Deposition And Stratigraphic Sequence Evolution Of Cretaceous In Halahatang Depression Of The Tabei Uplift And Potential Reservior Prediction

Halahatang depression is located in the central of North Tarim Uplift.In the view of the weak research and ambiguous understanding of the sequence and sedimentary evolution of the Lower Creataceous,the thesis carry out research on the sequence stratigraphic framework and sedimentary facies,through comprehensive analysis of cores,well logs and seismic data.The author established the sequence stratigraphic framework and on the base of this framework,the time-space evolution of sedimentary system is analyzed.High frequency sequence division and comparison is used in important sequence,which is combined with analysis of hydrocarbon accumulation condition,the favorable zone is predicted.In the study area the Kapushaliang group is a regional second-order sequence which is limited by angular unconformity.This second-order sequence is a sedimentary cycle of transgression to regression,in which five third-order sequences are recognized as well as four important maximum flooding surfaces.There are two types of third-order sequence boundary.One is sedimentary transformation,the other is the local unconformity.The sedimentary cycle in the third-order sequence change with the second-order sequence.In the early stage,the low system tract is developed;in the middle stage the transgressive systems tract is developed but almost have no low system tract;in the late stage,the high system tract is developed well the low system tract and the transgressive system are thin.The Creataceous in the study area is shallow lacustrine deposits which include facies of braid-river,meandering river delta and shore-shallow lacustrine.The lower sedimentary is mainly composed of braid-river,meandering-river delta;the middle sedimentary is mainly composed of shore-shallow lacustrine and delta-front;the upper sedimentary is mainly meandering-river and meandering-river delta.The sediments source is in the south and in the plane the sedimentary can be divided to 3-4 facies belts,delta plain,proximal delta front,distal delta front,and prodelta-lacustrine.The research show that in the study area the oil migrated in the TK unconformity and then arrived to trap from faults.So the faults in the study area are very useful in predicting favorable zone.The favorable facies belts are distal delta front and shore-shallow lacustrine,where develop lithologic lenticular such as delta front far bar sand and beach bar.The river channel sand matched with fault can become structural lithologic traps.