Research On Volume Estimation Algorithm Of Shale Fracturing Reformation

Shale gas is the main exploitation resource of unconventional petroleum resources.Because of its abundant resources,people pay more and more attention to it.However,due to its physical properties of low porosity,low connectivity and low permeability,reservoir fracturing technology is needed to improve its rock physical properties.At present,the hydraulic fracturing technology is the most widely used in the exploration and development of shale reservoirs in China,which is mainly a fracturing technology that uses hydraulic action to form artificial fractures in shale gas reservoirs and greatly improves the fluid flow capacity in shale gas reservoirs.In the process of hydraulic fracturing,there is a complex fracture network structure in the reservoir.As a very important penetration space in shale reservoir,these fracture networks not only improve the heterogeneity of rock,but also act as the main migration channel of shale gas in shale reservoir,which has a very important influence on the final productivity of shale gas wells.Therefore,as the main measure of shale gas reservoir stimulation,shale reservoir fracturing technology has very important research significance for shale gas exploration and development.How to accurately estimate the fracturing volume and find out the influencing factors of fracturing effect is the main problem of this paper.The distribution of microseismic events in the process of hydraulic fracturing is very irregular,and most of the traditional methods use some regular single model to estimate SRV,which can not be well treated for the cross overlap of fracturing volume in the actual fracturing process,so that the final calculation results are very rough.In this paper,the stress effect of shale fracturing reservoir is analyzed,and the minimum closed ellipsoid algorithm is proposed to estimate SRV.In view of the actual fracturing process,the multistage fracturing volume overlap and the complex fracture network formed by single stage fracturing are analyzed.Firstly,the density clustering algorithm is used to deal with the microseismic events of each stage,and the abnormal microseismic events are eliminated.Then,the minimum closed ellipsoid corresponding to each stage of microseismic events is estimated by the minimum closed ellipsoid algorithm,and the relevant parameters of the ellipsoid are obtained.Then,the gridding of the fracturing operation area is carried out,and the relationship between each fracturing volume is estimated.Secondly,in this paper,in the process of shale fracturing,some reservoir fracture network structure expansion mechanism is very complex,there are some complex fracture network can not be described by a single ellipsoid model,this paper studies the irregular three-dimensional model construction method,through the construction of three-dimensional irregular polyhedron to estimate the SRV,first of all,using DBSCAN algorithm will microseismic event points according to the spatial distribution density is divided into different clusters,eliminate the interference of microseismic event abnormal location points,and then through the Delaunay triangulation algorithm to calculate the microseismic event points,forming the initial convex hull,finally through the boundary depression algorithm proposed in this paper to eliminate the initial convex hull of non-productivity area,construct a closed three-dimensional irregular envelope,by calculating the volume of its internal tetrahedron to obtain the overall fracturing volume.Finally,this paper analyzes the productivity of SRV after fracturing.Firstly,the fracture volume is calculated by the filtration model,and then the SRV is calculated.The proportion of fracture volume in the unit reservoir,the fracture volume density,is used as the evaluation standard of shale gas productivity benefit,which makes up for some unreasonable problems in the productivity prediction of SRV after fracturing.