Fine Logging Evaluation Of Natural Fractures In The Keshen 8 Ultra-Deep Gas Field, Kuqa Depression

The Bashijiqike Formation in the Keshen 8 gas field is defined as naturally fractured sandstone reservoir which shows ultra-low matrix porosity and permeability.The extensively-developed natural fractures increase the total formation permeability,thus resulting in high productivity in the petroleum wells.Hence,fracture characterization in the Bashijiqike Formation,including geometrical features,development pattern and effectiveness evaluation,will provides significant in formation for the reservoir development.In this study,borehole imaging log,dipole shear log,cores,casting thin sections and testing data were integrated.Based on core-image integration,natural fractures in the target formation were finely evaluated.The study indicates that natural fracture in the Bashijiqike Formation mainly results from tectonic deformation?tectonic origin?;and diagenetic fracture is poorly developed.High fracture dip generally varies between 60°and 90°.The Keshen8 gas field belongs to a folded anticline and develops a mass of thrust faults,dip azimuth of natural fractures is opposite with formation azimuth.Furthermore,fracture pattern is controlled by regional stress and lithofacies.Fracture effectiveness can be evaluated via a combination of electrical and sonic imaging log.Permeability derived from stoneley wave represents fracture permeability which is distinctly larger than matrix permeability.Moreover,the determination of maximum horizontal stress(S_Hmax) orientation indicates that gas productivity in the Keshen8 gas field shows poor correlation with S_Hmax orientation.The gas productivity is more related to fracture intensity.The research above make significant contribution to the further development in Kenshen area.