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08 July 2022, Volume 41 Issue 3 Previous Issue   

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Volumetric Fracturing 2.0 Process for Unconventional Oil and Gas Reservoirs and R&D Suggestions Zheng Xinquan, He Chunming, Yang Nengyu, Weng Dingwei, Cai Bo, Yi Xinbin 2022, 41(3): 1-9.  DOI: 10.3969/j.issn.1002-302x.2022.03.001 Abstract ( )   PDF (2962KB) ( )   PetroChina’s renovation technology for horizontal well volumetric fracturing of unconventional oil and gas reservoirs started from scratch and experienced from 1.0 version to 2.0 version. The volumetric fracturing 2.0 process focuses on “multiple clusters + small cluster spacing + current-limiting perforation + temporary blocking and steering + large pumping capacity + high-strength sand-injection + quartz sand replacing ceramic grain + using slickwater for continuous sand-injection”. This process effectively boost production and efficiency and reduced cost for development of unconventional oil and gas resources. Shortening of cluster spacing holds the key to improve production and producing degree of unconventional oil and gas resources. The process of the “multiple clusters + small cluster spacing + current-limiting perforation + temporary blocking and steering” assembly is critical to high-efficiency and cost-effective renovation. Large injection capacity with cutting and distribution of fractures creates the conditions for quartz sand to replace ceramic grains. Multiple clusters perforation and large replacement operation solve the bottlenecks of using low-viscosity slickwater for continuous sand-injection. The volumetric fracturing 2.0 process has a good performance in PetroChina’s development of unconventional oil and gas resources. Based on the demand for horizontal well volumetric fracturing technology in PetroChina’s “14th Five-year Plan”, this paper comes up with the suggestions in five areas: (1) stepping up the basic research on renovation of unconventional reservoirs to support construction of the new technological system, (2) improving the scientific and economical properties of the critical parameters from the process to expand application of the process, (3) enhancing application of horizontal well stereo development technology to expand the new technological application areas, (4) enlarging application of cost-effective materials to carry out the volumetric fracturing 2.0 process operation on a large scale, and (5) promoting research and application of new fracture-monitoring technology to improve the new process for fractural renovation.

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Development and Application of Shale Oil Horizontal Well Volume Fracturing Technology in Changqing Oilfield Shi Daohan, Zhang Kuangsheng, Tang Meirong, Tao Liang, Du Xianfei 2022, 41(3): 10-17.  DOI: 10.3969/j.issn.1002-302x.2022.03.002 Abstract ( )   PDF (3327KB) ( )   Horizontal well volume fracturing technology holds the key to high-efficiency shale oil development. This paper reviews the development process of shale oil horizontal well volume fracturing technology at Changqing Oilfield in the past decade and summarizes the new progress in the three areas – volume fracturing transformation pattern, key tools and low-cost materials. The innovative efforts lead to the volume development technological model, namely the “three-dimensional, long horizontal section, subdivision cutting, cluster perforation, soluble ball seat, variable sticky slippery water slip, multi-scale support” model. The paper also comes up with the “pressure-increases-permeability” integrated design to make single fracturing become a trinity of making fractures, increasing energy and displacing oil. The formation energy is increased and oil and water permeability replacement accelerated in the fracturing process, thus maximizing the primary producing degree of the single-well fracture-controlled reserves. The new materials are independently developed, such as soluble metal ball seats and dynamic temporary plugging materials. The multi-functional variable viscosity slippery water and combinations of different granular quartz sand can improve permeability and conductivity of fractures in different sizes. The research results were applied to more than 450 shale oil horizontal wells at Changqing Oilfield. The initial production was raised to 18t/d from 9.6t/d. The annual cumulative oil production was boosted to 4931 tons from 2380 tons. The single-well EUR was brought up to 2.6×104t from 1.8×104t. The annual oil production topped 100×104t in 2019. The Qingcheng 1-million-ton shale oil demonstration zone was constructed in 2020. The research results provided the scientific basis for development of horizontal well volume fracturing technology.

