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Chinese Content
Abstract217)      PDF (576KB)(391)      
2023, 46 (3): 200-.
Field Test and Evaluation of Non-sequential Fracturing Technology in Horizontal Wells
ZHU Juhui
Abstract211)      PDF (2986KB)(227)      
Due to strong heterogeneity between horizontal well sections or encounter faults, large natural fracture zones during drilling, casing deformation of shale gas wells in Sichuan Basin often occurs, which will result in conventional mechanical segmentation tools cannot pass through the casing deformation section, posing a huge challenge to the efficient stimulation of shale gas horizontal wells. To this end, a non-sequential fracturing process suitable for unconventional oil and gas reservoir horizontal wells is proposed. This process is different from the traditional sequential fracturing from target B in the horizontal section to target A, but instead achieves cluster perforation and fracturing at any position of the horizontal segmented reconstruction well section, and the entire well section can be temporarily sealed after each fracturing. For well sections that may be at risk, it is recommended to avoid them and fracturing the normal well section first, and then fracturing the risky well section. For horizontal sections affected by faults or casing wells, highly targeted solutions are provided. Taking the A1 well of shale gas in southern Sichuan as an example, on-site experiments verified the feasibility of non-sequential fracturing technology for horizontal wells, and to some extent, the negative impact of large fracture zones on the volume of stimulation was reduced, effectively avoiding repeated coverage of the stimulation area. In addition, the minimum outer diameter of the tool string used in this process is only 79 mm, which is also adaptable and targeted for the casing transformation well section. It can be a beneficial supplement to the plug segmentation process and has broad promotion and application value. 
2023, 46 (4): 51-56.
Application of Low Friction Cementing Technology in Changqing Oilfield Ultra-long Horizontal Well
ZHU Hong, LI Bo, LUO Yanqing, DONG Zhiming, JIANG Min
Abstract157)      PDF (3412KB)(201)      
Well Hua H90-X belonging to shale oil platform H90 of Changqing Oilfield,is a horizontal well with horizontal length more than 5 000 m,its completion drilling depth is 7 339 m and the horizontal section length is 5 060 m,setting the longest horizontal well record in the new Asia-Pacific onshore oil well. There are many difficulties such as high flow friction of cement slurry,high operation pressure,complex three-dimensional trajectory of well bore,and easy accumulation of cement slurry with sand to block the annulus in the ultra-long horizontal section of the well. Therefore,a low friction cementing cement slurry system is developed to reduce the friction generated during the cementing process and ensure operation safety and cementing quality. The friction of 1. 35 g / cm 3 pressure-resistant low friction system is 20. 39% lower than that of expanded perlite,which increases the compressive strength of cement stone. The friction of low friction tail slurry is 27. 75% lower than that of high strength and toughness tail slurry,so as to ensure the compactness of cement stone and improve the cementation quality of cement stone. Through software simulation the parameters are optimized,the maximum displacement construction pressure is 28 MPa,which is 6 MPa lower than the average construction pressure of the same well type cementing construction in the same block,and the bump operation pressure is reduced by 20. 6% ,effectively reduce the risk of leakage and further improve the cementing quality.
2023, 46 (2): 21-26.
Chinese Conent
Abstract141)      PDF (1152KB)(284)      
2023, 46 (2): 190-.
Influence of Metal Casing on Downhole Electromagnetic Wireless Transmission
WU Yan , WANG Furong , HAN Xiong , WANG Xiao , PANG Dongxiao , CHEN Qing
Abstract135)      PDF (1457KB)(264)      
Electromagnetic wave wireless transmission technology can realize real-time transmission of downhole data to the surface,so that the workers on the surface can obtain formation parameters in time. However,due to the influence of downhole casing,the electromagnetic wave signal received from the surface is much weaker than the signal transmitted from open hole. Through the impedance analysis of the wireless transmission channel of electromagnetic waves in cased wells,it is clarified that the key mechanism of the transmission difficulty of cased wells lies in the impedance distribution of the electromagnetic wave transmitting antenna. On this basis,a coupling model of casing and tubing is established,a new distribution parameter calculation method is proposed to calculate the distribution parameters of the coupling model,and the results are verified by simulation. At the same time,the penetration coefficient is defined to quantitatively describe the influence of the casing on the electromagnetic signal transmission,such as the length of the transmitter,the signal frequency and the physical parameters of the pipe string,and the field test results prove the reliability of the penetration coefficient. The analysis results obtained can be used for the improvement and optimization of electromagnetic wave wireless transmission systems,which are of great significance for enhancing signal stability and increasing transmission depth. 
