Genetic Model And Distribution Of Ordovician Paleokarst Fracture-Cave Reservoir In Lungu7 Area

The Lungu 7 area is a major development test area for fractured-vuggy carbonate reservoirs in Tarim Oilfield.It has various types of reservoirs,complex genesis,and strong heterogeneity,making it difficult to identify and predict reservoirs.The Lungu 7 area has entered the stage of water injection and gas injection development,but the single well controlled reserve scale is small,the productivity is low,and the connection relationship between fractures and caves is complicated.The existing understanding of traditional buried hill karst reservoirs cannot meet production needs.This dissertation takes the Ordovician Yingshan Formation karst fracture-cavity reservoir in Lungu 7 area as the research objective,and takes reservoir geology and karst geology as theoretical guidance,and comprehensively utilizes similar outcrop areas,cores,logging,seismic and production Dynamic data,identify and characterize faults and karst fractured-vuggy reservoirs,comprehensively consider factors such as karst paleomorphology and faults,and re-understand the genesis mode and distribution law of karst fractured-vuggy reservoirs under different control factors.The Lungu 7 area has experienced multiple periods of tectonic uplifting,and the development of small faults is disorderly.The intelligent fault identification method is used to combine various seismic attributes such as conventional seismic profiles and instantaneous phases to realize the fine description of low-order faults,which clarifies the Lungu 7 There are three groups of fault systems in the area near east-west direction,near north-south direction and northeast-southwest direction.The overall faults are mainly class II and class III faults.A combination of impression method and residual thickness method was used to restore the morphological characteristics of ancient karst landforms,and three types of landform units were divided: peak depressions,karst depressions,and valley bottoms of hills;3 types of karst microlandforms: remnant mounds,Depressions and valleys;and identify the distribution of ancient surface water systems based on the morphology of ancient karsts.Through the observation of similar outcrop areas,the morphological characteristics and spatial distribution of fractures and caves of buried hill surface karst and fault-controlled karst are summarized.Comprehensive use of core,drilling and logging,electrical imaging and conventional logging data to identify fracture-cavity reservoirs of different scales and divide them into unfilled caves,breccia-filled caves,sand-mud-filled caves,fractures,and fracture-cavity reservoirs.Layer type.On this basis,through the combination of well-seismic,bead-like,sheet-like reflections,and cluttered reflections are used as identification marks,and amplitude-like seismic attributes are combined to achieve cross-well characterization of karst fractured-vuggy reservoirs.Based on the above results,the control effect of ancient geomorphology and faults on karst fracture-cavity reservoirs is analyzed,and it is believed that the fracture-cavity reservoirs controlled by karst ancient geomorphology are distributed in the high part of the remnant mound.The range of collective development becomes deeper downwards,and underground river systems can develop near the valleys,and the genetic model of karst fractured-vuggy reservoirs under different karst main controlling factors in the study area has been established.Based on the full analysis of karst landforms,faults and fractured-vuggy reservoirs,the Lungu 7 area is divided into: ancient landform + fault control area,ancient underground river fractured-vuggy system development area and fault control area.The research results show that the oil reservoir type in Lungu 7 area is a fracture-cavity reservoir controlled by the degree of karst development.It is formed by a large number of karst fracture-cavity reservoirs of different genesis and scales superimposed in space.The research results of the thesis deepen the genetic model and distribution of carbonate karst fracturedvuggy reservoirs in Lungu 7 area,and have practical guiding significance for the efficient exploration and development of deep fractured-vuggy carbonate reservoirs in the Tarim Basin.