PROBE INTO SUBLACUSTRINE FAN OF TRIASSIC IN AKEKULE AREA,TARIM BASIN

Based on the observation of cores,grain sizes of the middle oil member are coarser in Akeyasu area at northern study area of Triassic,and the lithologies include conglomerate and pebbled sandstone.The compounds of pebbles are complicated with significantly various grain sizes and poor sorting,the sediments are supported by matrix,and Bouma sequences are well developed.Integrated with analysis of logging data and seismic data,the sedimentary facies of northern Akekule area are confirmed as sublacustrine fan.The fan can be divided into three subfacies that include middle fan,fringe fan and canyon,the middle fan is the principal part,in which,the depositional grain sizes are the coarsest,the middle fan can be divided into braided channels and inter-channels mircrofacies.Fringe fan is distributed outmost of sublacustrine fan,being transitional belt between sublacustrine fan and basin.Canyons are transportation way of terrestrial source area for sublacustrine fan,and the main deposition is sandstone (pebble) and mudstone,logging data presents two-stage positive rhythm layers,the feature is corresponding with depositional characteristic of sublacustrine fan.Sandstones of canyon and middle fan is all favorable petroleum accumulation bodies in the area.