Research On Formation Ability Of Artificial Fracture Network In Tight Reservoir

Tight oil and gas reservoirs must be hydraulic fractured to form effective productivity.The artificial fracture network formation ability of reservoirs is the core issue of reservoir reconstruction.So far,people mainly use the ?brittleness? as the parameter of ?compressibility? to evaluate the artificial fracture network formation ability.However,?brittleness? belongs to small-scale and scalar mechanical property of core,which is not sufficient enough to represent the three-dimensional expansion rule of artificial fractures in large-scale rock mass.In view of the complex geological conditions in China,this paper analyzes the rules and influencing factors of artificial cracks in three-dimensional space.It is concluded that the matrix brittleness is often not a restrictive factor in determining the formation capacity of the reservoir seams,and more factors should be taken into account,including brittleness of the reservoir,horizontal stress difference,interlaminar stress difference,bedding,the degree of natural fracture development and local structure,etc.The paper attempts to propose an evaluation method of the formation capacity of the tight reservoir artificial fracture network.This method is applied to the evaluation of shale gas reservior in Baojing of Hunan and tight gas reservoir in Jinlin.It is concluded that local small structure and inclined bedding are important factors affecting the formation ability of the fracture network of well S in the shale gas reservoir of Baojing,Hunan.The local small structure causes high horizontal stress and stress difference,and the inclined bedding affects the shape and width of vertical cracks,which affects the construction pressure,the efficiency of adding sand and the complexity of fracture network.The factors influencing the difference of post-fracturing effect between well A and B in Yingtai fault depression of Jilin oilfield are the degree of natural fracture development.Excessive expansion of vertical fractures under large displacement is an important problem that affects the formation ability of layered formation.This paper is a preliminary exploration of the evaluation method for artificial fracture network formation capacity of tight reservoirs,which still belongs to semi quantitative analysis and needs to be further improved and developed to the direction of quantitative evaluation.