Horizontal Drilling Technology Research Articles

EXPERIMENTAL STUDY ON THE FRACTURE CONDUCTIVITY IN SHALE OIL PRODUCTION

Unconventional oil and gas resources, such as shale oil and gas, are gradually attracting great attention from all countries of the world. Horizontal drilling and large-scale hydraulic fracturing technology are used to efficiently extract oil from shale formation. Effective placement of the proppant in the fractures and high long-term conductivity are the keys to solve the problems of oil well flow rate increase in shale oil and gas fields. In this work, the sieve analysis method and FCMS-V fracture conductivity determination device, as well as scanning electron microscope are used. They are used to experimentally investigate the filtration characteristics of hydraulic fracturing fractures and establish the key factors affecting the filtration characteristics. The object of the study is the core of the oil-saturated DG shale formation of Songliao Basin. Also in this paper, the indentation and crushing mechanism of proppant under reservoir conditions is studied. The influence of various factors was evaluated qualitatively and quantitatively. The following studies were conducted: the effect of sand granule size on conductivity, the effect of grain size distribution on conductivity, the effect of proppant concentration on conductivity, the effect of fracture closure pressure on conductivity, and the effect of proppant indentation on conductivity. The granule sizes of the proppant used range from 30/50 to 70/140 mesh. Proppant concentration: 2,5; 5; 10 kg/m2. Ratios of granule sizes for used mixtures: 1:1:1, 1:2:7, 1:4:5.And crack clamping pressure from 20 to 40 MPa. As a result of the study, dependences of initial and long-term fracture conductivity on clamping pressure, granulometric composition of proppant and its concentration were obtained. Using a scanning electron microscope, the degree of indentation and crushing of proppant under reservoir conditions in two media, namely shale core and steel plates, was visually evaluated. The results of experimental studies can be used to optimize the shale oil development system and have scientific and practical significance for shale oil production in continental deposits.

RESEARCH INNOVATIONS IN DIRECTIONAL AND HORIZONTAL DRILLING AND SIDETRACKING TECHNIQUES

Directional and horizontal drilling, and sidetracking techniques have become integral components of the oil and gas industry, which allows access to hydrocarbon reserves in challenging environments. This paper provides an overview of these drilling methods and explores recent trends in the development of technical equipment for horizontal drilling and sidetracking. Directional drilling allows for drilling at various angles, including horizontal and multilateral, providing access to reservoirs beneath the Earth's surface. This technique involves specialized equipment and precise control of the drill bit's direction and deviation, resulting in better reservoir management, increased productivity and reduced environmental effect. Horizontal drilling, on the other hand, involves drilling laterally through subsurface rock formations, particularly beneficial for accessing unconventional reservoirs (shale formations). Horizontal drilling allows operators to access more of the formation, resulting in increased productivity and reduced environmental footprint. Sidetracking techniques are employed to redirect the path of a wellbore, necessary for avoiding geological hazards, accessing untapped reservoirs, or bypassing damaged sections of the well. This process requires careful planning, specialized equipment, and skilled personnel to ensure successful execution while minimizing risks. The paper also discusses modern trends in the development of technical equipment for horizontal drilling and sidetracking technology. These include automation and robotics to improve drilling efficiency and safety, advancements in drilling fluids and measurement-while-drilling (MWD) technologies for better wellbore stability and real-time data acquisition, and innovations in extended reach drilling (ERD) tools and casing and cementing solutions. Additionally, there is ongoing development in sidetracking techniques to improve efficiency and reliability, such as whipstock and casing exit technologies. The Ultrashort-Radius Radial System (URRS) is highlighted as an advanced drilling technology, enabling access to reservoirs with restricted space or challenging geometries. Although challenges such as cost and adaptation to downhole conditions remain, ongoing research and development is aimed at overcoming these barriers and demonstrating the feasibility of innovative drilling technologies. Ultimately, these advances contribute to the industry's goal of maximizing hydrocarbon production while ensuring operational efficiency and environmental sustainability. Keywords: directional drilling, horizontal drilling, sidetracking techniques, technical equipment development, ultrashort-radius radial system, laser drilling.