2023, 46 (2): 1-7.
Analysis of BTR Managed Pressure Drilling in Deepwater Platform
LIU Shujie , WU Yanhui , ZHAO Peng
Abstract130)      PDF (2162KB)(182)      

Narrow density window, simultaneous leakage and influx, high temperature and high pressure have become the difficult problems faced by and to be solved urgently for realizing safe and efficient drilling in deep water drilling. The managed pressure drilling technology has achieved good application effect on land and shallow sea in China, but the research on this technology and equipment system has not been systematically carried out in the domestic deep-water field. Based on the investigation and analysis of the drilling engineering needs of a work area in the South China Sea, this paper proposes the deep-water managed pressure drilling technology below the tension ring, and describes the deep-water managed pressure drilling riser pipe system and managed pressure drilling platform manifold system from the aspects of system composition and function; the comparison and analysis are made between the jack-up platform and the floating platform in terms of the working state of the platform, the deployment sequence of the riser system of the managed pressure drilling, and the characteristics of the drilling fluid circulation; taking the bottom hole pressure as the research objective, the simulation calculation of the influence of rig heave, large displacement drilling, booster injection / throttling parameters and other factors on it were carried out. On this basis, it is pointed out that China′s deep-water managed pressure drilling should carry out key research from the aspects of technology, bottom hole pressure fluctuation mechanism and control methods, and real-time hydraulic calculation software development to enrich China′s deep-water drilling technology, meet the needs of deepwater drilling projects, and help efficient exploration and development of deep-water oil and gas resources. 

2023, 46 (4): 1-6.
Study on the Gas Flow Law of Ground Nitrogen Extraction Operation
XU Qicong , , LI Zhongquan , YAO Shun
Abstract129)      PDF (1989KB)(216)      
Nitrogen drilling and completion of reservoirs is one of the revolutionary technologies for effectively utilizing reserves and releasing production capacity in low-permeability gas reservoirs such as tight sandstones. During the nitrogen drilling and completion operation of the reservoir, the wellhead is in an open state during the tripping and completion of the well string. At this time, it is necessary to use the wellhead nitrogen suction technology to control the flow of natural gas produced by the formation to the outlet of the sand discharge pipeline for treatment. Therefore, based on numerical simulation methods, the article systematically studied the gas flow law during nitrogen suction operation under open well conditions, considered the diffusion phenomenon of natural gas, established a gas flow model, and quantitatively analyzed the main factors affecting the nitrogen suction effect. Research has shown that the effectiveness of nitrogen suction is mainly influenced by injection method, nitrogen suction volume, installation position of suction device, length of sand discharge pipeline, and natural gas production. The concentric injection method has better suction effect compared to the oblique insertion injection method; under low suction volume, the larger the nitrogen injection volume, the higher the suction rate. As the suction volume continues to increase, the suction rate reaches its peak and then decreases; the closer the suction device is to the outlet of the sand discharge pipeline, the shorter the sand discharge pipeline, and the lower the gas production of the formation, the better the suction effect, and the lower the critical suction volume required to achieve complete suction. The research results provide theoretical support for optimizing the design of nitrogen suction process and ensuring safe operation under open well conditions for nitrogen drilling and completion in reservoirs. They have been applied on-site in Sichuan Datachang Gas Field, achieving 100% suction of natural gas produced in the formation under open well conditions for nitrogen drilling and completion in reservoirs, ensuring operational safety. 
2023, 46 (3): 1-8.
Design and Field Test of Special-Shaped Cutter PDC Bit in Gravel Layer
YAN Hui , LI Ning , YANG Junqi , CHEN Long , TANG Pengwei , JIANG Jiaguo
Abstract126)      PDF (3417KB)(232)      
The gravel layer of Kuqa Piedstone in Tarim Basin is developed, with high gravel content, large particle size, high compressive strength and poor drillability in Bozi block, which are the key factors resulting in low drilling efficiency and complex drilling accidents. In this paper, the formation lithology characteristics, drilling characteristics and failure mode analysis of the large gravel layer in the fore-salt section are carried out, and on the basis of this, the special-shaped cutter structure design of the PDC bit, the optimization of cutters layout and rock breaking efficiency are studied, and the design scheme of the special-shaped tooth PDC bit with strong impact resistance and aggression is formed. The design scheme not only improves the anti-impact but also improves anti-eddy performance and the rock breaking efficiency of PDC special cutter bit, which effectively expands the application range of PDC special-cutter bit in gravel layer. This bit has been tested in the high gravel layer of Kuqa Piedstone and achieved excellent application results. The single bit footage reaches 545 m, the average ROP is 4. 72 m/ h, compared with the PDC bit used for this formation in the same adjacent well, the single bit footage increased by 35% , the average ROP by 55% , it successfully solved the problems of low ROP and short footage of single bit in Kuqa formation and other formations. 
