Drilling Cycle Research Articles

Research Progress of High-Temperature Resistant Functional Gel Materials and Their Application in Oil and Gas Drilling.

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.

An Advanced Long Short-Term Memory (LSTM) Neural Network Method for Predicting Rate of Penetration (ROP).

Rate of penetration (ROP) is an essential factor in drilling optimization and reducing the drilling cycle. Most of the traditional ROP prediction methods are based on building physical model and single intelligent algorithms, and the efficiency and accuracy of these prediction methods are very low. With the development of artificial intelligence, high-performance algorithms make reliable prediction possible from the data perspective. To improve ROP prediction efficiency and accuracy, this paper presents a method based on particle swarm algorithm for optimization of long short-term memory (LSTM) neural networks. In this paper, we consider the Tuha Shengbei block oilfield as an example. First, the Pearson correlation coefficient is used to measure the correlation between the characteristics and eight parameters are screened out, namely, the depth of the well, gamma, formation density, pore pressure, well diameter, drilling time, displacement, and drilling fluid density. Second, the PSO algorithm is employed to optimize the super-parameters in the construction of the LSTM model to the predict ROP. Third, we assessed model performance using the determination coefficient (R 2), root mean square error (RMSE), and mean absolute percentage error (MAPE). The evaluation results show that the optimized LSTM model achieves an R 2 of 0.978 and RMSE and MAPE are 0.287 and 12.862, respectively, hence overperforming the existing methods. The average accuracy of the optimized LSTM model is also improved by 44.2%, indicating that the prediction accuracy of the optimized model is higher. This proposed method can help to drill engineers and decision makers to better plan the drilling operation scheme and reduce the drilling cycle.

Effects of a polyamine inhibitor on the microstructure and macromechanical properties of hydrated shale

China is rich in shale gas resources; however, wellbores in shale gas reservoirs are frequently unstable. This has a serious impact on the shale gas drilling cycle. Polyamine, a common additive in water-based shale drilling fluids, can effectively inhibit shale hydration. However, there is a lack of quantitative research on the effect of polyamine inhibitors on the microstructure and macromechanical properties of shale. Therefore, this study investigated those issues via a systematic hydration experiment carried out on shale from the Longmaxi Formation. The results show that microfractures are created and expand during shale hydration, that they also connect to form a complex microfracture network, and that 3% polyamine inhibitors (polyamine solution with volume fraction of 3%) can effectively inhibit their evolution. The ultrasonic velocities and UCS of the Longmaxi shale are significantly anisotropic; the former first increases and then decreases with the laminae angle, reaching its maximum when the laminae angle is 30°. The UCS of the shale is highest and lowest, respectively, when the laminae angles are 0° or 90° and 30°. In general, these UCS appear as a “U" pattern, high on two sides with a dip in the center. Polyamines can effectively inhibit both the expansion of shale and the reduction of P-wave and S-wave velocities, the UCS, and elastic modulus. The UCS of a shale sample was reduced by 28%–40% after immersion for 96 h in water, compared to 2%–20% after immersion in a 3% polyamine inhibitor for the same amount of time. The inhibiting effect of the polyamine was remarkable.

Research and Practice of Risk Early Warning Technology for Lost Circulation with Drilling under the Conditions of Geological Engineering Information Fusion: The Example of the Yuanba Area

In the Yuanba area, many lost circulation accidents occur due to the complex geological structure, broken strata, and developed fractures, which seriously affect construction safety and drilling costs. Therefore, the Yuanba district is the focus of this paper. Firstly, a three-dimensional geomechanical model is established through multi-source information fusion to identify the main geological risk factors of lost circulation, according to the data on drilling and well logging in the operation area. Then a risk warning model and evaluation methods for loss circulation, based on geological engineering data fusion, are established, through which the characteristic parameters of various loss of circulation risks can be calculated in real time, parameters along the well trajectory can be extracted and compared, and thus, the risk of lost circulation is warned and analyzed in real time. The early warning of lost circulation risk can be achieved during drilling operations, which can improve the drilling efficiency and shorten the drilling cycle as a result.

