Characters And Fracture Prediction Of Tight Clastic Reservoirs

T3X formation in West Sichuan depression has become impotant exploration object nowadays. which has superior gas pool’s form condition, has achieved subtle result, and has superior exploration prospect. But because of many difficultly problem such as complex geology condition because of being located on Longmenshan front edge, low seismic-geology reservoir research technology etc, the exploration is difficult and slow. In order to have a better understanding of the characters of dense reservoir, we have carried out systematic research in this article.Based on analyses of regional geology background and information of outcrop, drilling, logging, laboratory test and seismic, mainly by seismic-logs-geology synthetic study, using many multi-disciplinary technology methods, this article has carried out detailed study on the problem of sourcearea, sedimentary facies, sequence stratigraphy, reservoir character, fracture prediction, mechanism of high quality sand, and superior reservoir prediction of T3X formation in west Sichuan.By the comprehensive studies of regional tectonical background, sedimentation evolution and interconnection of basin_mountain, the tectonical_sedimentary evolution of Long Men Shan Moutain and chuanxi foreland basin can be devided into three stage, eg. Early peripheral foreland basin stage, medium foreland basin developing stage and later foreland basin atrophy stage. The author proposes that the sedimentary stage of Xujiahe formation in west Sichuan depression was mainly influnced by the overthrusting of Long men shan mountain.Combined with regional tectonical evolution, this article carries out research based on sequence stratigraphy and seismic stratigraphy on Xujiahe formation reservoir. Through such study, the Xujiahe 2-4 section are devided into 3 long-term and 15 medium-term cycles, the contrast frame of sequence stratigraphy are constructed based on the combined method of loging and seismic data, and moreover unify the reflectivity horizon throughout Dayi and Yazihe region. The Xujiahe formation sedimentary face maps in west Sichuan are established constrained by the long-term cycles. The main source area are identified of Xujiahe formation sedimentation. Such view are expressed that lower Xujiahe formation are mainly formed in ocean and the upper in land envioment. We proposed favorabla reservoir region in each section, analysis the favorable reservoir fomed conditions.According to plenty of data of testing and anlysis, the article carries out study about lithology character and diagenesis of Xu jia he formation. We come to a conclusion that the rock is mainly compsosed of debris quartz sandstone and feldspar debris quartz sandstone, the textural maturity is medium, the accumulation room is mainly composed of secondary hole, the pore space type is mainly composed of medium hole and fine throat type. The property of reservoir is subaltern, which porosity and permiality is low. The main distructive diagenesis involve compaction, pressolution and agglutination, the main constructive diagenesis involve corrosion and cataclasis. Now the diagenesis has come to later period of medium diagenesis.Through analysis of fracture geology cause and application of seismical fracture prediction means, we carried out fracture prediction,analized the advantage and disadvantage of each means. Moreover we point out that the Packaged fracture prediction means are comprehensive predicition of geology and P-wave anisotropy fracture prediction.Based on the comprehensive anlysis of reservoir development condition, we approach the form mechanism of favorable reservoir, and make clusion that the quality reservoir are influenced by multi-factor such as structure evolution, sedimentary faces, diagenesis and fracture.