Evaluating tidal impact on ground source heat exchanger performance under fluctuating groundwater levels

Coastal regions undergo dynamic changes due to tidal forces, posing distinct challenges for groundwater management and utilization of ground source heat pump (GSHP) systems. This study examines the impact of tidal fluctuations on groundwater levels and the performance of ground heat exchangers (GHEs), specifically focusing on the suitability of horizontal directional drilling (HDD) technology in high-tidal zones. Itoman City in Okinawa Prefecture, Southern Japan, serves as an ideal location for this study due to its complex coastal hydrogeological conditions and increasing interest in renewable energy solutions. Employing a comprehensive approach involving field experiments, FEFLOW software simulations, and model validation, we aim to elucidate the intricate relationship between tidal dynamics, groundwater behavior, and GHE performance. Furthermore, our investigation assesses the effectiveness of HDD-GHEs installed in highly tidal-affected zones to determine the optimal installation depth for this type of GHE in coastal regions. According to our research, the layer at a depth of 30 m is most affected by tidal influence and fluctuations in groundwater levels in coastal regions. This layer is the most suitable for installing horizontal HDD-GHEs, with an average heat exchange rate of about 89 W/m. This rate is approximately four and two times higher than the depths above and below this layer, respectively, due to groundwater saturation and flow in the formation. Furthermore, we noticed that the heat exchange rate increases from the top to the bottom of this layer, but the extent of this increase diminishes as the depth increases. This is because deeper depths are less affected by tidal fluctuations in groundwater levels.

Optimization of double layered horizontal directional drilled ground heat exchangers by water injection into the borehole

Ground Heat Exchangers (GHEs) drilled using Horizontal Directional Drilling (HDD) technology have been proven to be a cost-efficient way of installing ground source heat pump systems (GSHP). They can also be installed in places where conventional horizontal ground heat exchanger (HGHE) would not be possible e.g., due to lack of land.In this research, a double layered horizontal borehole was installed as a GHE in Saga City, Japan. The two holes had a diameter of 114.3 mm and a length of 59 m and 56 m, respectively, while reaching depths of 5 m and 9.5 m. A polyethylene pipe with an outer diameter of 60 mm was inserted as a borehole heat exchanger (BHE). In March 2022, a two days thermal response test (TRT) showed the influence of rainfall on the system. A numerical model developed in FEFLOW based on the GHE dimension and the region's geology was validated using the measured temperatures of the heat medium at the return point and outlet of the GHE during the TRT. The validated model was then used to carry out sensitivity analysis examining different conditions of water injection into the borehole. The result of the sensitivity analysis showed that water injection into the borehole can improve the performance of the system and reduce the temperature change of the heat medium. Varying the injection rate can improve performance to a certain degree and the injection point has a strong influence on the performance. The injection temperature was also found to play a role in the performance, but even high temperatures in the case of heating showed significant improvement. Lastly, the influence of permeability was investigated and showed that impermeable layers are more favorable for injection compared to permeable layers.

Drilling technology of long horizontal section of shale oil

As an important supplementary energy resource, shale oil has attracted worldwide attention due to its huge reserves and rich comprehensive utilization levels. The world is rich in oil shale resources. According to statistics, if the oil shale of 33 countries and regions in the world is converted into shale oil, it will be about 400 billion tons. With the continuous maturity of horizontal well drilling and completion technology in shale oil gas reservoirs and the application of other advanced technologies in horizontal well drilling, mature shale oil gas drilling and completion matching technologies have gradually formed at home and abroad after years of research and drilling practice. In terms of measurement technology, China has been able to produce single-point, multi-point, wired, wireless inclinometers and MWD measuring instruments while drilling and has mastered their usage methods. In terms of control technology, various specifications and types of fixed-angle and ground-adjustable curved shell screw drilling tools have been produced in China. Large deformation analysis and trajectory prediction methods for lower drilling tool assemblies have been completed. Various lower drilling tool assemblies and their usage processes required for wellbore trajectory control have been improved and mastered. In the construction of inclined and horizontal sections, attention should be paid to the response law of drilling tool combinations to drilling pressure in different formations, especially the response law of composite drilling. Reasonable drilling tool combinations should be selected for the control of wellbore trajectory in stable and horizontal sections, especially in the long stable and horizontal sections.