2023, 46 (3): 9-15.
Experimental Research on Response Characteristics of PDC Bit in Fractured Formation While Drilling
MAO Min , YANG Yi , ZHANG Ligang , , JI Jianfei , XUE Dongyang , LI Hao , , MIAO Zhenhua , TAN Jiaxing
Abstract120)      PDF (2007KB)(247)      
Fractured reservoirs are characterized by strong heterogeneity and anisotropy,which makes it difficult to predict fractures. It is the key to identify fractured reservoirs while drilling to clarify PDC bit drilling response characteristics. The cement stone specimens with no fracture,filled fracture and open fracture parameters were prepared,and used these specimens into micro-PDC bit drilling experiment. The direct parameters,such as weight on bit,rotation speed,torque and drilling time,were monitored during drilling of cement specimens with different fracture types. The derived parameters such as mechanical specific energy,mechanical specific energy anomaly factor,mechanical specific energy fluctuation factor and torque fluctuation factor were calculated. The drilling response characteristics of PDC bits with different fracture types were revealed. The characteristic map,evaluation index system and classification standard of different fractures were constructed. It has been applied in the Bozhong 19-6 gas field,and the coincidence rate with drilled logging interpretation reached more than 82% . This research results provide a basis for the identification and diagnosis of fractured reservoirs while drilling.
2023, 46 (1): 1-7.
Abstract114)      PDF (546KB)(162)      
2023, 46 (4): 200-.
Chinese Content
Abstract111)      PDF (1260KB)(181)      
2023, 46 (4): 201-.
Research and Application of Safe Slimhole Drilling Technology for Deep Well with Ultra-large Annulus: A Case Study From Plenglai Gas Filed of Sichuan Basin
LIU Deping, DAI Rui, PENG Cong, SUN Zheng, YANG Can, LIN Kang, CAI Gang
Abstract106)      PDF (1280KB)(254)      
Due to the strong reservoir heterogeneity in Sichuan-Chongqing area,in order to increase the means of handling downhole complexities in deep and ultra-deep well sections,a stand-by casing is often used during well design to block out potentially complexities,of which handling is more difficult. If the drilling operation is relatively smooth and the stand-by casing is not utilized,the drilling and completion method for deep slimhole well with ultra-large annulus will be implemented. If the drilling mud density window of target formation is narrow, easily causing leak and collapse,and it′s difficult to deal with,therefore,stuck pipe is likely to occur. To ensure the safe drilling of this kind of well,taking well DB-1 in Penglai gas area as an example,in this paper the difficulties of slimhole drilling for well with ultra-large annulus were analyzed,which includes poor well cleaning,difficulty in loss prevention and treatment and easy stuck pipe,and the technical solutions of this technology has been researched. The safe slimhole drilling technology for deep well with large annulus suitable for DB-1 well is formed through optimization of drilling parameters,drilling fluid properties and study of slimhole drilling supporting technologies. Through field application,it is proved that safe slimhole drilling and completion has been realized in well DB-1,and the drilling task of this well has been successfully completed,which has a good guiding significance for the safe drilling of similar Wells.
2023, 46 (2): 15-20.
Chinese Content
Abstract105)      PDF (1133KB)(321)      
2023, 46 (1): 0-.
