Palaeogeomorphology Restoration And Gas-bearing Evaluation Of Pre-carboniferous System In Southwestern Ordos Basin

The geological conditions of the lower Paleozoic strata in the southwest of Ordos Basin and the existing exploration practice show that the lower Paleozoic strata in the area are rich in natural gas resources.Due to the lack of research on the lower Paleozoic strata in the early stage,the types and distribution of reservoirs in the area are unclear.Therefore,in combination with 2D and 3D seismic data,geological data and logging data,this paper identifies the lower Paleozoic strata in the southwest area of Ordos Basin,and studies the formation and evolution process of the central palaeouplift and the palaeogeomorphology of the pre-Carboniferous.Curvature body,coherence technology and ant body technology are used to predict reservoir fractures and define fracture distribution characteristics.The types of lower Paleozoic reservoirs in the central paleo uplift of the basin are defined and classified,and their reservoir properties are evaluated,and favorable gas-bearing areas are predicted.It provides scientific theoretical basis for the exploration and development of pre-carboniferous reservoirs in the southwest area of Ordos Basin.The results show that:The overall structure of the study area shows a tectonic trend of gradually rising from west to east.The western and eastern fault zones are relatively developed,while the central fault zone is relatively less.The development of faults plays a certain role in the migration and blocking of natural gas.The traps formed in the area are mainly fault block traps.The erosion surface structure of the target layer in the study area is mainly influenced by the hercynian,Indosinian,Yanshan and Xishan tectonic movements,among which the Yanshanian tectonism is relatively strong.The pre-carboniferous palaeogeomorphology in Longdong area is divided into karst highland,terrace and sub-depression sub-geomorphology units,which are different from the jingbian trench model.By elaborating the palaeogeomorphology,the theory of central palaeouplift palaeogeomorphology controlling the reservoir is proposed for the first time,which has certain guiding significance for the exploration and development of the upper and lower Paleozoic natural gas.