Analytical and semi-analytical methods for modeling liquid inflow to a horizontal well (review)

The efficiency of using horizontal drilling technology largely depends on a number of factors, including the geological structure of the productive formation, fracturing, anisotropy, heterogeneity, porosity, and permeability. This necessitates the design of the process of oil inflow to the horizontal section of the well. The article presents analytical and numerical methods used in modeling liquid inflow to horizontal and multilateral wells. The main attention is paid to taking into account the anisotropy of reservoir permeability, the trajectory of the horizontal wellbore and hydraulic pressure losses due to friction.

Assessment of the technical level of installations horizontal directional drilling

The article considers the concept of the technical level (TL) of engineering products, the regulatory and technical foundations and the need to assess the TS at each stage of the machine’s life cycle. The fundamentals of horizontal directional drilling (HDD) technology work are considered. The review and classification of modern HDD installations depending on the technical parameters of the equipment is given. The results of an expert assessment of the indicators of the significance of HDD equipment parameters are presented. Calculations of specifications TL for the presented equipment were carried out. The results of the study are presented in graphical form. The article is published based on the results of the research work carried out as part of the competition for grants for the implementation of research work by scientific and pedagogical workers SPbGASU in 2023. Keywords: technical level, technique, horizontal directional drilling, efficiency, parameter

Borehole TV Imaging Technology for Horizontal Directional Drilling Based on an Optimization Algorithm for Structural Planes

The horizontal directional drilling technology combined with the borehole TV imaging technology can be used to obtain most of the geological information in conventional adit exploration. This combination has little impact on the environment and is free from topographic constraints, thus contributing to green exploration. However, conventional algorithms for structural planes fail to accurately extract information on the attitudes of incomplete structural planes in boreholes of any azimuth. Moreover, existing borehole TV devices are mostly cable-based and, thus, difficult to put in place in horizontal drilling. They are prone to get stuck in the collapse section of boreholes, thus damaging the devices. Given these challenges, this study develops an optimization algorithm for structural planes: (1) first, information on multiple points in the 2D unfolded view is fitted using a sinusoidal function curve, three arbitrary points are constructed using the fitted curve, and the normal vector of the plane determined by the three points is calculated; (2) the normal vector in the geodetic coordinate system is obtained after two rotations of the spatial coordinate system based on the theory of transformation of Cartesian coordinate system; (3) finally, the dip angle and dip direction of a structural plane are calculated using the normal vector in the geodetic coordinate system. By making the best use of the information on multiple points in the 2D unfolded view, the optimization algorithm can overcome the defect that is difficult for conventional two-point methods to locate the highest and lowest points of discontinuous structural planes. Therefore, the optimization algorithm applies to calculating the attitudes of structural planes in boreholes of any azimuth. Based on this optimization algorithm, this study successfully develops a cable-free, storage-based TV device for boreholes of any azimuth. This device was employed for laboratory experiments on 20 complete structural planes and 32 incomplete structural planes. As indicated by the experiment results, the optimization algorithm proposed in this study is applicable to many types of structural planes, with a dip direction error of less than 10° and a dip angle error of less than 5°, thus meeting the production requirements.

Production prediction based on ASGA-XGBoost in shale gas reservoir

The advancement of horizontal drilling and hydraulic fracturing technologies has led to an increased significance of shale gas as a vital energy source. In the realm of oilfield development decisions, production forecast analysis stands as an essential aspect. Despite numerical simulation being a prevalent method for production prediction, its time-consuming nature is ill-suited for expeditious decision-making in oilfield development. Consequently, we present a data-driven model, ASGA-XGBoost, designed for rapid and precise forecasting of shale gas production from horizontally fractured wells. The central premise of ASGA-XGBoost entails the implementation of ASGA to optimize the hyperparameters of the XGBoost model, thereby enhancing its prediction performance. To assess the feasibility of the ASGA-XGBoost model, we employed a dataset comprising 250 samples, acquired by simulating shale gas multistage fractured horizontal well development through the use of CMG commercial numerical simulation software. Furthermore, XGBoost, GA-XGBoost, and ASGA-XGBoost models were trained using the data from the training set and employed to predict the 30-day cumulative gas production utilizing the data from the testing set. The outcomes demonstrate that the ASGA-XGBoost model yields the lowest mean absolute error and offers optimal performance in predicting the 30-day cumulative gas production. Additionally, the mean absolute error of the unoptimized XGBoost model is markedly greater than that of the optimized XGBoost model, indicating that the latter, refined through the application of intelligent optimization algorithms, exhibits superior performance. The insights gleaned from this investigation have the potential to inform the development of strategic plans for shale gas oilfields, ultimately promoting the cost-effective exploitation of this energy resource.

