Search Results (30)

Coalbed methane (CBM), a significant unconventional natural gas resource, holds a crucial position in China’s ongoing energy structure transformation. However, the inherent low permeability, high brittleness, and strong sensitivity of CBM reservoirs to drilling fluids often lead to severe formation damage during drilling operations, consequently impairing well productivity. To address these challenges, this study developed a novel low-damage, plugging, and anti-collapse water-based drilling fluid gel system (ACWD) specifically designed for coalbed methane drilling. Laboratory investigations demonstrate that the ACWD system exhibits superior overall performance. It exhibits stable rheological properties, with an initial API filtrate loss of 1.0 mL and a high-temperature, high-pressure (HTHP) filtrate loss of 4.4 mL after 16 h of hot rolling at 120 °C. It also demonstrates excellent static settling stability. The system effectively inhibits the hydration and swelling of clay and coal, significantly reducing the linear expansion of bentonite from 5.42 mm (in deionized water) to 1.05 mm, and achieving high shale rolling recovery rates (both exceeding 80%). Crucially, the ACWD system exhibits exceptional plugging performance, completely sealing simulated 400 µm fractures with zero filtrate loss at 5 MPa pressure. It also significantly reduces core damage, with an LS-C1 core damage rate of 7.73%, substantially lower than the 19.85% recorded for the control polymer system (LS-C2 core). Field application in the JX-1 well of the Ordos Basin further validated the system’s effectiveness in mitigating fluid loss, preventing wellbore instability, and enhancing drilling efficiency in complex coal formations. This study offers a promising, relatively environmentally friendly, and cost-effective drilling fluid solution for the safe and efficient development of coalbed methane resources. Full article

The Arctic region is rich in oil and gas resources and has great potential for development. It has become a new hot spot for international development. However, the harsh climatic and geological conditions and fragile ecosystems in the Arctic region put forward stringent technical requirements for oil and gas development. Polar permafrost has an impact on the growth of plant roots and the absorption of water. When drilling activities are carried out, the permafrost layer may be broken, resulting in the erosion of polar soil and disorder of the water balance, thus affecting local vegetation and ecosystems. Moreover, the legal system of polar environmental protection is lacking, and it is necessary to form a perfect risk assessment method to improve the relevant laws and regulations. Therefore, it is very important to study the environmental risk identification technology for polar drilling. For polar drilling, it is necessary to establish a risk source classification and identification method for environmental pollution events. However, at present, it mainly faces the following challenges: poor polar environment, lack of monitoring data, and lack of a legal system for polar environmental protection. By systematically discussing risk identification technology, the application and applicable models of different types of risk evaluation methods are categorized and summarized, the advantages and disadvantages of different types of risk evaluation methods and their application effects are analyzed based on the unique environment of the polar regions, and then the development direction of the future environmental risk identification technology for polar drilling is proposed. In order to accelerate the development of polar drilling environmental risk identification technology, research should be focused on the following three aspects: ① Promoting the multi-dimensional integration of polar drilling environmental pollution index data, to make up for the short board of less relevant data in the polar region. ② Combining the machine modeling algorithm with risk evaluation of polar drilling environmental pollution to improve the scientificity and accuracy of the evaluation results. ③ Establishing a scientific and accurate polar drilling environmental pollution risk identification system to reduce pollution risk. Full article

