China Petroleum Exploration ›› 2020, Vol. 25 ›› Issue (6): 94-104.DOI: 10.3969/j.issn.1672-7703.2020.06.010

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Influence of natural fractures on fracturing of horizontal shale gas wells and process adjustment

Zhou Xiaojin, Yong Rui, Fan Yu, Zeng Bo, Song Yi, Guo Xingwu, Zhou Nayun, Duan Xiyu, Zhu Zhongyi   

  1. Research Institute of Shale Gas, PetroChina Southwest Oil & Gasfield Company
  • Online:2020-11-12 Published:2020-11-12
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Abstract: Network fracturing is the practical implementation of the development mode of “fracture-controlled reserves” in shale gas wells. Natural fractures are an important factor affecting hydraulic fracture propagation and post-fracturing effects. In China and elsewhere numerical simulation is the normally adopted method for studying naturally occurring fractures. However, based on field practice and statistical data analysis, this paper uses the classification method to examine the influence of natural fractures with different characteristics on fracturing operations and post-fracturing effects and carries out field research and evaluation of improvements to reservoirs in which natural fractures are developed. The results show that: (1) For reservoirs with natural micro-fractures, problems such as difficulty of proppant adding, small stimulated reservoir volume, and poor simulation effect can be addressed by adopting “pad high-viscosity fracturing fluid + low-viscosity slick water carrying proppants”. (2) For reservoirs with large-scale natural fractures, the complexity of fractures following artificial fracturing is low and the fracturing effect is not favorable. Large-scale natural fractures intersecting with wellbores at large angles are the geological factor that may be responsible for casing deformation and frac hit. There are some uncertainties regarding the effects of temporary plugging diversion fracturing processes on fracture propagation interaction and improvements in stimulation effects. (3) Follow-up research should focus on improvement of fracturing effects when large-scale natural fractures are parallel to the wellbore, as well as prevention of casing deformation and frac-hit when large-scale natural fractures intersect with wellbores.

 

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