Provenance System, Sedimentary Facies And Reservoir Characteristics Of Bashijiqikeian-Kumugliemuian In Western Kuqa Depression

The reservoir characteristics of Cretaceous Bashijiqikeian-Paleogene Kumugliemuian inwestern Kuqa Depression were analyzed by applying the techniques of provenance,sequence stratigraphy together with depositional system and reservoirmicro-characteristics.In studied region, western part and eastern part had different heavy mineral assemblage.Sediment of Bashijiqikeian-Kumugliemuian was deduced to have two provenancesystemswhich came respectively from the west Wensu uplift and the East-Southeast provenance byanalyzing the heavy mineral assemblage and the distribution of heavy mineral assemblagezone. Relatively, the west provenance was a near-end provenance, and the east provenancewas a far-end provenance. The provenance of Kumugeliemuian inherits somecharacteristics of Bashijiqikeian.According to the theory of base-level cycle, Bashijiqikeian-Kumugliemuian was dividedinto four long-term cycles from bottom to top, and there was only one long-term cycle andfour to seven middle-term cycles for Bashijiqikeian, and Kumugliemuian was divided intothree long-term cycles. Based on comparison result of divided middle-term cycles ofBashijiqikeian, strata contour and seismic data, the northwest part was inferred to anancient uplift that the bottom had been overlapped in the initial depositional stage anderosion occurred during the depositional or post-depositional period. Combined with stratacontour of Kumugliemuian, it was found that the northwest part changed from the upliftingto subsiding in the Bashijiqikeian period, which might have a significant impact on thereservoir characteristics of northwest part. By analyzing cores, logging data and drawingsandstone/strata contour, it was deduced that sediment of Bashijiqikeian mainly developedbraided delta front underwater distributary channel and river mouth bar microfacies, andKumugliemuian developed marine invasion facies, including lagoon, littoral deposit andbraided delta facies.Generally, the east reservoir rock was represented by feldspathic litharentie, which wasbetter sorted, looser and sub-angular to sub-rounded. Its space was primarily composed byprimary inter-granular pore, accompanied by a few dissolved inter-granular pores.Dolomite and analicime were the typical cement materials. The west reservoir rock wasrepresented by lithic arkose, which was worse sorted, more compacted and angular tosub-rounded, with the space primarily composed by inter-granular dissolved pore, andanhydrite, calcite and dolomite were the main cement materials. Dividing the diagenesisstages based on authigenic mineral assemblage, reservoir space type and ratio of claymineral mixed layer (S %), Bashijiqikeian-Kumugliemuian reservoir was in the middlediagenesis A1-A2 stage. Factors including sedimentary facies, rock type, tectonic action anddiagenesis had a combined impact on the quality of reservoir. For Bashijiqikeian reservoir,the east part was Typeâ… and the west part belonged to Type â…¢. For Kumugliemuianreservoir, the middle-east part was Typeâ… , and the west part belonged to Typesâ…¡ and â…¢.