Study On Logging Reservoir Evaluation Of The Qixia And Maokou Formation Of Lower Permian In Sichuan Basin

In the middle of Sichuan basin,Maokou and Xixia Formation carbonate reservoirs,due to the development of fracture and dissolution pores,pore structure of these reservoirs is very complicated with obvious heterogeneity,creating difficulties to reservoir logging evaluation.This article puts geological data including core analysis,logging,drilling and gas testing combined,making the most use of log data such as conventional log,natural gamma ray spectrometry log,electricity imaging log,array acoustic logging and ECS log data,forming a set of logging evaluation technology and method.Reservoirs in the study area mainly consist of limestone and dolomite while Maokou formation of part wells contain some silicon and exist heterogeneous rock structure.Reservoir space mainly consists of crack and pores,resulting to the large difference of reservoir physical properties.The gas test shows that possibility of gas-bearing is good.In combination with conventional,imaging and acoustic logging,different rock properties,heterogeneous rock structure,gas content and log responses of different reservoirs have been studied.Combine with cross plot technique and image mode method,creating logging identifying methods for rock properties,heterogeneous rock structure and different reservoir types.Based on the analysis for log response of crack and hole,this article studies fracture recognition using conventional log and electricity imaging log and fracture parameter including angle,opening and fracture porosity calculation methods as well as methods using electricity imaging log to recognize hole and calculate its parameters.Combined with conventional logging and ECS logging,this article takes advantage of optimization algorithms to solve reservoir mineral composition.Using core scale log to multivariate function fitting and the skeleton logging value is determined,meanwhile combine with rock volume physical mode to establish porosity calculation model.Make use of the relation between porosity and permeability,FZI flow unit index method to construct model for calculating permeability.Based on Archie equation,combine with rock electrical parameters by experiments,the saturation calculation formula is determined.Combine with gas test data,use pore-electricity intersection,P^1/2 discrimination,vertical and horizontal wave velocity ratio and dual-porosity overlapping methods to process the gas potential of reservoirs.Define the least porosity of effective reservoir by means of porosity-water saturation intersection.Take advantage of the stoneley wave energy attenuation and image log to calculate areal porosity and form the evaluation criterion for effective reservoirs.On the basis of the foregoing,determine the reservoir logging evaluation method for this study area at last.