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Development and Application of Shale Gas Volume Fracturing Technology in Southern Sichuan Basin Fu Yongqiang, Yang Xuefeng, Zhou Lang, Deng Qi, Zhou Xiaojin, Wang Qiang, Hu Junjie, Yao Zhiguang, Wen Li 2022, 41(3): 18-25.  DOI: 10.3969/j.issn.1002-302x.2022.03.003 Abstract ( )   PDF (2219KB) ( )   China’s Sichuan Basin is rich in shale gas resources. Following the exploration efforts for more than a decade, PetroChina’s shale gas fields in the southern region of Sichuan came under large-scale development with economic performance. PetroChina has owned the key technology of shale gas exploration and development. PetroChina has also developed a system of shale gas fracturing theories, technologies and methods and become a leader in some areas of the industry. Shale gas fracturing in the southern region of Sichuan has experienced four development stages – pilot experiment, independent research and development, perfection of the system, and technological upgrading. A volume fracturing technology system for 3500-meter shallow shale gas horizontal wells has been developed, which is focused on volume fracturing process technology, auxiliary volume fracturing technology, fractured seams monitoring and post-fracturing effect evaluation technology and factory-style fracturing technology. This paper studies and summarizes the shale gas fracturing technological progress and application results at the current stage, analyzes the existing technological limitations and fracturing bottlenecks in South Sichuan, and proposes to improve fracturing theoretical research to highlight the geological characteristics of the shale gas reservoirs with the different buried depths. It is of great urgency to improve the productivity of the shallow and old areas. As for shale gas buried less than 3500 meters, the efforts should be focused on improving production of shallow and new wells as well as the producing degree of the reserves. As for shale gas buried more than 3500 meters, it is necessary to improve the single-well production and guard against the complicated conditions, thus maintaining high-efficiency shale gas development in the future.

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Innovative Technology and Development Trend for Efficient SAGD/VHSD Development of Super-heavy Oil Liao Guangzhi, Li Xiuluan, Wang Zhengmao, Sun Xinge, Zhang Zhongyi, Ma Hongbin, Zhang Shengfei 2022, 41(3): 26-34.  DOI: 10.3969/j.issn.1002-302x.2022.03.004 Abstract ( )   PDF (5049KB) ( )   China is rich in onshore super-heavy oil resources. However, it is difficult for the conventional thermal recovery technology to bring the resources under effective development owing to the “solid state” of in-situ oil and strong heterogeneity of the reservoirs. Based on tenacious research for 15 years China National Petroleum Corporation has developed a series of technologies for super-heavy oil development, such as the theoretical method for oil drainage of strong-heterogeneous super-heavy oil, the dual-horizontal steam-assisted gravity drainage/vertical-horizontal steam drainage (SAGD/VHSD) technology, the high-temperature and high-pressure production process system, and high temperature and complex produced liquid/heat recycling technology, thus establishing the SAGD/VHSD technology suitable for efficient development of China’s onshore strong-heterogeneous and super-heavy oil. With the help of the new-generation efficient super-heavy oil development and EOR technology, the shallow super-heavy oil reservoirs were brought under efficient development in Xinjiang oilfield while the middle-deep super-heavy oil reservoirs came under EOR engineering construction in Liaohe oilfield, helping keep the heavy oil production stable at 10 million tons. Under the background of “carbon peaking and carbon neutral”, the super-heavy oil development is in transition to green environmental technological system, such as in-situ upgrading, electric heating assisted steam, and wind, solar energy and hydrogen combined to generate steam.

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Suggestions on Research and Development of Mechanical Recovery Digitalization Technology Yang Nengyu, Sun Yizhen, Zhao Hanjun, Zhao Ruidong, Zhang Xishun, Wang Cai, Shi Junfeng, Chen Shiwen, Chen Guanhong 2022, 41(3): 35-42.  DOI: 10.3969/j.issn.1002-302x.2022.03.005 Abstract ( )   PDF (2887KB) ( )   The low-yield wells and low-efficiency wells are on the rise year by year after the oilfields enter their middle and later development periods. The management work will become more complicated at the same time. Digitalization and intelligent transformation of the mechanical recovery system is an inevitable option for energy saving and high-efficiency production. This paper briefs about PetroChina’s current conditions of mechanical recovery system and digitalization technology as well as the main integral parts of mechanical production IOT. It also elaborates on the work-showing map pattern of a pumping well, a key project constructed at the present time, the electricity parameter pattern of a pumping well and the multi-parameter pattern of a rodless pumping well. The paper analyzes development and adaptability of mechanical production system optimization technology and intelligent adjustment control technology. Based on production at the oilfields, this paper comes up with some suggestions on mechanical recovery methods: (1) The method for pumping well digitalization should be based on the electric parameter-focused pumping units and multiple parameters-focused rodless pumping units. (2) The plan for in-depth application of mechanical recovery data should be centered on control over data quality and study of data value. (3) It is necessary to accelerate the cost-effective and intelligent control system for pumping wells. Digitalization technology of the mechanical recovery system can help solve the bottlenecks of low production and low efficiency, effectively improving the fine production level and management efficiency.