Drilling speed-up and production-increasing development practice of ultra deep clastic reservoir based on Geology-Engineering integration in the Tarim Basin, Northwest China

Kelasu structural belt in Tarim Basin has a large reservoir burial depth and complex geological conditions, and challenges such as ultra-deep, high temperature, high pressure, and high stress lead to big problems related to well control safety and project quality. To solve these key technical problems that set barriers to the process of exploration and development, a set of drilling technology processes via geology-engineering integration is established with geomechanics as the bridge. And an integrated key drilling engineering technology for the safe speed-up of ultra-deep wells was formed, integrating well location optimization, well trajectory optimization, stratum pressure prediction before drilling, stratum drillability evaluation, and bit and speed-up tool design and optimization. Combined with seismic data, logging data, structural characteristics, and lithology distribution characteristics, the rock mechanics data volume related to the three-dimensional drilling resistance characteristics of the block was established for the first time, and the vertical and horizontal heterogeneity was quantitatively characterized, which provided a basis for bit design, improvement, and optimization. During the process of drilling, the geomechanical model shall be corrected in time according to the actual drilling information, and the drilling “three pressures” data shall be updated in real-time to support the dynamic adjustment of drilling parameters. Through field practice, the average drilling complexity rate was reduced from 18% to 4.6%, and the drilling cycle at 8500 m depth was reduced from 326 days to 257 days, which were significantly better than those of the vertical wells deployed in the early stage without considering geology-engineering integration.

Sensor-based strategies for accurate prediction of drilled hole surface integrity of CFRP/Al7075 hybrid stack

The airplane structure is often made up using carbon fiber reinforced plastic (CFRP) stacking with a metallic sheet to improve excessive load carrying and shock-absorbing capability with reduced fuel economy. It is a challenging task to drill dissimilar CFRP-Al metallic stack because the hot continuous metallic chip mutilates the hole surface in addition to drilling-induced delamination. The present work addresses the parametric effect on delamination, roughness, and circularity error of the drilled hole along with chip morphology using different drill geometry on the fabricated CFRP [0°/-45°/90°/45°]2s stack over an aluminum 7075 sheet. A drill tool dynamometer was used to capture axial thrust with associated torque variations during drilling which were further used in process monitoring. The most critical unlike interface drilling has been scrutinized using instantaneous force-torque slopes along with scanning electron micrographs. The machining time loss during CFRP→Al interface drilling has also been processed. Finally, a comparative assessment has been made on the predictability of hole quality features among various sensor-based strategies using response surface methodology. The drilled-hole surface quality was significantly improved at high spindle speed (2250 rpm), and low feed rate (0.025 mm/rev) using a low drill point angle (110°). The thrust force was found to be a prime indicator of drilled hole integrity than torque whereas peak torque and its slope in the initial stages of the drilling cycle strongly correlated with surface delamination. The top surface delamination was somewhat severe (≥ 1.6) at high drill thrust (≥ 40 N) with high torque (≥ 0.45 Nm).

Development of a generator for percussive ultrasonic drills used in asteroid exploration based on impedance characteristics analysis

Percussive ultrasonic drills participate in asteroid exploration missions. Since space environments are complex and working loads vary dramatically, it is necessary to design a drive that better matches the percussive ultrasonic drill to make it achieve high-speed drilling with low power consumption. Impedance characteristics under different load conditions and the load varying in one drilling cycle are investigated based on analyzing the working principle of the percussive ultrasonic drill. An ultrasonic drill driver with automatic scanning resonant frequency and digital phase-locked loop frequency tracking control is designed according to the load characteristics. Series capacitance impedance matching ultrasonic drills is experimentally studied. Vibration amplitude and impedance characteristics of the ultrasonic drill driven by the designed driver are measured to evaluate the frequency tracking ability and the impedance matching. Finally, ultrasonic drilling experiments are conducted in room, low, and high temperature environments to investigate the driving performance. Under room temperature and 5 N drilling pressure, the speed of ultrasonic drilling into soft sandstone is 52 mm/min, and the power consumption is less than 70 W. The experimental results indicate that the designed driver can drive the percussive ultrasonic drill to achieve stable and high-speed drilling with low power consumption and low drilling pressure.