Innovation and Practice of Drilling Technology for Deep Shale Gas Wells in Sichuan
YANG Ruifan
Abstract105)      PDF (3857KB)(136)      

According to the problems of deep buried reservoirs in Sichuan Basin, developed fractures and caves, lost-circulation intervals, pipe stuck in faults and fracture zones, highly compacted formation and high temperature, poor drillabiility, frequent failure of downhole tools and etc. , a series of unique drilling technologies have been explored through multiple approaches in recent years. Combining the interaction mechanism of oil-based drilling fluid and shale, multi-stage micro-nano sealing agents and emulsifiers have been developed, the strong plugging technology of oil-based drilling fluid has been formed to cope with the complications of loss, wellbore wall instability and sticking in the drilling process; focusing on the drillability and abrasiveness of the formation, the customized bit was designed to achieve efficient rock breaking in the difficult-to-drill formation; by introducing oscillating screw and enhanced torque impactor, the vibration classification control technology has been formed to improve the stability of downhole tools; the self-developed cooling device is applied to high temperature resistant rotary guide tools, reducing the failure rate of downhole tool; with reference to the mature technology of pressure control and density reduction in the " Three high" well, precise pressure control and density reduction have been implemented to release power for speed increase. These series of technologies have strongly supported the exploration and development of deep shale gas in Sichuan Province and met the needs of sustainable exploration and development of deep shale gas.

2023, 46 (4): 13-19.
Research on the High-Activity Low-Density Cement Slurry and Its Strength Formation Mechanism
WANG Haiping , LI Zhi , DONG Zhiming , WEI Zhousheng , SU Hongsheng , YU Junjie , LIU Kaiqiang
Abstract101)      PDF (3560KB)(153)      
Hollow light particles are prone to crush under high temperature and high pressure at the bottom of the hole, resulting the deterioration of rheological properties of low-density cement slurry, which leads to increase of friction resistance, density and cement loss risk. To deal with the phenomenon, a high-activity low-density cement slurry system (HALDCP) with constant density and secondary hydration characteristics was developed, using high active composite solid materials and supporting activators. Isothermal microcalorimeter, x-ray diffractometer, thermal gravimetric analyzer, scanning electron microscope were applied to analyze the development rule of early hydration, chemical structure of hydration products, microstructure and compressive strength. The results indicated that HALDCP had constant density and rheology. In HALDCP, alkaline hydration products and hydration heat generated by Portland cement activated composite lighting materials, which made the hydration process of the slurry had secondary hydration and formed “Double exothermic peaks”. At the meanwhile, it increased hydration heat and the content of hydration products. Ca(OH)2 was depleted by the hydration of HALDCP to form lots of calciumite and C-(A)-S-H, increasing hydration products of the cement, solid volume fraction, microstructural density. In contrast with enameled perlite cement with low density, the compressive strength of HALDCP hydrating for 28 days enhanced 16. 7% , and had good durability. 
2023, 46 (3): 154-153.
Abstract96)      PDF (1316KB)(141)      
2023, 46 (1): 202-.
Calculation Model of Cuttings Bed Thickness in Horizontal Wells Considering Drill String Rotation
BAI Mingna , , XIE Jiangfeng , , CHEN Haiyong , OUYANG Yong , , AN Jintao , ZHANG Qian , KAN Zhengyu
Abstract95)      PDF (1779KB)(239)      
In the drilling process of horizontal well,poor hole cleaning can lead to downhole complexities such as increase in friction torque of drilling tools,sticking and sharp increase in annulus pressure,which seriously restricts the horizontal well extension ability. In previous studies,the important effect of drill pipe rotation speed on wellbore cleaning is often ignored,and the influence of drill pipe rotation on annulus flow field is also not considered in the established models. In order to explore the comprehensive effect of drill pipe rotation speed and displacement on cuttings migration,this study first established a calculation model of cuttings bed thickness in horizontal wells considering the condition of drill pipe rotation after calculating the eccentric annulus flow field when the drill pipe rotates in horizontal wells and analyzing the three-dimensional stress of cuttings particles. In the process of horizontal section drilling,due to gravity,the drill pipe sinks at the lower edge of the annulus,forming a narrow annulus area. The model calculation results show that the axial flow rate of the drilling fluid in this area is slow, which is often not enough to reach the critical flow rate of rock cuttings startup,resulting in cuttings deposition. At this time,the circumferential velocity of the drilling fluid caused by the rotation of the drill pipe can bring the cuttings into the high-speed basin at the upper edge of the annulus,thus achieving the effect of efficient rock carrying. Then,the model is used to calculate the seven kinds of annulus sizes commonly used in the field,and the drill pipe rotation speed under different hole sizes is recommended. Finally,the model is used to compare and analyze the actual drilling situation in Mahu Lake,which verifies the reliability of the model and also proves that the model has a certain guiding role in engineering practice. 
2023, 46 (2): 8-14.