To address the technical challenge of high polymer gel viscosity reducers losing viscosity at elevated temperatures and difficulty in controlling fluid loss, a polymer-based nano calcium carbonate composite high-temperature tackifier named GW-VIS was prepared using acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinylpyrrolidone (NVP), and nano calcium carbonate as raw materials through water suspension polymerization. This polymer gel can absorb water well at room temperature and has a small solubility. After a long period of high-temperature treatment, most of it can dissolve in water, increasing the viscosity of the suspension. The structure of the samples was characterized by infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy, and their performance was evaluated. Rheological tests indicated that the 0.5% water suspension had a consistency coefficient (k = 761) significantly higher than the requirement for clay-free drilling fluids (k > 200). In thermal resistance experiments, the material maintained stable viscosity at 180 °C (reduction rate of 0%), and only decreased by 14.8% at 200 °C. Salt tolerance tests found that the viscosity reduction after hot rolling at 200 °C was only 17.31% when the NaCl concentration reached saturation. Field trials in three wells in the Liaohe oilfield verified that the clay-free drilling fluid supported formation operations successfully. The study shows that the polymer gel has the potential to maintain rheological stability at high temperatures by forming a network structure through polymer chain adsorption and entanglement, with a maximum temperature resistance of up to 200 °C, providing an efficient drilling fluid for deep oil and gas well development. It is feasible to select nano calcium carbonate to participate in the research of high-temperature resistant polymer materials. Meanwhile, the combined effect of monomers with large steric hindrance and inorganic materials can enhance the product’s temperature resistance and resistance to NaCl pollution. Full article

Hot water drilling is a drilling method that employs high-temperature and high-pressure hot water jetting to achieve ice melting drilling. Characterized by rapid drilling speed and large hole diameter, it is widely used for drilling observation holes in polar ice sheets and ice shelves. Understanding the hole-enlargement process at the bottom of hot water-drilled holes is crucial for rationally designing the structure of hot water drills. However, due to the complexity of heat transfer processes, no suitable theoretical model currently exists to accurately predict this process. To address this, this paper establishes an experimental platform for hot water drilling and conducts 24 sets of experiments under different drilling parameters using visualization techniques. The study reveals the influence mechanisms of drilling speed, hot water flow rate, hot water temperature, downhole drill shape, and nozzle structure on the hole-forming process at the borehole bottom. Experimental results indicate that the primary hole enlargement occurs near the nozzle, achieving 69–81% of the theoretical maximum borehole diameter. The thermal melting efficiency at the borehole bottom is approximately 80%, with about 20% of the input hot water energy heating the surrounding ice. Under identical hot water parameters, jet shapes and drill shapes exhibit minimal impact on borehole geometry. But the improvement of the jet speed and hot water temperature can accelerate the hole-forming process. Full article

In this study, survey methods including seismic techniques and controlled-source audio-frequency magnetotelluric, drilling, and pumping tests were employed to investigate the geothermal systems and their formation mechanisms in northern Shanxi Province, China. The following characteristics were observed: (1) Geothermal resources in northern Shanxi Province are primarily located in Archean metamorphic rocks and fracture zone aquifer groups. The direct heat source is likely uncooled magma chambers in the middle-upper crust, whereas the overlying layers consist of Quaternary, Neogene, and Paleogene deposits. (2) The high-temperature geothermal system is of the convective-conductive type: atmospheric precipitation and surface water infiltrate pore spaces and fault fractures to reach thermal storage, where they are heated. Hot water then rises along the fracture channels and emerges as shallow hot springs, and ongoing extensional tectonic activity has caused asthenospheric upwelling. The partial melting of the upper mantle forms basic basaltic magma, which ascends to the middle-upper crust and forms multiple magma chambers. Their heat is transferred to the shallow subsurface, causing geothermal anomalies. (3) Borehole YG-1 findings revealed that these geothermal resources are primarily static reserves. Our findings provide a foundation for further geothermal development in the region, including the strategic deployment of wells to improve geothermal energy extraction. Full article

The sampling and observation of subglacial lakes play a vital role in studying the physical and chemical properties as well as the microbial characteristics of water within these Antarctic subglacial lakes. Compared to existing techniques, such as deep ice core drilling and clean hot water drilling, recoverable autonomous sondes, inspired by the spinning and reeling silk behavior of spiders, offer several advantages, including lightweight design, low power consumption, and minimal external pollution. Over the past six years, Jilin University, with support from the Ministry of Science and Technology of China, has developed an environmentally friendly sampling and observation system for Antarctic subglacial lakes, utilizing a recoverable autonomous sonde. The whole system includes a melting sonde, detection and control unit, scientific load platform, and ice surface auxiliaries. Extensive laboratory and joint system tests were conducted, both on key components and the complete system, including field tests in ice lakes. The results of these tests validated the feasibility of the underlying principles, the long-term reliability of the system operation, and the cleanliness of the drilling process. Ice penetration speed up to 2.14 m/h was reached with 6~6.5 kW melting tip power and a 660 mL lake water sample was collected. The relevant design concepts and technologies of the system are expected to play an important role in the clean detection and sampling of subglacial lakes in Antarctica, Greenland, and other regions. Full article