Study on the Mechanism of High-Efficiency Rock Breaking by Hydraulic Jet Based on Explicit Dynamics

High-efficiency rock breaking by hydraulic jetting is the key to radial horizontal drilling technology. In order to improve the drilling efficiency of hydraulic jet rock breaking in radial horizontal wells, based on LS-Dyna display dynamics, a numerical simulation model of single-nozzle jet rock breaking was established to analyze the influence of different nozzle parameters on the rock-breaking effect. Then, the numerical simulation model of the spin multi-nozzle jet bit was established, and the influence of different rotation speeds on the rock-breaking effect of the jet bit was analyzed. Finally, the rock-breaking drilling characteristics of the spin multi-nozzle jet bit and the conventional multi-nozzle jet bit were compared and analyzed. The results show that when the jet impacts the rock surface, the larger the inclination angle is, the larger the rock-breaking width formed by the jet is. The smaller the dip angle, the greater the rock-breaking depth. When the inclination angle is greater than 60°, it is difficult to meet the needs of reaming. The width and depth of the nozzle gradually increase with the increase of the diameter. When the nozzle diameter is greater than 1.3 mm, the growth rate of rock-breaking depth begins to decrease. The optimum nozzle diameter is 1.3 mm. When v = 50 m/s, the damage caused by the jet to the rock surface is very small, because the condition of rock fracture is not reached with this velocity. This shows that there is a critical value of the water jet impact velocity, and only when the velocity is reached, will the rock break. When the velocity is v = 150 m/s, v = 200 m/s, v = 250 m/s, v = 300 m/s, the rock breaks. At the same time, the higher the speed, the higher the degree of rock fracture, the greater the fracture depth, the greater the fracture area, and the better the fracture effect. The tangential and radial velocity of the jet increases the shear and tensile failure rate of the sample, and improves the rock-breaking efficiency of the jet, which has a certain guiding significance for improving the rock-breaking drilling efficiency of radial horizontal well drilling.

Upstream oil and gas mergers and acquisitions: Domestic transactions in the U.S

This paper investigates drivers of mergers and acquisitions in the upstream industry by applying an empirical approach based on domestic transactions during last two decades in the U.S. The oil and gas industry, particularly, upstream industry has seen rapid developments in recent years. The discovery of new resources in unconventional oil and gas parallel to the horizontal drilling and fracking technology, the U.S oil and gas market shows changing patterns which is also reflected in investments in the oil and gas industry. Mergers and acquisitions in the upstream industry in the U.S has experienced increasing patterns, especially in domestic levels (post Shale revolution, booms and changing dynamics over last two decades). Our study recognizes that underlying facts of mergers and acquisitions investments in the oil and gas industry can vary from other industries and can be different than traditional economic explanations. The empirical results suggest that industry-specific variables have stronger influence on mergers and acquisitions than economic and political indicators. The drivers can be different based on various transaction forms and deal levels. Our findings provide a comprehensive view, test various theories of mergers and acquisitions and direct to sector-specific stylized facts of the U.S oil and gas market.

Transient Pressure Behavior of Finite-Conductivity Fractures in Horizontal Wells Considering Interference of Water-Injection Wells

Fractured horizontal wells and water-flooding development are effective means to stabilize oil production in low-permeability reservoirs; however, transient pressure behavior analysis based on a single-well testing model ignores the interference effect caused by water-injection wells. With advancements in horizontal drilling technology, multiple-fracture horizontal wells are widely used in tight reservoirs, and researchers have concluded that pressure drops in hydraulic fractures cannot be ignored. In this paper, we present a well testing model that considers the effects of finite-conductivity fractures and the interference of water-injection wells. The analytical solutions were derived based on the source function and superposition principle, and the characteristics of the transient pressure behavior at the bottom hole are analyzed and discussed. The typical pressure curve of our model showed that seven flow regimes exist: wellbore storage stage, transitional flow, first linear flow, fracture interference flow, second linear flow, pseudoradial flow, and interference flow. Furthermore, the results of the sensitivity analysis indicated that the flow regimes are greatly affected by the properties of the fractures and water-injection wells. The length of the fracture mainly affects the transitional flow, first linear flow, fracture interference flow, and second linear flow regimes, whereas the number of fractures predominantly affects the first two stages. The fracture spacing has a significant effect on the fracture interference flow and second linear flow regimes, and the water-injection rate mainly affects the interference flow regime. The well spacing determines when the interference effect occurs. These findings will support more accurate modeling of well production performance considering the impact of water-injection wells.

