Leikoupo Formation In Yilong-Pingchang Area Structural Style Analysis

The Yilong-Pingchang area is located in the northeastern part of the Sichuan Basin,between the central Sichuan gentle fold belt and the Dabashan fault fold belt.It is a favorable gas reservoir area on the northwestern margin of the Yangtze Plate.Overlying structures and typical compression structures are relatively developed.In this paper,guided by the principles of seismic exploration,structural geology,petroleum geology and other multidisciplinary theories,combined with geology,drilling coring,seismic data and various analytical data,the main research is the Leikoupo Formation in the upper structural layer of the study area.Object:Interpretation of horizons and faults for more than 300 two-dimensional survey lines and some three-dimensional work areas in the study area,and through time-depth conversion and correction,draw the target layer structure map,thickness map,iso-T0 map,and fault formation period map.In order to obtain an overall understanding of the Leikoupo Formation.details as follows:(1)The Yilong-Pingchang area has experienced multiple tectonic movements such as Jinning,Chengjiang,Tongwan,Caledonian,Indosinian,Yanshan,and Himalayas,among which the Indosinian,Yanshan and Himalayas have influenced the research area.The structure has the greatest impact,and a large number of thrust faults are the result of structural superposition and transformation at different stages.(2)According to the regional characteristics of the fault pattern,the study area is divided into two structural belts: the southern caprock detachment type low-gradual structural belt and the piedmont basement-involved high-steep structural belt.The southern caprock detachment type low-gradient structural belt mainly includes the Yilong-Yingshan area and the Pingchang area.The terrain is flat,medium and small-scale faults are relatively developed,mainly mainly northwest-trending faults;the piedmont basement is involved in the high-steep structural belt It is located in the northeastern part of the study area.The faults are well developed,mainly NW-trending and part of N-E-trending faults,with large undulations,most of which are thrust faults.(3)Under the joint control of Dabashan thrust nappe compression and surrounding mountains,the structure of the study area is mainly in compression style.At the same time,the compression stress propagates from northeast to southwest,leading to thrusting and overthrusting,forming a series of caprock slippage tectonic styles.On the plane,these structural styles are mainly normal,oblique,near-parallel,echelon,and branch faults.On the cross section,there are two types of base-entanglement and cap-slip fractures.There are mainly two structural styles.The former can be divided into hedging,backflushing,and imbricated thrust structural styles,while the latter includes fault-bending folds,imbricated thrust wedge,thrust imbricated fault blocks,and imbricated recoil.Construction style.(4)The structure in Yilong-Pingchang area has experienced multiple periods of tectonic movement and has a long time of evolution.The present NEE-trending and NW-trending structures have undergone multiple periods of development and evolution.Studies have shown that the NEE-trending structures developed in India.The branch stage was finally finalized in the early Himalayas: the NW-trending structure began to form in the late Yanshan period and was finally finalized in the late Himalayas.(5)Structural evolution and structural style are closely related to hydrocarbon migration.Through analysis of the relationship among structural features,formation stages,and structural deformation in the study area,it is clear that structural deformation plays a vital role in controlling gas The effect and storage conditions were evaluated based on this.It is believed that backwash and recoil structures are conducive to the accumulation of oil and gas,and the conditions for recoil structures are the best,and imbricated thrust structures are mostly developed in the piedmont.Therefore,this structural style has relatively poor conditions in terms of hydrocarbon accumulation and accumulation.