In recent years, global efforts toward sustainable energy have intensified, aiming to reduce carbon emissions and boost energy efficiency. Heating in winter and hot water for hygiene are essential, especially in cold climates where heating demands significantly impact household energy consumption. This study examines a city in western Inner Mongolia, characterized by a severe cold climate and unique geology. A test system with dual U-shaped buried pipes for ground source heat storage and extraction was constructed, utilizing two layout schemes. Drilling tests measured formation parameters, highlighting how pipe layout and soil characteristics influence heat storage. Short-term 5-day cycles and cross-seasonal 60-day cycles were tested. Results showed upper soil suited for frequent short-term storage, while lower soil favored long-term energy retention. Increasing buried pipes raised soil temperature and storage capacity, enhancing thermal stability in short-term cycles. However, while the long-term storage capacity improved, heat loss also rose. Effective ground source heat pump design in cold regions should consider environmental temperatures, pipe optimization, soil characteristics, and heat storage duration to achieve stable, efficient operation. Full article

Addressing the high friction and torque challenges encountered in drilling processes for high-displacement wells, horizontal wells, and directional wells, we successfully synthesized OAG, a high-temperature and high-salinity drilling fluid lubricant, using materials such as oleic acid and glycerol. OAG was characterized through Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The research findings demonstrate the excellent lubricating performance of OAG under high-temperature and high-salinity conditions. After adding 1.0% OAG to a 4% freshwater-based slurry, the adhesion coefficient of the mud cake decreased to 0.0437, and at a dosage of 1.5%, the lubrication coefficient was 0.032, resulting in a reduction rate of 94.1% in the lubrication coefficient. After heating at 200 °C for 16 h, the reduction rate of the lubrication coefficient reached 93.6%. Even under 35% NaCl conditions, the reduction rate of the lubrication coefficient remained at 80.3%, indicating excellent lubrication retention performance. The lubricant OAG exhibits good compatibility with high-density drilling fluid gel systems, maintaining their rheological properties after heating at 200 °C and reducing filtration loss. The lubrication mechanism analysis indicates that OAG can effectively adsorb onto the surface of N80 steel sheets. The contact angle of the steel sheets increased from 41.9° to 83.3° before and after hot rolling, indicating a significant enhancement in hydrophobicity. This enhancement is primarily attributed to the formation of an extreme-pressure lubricating film through chemical reactions of OAG on the metal surface. Consequently, this film markedly reduces the friction between the drilling tools and the wellbore rocks, thereby enhancing lubrication performance and providing valuable guidance for constructing high-density water-based drilling fluid gel systems. Full article

Gel plugging agents have become one of the preferred methods for plugging in complex and severe loss conditions during drilling due to their good adaptability to loss channels. To address the common issue of poor temperature resistance in gel-based plugging agents, high-temperature-resistant gel plugging materials were synthesized through the molecular design of polymers, modifying existing agents. Based on the temperature and salt resistance of the aqueous solution of an acrylamide (AM)/N-vinylpyrrolidone (NVP) binary copolymer, temperature-resistant monomer sodium styrene sulfonate (SSS) was introduced and reacted in a polyvinyl alcohol (PVA) aqueous solution. Using ammonium persulfate (APS) as an initiator and crosslinking with N,N-methylenebisacrylamide (MBA), a gel plugging material resistant to 140 °C was synthesized. The structure, thermal stability, water absorption and expansion, and plugging performance of the gel were studied through hot rolling aging, thermogravimetric analysis, infrared spectroscopy, electron microscopy scanning, sand bed experiments, and drag reduction experiments. The results show that the gel material has good thermal stability and water absorption and expansion at 140 °C, and its temperature-resistant plugging performance is excellent, significantly slowing down the loss rate of drilling fluid. This provides a basis for the further development of gel materials. Full article

