In order to generate a new fracture far away from the original fracture in refracturing and effectively enhancing productivity, the technology of hydraulic refracturing guided by directional boreholes was presented. The effects of induced stress generated by the original hydraulic fracture, fracturing fluid percolation effect, wellbore internal pressure, and in situ stress on stress field distribution around wellbore were considered to obtain a fracture initiation model of hydraulic refracturing guided by two directional boreholes. The variation of maximum principal stress (σmax) under different conditions was investigated. The researches show that the directional boreholes result in a “sudden change region” of maximum principal stress around wellbore, reflecting dual stresses effects from vertical wellbore and directional boreholes on the rock. The width of sudden change region decreases as the distance from wellbore increases. Due to sudden change region, the refracturing fracture tends to initiate around directional boreholes. Whether the new fracture initiates and propagates along directional boreholes depends on comprehensive effect of borehole azimuth, borehole diameter, borehole spacing, horizontal stress difference, height, and net pressure of original fracture. The specific initiation position can be calculated using the theoretical model proposed in this paper. Affected by induced stress of the original fracturing, the rock tends to be compressed during refracturing, i.e., increased fracturing pressure. Sensitivity analysis with “extended Fourier amplitude sensitivity test (EFAST)” method shows the initiation of new fracture is mainly controlled by directional boreholes parameters and has little relation with in situ stress and parameters of original fracture. The influence rank of each parameter is as follows: borehole diameter > borehole spacing > original fracture net stress > borehole azimuth > horizontal stress difference > original fracture height. During design of refracturing, in order to better play the role of directional boreholes, and create a new fracture far away from original fracture, the optimal design is conducted with measures of optimizing boreholes azimuth, increasing borehole diameter and reducing borehole spacing if conditions permit. The research provides the theoretical basis for hydraulic refracturing guided by directional boreholes, which is helpful for the design of fracturing construction programs.
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August 2018
Research-Article
Study on Fracture Initiation Mechanisms of Hydraulic Refracturing Guided by Directional Boreholes
Tiankui Guo,
Tiankui Guo
College of Petroleum Engineering,
China University of Petroleum,
Huadong 266580, China
China University of Petroleum,
Huadong 266580, China
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Facheng Gong,
Facheng Gong
College of Petroleum Engineering,
China University of Petroleum,
Huadong 266580, China
China University of Petroleum,
Huadong 266580, China
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Zhanqing Qu,
Zhanqing Qu
College of Petroleum Engineering,
China University of Petroleum,
Huadong 266580, China
China University of Petroleum,
Huadong 266580, China
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Xuxin Tian,
Xuxin Tian
College of Petroleum Engineering,
China University of Petroleum,
Beijing 102249, China
China University of Petroleum,
Beijing 102249, China
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Binyan Liu
Binyan Liu
College of Petroleum Engineering,
China University of Petroleum,
Beijing 102249, China
China University of Petroleum,
Beijing 102249, China
Search for other works by this author on:
Tiankui Guo
College of Petroleum Engineering,
China University of Petroleum,
Huadong 266580, China
China University of Petroleum,
Huadong 266580, China
Facheng Gong
College of Petroleum Engineering,
China University of Petroleum,
Huadong 266580, China
China University of Petroleum,
Huadong 266580, China
Zhanqing Qu
College of Petroleum Engineering,
China University of Petroleum,
Huadong 266580, China
China University of Petroleum,
Huadong 266580, China
Xuxin Tian
College of Petroleum Engineering,
China University of Petroleum,
Beijing 102249, China
China University of Petroleum,
Beijing 102249, China
Binyan Liu
College of Petroleum Engineering,
China University of Petroleum,
Beijing 102249, China
China University of Petroleum,
Beijing 102249, China
Contributed by the Petroleum Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received October 8, 2017; final manuscript received March 3, 2018; published online April 9, 2018. Assoc. Editor: Ray (Zhenhua) Rui.
J. Energy Resour. Technol. Aug 2018, 140(8): 082901 (14 pages)
Published Online: April 9, 2018
Article history
Received:
October 8, 2017
Revised:
March 3, 2018
Citation
Guo, T., Gong, F., Qu, Z., Tian, X., and Liu, B. (April 9, 2018). "Study on Fracture Initiation Mechanisms of Hydraulic Refracturing Guided by Directional Boreholes." ASME. J. Energy Resour. Technol. August 2018; 140(8): 082901. https://doi.org/10.1115/1.4039618
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