Identification And Evaluation Of Fracture Reservoir In The Second Member Of Xujiahe In Yuanba Area

The second member of Xujiahe in Yuanba gas field is a typical tight sandstone reservoir,which is characterized by complex pore structure,poor physical property and strong heterogeneity.For this kind of reservoir,fracture can make some poor reservoir rocks become profitable by offering space and migration pathways for oil& gas.At present,the Yuanba gas field uses rolling development,and the exploration of continental strata is at the early stage.As the favorable continental gas reservoir,the second member of Xujiahe gas reservoir mainly relies on fracture to get Industrial flows.Therefore,the research on fracture characteristics and distribution can provide evidence for the further exploration and development.At first,this paper makes full use of the core fracuture observation to analyse the occurrence,horizon,lithology,fracture face,filling condition,density,length,width of the fractures.It is conclude that there are mainly low angle and horizontal fractures in the second member of Xujiahe reservoir,and the fractures are often effective for most of then are half-filled or open.Imaging logging fracture identification is carried out according to the core data,and the fractures are classified as the open fractures,the half filled fractures and the full filled fractures.Then,fracture occurrence and strike are calculated.After analysing the response characteristics of the fracture in the conventional well logging data,the fracture width and porosity are explained.Using discriminant analysis,R/S fractal method,BP neural networks to identify the fractures in the the second member of Xujiahe reservoir.At last,this paper establishes a comprehensive criterion of identification which is based on the conventional logging,and the comprehensive identification result is consistent well with the core data.Based on core observation and logging interpretation,this paper concludes that bed thickness,fault and regional tectonic stress have different effects on the development of natural fractures.A method of combination evaluation is used to evaluate fractures in second member of Xujiahe reservoir,and the research area is divided into fracture developed area,fracture relatively developed area and fracture poor developed zone.The evaluation results are in good agreement with single well fracture interpretation,testing data and production test data.