Geothermal resources are a sustainable and valuable source of energy that offers considerable economic and social advantages. The present investigation centers on the accessibility of geothermal reservoirs in Reshi Town, Taoyuan County, Changde City, located in the Hunan Province of China. Geophysical exploration techniques are of paramount importance in the identification and exploration of geothermal resources. The present investigation utilized an integrated geophysical approach that incorporates induced polarization (IP), magnetotelluric (MT), and joint profile techniques. The primary objective of this study was to examine the distribution of formation lithology, subsurface electrical structures, karst fracture development zones, and the location and occurrence of deep and large thermal reservoirs in Reshi Town, Changde City. The research encompassed a comprehensive process that included the collection of data, its subsequent interpretation, inversion, and validation through drilling. The joint profile approach provided comprehensive data on fault structures within the study region. Using magnetotelluric sounding, areas with lower electrical resistance were found along lines L2, L3, and L4. This showed that thermal water reservoirs were underground. The induced polarization sounding method exhibited a distinct response to geothermal water, including minerals, suggesting the presence of a high-temperature geothermal reservoir, along line 1. Drilling operations carried out at two different locations, ZK01 on line L3 and ZK02 on line L4, confirmed the existence of underground hot water. The drilling findings have verified the existence of faults F3 and F4, which act as important channels for geothermal fluids. The present research offers a dependable geophysical foundation for the forthcoming development of geothermal resources in Reshi Town, and areas with similar geological conditions. Full article

Natural electric field frequency selection method was proposed by Chinese scholars in the 1980s on the basis of imitating the field observation method of the magnetotelluric method (MT). It can only measure the magnetotelluric field components of one or several frequencies on the surface to determine the existence of underground geological bodies. This method has played an important role in shallow groundwater exploration. This paper mainly discusses the application of frequency selection method in the exploration of underground hot water in the Maoyanhe Scenic spot, Zhangjiajie City, Hunan Province, in order to illustrate the effectiveness of the frequency selection method in water exploration. According to the situation of the construction site, nearly 20 geophysical prospecting survey lines of varying lengths were laid flexibly within the red line of the Maoyan River Scenic Spot. Firstly, three-frequency (170 Hz, 67 Hz and 25 Hz) measurements were carried out on each survey line to preliminarily determine the possible horizontal location of underground hot water. Secondly, in the vicinity of the low potential anomaly of the three-frequency curve, the fine measurement by using multi-frequency bipolar profile method was further carried out. The specific distribution of underground hot water was determined based on the principle of frequency domain sounding and the static effect characteristics of the electromagnetic method so as to provide a scientific basis for the drilling layout. Finally, the reliability of the frequency selection method is verified by two verification boreholes. The results indicate that the frequency selection method is one of the effective geophysical exploration methods in groundwater exploration. Full article

With the development of oil exploration, the number of complex situations encountered in the drilling process is continuously increasing. During the operation of large displacement and horizontal wells, the safe density window of drilling fluid is narrow in complex formations and the lost circulation problem is becoming increasingly prominent. This can easily cause the drilling fluid to enter the formation from inside the well through lost circulation channels, which will prolong the drilling cycle, increase drilling costs, affect geological logging, and could cause a series of malignant accidents (such as blowout, sticking of a drilling tool, borehole collapse, and well abandoned). According to the severity, common lost circulation can be classified into three types: fractured lost circulation, karst cave lost circulation, and permeability lost circulation. Currently, researchers are developing different types of lost circulation materials (LCMs) for various lost circulation situations. Compared with conventional lost circulation control methods, the polymer gel lost circulation control technique applies a three-dimensional cage-like viscoelastic body formed via the crosslinking reaction of polymer gels. These materials have strong deformability and can enter fractures and holes through extrusion and deformation without being restricted by lost circulation channels. They then settle in the lost circulation formation and form a plugging layer through a curing reaction or swelling effect. Among the polymer gel LCMs, high-temperature resistant polymer gels can either be used alone or in combination with other LCMs, bringing the advantages of adjustable gelation time, strong lost circulation control ability, and strong filtration ability of the plugging slurry. Moreover, they are suitable for the lost circulation control of microporous leaky layer and have limited influence on the performance of drilling fluids. Therefore, the high-temperature resistant polymer gel lost circulation control technique is increasingly becoming a hot spot in the research of LCMs nowadays. This paper summarizes the research progress into high-temperature resistant functional gels for profile control and water shutoff, lost circulation prevention and control, and hydraulic fracturing. Furthermore, the current application status of high-temperature resistant gels and high-temperature resistant gel temporary plugging agents is demonstrated, followed by a detailed overview of the gel-breaking methods. Overall, this research lays the theoretical foundation for the application and promotion of high-temperature resistant gels. Full article

