Theory and Application of Pseudo-Reservoir Hydraulic Stimulation for Coalbed Methane Indirect Extraction in Horizontal W
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Original Paper
Theory and Application of Pseudo-Reservoir Hydraulic Stimulation for Coalbed Methane Indirect Extraction in Horizontal Well: Part 2—Application Qian Wang ,1,2,7 Xianbo Su,3,4 Linan Su,5,7 Hongyu Guo,1 Jinxing Song,1 and Zengliang Zhu6 Received 12 October 2019; accepted 24 April 2020
This paper provides details of the application of pseudo-reservoir stimulation technique to a U-shaped coalbed methane (CBM) well (i.e., Well ZU-01) in Jiaozuo mining area. Multistage hydrojet fracturing and channel fracturing were adopted to promote fracture network forming and fracture vertical propagation in pseudo-reservoir. The results of the pseudoreservoir stimulation indicate that influenced by the reservoir lithology and coal structure between the horizontal well and coal seam, the fractures at the first stimulation stage only propagated in the pseudo-reservoir. However, the stimulations at the second, third and fourth stages achieved integrated stimulation of pseudo-reservoir and coal seam. The gas production rate of Well ZU-01 was only 1000 m3/d in the stable production stage. However, through negative-pressure extraction in the mine roadway, the joint gas extraction rate from the underground roadway and Well ZU-01 reached 6000 m3/d. After 450 days of extraction, the cumulative gas production was 15.55 9 105 m3, and the CBM extraction rate reached approximately 50%, indicating that good pseudo-reservoir stimulation and gas pre-extraction effects were achieved. The results of the adsorption/desorption and wettability tests show that water blocking damage caused by the slickwater fracturing fluid severely hindered the gas desorption and production processes, which was the main reason for the low gas production of the well. However, the water blocking damage was mitigated through negative-pressure extraction, resulting in a significant increase in CBM production. KEY WORDS: Pseudo-reservoir stimulation, Multistage hydrojet fracturing, U-shaped CBM well, Jiaozuo mining area, Water blocking damage.
1
School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, Henan, China. 2 School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072, Australia. 3 Unconventional Gas Research Institute, Henan Polytechnic University, Jiaozuo 454000, Henan, China. 4 Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region, Jiaozuo 454000, Henan, China. 5 School of Minerals and Energy Resources Engineering, The University of New South Wales, Sydney, NSW 2052, Australia. 6 Shanxi Resources and Environment Survey of Coal Geology, Taiyuan 030031, Shanxi, China. 7 To whom correspondence should be addressed; e-mail: [email protected], [email protected]
INTRODUCTION Impelled by the robust economy, global energy consumption has gradually increased in recent years, and a series of environmental problems caused by the combustion of fossil energy, the predominant component of the energy consumption, have attracted extensive concern worldwide (IEA 2
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