Sequence Stratigraphy And Sedimentary Facies Study Of Leikoupo Formation In The Southern Part Of The Western Sichuan Depression

The west Sichuan depression area located in a croton background during Palaeozoic Erathem and evolved gradually into a foreland basin with the uplift of Longmenshan. This area was shallow water carbonate platform sediment in Mid Triassic. Recently, there are many achievements about Mid Triassic Leikoupo group in the whole Sichuan basin. And since there are many great achievements in Zhongba gas field exploration in 1970s, good reservoirs and hydrocarbon evidence are found in different district. However, the exploration process of marine formation in west Sichuan depression is slow and no great achievement by now. The main reason is the inadequacy study of this area. This paper uses sequence stratigraphy theory, utilizes the present seismic section sufficiently, combines outcrops and logging data, and divides the sequence of Leikoupo group in south part of west Sichuan depression. The Leikoupo group is divided in to SQ1 and SQ2, two three-third sequences in which each three-third sequence is divided into transgression system tract (TST) and high system tract (HST), and fulfilled lateral comparison. The sequence stratigraphy framework of Leikoupo group in study area is built up. Through the comparison of sequence, there was Tianquan paleo-uplift of Indo-Chinese epoch. Using three-third sequence as compilation unit, and using the seismic shape, inner texture and physical parameter of seismic reflected wave as compilation elements, the seismic facies flat sheets of Mid Triassic Leikoupo goup SQ1 and SQ2 sequence are compiled. On these basis, combined logging and outcrop d?? seismic facies are changed into sedimentary facies. Using system tract as unit, four period sedimentary facies maps of Mid Triassic Leikoupo group are compiled, and the main sedimentary facies are open platform, restricted platform and evaporation. Though the sedimentary facies study, this paper predicts the beneficial reservoir facie belt of Leikoupo group formation in the south part of west Sichuan depression, suggesting that the carbonate grain shore overlapped on the paleo-uplift ramp is beneficial facies belt and regarding the key area of further exploration.