As the laws of structure deformation and structural stress variation under freezing construction around high-rise buildings are not clear and no engineering experience can be referred to, freezing method construction in this situation is paired with huge safety risks. In this paper, freezing construction was successfully carried out around the main shaft tower in Chensilou Coal Mine by taking the following protective measures: symmetrical drilling, local freezing and hot water circulation. The elevation of the shaft tower foundation is continuously measured during the process of drilling, frost heaving and thaw settlement (hereinafter referred to as the DHS process). Benefiting from these protective measures, the maximum inclination value (−0.406 mm/m) of the shaft tower is controlled at well below the allowable value. The observation data informed the settlement and inclination of the tower foundation during the DHS process. A numerical model of the shaft tower is further established based on the observation data to reveal the tower structure’s law of stress variation during the DHS process. In addition, the fitting equation between the tower inclination value and the structural stress is obtained, which can provide a reference for freezing construction of similar high-rise buildings. Full article

The problem of wellbore stability has a marked impact on oil and gas exploration and development in the process of drilling. Marine mussel proteins can adhere and encapsulate firmly on deep-water rocks, providing inspiration for solving borehole stability problem and this ability comes from catechol groups. In this paper, a novel biopolymer was synthesized with chitosan and catechol (named “SDGB”) by Schiff base-reduction reaction, was developed as an encapsulator in water-based drilling fluids (WBDF). In addition, the chemical enhancing wellbore stability performance of different encapsulators were investigated and compared. The results showed that there were aromatic ring structure, amines, and catechol groups in catechol-chitosan biopolymer molecule. The high shale recovery rate demonstrated its strong shale inhibition performance. The rock treated by catechol-chitosan biopolymer had higher tension shear strength and uniaxial compression strength than others, which indicates that it can effectively strengthen the rock and bind loose minerals in micro-pore and micro-fracture of rock samples. The rheological and filtration property of the WBDF containing catechol-chitosan biopolymer is stable before and after 130 °C/16 h hot rolling, demonstrating its good compatibility with other WBDF agents. Moreover, SDGB could chelate with metal ions, forming a stable covalent bond, which plays an important role in adhesiveness, inhibition, and blockage. Full article

Northeast China is an area with high energy consumption and high carbon emissions, and the utilization of geothermal resources can effectively overcome these problems. However, there are few geothermal manifestations in Northeast China and no systematic method for geothermal exploration at present, which hinders the utilization of geothermal resources. Here, a systematic analysis, including hydrochemistry, petrology, isotopes, controlled source audio magnetotelluric sounding, drilling, and temperature curve of two boreholes was carried out to investigate the genesis of geothermal resources in Tonghe County, Northeast China, along the Yilan-Yitong lithospheric fault (YYF). We found that the geothermal water is alkaline Na-HCO₃ type water, is of local meteoric origin, and is recharged from the hilly area with an elevation of ~280 m around the study area. We established a geothermal water circulation path model: (1) cold water infiltrated along the YYF to a depth of 2–3 km, (2) cold water was heated by mantle heat, and (3) hot water was stored in sandstone/siltstone, forming a sandstone geothermal reservoir with a temperature of ~70 ℃. These results have important guiding significance for the scientific exploration of geothermal resources in Northeast China. Full article