Microscale thermo-hydro-mechanical modeling of thermal recovery of shale gas

The development of horizontal drilling and hydraulic fracturing technologies have made the commercial extraction of shale gas resources come true. However, significant amounts of shale gas are still unattainable even with these technical breakthroughs. One major reason is that up to 85% of total gas-in-place in shale reservoirs could be adsorbed gas. Thus, how much more adsorbed gas can be released will significantly impact the ultimate gas recovery. In recent years, the concept of using thermal stimulation to enhance shale gas recovery has been proposed as more gas desorbs under the higher temperature conditions. In this paper, a fully coupled thermo-hydro-mechanical (THM) model is developed to characterize gas transport and extraction in shale matrix from the microscopic perspective during thermal treatment. A set of partial differential equations are defined to model the coupled processes involved: (1) geomechanical deformation of heterogenous shale matrix; (2) gas adsorption/desorption and flow in heterogenous shale matrix; and (3) thermal transport in heterogenous shale matrix. All these processes are linked together through the porosity and apparent permeability models. This microscale THM model is verified against an analytical solution available in the literature. The verified model is then applied to investigate rock and fluid responses in shale during thermal treatment and the impacts of operation and rock physical parameters on gas recovery. Simulation results indicate that a greater thermal treatment temperature, a lower bottom hole pressure, a larger total organic carbon content and a larger Langmuir volume enhances ultimate gas recovery; and that shale thermal properties and matrix permeability impact initial gas recovery but does not impact ultimate gas recovery.

Formation Damage Caused by Wax Deposition Results in Shale Production Decline

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210414, “First Evidence for Shale Production Decline as a Result of Formation Damage Caused by C60+ Paraffin Wax Deposition: A Permian Case Study,” by Amir Mahmoudkhani, SPE, Locus Fermentation Solutions, and Jonathan Rogers and Martin Shumway, SPE, Locus Bio-Energy Solutions, et al. The paper has not been peer reviewed. _ Analysis of production decline curves revealed that three candidate wells in West Texas depleted faster than indicated by a type decline curve, indicating a potentially abnormal permeability-reduction mechanism. A biosurfactant-based squeeze program was recommended and applied in three horizontal wells. The biosurfactant treatment offers an alternative and economical method for remediation of formation damage caused by high‑molecular‑weight paraffin wax deposition in porous media that does not require costly intervention techniques to apply. Introduction The Bone Springs horizontal oil play in the Delaware Basin spans from southeast New Mexico into West Texas. Stacked, multipay reservoirs, each with diverse rock properties, possess upside but also complexity. The initial targets in the play were conventional sandstones. Wells then tapped into carbonate lenses and, ultimately, low-permeability sandstones. As a result of horizontal drilling technology combined with hydraulic fracturing, very thin sands and other facies are now being produced. Generally, reservoir quality of this unconventional hydrocarbon system is controlled by carbonate content, where increased carbonate content typically is associated with lower productivity. Experimental Methods All crude oils exhibited precipitation of organics at ambient laboratory temperatures. Even after storing crudes at the bottomhole temperature of 140°F, a small amount of wax remained insoluble in bulk liquid. Samples of formation drill cuttings were received for various depth intervals between 8,500 and 12,000 ft. X‑ray diffraction analyses of solids revealed quartz as the major mineral phase, with clays and carbonates account for remaining phases. Combined fractions with 160-micron size were used for microcolumn oil-recovery screening tests. Carbon distributions of oils and waxes were performed by high-temperature gas chromatography (HTGC). The Du Noüy ring method was used to measure static surface tensions of biosurfactant solutions at different concentrations and was applied to calculate critical micelle concentrations at ambient temperature. Interfacial tension (IFT) measurements were performed using a drop-shaped tensiometer using the pendant-drop method. Finally, the IFTs of oil in synthetic formation water and in biosurfactant solutions prepared in city tap water were determined. Contact-angle measurements also were performed. The wax-appearance temperature (WAT) of crude and wax samples was determined by the differential scanning calorimetry method. Spontaneous imbibition experiments were performed using the Amott-cell method at reservoir temperature. Berea sandstone core plugs (25×50 mm) with a permeability of 385 md and porosity of 18.4% were used. Core plugs were saturated with homogenized crude oil samples at 140°F for 7 days.