Geology-engineering integration to improve drilling speed and safety in ultra-deep clastic reservoirs of the Qiulitage structural belt

The Qiulitage structural belt in Tarim Basin has a large reservoir burial depth and complex geological conditions. Challenges such as ultra-depth, high temperature, high pressure and high stress lead to significant problems related to well control safety and project efficiency. To solve these key technical issues that set barriers to the process of exploration and development, a drilling technology process via the integration of geology and engineering was established with geomechanics as the bridge. An integrated key drilling engineering technology was formed for improving the drilling speed and safety of ultra-deep wells, including well location optimization, well trajectory optimization, formation pressure prediction before drilling, stratum drillability evaluation, and bit and speed-up tool design and optimization. Combined with the seismic data, logging data, structural characteristics, and lithology distribution characteristics, a rock mechanics data volume related to the three-dimensional drilling resistance characteristics of the block was established for the first time. The longitudinal and lateral heterogeneities were quantitatively characterized, providing a basis for bit design, improvement and optimization. During the drilling process, the geomechanical model was corrected in time according to the actual drilling information, and the drilling “three pressures” data were updated in real time to support the dynamic adjustment of drilling parameters. Through field practice, the average drilling complexity rate was reduced from 18% to 4.6%, and the drilling cycle at 8,500 m depth was reduced from 326 days to 257 days, which comprised significant improvements compared to the vertical wells deployed in the early stage without considering geology-engineering integration. Cited as: Chen, C., Ji, G., Wang, H., Huang, H., Baud, P., Wu, Q. Geology-engineering integration to improve drilling speed and safety in ultra-deep clastic reservoirs of the Qiulitage structural belt. Advances in Geo-Energy Research, 2022, 6(4): 347-356. https://doi.org/10.46690/ager.2022.04.09

Modeling Evolution of Cutting Force in Ultrasonically Assisted Drilling of Carbon Fiber Reinforced Plastics.

In this study, the effects of process parameters (feed rate, spindle speed, and ultrasonic power level) on the cutting force and delamination in the ultrasonic vibration-assisted drilling of carbon fiber-reinforced plastics (CFRPs) have been investigated. A series of drilling tests under various conditions defined by the design of experiment technique were conducted. The evolution of the cutting force during drilling cycles was measured and analyzed. Experimental analysis results based on the Taguchi method and analysis of variance show that the spindle speed is an influential factor affecting the cutting force with a contribution of 75.36%, and the feed rate significantly affects the delamination damage with a contribution of 46.57%. In addition, the cutting force was found to increase with drilling cycles at different rates, which depends on the process parameters used in drilling. The evolution behavior of cutting force was well fitted based on the process parameters by proposed regression models. Experimental validation indicates that the predicted forces show reasonable agreement with measured values under different conditions and reveal good prediction performances, with a root mean square error of 5.6 and a mean absolute percentage error of 5.8%. In drilling tests with variable cutting conditions, the evolution of the cutting forces predicted based on the selected parameters was successfully verified when compared with the measured results, with RMSE and MAPE values of 7.55 and 5.61%, respectively. As a conclusion, this predictive model provides an effective basis for selecting appropriate drilling parameters to suppress the cutting force on CFRP composites.

Study on intelligent prediction method of rock drillability based on Bayesian lithology classification and optimized BP neural network

With the rapid development of shale gas in northeastern Sichuan province, problems such as low drilling rate, long drilling cycle and serious bit wear are becoming more and more prominent in shale gas drilling process. This paper proposes new prediction theory with two steps based on logging data sensitive to lithology by introducing Bayesian classifier and Self Adaptive Double Chain Quantum Genetic Algorithm (S-DC-QGA) which could optimize BP neural network prediction model. In the first step, the Bayesian network classifier achieved the classification and recognition of lithology, improved the correlation of model sample data, and enhanced the accuracy and speed of lithology classification. In the second step, S-DC-QGA characterized as the global optimization is used to optimize the number of hidden layer nodes, weights and thresholds of the BP neural network. Results showed that Bayesian lithologies classification enhanced the correlation of samples, moreover optimized BP neural network solved overfitting, random initial weights of BP itself and oscillation of fitting and generalization ability with slight change of network parameters, improving the prediction accuracy of rock drillability parameters and the generalization ability of the model. The findings of this study can help for better drilling design and improvement of mechanical drilling speed.

