Mechanisms and impact patterns of frac hits between shale gas wells
In the process of volumetric fracturing of shale gas reservoirs by horizontal well volume fracturing in the southern Sichuan Basin,geological and engineering factors make it easy for hydraulic fractures to communicate with large-scale natural fractures in a single direction and propagate excessively,inducing rapid pressure increase in adjacent wells.This ultimately results in frac hits,casing deformation and other problems,which have a direct effect on the shale gas production of individual wells.To address the diverse patterns of frac hits,unclear understanding of mechanisms,and limited effectiveness of control measures in shale gas reservoirs of the southern Sichuan Basin,this paper establishes a fully-coupled numerical simulation model for multi cluster synchronous expansion of shale gas horizontal well fracturing.Then,the impact patterns of different types of frac hits are illustrated.Finally,the effective methods for treating frac hits are proposed.And the following research results are obtained.First,in the reservoirs with developed natural fractures,the fractures induced by horizontal well volume fracturing tend to propagate along the dominant bands of large-scale natural fractures in a single direction,which has a direct or indirect impact on adjacent wells,causing abnormal pressure increase.Second,the impact of frac hits can be alleviated to some extent if a shale gas horizontal well avoids fracturing in high-risk stages or the fracturing intensity is reduced.Third,when there is a depleted adjacent well near the fractured well,fractures are more likely to propagate to the low-stress zones of the adjacent well,resulting in frac hits,and the extent of frac hits is closely related to the elastic properties of rock pores.In conclusion,frac hits of shale gas horizontal wells can be reduced effectively by avoiding perforating in high-risk stages and controlling fracturing intensity reasonably.The research results can provide technical guidance for the fracturing development of shale gas reservoirs by horizontal well volume fracturing in similar shale gas blocks at home and abroad.
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