Optimization of ROP-Increase Prediction Model Based on Mechanical Specific Energy Theory
MU Huayan , , SUN Jinsheng , , DING Yan , CUI Meng , WANG Ren , CUI Yi
Abstract95)      PDF (1441KB)(219)      
Improving drilling efficiency is an important part in the process of oil drilling. The optimization of drilling operation is mainly achieved by adjusting drilling parameters, reducing mechanical specific energy and increasing ROP. The specific mechanical energy(MSE) is one of the main indexes to evaluate drilling performance. However, complex drilling operations cause the limitations of most evaluation models in the application process, and formation uncertainty will lead to the problems such as reducing generalization ability of ROP prediction model and non-production time. In this study, multiple prediction models are established for different formations of the target well, the best performance model is selected by evaluation. Firstly, the controllable parameters affecting ROP are analyzed based on the theory of MSE and mutual information method. Secondly, the historical mean value is used as the ROP-increase threshold to convert the regression prediction into the classification prediction, and the prediction performance of classification algorithm models such as K nearest neighbor (KNN), multilayer perceptron (MLP), na?ve Bayes (NB), and logistic regression(LR) is evaluated. Finally, the KNN model suitable for each formation of the target well is optimized, and applied to adjacent well in the same area. The actual verification results show that the prediction accuracy in the four formations of the adjacent well is 0. 94, 0. 94, 0. 92, 0. 96, respectively, and the AUC value is 0. 98, 0. 97, 0. 96, 0. 98, respectively. The model performs well and can help scientific decision-making of drilling construction. 
2023, 46 (3): 16-21.
Status and Development Trend of Ultra-short Radius Drilling Technology
ZHANG Yong , LIU Xiaomin , HUA Zejun , XUE Xianbo , ZHANG Wenbo , GUAN Haolun
Abstract94)      PDF (2268KB)(332)      
With the continuous deepening of oil and gas development,the ultra-short radius drilling technology is widely considered as one of the effective means to restore old oil fields for production increasement. Currently, there are two mainstream ultra-short radius drilling technologies at home and abroad:ultra-short radius drilling technology based on flexible drilling tools and ultra-short radius drilling technology based on high build up rate screws. The supporting technologies,advantages and disadvantages and their applications of the above two ultrashort radius drilling technologies are investigated and analyzed. The ultra-short radius drilling technology based on flexible drilling tools,of which the radius of curvature is small,is suitable for developing thin reservoir with thickness less than 3 m or remaining oil reservoir at upper wellbore in horizontal wells,improving oil recovery. The ultra-short radius drilling technology based on high build up rate screws,of which the horizontal displacement is large,can achieve accurate targeted potential tapping with fixed depth and orientation of reserves around the well. Based on the application effects of the two technologies,the future development trends of the two technologies are proposed in order to continue the development of ultra-short radius drilling technology.
2023, 46 (2): 41-45.
Stable Production Technology and Practice in Weiyuan Shale Gas Well at Low Pressure and Low Production Stage
Abstract91)      PDF (1574KB)(248)      
Weiyuan shale gas well has the characteristics of high production and rapid decline in the initial stage of production. According to the production characteristics, it can be divided into three production stages:flowback after fracturing stage, rapid decline stage, low pressure and low production stage. There are obvious differences in production characteristics in different stages. At low pressure and low production stage, gas well production is low, pressure is low, decline rate is slow, production period is long, and production contribution reaches 60% . The production is easily affected by many factors, such as liquid loading of gas well, frac hit water flooding, system export pressure fluctuation, wellbore plugging and so on. It is the main stage for the implementation of stable production technology. In view of the factors affecting the production and different types of problem wells, technical countermeasures for stabilizing production of old wells with pressurization, foam drainage, plunger, gas lift,shaft cleaning and their combination has been innovatively formed. For instance, priority should be given to pressurization and foam drainage measures for wells with slight fluid accumulation, foam drainage or plunger technology is preferred for intermittent effusion wells, gas lift measures such as opening or closing wells are preferred for wells with serious fluid accumulation, wellbore cleaning or coiled tubing flushing shall be adopted for blocked wells, for water flooded wells with fracturing and channeling, priority should be given to synchronous depressurization gas lift, coiled tubing gas lift and displaced flow. Through the practice of stable production technology at low production stage, a special technical template is formed to effectively solve various production problems of gas Wells, maximize the production of gas Wells, improve the sustainable and stable production capacity of old Wells, and realize the efficient development of shale gas. 
2023, 46 (1): 71-76.