An Experiment-Based Study of Formation Damage Using a Microetching Model Displacement Method.

In the field of oil and gas exploration, drilling fluid is regarded as the essential “blood” for drilling, which mainly helps to control the formation pressure and remove cuttings from the well. During the drilling fluid cycle, the drilling fluid penetrates into the pores of the formation rock, thus blocking the rock pores and resulting in a decline in oil and gas recovery efficiency. Therefore, it is very important to understand the microscopic mechanism of formation damage caused by drilling fluid. However, as an important component of formation damage, the microscopic mechanism of fluid damage has not yet been clearly revealed. In this study, a new microetching model (MEM), along with displacement equipment, was designed. The pore network of rock samples was extracted from thin-section images and etched to a thin aluminum sheet by laser. Oil-based drilling fluid was used to displace the stratum water in the MEM. The displacement process was recorded by a camera and analyzed. A core flooding experiment, permeability measurement, and SEM observations were performed. The results show that, for low-porosity and low-permeability sandstone, the main forms of formation damage by drilling fluid include solid damage and liquid damage. Solid damage is mainly caused by the blockage of small pores and narrow throats with solid particles of the size 0.1~30.0 μm in drilling fluid, while liquid damage is mainly caused by the water lock and hydrocarbon lock effects formed by the oil–water two-phase interface, gas–water two-phase interface, or the oil–gas–water three-phase interface.

The posibility analysis of high-pressure drilling in Block A in Field F

The drilling and shut-in regulations for peripheral oil fields currently follow the standard of the old area of placanticline, i.e., the wellhead pressure of water injection wells within 600m of the drilling well is reduced to below 3MPa before drilling. The regulations did not take into account the depth of the target formation, structural development, reservoir properties and oil and water well connectivity in the peripheral oilfield, which made it difficult to relieve pressure in most of the wells and resulted in longer drilling and shut-in cycles and greater impact on production. In order to minimize the impact of drilling and shut-in on field development and to explore drilling and shut-in limits and standards suitable for peripheral fields, drilling tests were conducted in Block A for infill wells. The feasibility of high pressure drilling in the peripheral low permeability oilfield was analyzed by analyzing the drilling site conditions, the quality of post-completion cementing and the logging data of the completed wells under different pressure conditions.

High power water jet guided laser drilling of angular holes through nickel superalloy

This paper investigates the basic characteristics of water jet guided laser drilling process using a high power laser with a maximum average power of 400 W to drill 0.7 mm diameter angular holes (60° to the surface) through 1.6 mm thick nickel superalloy (resultant hole length of 1.85 mm). Experimental trials were performed using average powers of up to 148 W to understand the effect of different process parameters on the hole quality and cycle time. Process parameters investigated included shielding gas flow rate, water jet pressure, trepanning speed, pulse frequency, and average power. The results found water jet pressure and average power to be significant in controlling the recast layer thickness and drilling cycle time. At higher power and throughput, average recast layer thicknesses of ∼30 μm could be obtained with a cycle time of 3 seconds. This surpasses the quality of holes, which can be produced via state-of-the-art laser drilling techniques without a significant reduction in productivity.

Modeling and Simulation of Rock Bits Based on Mega Drilling Data

Rock bits directly undertake the task of fracturing rock under earth during drilling operation. Accurate prediction of Rate of penetration (ROP) play an important role in reducing drilling costs and shortening the drilling cycle. This paper introduces ROP prediction methods including empirical mathematical modeling, computer simulation of bit-rock interaction and BP neural network model based on mega drilling data. The most significant factors affecting ROP are summarized as follows: weight on bit(WOB), rotation speed, rock formation properties, bit cutting structure, etc., which have a complex multi-parameter nonlinear relationship with ROP. The drilling data features complexity and big volume. Therefore machine learning is a best way to model the relationship between main factors and ROP. The advantages and disadvantages of the different ROP modeling methods are analyzed and compared. It shows that the BP neural network model based on mega drilling data demonstrates high accuracy, and is the future development direction in ROP prediction.