3D Horizontal Well Fast Drilling Technology in X Gas Field

The design trajectory parameters of 3D horizontal wells in X gas field are not uniform, the construction is random, and the lack of standardization is not enough to achieve rapid drilling. Based on the analysis of the construction data and construction difficulties of the completed 3D horizontal well, according to the different design trajectory parameters and types, by standardizing the drilling tool assembly and well trajectory design, making full use of the characteristics of the drilling tool assembly and the formation law, and using the supporting tools to control the sand carrying and lubricity of the mud, control the solid content, and reduce the friction and torque of the 3D horizontal well, this paper studies and summarizes the 3D horizontal well rapid drilling technology. The field application shows that the 3D horizontal well rapid drilling technology can effectively reduce downhole faults, greatly improve the drilling speed, and achieve the effect of increasing speed and efficiency and saving costs. The 3D horizontal well rapid drilling technology plays a very good technical guarantee for the development of the gas field, and also provides a certain reference for peers.

A COMPREHENSIVE REVIEW OF HYDRAULIC FRACTURING TECHNIQUES IN SHALE GAS PRODUCTION

Shale gas has emerged as a significant source of natural gas due to advancements in hydraulic fracturing and horizontal drilling technologies. This extraction method has facilitated drilling and production activities in regions previously untouched by oil and gas development. Hydraulic fracturing, a well-stimulation technique suitable for low and moderate-permeability reservoirs, relies on the successful drilling of horizontal wells and the creation of multiple hydraulic fractures to ensure economic viability. While shale gas presents significant energy production opportunities, concerns have been raised regarding its environmental impact. To mitigate these risks and determine the most effective approach for shale gas extraction, alternative fracturing technologies are being investigated. Notably, a considerable number of perforation clusters in shale gas horizontal wells do not contribute to production, highlighting the potential for refracturing. Therefore, a comprehensive analysis is required to evaluate the performance of hydraulic fracturing and alternative fracturing technologies in shale gas wells, considering factors such as cost-effectiveness, environmental impact, and gas extraction efficiency. This article aims to evaluate the hydraulic fracturing technology's capability to enhance gas recovery in shale gas formations as well as its environmental implications. The focus of this research is primarily on the hydraulic fracturing technique employed in shale gas development, its production capability, and associated environmental concerns. Through a systematic evaluation, this study provided valuable insights into the potential of hydraulic fracturing in maximizing gas recovery while addressing environmental challenges in shale gas formations.

Inspecting the corrosion state of underground reinforced concrete structures

Unnoticed corrosion in underground reinforced concrete structural members – such as foundations, retaining walls, or piles – may severely threaten the integrity of structures. However, condition assessment of the ground-buried structural parts is challenging, because the areas of interest are hardly accessible for visual inspection or non-destructive testing. An example of particular practical relevance is reinforcement corrosion at the back-side of the lower end of cantilever retaining walls, near the construction joint between stem and heel of the base slab. The collapse of a cantilever retaining wall in Austria was a tragic reminder of the dangers of unnoticed corrosion. The drawback of current inspection methods is that they are laborious and costly, but still, only a tiny fraction of the structure can be inspected. Considering that the degree of corrosion can vary significantly along a structure, such local information includes a risk that corrosion elsewhere remains undetected.A novel inspection system is proposed here, combining the well-proven half-cell potential measurement technique with steered horizontal underground drilling technologies. With this approach, a tailor-made probe is brought in proximity to the concrete surface in the soil and electrochemical measurements are performed to characterize the corrosion condition. The main advantage is that virtually the entire length of the structure can be inspected, thus overcoming the limitations of highly local inspection. Moreover, the proposed technique includes a method to constantly monitor the functionality of the potential measuring probe, based on electrical resistance measurements. The feasibility of the approach was confirmed in laboratory experiments on a mortar block in soil. These findings were confirmed in a field experiment. The results suggest that local corroding zones of practice-relevant size can be detected for a distance between the reference electrode and the steel surface of at least 25 cm. On the basis of this work, underground corrosion inspection of cantilever retaining walls is considered feasible, and the development of similar technologies as the one proposed here may in the future considerably enhance condition assessment of structures buried in the ground.

