Study On Characteristics And Structure Pattern Of Fault-Karst Reservoir Bodies Of Yijianfang Formation Of Ordovician In Halahatang Area

Tarim Basin is the most important carbonate petroliferous basin in China,with abundant oil and gas resources.Ha 15 fault zone in Halahatang area has experienced superimposed transformation of multi-stage tectonic movement and karstification,forming fault-karst caves,pores and fractures and other reservoir spaces in the carbonate strata around the fault zone,forming complex fault-karst reservoir bodies.Based on the study of the reservoir characteristics of Yijianfang Formation in Halahatang oilfield,this paper selects the southern section of ha15 fault zone to study the structural model of fault-karst,analyzes the structural characteristics of fault-karst in the study area,reveals its development law and influencing factors,so as to guide the exploration and development of fault-karst reservoir bodies.In this paper,from outcrop,core and thin section,conventional logging and imaging logging,etc.,three types of reservoir spaces are identified:fault-karst cave,karst fracture and karst pore.According to the differences of different reservoir spaces and their combinations,the reservoir bodies are divided into two types:Fault-karst cavity type and fault-karst fracturecavity type.The two types of reservoir bodies are identified by the combination of cross plot decision tree and conventional logging.According to outcrop,core,cast thin section,logging and seismic data,the characteristics of reservoir are analyzed and described.This paper analyzes the controlling effect of rock properties and structural faults on the development of fault-karst reservoir bodies;Using seismic data to extract seismic variance volume attribute,analyzed and described the fault profile and plane distribution characteristics,Then divided the fault into compression section,tension section and translation section according to its stress characteristics;Extracting root mean square amplitude attribute volume to describe the shape and distribution of fault-karst reservoir bodies.Finally,according to the development and distribution characteristics of faults and fault-karst reservoir bodies,the structural model of fault-karst reservoir bodies is established.It is found that the carbonate rocks in Ha 15 fault zone are mainly cal cite,and the porosity and permeability of bedrock are poor.The main reservoir spaces are fault-karst cave,karst pores and fractures.Most of the reservoir spaces are full filled,followed by unfilled and semi filled,and the fillings are mainly argillaceous,calcareous and asphaltene;The reservoir bodies mainly show the characteristics of beaded reflection,flaky reflection and disordered reflection on seismic section,flaky reflection and disordered reflection;The variance volume attribute data volume reflects the fault boundary clearly;The fault-karst reservoir bodies show round,oblate,long or irregular along the fault in the root mean square amplitude attribute volume plan.Based on the research above,the structural pattern of fault-karst reservoir bodies is established.According to the pattern,the development and distribution of fault-karst reservoir bodies are controlled by the fault system,the fault-karst reservoir bodies is relatively developed near the main fault,and also highly developed at the intersection of faults;The fault-karst reservoir bodies is most developed in the extension section,and is poorly developed in the translation section.