Well Profile Optimization and Drilling Matching Technology of for Horizontal Wells in Sulige Gas Field

The tight gas reservoir in Sulige Gas Field is deeply buried, the problem of formation and leakage during drilling is prominent, and the penetration rate is low. The early horizontal wells adopt the conduit+third wellbore structure, which makes it difficult to achieve the purpose of continuously increasing drilling speed and reducing drilling cost. Analyze that problems exist in the well structure of conduit+third spudding, On the basis of stratum 3 pressure profile, leakage and wellbore stability, and improvement of penetration rate, the optimization idea and feasibility analysis of wellbore structure were carried out, the sealing section was optimized, the wellbore size was optimized, and the second spudding wellbore structure of slim hole was formed. Based on this wellbore structure, the key drilling matching technologies, such as well trajectory control, optimization of personalized drill bits and matching speed-up tools, and optimization of segmentation measures of drilling fluid with strong inhibition and high efficiency lubrication, were studied. The field application proves that the research results are effective, which solves the problem of collapse and leakage coexist, while leakage occurs at the top and occurs at the bottom in long open hole sections, improves the penetration rate of each well section, and greatly shortens the drilling cycle. The field application results show that the structural design of the second spudding of slim hole is reasonable, and the matching drilling technology has been remarkable speeded-up, which can be popularized and applied in horizontal well drilling in Sulige gas field.

Improving drilling speed and borehole quality in ultra-deep complex formations through rock mechanics research

Halahatang oilfield in Tarim Basin is a typical ultra deep fractured vuggy carbonate reservoir, which is the main production area of crude oil in Tarim Basin. The wellbore instability is serious in Triassic and lower strata (the borehole enlargement rate is 22% - 31%). Due to the complex rock characteristics, the drilling cycle for single well is long (124 days on average), and it is difficult to speed up. Based on the log interpretation curves, the calculation methods of pore pressure, collapse pressure and fracture pressure profiles established, and the spatial distribution characteristics of three pressures in this area were analysed; The rock drillability, rock hardness, compressive strength and abrasiveness of the roller bit and PDC bit single well measured by laboratory tests. Based on the statistical regression method, the relationship between the above drilling rock mechanical parameters and logging acoustic time difference and the formation drillability profile single were studied. The research results guide the drilling design optimization and operation of 15 wells in Ha 8 and Ha 12 blocks, The average drilling cycle is reduced by 21% (from 124 days to 98 days), and the hole enlargement rate is reduced from 24% to less than 10%.

Wellbore stability mechanism of igneous rock in Shunbei block

Shunbei area is located in the belt structural of the northern margin of the shuntuogole low uplift. The proven oil reserves of the adjacent blocks are 142.93 million tons, which has the potential of exploration and development. In the igneous strata of Shunbei block, there are many complicated conditions, such as wellbore collapse, stucking pipe and so on, which seriously restrict the exploration and development speed and benefit of the block. In order to solve this problem, firstly, the composition, microstructure, mechanical properties and other parameters of igneous rock intrusion in Shunbei block are determined through laboratory experiments. The experimental results show that the igneous rock intrusion in Shunbei block does not contain expansive clay minerals, has weak hydration ability, and has developed micro fractures. Thirdly, the wellbore stability model considering fractures is established, and the influencing factors of wellbore instability are analyzed by combining the mechanical properties of igneous rocks, porosity and permeability characteristics, and in-situ stress state. The results show that the micro fractures and weak surfaces have a controlling effect on wellbore stability. The longer the immersion time is, the deeper the drilling fluid invasion depth is, and the higher the wellbore collapse pressure is. Finally, according to the microstructure and physicochemical properties of igneous intrusions, the main points of drilling fluid technology are determined, that is, the anti sloughing drilling fluid technology is mainly strong plugging. In this paper, through the analysis of the rock characteristics of igneous rocks and the main controlling factors of wellbore instability mechanism in Shunbei block by using the method of mechano-chemical synthesis, the clear main controlling factors of wellbore stability are of positive significance for ensuring the safe well construction, shortening the drilling cycle, reducing the drilling cost and improving the development efficiency in Shunbei block.

