Identification And Evaluation Of Lithological Trap In The Shushanhe Formation In Ninth District Of Tahe Oilfield

Tahe Oilfield is located in the Northeast of the Tarim Basin in Sinkiang.At present,exploration and exploitation of oil and gas in clastic rocks in Tahe Oilfield has entered the middle and late stages,and the exploration targets have shifted from large-scale structural traps to small-scale lithologic traps.With the breakthrough of exploration of lithologic reservoirs in T903 well area in recent years,the Northwest petroleum Bureau has paid more attention to the Cretaceous Shushanhe Formation in ninth district of Tahe Oilfield.The exploration degree of lithologic traps in the Cretaceous Shushanhe Formation is relatively low,and lack of geological data.There are many problems that hinder the exploration of oil and gas in the Shushanhe Formation.The main stratigraphy of the study is the Cretaceous Shushanhe Formation.Based on the analysis of logging curves and seismic data,under the guidance of high-resolution sequence stratigraphy theory,the Cretaceous Shushuhe Formation is divided into 1 long-term cycle(KLSC1)and 3 medium-term cycles(KMSC1 ~ KMSC3)and several short-term cycles,and established isochronous stratigraphic framework.This paper studies the transverse and vertical distribution characteristics of sand bodies and sedimentary facies in isochronous stratigraphic frame.The KMSC1 cycle of the Shushanhe Formation are mainly braided river delta front subfacies,microfacies include underwater distributary channel and diversion bay,sand bodies served as reservoirs in the study area are mainly underwater distributary channel sands,and the continuity of sand bodies is good.The oil and gas reservoirs of logging explanation are mainly concentrated in the cycle of the upper layer(sand group 2 and sand group 3).The KMSC2 cycle in Shushanhe Formation are mainly shore-shallow lake subfacies,and microfacies include shallow lake mud and sand dam,mainly developing sand bar sand bodies,and massive distribution in the plane,the horizontal sand bodies are not continuous.But oil and gas layer mainly concentrated in the lower part of the cycle(sand group 4 and sand group 5).The KMSC3 cycle of the Shushanhe Formation are mainly braided river delta front subfacies,and microfacies are underwater distributary channel and diversion bay,and characterized by developed sandbody,good continuity,but there is no oil and gas.Through comparison and analysis of the extracted seismic attributes,it is show that the average absolute amplitude attribute is good for reflecting sand and mud.On the basis,statisticsing and analyzing correlation between the average absolute amplitude attribute value at the well point and sandstone thickness,which could reveal distribution of the sand body.The conventional wave impedance inversion profiles in the study area can not distinguish well sandstone and mudstone,and the pseudo-acoustic inversion can be used to identify more than 8m sand bodies.There were 11 traps in the KMSC1 ~ KMSC2 cycle of the Cretaceous Shushanhe Formation in ninth district of Tahe Oilfield,including 8 lithologic traps and 3 tectonic-lithologic traps.According to the development of sand bodies,sealing ability of cap rock,oil-bearing properties,and the oil source of the integrated situation,optimized one ? class trap.