Phenomenon and mechanism of multi-well frac hits hydraulic fracturing in Weirong deep shale reservoir
The reservoirs of Wufeng Formation and Longmaxi Formation in Weirong deep shale gas field have deep burial depth,complex geological structure,strong heterogeneous natural fractures,high ground stress and large horizontal ground stress difference,and discontinuous structures are prone to disturbance and instability under high critical stress environment.Under the joint action of local continuous fracture zone development and high stress environment,frac hits in adjacent wells and multi-well roadway occurred under the condition of 400 m well spacing in the early stage,which led to the decrease of productivity of a large number of production wells,borehole instability and casing change of continuous wells.In view of the above problems,based on the idea of geological-engineering integration,the distribution characteristics of multiple complex natural fractures and the disturbance effect of complex fracture propagation stress are taken into account,and a well group fracturing complex fracture propagation model based on DFN-FEM is established in this paper.The results show that:(1)Natural fracture zone and large fracture are the main geological factors of multi-well roadway pressure channeling.(2)The smaller the normal stiffness of natural fracture surface,the larger the fracturing stress disturbance range and the more serious the frac hits.(3)The smaller the internal friction angle and cohesive force,the easier the rock is to break and induce frac hits.(4)The fracturing sequence of well group has a significant influence on the type and degree of frac hits,and the staggered fracturing is the best.The research results can provide a basis for the prevention and control of inter-well interference and productivity recovery of Weirong shale gas horizontal wells,and then effectively support the safe and efficient development of deep shale gas fields represented by Weirong.
inter-well interferencemulti-well fracturingcomplex structuresdeep shale gasWeirong gas field
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