Karst Palaeogeomorphology Restoration And Reservoir Prediction Of Maokou Formation In Kaijiang Area

The Kaijiang area is located in the northeastern part of the Sichuan Basin,and most of them are in the karst slope zone,which is conducive to the development of karst reservoirs.However,the predecessors have less exploration and development work for the Maokou Formation in the Kaijiang area.In response to this problem,this paper calibrates the horizon based on the seismic data and the recent WT1 wells in the area and the review of some old wells.On the basis of the structural interpretation,the karst palaeography in the area is restored by the residual thickness method and the impression method,the karst paleo-geomorphology of the study area is discussed,and the paleo-geomorphic unit is divided.The geological lithology data,drilling data and seismic response characteristics are also utilized.To identify the reservoir type,and to analyze the control factors of reservoir development in the Maokou Formation of the study area;finally,to extract the reservoir plane by extracting seismic attributes such as coherence,curvature and amplitude,combined with karst paleogeomorphology,fracture prediction and oil and gas detection.Spread predictions to determine favorable development areas for karst reservoirs.The results achieved are as follows:Most of the study area is located in the karst slope,which can be divided into three types of karst micro-geomorphic units,such as mounds,slopes and shallow shoals,and the well-measured wells are located between the karst slopes and the shallow ridges.The development of water flow and strong dissolution are conducive to the development of epigenetic karst reservoirs.The karst reservoirs of the Maokou Formation in the study area are mainly fracture-cavity karst reservoirs,including fracture-pore type and fracture-hole type.The reservoir types include karst weathering crust(grey rock karst fracture hole)and dolomite(intercrystalline dissolved hole),and the reservoirs in the Tanmuchang area are mainly distributed at the top of the Maokou Formation,and the reservoir distribution in the Wuyixi area In the middle of the Maokou group.The reservoir development of the Maokou Formation in the study area is mainly controlled by karst paleogeomorphology.The fractures caused by early tectonic movement make the karstification more intense.This karstification is the main controlling factor of reservoir development;the deep fault formed by the Caledonian period makes The magmatic hydrothermal fluid transforms the reservoir of the Maokou Formation along the lateral direction of the deep fault.This hydrothermal dissolution has become a secondary control factor for the development of the reservoir of the Maokou Formation.The reservoir type I favorable area in the study area is located in the karst slope ancient water flow development area,the fracture development is better,and the oil-bearing property is better.The second-class favorable area is in the area of hydrothermal dissolution modification,the crack is relatively developed,and the oil and gas is more concentrated.