High-resolution Sequence Stratigraphy And Sedimentary Facies Of The Jurassic Liangshan Formation In Gong 39 Well Area Of ??Gongshanmiao Oilfield, Sichuan Province

Taked the Lianggaoshan Formation in the Gong 39 well area of Gongshanmiao oilfield in the central Sichuan Basin as the object of study,the theories and techniques such as high resolution sequence stratigraphy,sedimentology,petroleum geology and logging geology are used to achieve the sequence stratigraphy and sedimentary facies study in Lianggaoshan Formation,which are finished on the conditions of full investigation of previous research results and combing with the basic geological data and logging data.According to the above research methods,quantitative analysis of wavelet transform of log data help to identify several sequence interfaces with different properties and genesis of the Lianggaoshan Formation.The sequence interfaces include 1 long-term base level cyclic sequence(LSC),2 medium-term base level cyclic sequences(MSC)and 7 short-term base level cyclic sequences(SSC).Based on the analysis of sequence structure of high resolution sequence stratigraphy and different levels of base-level cycles in wells,the sequence stratigraphic comparison is carried out by the comparison unit of the medium-term base level cyclic sequences,and a high-precision sequence stratigraphic framework is established based on the short-term base level cyclic sequence.Through the detailed observation on the drilling cores of the Lianggaoshan Formation in the Gong 39 well area of Gongshanmiao oilfield in the central Sichuan basin,combining with regional geologic background,drilling and logging data,the sedimentary microfacies of the Lianggaoshan Formation are analyzed.It is considered that the Lianggaoshan Fonnation mainly develop the 3 parfacies of lakefront,shallow lake and half-deep lake.The microfacies types are mainly the lakeside mud,lakeside sand dam,shallow lake mud,beach bar and sheet sand,and turbidite is developed in some areas.The characteristics of each type of microfacies are described in detail.At the same time,the comparison of sedimentary facies are carried out insided the stratigraphic framework which are based on the short-term base level cycle.Through the isoline maps of sand ratio and sandstone thickness,the plane distribution of sedimentary microfacies boundary is determined and sedimentary microfacies maps are established.On this basis,the evolution law in vertical and horizontal of the sedimentary facies in the Lianggaoshan Formation are analyzed,and the sedimentary facies models in the study area are established in different sedimentary periods and backgrounds.On the basis of the above research,according to the collected data and the previous research results and combining with the present situation of exploration and development,the distribution and the plane distribution characteristics of main sand bodies in the Lianggaoshan Formation of the research area are analyzed inside the high-resolution sequence stratigraphic framework.Sandstone in bar of the shore-shallow lake is thought to be a favorable reservoir rock,which can select two favorable areas.