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Renovation and Demonstration Zone for Artificial Lift Efficiency Improvement Constructed in Daqing Oilfield Cai Meng 2022, 41(3): 43-49.  DOI: 10.3969/j.issn.1002-302x.2022.03.006 Abstract ( )   PDF (3309KB) ( )   Artificial lift is the main oil production mode in Daqing Oilfield but now faces a series of issues, such as large quantities of artificial lift wells, difficult to control total energy consumption, one reservoir block quite different from another one, difficult to improve artificial lift indictors, prominent contradiction between less working staff and more oil wells and difficulty in management. Therefore, the study was made of the renovation technology to improve artificial lift efficiency for old oilfields. Five major projects were launched for this purpose, such as artificial lift efficiency improvement, wellbore treatment, artificial lift digitalization, artificial lift standardization, and construction of the demonstration zone. A series of technologies, including node analysis technology of pumping unit, even thickness elastomer PCP production technology and ultra-long stroke production technology, are applied for artificial lift efficiency improvement, thus the reasonable flow pressure. In the area of wellbore treatment, a measure chart was formulated to raise the wellbore treatment level. As for inspection, appraisal, maintenance and operation of new products and new technology, a total of 25 items of criteria were formulated and revised during the 13th Five-Year Plan period. In the area of artificial lift digitalization, the diagnosis and analysis model for the working conditions, which is based on the electrical parameters, was established in the efforts to develop the electrical parameter-based pumping unit and automatically-optimized operational technology.The efficiency-improving technological integration was applied in the two demonstration zones in A Oilfield in the old oil area and B Oilfield in the surrounding area. A total of 131×104 kW·h of electric energy was saved following adoption of those measures. The pump inspection rate decreased by 2.0% and 0.9% respectively in the two zones, showing remarkable application results.

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Development and Application of Intelligent Intermittent Oil Extraction Technology for Low-yield Wells at Changqing Oilfield Liu Tianyu, Yan Juan, Feng Shousong, Yu Yang, Lu Mei, Ai Xin, Li Mingjiang 2022, 41(3): 50-57.  DOI: 10.3969/j.issn.1002-302x.2022.03.007 Abstract ( )   PDF (3170KB) ( )   Changqing Oilfield has conducted intermittent oil extraction service cumulatively for 64000 well times during the 13th Five-year Plan period. The key indexes of artificial lifting, such as pumping efficiency and system efficiency, were kept at a relatively high level in terms of a low-permeability oilfield. To meet the development trends of digitalization and intelligence and break the bottleneck of traditional artificial intermittent oil extraction, an intelligent intermittent oil extraction technology suitable to Changqing Oilfield was developed on the basis of the established Internet of things so that the intermittently-extracted oil wells could be brought under concentrated management and control at a relatively low cost. The software platform for intermittently-extracted oil wells was studied and developed to bring about intelligence in four areas – determination of production system for oil wells, optimization and adjustment, control over turn-on/turn-off, and supervision of indicators. Thanks to the intelligent intermittent oil extraction technology, the basis for formulation of the intermittent oil extraction system became more reasonable while the technological results were more prominent. Meanwhile, the intelligence technology also reduced dependence of intermittent extraction service on manpower and cost of workforce.

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Practice and Thinking of Tight Gas Drainage Recovery Li Siying, Tian Wei, Jia Youliang, Li Xuri, Song Jie, Wang Yixuan 2022, 41(3): 58-66.  DOI: 10.3969/j.issn.1002-302x.2022.03.008 Abstract ( )   PDF (4591KB) ( )   The gas-water relation is complicated in Sulige tight gas reservoirs with a wide scope of formation water distribution. The gas well in the area is usually water-bearing. The unique low permeability, low pressure, and low abundance of such gas reservoirs lead to insufficient gas supply capacity, low gas production and rapid decline in gas wells, and serious liquid accumulation in the entire life cycle. To keep production of the tight gas field stable and cost-effective, three backbone technologies – foam drainage, velocity string and plunger gas lift – were developed as the main technological series of drainage gas recovery and the key auxiliary tools. As a result, the technological policy for drainage gas recovery was formulated for the life cycle of a gas well to meet the need for differentiated applications at the gas fields. Focusing on the special well conditions, the horizontal well plunger drainage gas recovery technology and casing plunger drainage gas recovery technology were developed to effectively solve the bottlenecks for application of the complicated wellbore drainage gas recovery technology. The 50.8mm-diameter coiled tubing completion and production integration technology was developed to satisfy the demand for high-efficiency drainage of gas wells, saving the production cost. The intelligent gas-well management platform was established to liberate manpower from on-site management and bring the gas wells under intelligent management. The drainage gas recovery technology was studied in the light of the existing technological bottlenecks. It is necessary to continue the research on the characteristic technological series of tight gas drainage recovery, make continuous breakthroughs in the lower limit of recoverable tight gas volume and further promote high-quality development of gas fields.

