Fracturing Technologies with Profile Control and Water Shutoff for Medium and High Water-Cut Wells in Ultra-Low Permeability Reservoirs of Changqing Oilfield
(2.National Engineering Laboratory of Low Permeability Oil and Gas Field Exploration and Development, Xi’an, Shaanxi 710018)
【Abstract】Due to the influence of the high-permeability zone, the water cut will increase and reservoir stimulation results are poor when conventional refracturing is implemented in the ultra-low permeability reservoirs of Changqing Oilfield at the medium and high water-cut development stage. Focusing on the long-term injection-production development practices of typical reservoirs and infill well production data, this paper uses 3D geological modeling to analyze the stimulation mechanism of fracturing with profile control and water shutoff in medium and high water-cut oil wells. The influence of fracturing parameters on the effect of repeated stimulation was studied, and a refracturing concept hinging on “profile control and water shutoff in the pad adding stage to control water cut and dynamic multistage temporary plugging fracturing to improve single-well production” was advanced. PEG-1 gel was developed through laboratory experiments and when the mass fraction of its main agent achieved 5%–10%, gel strength would be maintained at a high level. With an optimal injection flow rate of 1.5 m3/min and an injection volume of 300–600 m3, the high-permeability zones at the fracture depth of 40–80 m could be effectively plugged. In this way, the dynamic multistage temporary plugging fracturing technology was optimized. As a result, the net pressure in the fractures was increased to above 5.0 MPa, fractures extended from the low-stress zone to the high-stress zone, and the production of the oil remaining laterally was thereby produced. Field test results showed that average oil production improvement per well was 1.07 t/d and water cut was reduced by 9 percentage points after the measure was implemented, which indicated that the goal of increasing oil production while controlling water was accomplished by refracturing the medium and high water-cut wells. The proposed fracturing technology with profile control and water shutoff provides a new technical concept for the repeated stimulation of medium and high water-cut wells in ultra-low permeability reservoirs of Changqing Oilfield.
【Keywords】 ultra-low permeability reservoir; medium and high water-cut well; fracturing with profile control and water shutoff; oil production increase and water control; Changqing Oilfield;
(Translated by YAO J)
 WANG Dongqi, YIN Daiyin. Waterflooding performance evaluation in ultra-low permeability oil reservoir [J]. Special Oil & Gas Reservoirs, 2017, 24 (6): 107–110 (in Chinese).
 YANG Xiaoyan.Waterflood development effect study of heterogeneous reservoir [J]. Special Oil & Gas Reservoirs, 2019, 26 (2): 152–156 (in Chinese).
 ZHANG Yuyin, ZHAO Xiangyuan, JIAO Jun.Characteristics and major control factors of natural fractures in Chang 6 Formation in Ansai Area, Ordos Basin [J]. Complex Hydrocarbon Reservoirs, 2018, 11 (2): 25–30 (in Chinese).
 HUANG Ting, SU Liangyin, DA Yinpeng, et al.Research and field test on energy storage fracturing mechanism of horizontal wells in ultra-low permeability reservoirs [J]. Petroleum Drilling Techniques, 2020, 48 (1): 80–84 (in Chinese).
 YANG Hao, LI Xinfa, CHEN Xin, et al.Study on staged optimization method of staged fracturing for horizontal wells in low-permeability gas reservoir [J]. Special Oil & Gas Reservoirs, 2021, 28 (1): 125–129 (in Chinese).
 CAI Zhuolin, ZHAO Xurong, NAN Rongli, et al.Volume re-fracturing technology of temporary plugging and diverting with high displacement [J]. Fault-Block Oil & Gas Field, 2020, 27 (5): 661–665 (in Chinese).
 ZHOU Zongliang, CAI Mingjun, ZHANG Fanlei, et al. Residual oil occurrence state and time-shift characteristics of multi-media displacement of high water-cut reservoirs [J]. Fault-Block Oil & Gas Field, 2020, 27 (5): 608–612 (in Chinese).
 LIAO Yuemin, FU Meilong, YANG Songlin.Study and application of water plugging and profile control system of heat and salt resistant gel [J]. Special Oil & Gas Reservoirs, 2019, 26 (1): 158–162 (in Chinese).
 JIA Yuqin, ZHENG Mingke, YANG Haien, et al. Optimization of operational parameters for deep displacement involving polymer microspheres in low permeability reservoirs of the Changqing Oilfield [J]. Petroleum Drilling Techniques, 2018, 46 (1): 75–82 (in Chinese).
 ZHANG Li, YUE Xiang’an, WANG Youqi.Research on large scale heterogeneous model based EOR methods for ultra-high water cut reservoirs [J]. Petroleum Drilling Techniques, 2018, 46 (5): 83–89 (in Chinese).
 HOU Jianfeng, WANG Youjing, HU Yafei, et al.Reasonable waterflooding technical policy for extra low permeability reservoirs under dynamically fractures effect [J]. Xinjiang Oil & Gas, 2016, 12 (3): 19–24 (in Chinese).
 ZHANG Yanjun, GE Hongkui, XU Tianlu, et al.Experimental study on silt distribution law at the front end of fractures in volume fracturing [J]. Petroleum Drilling Techniques, 2021, 49 (3): 105–110 (in Chinese).
 ZHOU Dan, XIONG Xudong, HE Junbang, et al. Multi-stage deflective fracturing technology for low permeability reservoir [J]. Petroleum Drilling Techniques, 2020, 48 (1): 85–89 (in Chinese).
 ZHAO Zhenfeng, LI Kai, ZHAO Pengyun, et al. Practice and development suggestions for volumetric fracturing technology for shale oil in the Ordos Basin [J]. Petroleum Drilling Techniques, 2021, 49 (4): 85–91 (in Chinese).