Technical advances in well type and drilling & completion for high-efficient development of coalbed methane in China

Compared with the United States, Australia, Canada, and other countries, China's coalbed methane reservoir is featured by low formation pressure, low permeability, low gas saturation, and strong heterogeneity, which not only increases the difficulty of reservoir stimulation but also restricts the single well production and the recovery efficiency of coalbed methane (CBM). In view of this, the research and application of horizontal drilling and completion technology of CBM at home and abroad are reviewed to provide references and theoretical supports for the advancement of the horizontal well engineering technology of CBM in China. This paper introduces a series of horizontal drilling and completion technologies (e.g., the well type design, well structure optimization, well trajectory control, wellbore stability, completion optimization, reservoir protection, etc.). The advanced technologies and their adaptability, including screen pipe completion and stimulation with dual-layer tubular strings, radial horizontal well screen pipe completion and magnetic steering drilling, are dialectically discussed in this paper. In addition, a novel integrated engineering mode for the efficient and green development of deep CBM and coal through the underground “well factory” is proposed. The conclusions are as follows: (1) In view of the geological conditions and surface environment of the coal seam in China, the horizontal drilling and completion technologies of high rank coalbed methane should be further refined, and an integrated development for the coal measure gas is required; (2) More efforts should be made to strengthen the innovative research on horizontal drilling & completion technology for low-medium rank coals and the broken coal, so as to identify the efficient development mode for the complex coalbed methane reservoir; (3) When encountering major technical challenges during the green and efficient development of unconventional coal mines such as deep coal mines, low grade coal mines and thin coal seams in China, it is necessary to explore the development mode via in-situ conversion process based on underground “well factory” to realize the integrated green and efficient development of deep CBM and coal; (4) The high quality transformation with low-carbon and green energy in China will not only ensure national energy security, but also achieve the goal of “carbon peaking and carbon neutrality”.

The Powder River Basin: A persistent player in Wyoming’s energy landscape

The Cretaceous-Tertiary strata of Wyoming’s Powder River Basin have long been a source of natural resources, including coal, oil, and natural gas. Coal mining and oil drilling have been ongoing in the basin for more than a century. Coal mining started in the late 1800s, and today, Wyoming is the largest coal-producing state in the U.S. A coalbed methane boom-and-bust cycle in the 2000s left tens of thousands of wells idle or abandoned. Historical oil production has been largely from vertical wells in the Minnelusa/Tensleep, Muddy, Frontier/Turner, Shannon, Sussex, Parkman, and Teapot Formations. More recently, interest in unconventional source-rock reservoirs like the Mowry Shale and Niobrara Formation has grown in tandem with directional and horizontal drilling and hydraulic fracturing technology. Interest was so explosive that the state of Wyoming imposed new permitting regulations to keep activity under control. Like a bellwether for the energy industry, Wyoming has seen it all, from boom-and-bust cycles to fracking to carbon capture.

The history of Madison Group exploration and production in the North Dakota Williston Basin with an update on Madison Group source rocks

The Williston Basin has proven to be a global super basin in terms of oil production and reserves (Sonnenberg, 2020). Although recent production in the basin has been dominated by the Middle Member of the Bakken Formation, the Madison Group has yielded over a billion barrels of oil since 1951. The Madison Group consists of the Charles, Mission Canyon, and Lodgepole formations with various members in each. These formations are found in both the United States and Canada and led Williston Basin production until 2008. As with many petroleum plays, the Williston Basin enticed oil men for many decades with the prospect of oil before finally yielding to success. Success, which is so often accompanied by a bit of good fortune, is a matter of finances, persistence, and technology, ultimately paving the way to successful commercial wells. Many factors contributed to the ongoing production results in the basin and include seismic, horizontal drilling, and completion technologies, and of course, good geological assessments. The history of production in the basin is also detailed by the history of petroleum geochemistry. Source rock and oil geochemistry progressed from scratch tests, test tube pyrolysis, and standard physicochemical properties, such as API gravity, to detailed chemical investigations including high resolution gas chromatography and biomarker analysis.