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Study and Application of Shale Gas Well Deliquification Technology Xiang Jianhua, Wen Ming, Wang Qiang, Chen Man, Li Xiaorong, Wei Linsheng, Luo Xin, Li Bochun, Jiang Zeyin 2022, 41(3): 67-76.  DOI: 10.3969/j.issn.1002-302x.2022.03.009 Abstract ( )   PDF (3851KB) ( )   Long-term and economically-efficient production of shale gas is one of the basic requirements for shale gas development. The accumulated liquid of a shale gas well seriously affects gas production. The gas well deliquification tecnology is needed on a long-term basis. According to the tailored laboratory experiment and on-site test, shale gas production is accompanied with liquid in the later period. The liquid in the horizontal segment is mainly the formation flow while the liquid in the inclined segment is the plug flow. They are the locations for accumulation of liquid to take place in the wellbore. When liquid is accumulated in the inclined segment, the back-flow of liquid leads to accumulation of liquid in the horizontal segment. The liquid accumulated in the shut-in tube returns to the long horizontal segment where the liquid can be easily accumulated while the liquid surface of the wellbore drops. The productivity of the gas well will be limited when the tube is lowered into the horizontal segment. The eccentric leakage in the inclined segment reduces efficiency of plunger gas lift. Based on the characteristics of long-term low-pressure low production and wellbore gas-liquid flow of the shale gas well, this paper proposes the countermeasure of making full use of the shale gas well energy for economic and high-efficiency deliquification and gas production, optimizes pipe string, foam and plunger as three main technical processes for shale gas well deliquification, optimizes the technological plans and practices of various main processes, and helps the shale gas well flow by means of the auxiliary technical processes. When the shale gas well deliquification technology was used in the Changning Block in South Sichuan, gas-lift production and resumption of production needed less manpower and work while the water-flooded wells were reduced, effectively maintaining the productivity of old wells.

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Suggestions on CNPC Coiled Tubing Service Technology Development Hu Qiangfa, Zhu Feng, Lv Weiping, Gai Zhiliang, Zhang Fuqiang, Zhu Ye 2022, 41(3): 77-85.  DOI: 10.3969/j.issn.1002-302x.2022.03.010 Abstract ( )   PDF (2622KB) ( )   China National Petroleum Corporation (CNPC) has made significant progress in coiled tubing service technology and scored a rapid business growth in service volume following the continuous efforts for research and extension of coiled tubing service in the 13th Five-year Plan period. In the four areas of radial drilling sidetracking, ultra-deep well and deep-layer shale/tight oil and gas coiled tubing service, coiled tubing directional sand blasting perforation fracturing, and coiled tubing suspension completion and oil/gas production, CNPC has made important achievements in research of coiled tubing process technology and key tools, manufacture of equipment and software development. The coiled tubing service business has rapidly risen 22 percent year by year in the efforts to promote four main processes – coiled tubing rapid workover, coiled tubing velocity string and completion string, coiled tubing reservoir stimulation and coiled tubing logging and testing. With oil and gas development extending into deeper layers and longer horizontal section, coiled tubing technology will face a series of new challenges during the 14th Five-year Plan period. It is necessary to improve coiled tubing equipment and service competence, enhance promotion of the whole series of coiled tubing service technology, accelerate construction of technology sharing service platform and digitalized and intelligent software platform, and provide effective technological support for the dual strategy of “keeping oil production stable while increasing gas production and improving quality for higher efficiency”.