Key Technologies for Deep Horizontal Well Drilling of Shale Gas in Luzhou of Sichuan Basin

The drilling of deep shale gas horizontal wells in Luzhou block of Sichuan Basin has been chanllenged by long drilling cycle, low rate of penetration (ROP), high drilling tool vibration, poor drillability of special lithological formations, horizontal wellbore instability, high formation temperature, and high friction torque and sticking risk etc.. To solve these problems and to ensure operation safety and increase cost-efficiency, technological research was carried out on casing program design of horizontal wells, wellbore trajectory control and optimization of horizontal sections. As a result, the optimal parameters of the radical drilling method were recommended, and shock absorption, speed-up, and high efficient rock breaking technologies for special lithological formations were preferentially adopted. In addition, drilling fluid system and performance parameters were recommended based on pilot tests of ground cooling equipment. In this way, key drilling technologies with high operation safety and efficiency were formed for the deep shale gas horizontal wells in Luzhou block. Through the application of the key technologies in four wells in Luzhou block, the experimental results show that the drilling cycle was redcued by 14.5% and no downhole failure was reported for average well depth of 5,601.00 m and the horizontal section length of 1,884.00 m. So these technologies can meet the requirement of safe and efficient drilling as well as wide application scope in Luzhou.

Optimized and Fast Drilling Technologies for Horizontal Shale Oil Wells in the Cangdong Sag

During the drilling of horizontal shale oil wells in the Cangdong Sag, the low ROP (Rate of Penetration), high safety risk, and uncertain cementing quality impeded the efficient exploration and development of shale oil. To address these problems, investigations were implemented on the detailed prediction of formation leakage pressure and collapse pressure. They were then carried out the optimization of casing programs and borehole trajectories and the personalized design of PDC bits. Further, the matching technologies such as brine drilling fluid, rotary steering drilling, ductile cement slurry, and floating displacement cementing were integrated, forming an optimized and fast drilling technology for the horizontal shale oil wells in the Cangdong Sag. This technology was applied in 20 horizontal shale oil wells in the Cangdong Sag, and the cementing quality was improved by 30.4%. For the wells with a depth of more than 4 500.00 m, the average ROP increased by 20.2%, and the average drilling cycle was shortened by 30.6%. For wells with a depth of lower than 4 500.00 m, the average ROP increased by 82.9%, and the average drilling cycle was shortened by 49.9%. These results demonstrated that the proposed technology could meet the requirement for the optimized and fast drilling of horizontal shale oil wells in the Cangdong Sag, providing a technical means for the efficient exploration and development of horizontal shale oil wells and also a reference for the drilling technology optimization of unconventional oil and gas reservoirs in the oilfields of China.

ROP Improvement Technologies for Large-Cluster Horizontal Shale Oil Wells in the Changqing Oilfield

Large frictional torque, backpressure during slide drilling, low rate of penetration (ROP), poor recognition of reservoirs by geosteering, and other problems are encountered during the drilling of large-cluster horizontal shale oil wells in the Changqing Oilfield. In this regard, this paper studied the multi-layer layout of large-cluster horizontal wells, large offset design, three-dimensional well trajectory control technology, and drilling tools for ROP improvement. Technical breakthroughs were made in the optimized deployment of well patterns/sequences, the anti-collision design between dense well group trajectories, the completion of horizontal well in one trip, the evaluation and accurate control of reservoirs while drilling, and the safe drilling in water injection areas,etc. Finally, the ROP improvement technologies for large-cluster horizontal shale oil wells in the Changqing Oilfield were developed. The field tests of the technologies were carried out in large-cluster well platforms, the Platform Hua H40 and the Platform Hua H60. The maximum number of horizontal wells in the well clusters was 22, with an average drilling cycle of 18.9 d, which was shortened by 7.5% after using the technologies. The research and field application demonstrate that the ROP improvement technologies for large-cluster horizontal wells have realized the large-scale development of shale oil in the Changqing Oilfield, promoting the construction of the Longdong National Shale Oil Demonstration Base.