Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (1): 229-240.doi: 10.11743/ogg20220119

• Methods and Technologies • Previous Articles     Next Articles

Numerical simulation of evenly propagating hydraulic fractures with smaller cluster spacing in the horizontal well YYP1 for deep shale oil in the Shengli Oilfield

Haiyan Zhu1(), Xinqin Xu1, Anhai Zhong2, Qinxi Zhang3   

  1. 1.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu,Sichuan 610059,China
    2.Petroleum Engineering Technology Research Institute,Shengli Oilfield Company,SINIOPEC,Dongying,Shandong 257000,China
    3.Chunliang Oil Production Plant,Shengli Oilfield Company,SINOPEC,Dongying,Shandong 257000,China
  • Received:2020-07-20 Revised:2021-12-01 Online:2022-02-01 Published:2022-01-28

Abstract:

Shale oil in China is generally high in viscosity and stored in highly heterogeneous shale reservoirs, which often respond poorly to stimulation of staged volume fracturing (each stage) with multi?perforation clusters. Increasing the cluster number in each fracturing stage of a horizontal well to evenly facilitate fracture propagation has been considered an effective solution to the problem. This study is focused on the friction of fluids flowing through several thousand meters of fracturing strings and the perforation holes as well as the competition among fractures for the fluids, to establish a seepage-stress-damage model for the description of dynamic propagation of the fractures. The effectiveness of the model is demonstrated with actual fracturing data in the Shengli Oilfield, where numerical simulations were carried out to investigate the impact of different numbers of perforation clusters and perforation holes as well as varying fracturing parameters on fluid distribution, stress, and fracture geometry based on geological characteristics of shale oil reservoirs in the area. Findings include: The optimal propagation distance for crack?induced stress is ~10 m for fractures created by single perforation cluster. With a 10 m cluster spacing and three clusters, evenly propagated fractures can be achieved with a perforating density of 20 holes per meter with fluid displacement at 12 m3/min and fracturing fluid viscosity at 30 mPa·s. With four perforating clusters for each fracturing stage, the optimal cluster spacing is 10 m for an uniform distribution of fluid and even propagation of fractures being achieved. This study lies down a theoretical foundation for effective shale oil exploitation in the Shengli Oilfield.

Key words: smaller cluster spacing, multi fractures, even propagation, induced stress, seepage-stress-damage model, horizontal well, shale oil, Shengli oilfield

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