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Research and Application of Clean and Automation Technology for Downhole Service in Daqing Oilfield Wang Hongwei, Liu Chongjiang, Yao Fei, Song Xingliang, Xu Xiaoyu, Liu Yuchuan, Zhao Lichuan, Wang Pengcheng, Ma Baitao 2022, 41(3): 86-93.  DOI: 10.3969/j.issn.1002-302x.2022.03.011 Abstract ( )   PDF (3924KB) ( )   Daqing Oilfield focused on research and application of clean and automation service technology to change the traditional downhole service conditions of formation damage, safety risk and high labor intensity during the 13th Five-year Plan period. The green service requires “no fluid out of the well, no fluid on the ground, and no environmental pollution on the ground surface”. A series of clean service technologies focusing on wellbore overflow control with the effects on surface fluid collection and recovery was developed to solve the environmental pollution issues caused by fluid out of the well. This technological series was used cumulatively for 208,000 well times, recovering waste liquid for 382.7×104m3 and reducing waste solids for 6.3×104t. The coverage rate of clean service was raised to 100 percent from 23.6 percent. The automated service technology for workover was developed in the efforts to alleviate high labor intensity and high safety risks of downhole service. Development and application of systematic automated service equipment reduced the service personnel proportion of a single crew by 25 percent, saving labor cost for more than 1 million yuan a year and dramatically lowering labor intensity and safety risks. Development and application of clean and automation technology brought about safety, greenness and high-efficiency of downhole service and promoted transformation of labor organizational mode and production operational pattern.

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Research and Application of Cable-controlled Layered Water Injection Technology in Daqing Oilfield Tong Yin, Jin Zhendong, Liu Junli, Zhang Weichao, Li Jinghui, Guo Ying 2022, 41(3): 94-99.  DOI: 10.3969/j.issn.1002-302x.2022.03.012 Abstract ( )   PDF (2787KB) ( )   Layered water injection is an important characteristic technology in Daqing Oilfield, which has provided technological support for high-efficiency development of the oilfield. As the oilfield entered the ultra-high water-cut period, the remaining oil is highly dispersed with the complicated oil-water relations. The qualification rate of water injection dropped quickly while it is more difficult to keep oil production stable and control water cut. As a result, the cable-controlled layered water injection technology was developed to solve the contradiction between the amount of work for adjustment of more and more water-injecting wells and the limited adjusting personnel and satisfy the need for delicate oilfield development. This technology puts the pressure-monitoring system, the flow-monitoring system and the flow-controlling system into the preset cable intelligent water distributor so that the technical personnel at the office terminal can send the control instructions from the server software. The instructions are transmitted to the surface control box by means of the wireless network of the oilfield production. The cable microwave carrier technology is used to transmit the instructions to the intelligent water distributor by cable, bringing about real-time communications, acquiring downhole layered parameters information and controlling downhole layered injection amount. Four demonstration zones of intelligent layered injection technology were established to test the process adaptability against the background of different development contradictions.The cable-controlled layered water injection technology improves the proportion of water-absorbed thickness and effectively control the water-cut growth rate and the natural declining rate with the oil yield apparently increased, promoting digitalized transformation and intelligent development of the oilfield.

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Research and Field Application of Digital Layered Water injection Technology Based on Wave Code Communications Wang Erzhen, Yang Haien, Yu Jiuzheng, Yang Lingzhi, Ji Zhenning, Hu Gaixing 2022, 41(3): 100-105.  DOI: 10.3969/j.issn.1002-302x.2022.03.013 Abstract ( )   PDF (6714KB) ( )   The data cannot be monitored continuously from the conventional layered injection wells. It is necessary to make artificial inspection and adjustment on a regular basis to keep the qualification rate of layered injection. With the technological progress, the domestic oilfields gradually developed towards digital layered injection. Changqing Oilfield is mainly composed of ultra-low permeability reservoirs with a strong interlayer heterogeneity and a small amount of water injected into the thin layers. Based on tenacious research efforts, Changqing innovatively the digital water injection technology based on wave code communications, thus solving the bottlenecks of small water quantity test and distribution and developing the under-pressure operational mode suitable for the oilfield. This technology uses the pressure flow wave code to bring about wireless remote transmission of the surface and downhole data while the digital water distributor can automatically measure and adjust downhole stratified flow and make data acquisition. A total of more than 1200 wells were brought under field application. The distance of surface and downhole wireless data transmission reached 2800 meters and the qualification rate of layered water injection has been kept above 90 percent for a long period of time. The longest duration for effectiveness approached four years. The single-well testing cost was reduced by 50,000 yuan per year. The technology solved the technological bottlenecks of conventional layered water injection, substantially reduced labor intensity of personnel and improved the fining level of water injection at the oilfield.