Comprehensive Prediction Of Reservoir And Permeability Body In The Second Member Of T₃x Formation In Penglai Area,Central Sichuan

As early as the 1950s,oil and gas exploration began in Penglai area of central Sichuan.Up to now,the discovery of oil and gas in continental strata mainly includes Jurassic J₁l,J₁dn and T₂l¹ reservoir,Jurassic J₂s Formation and Upper Triassic T₃x Formation reservoir.Among T₃x formation,the second member of T₃x formation has the best gas bearing property.The second member of T₃x Formation in Penglai area is a typical tight sandstone,which has the characteristics of strong non average,low matrix permeability and high water saturation.The industrial gas reservoir is mainly distributed in the reservoir and permeability body,and the low prediction accuracy of the reservoir and permeability body seriously restricts the pace of exploration and development.In this paper,the geological characteristics of the second member of T₃x Formation in Penglai area are systematically studied,and the distribution of reservoir and permeability body is comprehensively predicted.The results have certain guiding significance for exploration and development of tight gas reservoirs in Penglai and central Sichuan area.The second member of T₃x Formation in Penglai can be divided into three sub members from the bottom to the top:T₃x¹,T₃x² and T₃x³,of which T₃x³is the main sub member of reservoir development;the overall structural pattern of the ventral structure in the study area is generally similar to that of the surface structure,and the fault layers from the bottom of T₃x formation are generally distributed,while the faults from the section to T₃x⁴ are mostly concentrated in the north and the east of the work area;the sandstone in the second member of T₃x is the main sub member of T₃x formation The microfacies are dominated by a small amount of distributary channel microfacies;the sandstones in the second member of T₃x formation are mainly medium and fine-grained lithic arkose and feldspathic lithic sandstone,which are well sorted and moderately sorted;the most important thing to destroy the pores in diagenesis is compaction,the main thing to improve the reservoir is dissolution,and the fracturing is very important to improve the permeability;the two types of reservoirs are mainly developed in the second member of T₃x formation.The lower limit of permeability is 0.085m D,and the lower limit of porosity is 8%and 4%for pore type reservoir and fracture pore type reservoir,respectively,according to the gas reservoir engineering method,productivity coefficient method,production-Kh relationship method and empirical statistics method.The non-linear logging prediction model established by random forest classification algorithm has been successfully used to predict the reservoir type of T₃x member,the non-linear logging prediction model established by support vector machine regression algorithm has been used to accurately predict the reservoir porosity,and the combination of the two models has effectively predicted the distribution of the reservoir permeability body in the second member of T₃x member of a single well;after the well earthquake combination analysis,the curvature,coherence and other attributes have been optimized,Combined with the reflection abnormal body sketched by the characteristics of seismic reflection structure,the seismic comprehensive prediction of reservoir permeability body in the study area is carried out.This paper summarizes the four in one characteristics of"fault,fracture,facies and position"to control natural gas enrichment.Combined with the research results of fault,sedimentary facies,well logging reservoir prediction and seismic reservoir prediction,the favorable exploration area of T₃x member in Penglai area is determined.