-gas was expressed. Such kind of mechanism allows to classify the deposits, that more than a century under developed in the South Caspian Depression and which located at the zone of mud volcanomaturity, to the category of replenished.

Assessment of municipal solid waste landfilling practices on the groundwater quality and associated health risks: a case study of Mardan-Pakistan

This study was conducted to investigate the quality of groundwater affected due to the municipal solid waste (MSW) used as a landfill. To assess the impacts, 13 groundwater samples were collected from solid waste dumping sites (SWDS) and 13 from safe sites (SS). Groundwater was analyzed for pH, turbidity, electrical conductivity (EC), total hardness (TH), Cl−, Ca+2, K+1, NO−2, NO−3, SO4−2; heavy metals such as Pb, Cr, Mn, Cu, Ni, Zn, Cd, Fe; biological parameter such as total coliform. Waste samples collected from SWDS showed that food and garden waste had the highest percentage by weight (30.5%) followed by fines (17.3%). The two groups (SWDS and SS) differ significantly for the mean value of EC, TH, Na, Ca, NO3− and SO4−2, Ni and TC. Samples collected from SWDS (84%) were found contaminated with total coliform (TC) ranged 2–22 (No./100 ml). It was analyzed that concentration of total dissolved solids (TDS), pH, EC, TH, NO3−, SO4−2, NO2−, Ca+2, Na+, TC, Cr, Ni, Zn, Cd and TC were more in the samples collected from 70–130 feet than 140–200 feet. TC found in 70–80 feet depth was significantly different from the rest of the groups. A questionnaire survey was also conducted from the people living near the dumping sites to assess the frequency of the water-related disease the community is suffering from. The results of the questionnaire survey revealed negative correlation between the diseases and distance from the landfill sites, and significant correlation was only observed for typhoid, cholera, skin allergies and gastroenteritis. The study confirmed that using MSW as a fill material has contaminated the groundwater quality, and leveling of land through MSW is not safe. Deep drilling is recommended for extraction of groundwater in the contaminated area to minimize the associated health risks.

A review on geothermal energy resources in India: past and the present.

By 2040, India hopes to have completed its energy supply to fulfill the country's rising energy demands. Renewable and conventional sources must be used in an environmentally acceptable manner to achieve sustainable growth. India must enhance its use of renewable and clean energy sources, including geothermal, wind, and solar, to satisfy its growing demand. While solar and wind energy output has increased significantly, geothermal energy has yet to be fully harnessed. Among the many forms of geothermal energy found on the surface are volcanoes, fumaroles, erupting geysers, steaming fields, and hot springs. A total of about 340 geothermal springs may be found in India, spread throughout both orogenic (in the Himalayas) and non-orogenic (in the Peninsula). There were 31 places extensively evaluated, and deep drilling was performed in sixteen of them. Average temperatures range from 35.0°C to the boiling point of water in these springs. Medium (100.0-200.0°C) and low (100°C) enthalpy geothermal energy resources/systems are found in India, with the latter being the most abundant. The essential component of a geothermal system is understanding the heat source and harnessing it. Studies so far have indicated that some geothermal areas have sufficient geothermal potential for direct heat usage and power generation. If the Puga (J&K) field is explored to a depth of at least 500 m, reservoir simulation studies have shown that it might produce more than 3 MW of power. India's diverse geothermal sites and the current status of exploration for future research are discussed in the paper.

Influence of micro-electrical discharge machining parameters on the surface morphology of the nickel-coated electrode

ABSTRACT During the machining of deep hole drilling in industries, Micro-Electrical Discharge machines are frequently exposed to pulse on time and high current, reducing tool life, micro-hole efficiency, machining accuracy, and production rate. As a result of this research, a ground-breaking strategy for overcoming the aforementioned industry problems has been discovered. In this analysis, nickel was coated on the brass electrode with a wall thickness of 2 µm to control the secondary reaction in the machining phase. Current, Voltage, Pulse-on time, and Capacitance parameters were investigated on the micro-coated tool in micro EDM. This article proposed the morphology wear behavior of the tool electrode by the Taguchi (L9 Orthogonal Array) design approach. Micro-holes are drilled with an aspect ratio of 20 on D2 steel using this technique. The coated tool will minimize tool wear and increase the material’s rate of removal and compromises the surface quality according to experimental results. Since a large taper angle was observed in the machining process by the Video Measuring Machine (VMM). The consistency of micro-holes on AISI D2 Steel has suffered, which is analyzed by Optical Microscope. In this research work the size of Crater wear discussed with SEM (Scanning Electron Microscope) images.

Analytical Model of Hole Diameter and Self-Guiding Machining Mechanism of BTA Deep Hole Drilling

The goal of this study was to explore the self-guided machining mechanism of boring and trepanning association (BTA) deep hole drilling and realize precise control of the machining quality. The motion analysis method was used to analyze the center motion trajectory of the drill during the entrance, and the self-guiding mechanism and hole-forming mechanism of BTA deep hole drilling were revealed. Considering the bending deformation of the drilling tube and the tool structure parameters, according to the elastic-plastic deformation theory and Hertzian contact theory, a novel analytical model of the extrusion contact between the guide pads and the hole wall of the BTA deep hole drilling was established for the theoretical prediction of the extrusion deformation and the machining hole diameter. Combined with the finite element method (FEM) simulation model, the variation law of the contact inclination angle, contact stress, and extrusion deformation of the guide pads and the hole wall with the drilling conditions were studied. The total extrusion deformation between the guide pad and the hole wall was between 10 and 50 μm. The maximum error between the FEM simulation results and the test results was 18.1%, and the maximum error between the analytical model results and the test results was 23.6%. The simulation and experimental results showed that the established extrusion contact model could accurately predict the extrusion deformation of the hole wall and the machining hole diameter.

Wellbore cooling and heat energy utilization method for deep shale gas horizontal well drilling

The downhole high-temperature problem has become a bottleneck that restricts the efficient development of deep shale gas resources in China. This study highlights the characteristics of the deep shale gas drilling process to develop a transient model of wellbore temperature distribution for deep shale gas horizontal section drilling through thermal resistance analysis, which is verified using experimental and field data. Based on this model, the influence of the circulation time, drilling fluid flow rate, drill pipe rotation speed, rate of penetration, drilling fluid inlet temperature, and drill pipe thermal conductivity on the wellbore temperature distribution during horizontal well drilling is investigated. The results indicate that an insulated drill pipe is the most effective measure for cooling down the wellbore. Subsequently, a system for wellbore cooling and heat energy utilization while drilling based on insulated drill pipes is established in conjunction with the organic Rankine cycle. The results show that the estimated maximum power generation of this system was 990.120 kW when the bore diameter is 215.9 mm, the design depth of the well is 6095 m, the vertical depth of the well is 4313.76 m, and the inlet temperature is 20 °C.