The Reservoir Fracture Characteristics And Distribution Evaluation Of The H Group In X Area

Fracture characteristics and degree of development are the key geological factors for the production of tight reservoirs with low porosity and low permeability.It can be used as a seepage channel to greatly improve the permeability,and can provide certain space for oil and gas storage.The H formation in X area is an important formation with great potential for exploration and development in the east China sea.Due to multiple tectonic movement,the characteristics of fracture development in reservoir are complicated and changeable,and the genesis and development rules of fractures are not clear.At the same time,it is difficult to identify different types of fracture wellbore,and the fracture distribution is not clear.Previous studies have not carried out targeted crack research in the research area.So,in order to define the macroscopic and microscopic characteristics of core fractures,the effective fracture development in a single well,the fracture stage and the development control factors in the study area,and in order that a fracture distribution evaluation method suitable for this region was established to determine the effective fracture development area,on the basis of literature research,the development characteristics and identification of fracture,the influencing factors of fracture development and the evaluation of fracture distribution are studied by the subject theories of reservoir geology,fracture mechanics and geophysical logging in this paper.There are the following results have been achieved.Firstly,through comprehensive analyzing core data and imaging fracture identification data,the major fracture types and basic characteristics in the study area were defined.Natural fractures in the study area mainly include bedding fractures and structural fractures.Both bedding fractures and structural fractures are dominated by filling fractures with low efficiency.Bedding fractures are mainly horizontal fractures and low-angle oblique fractures,while tectonic fractures are mainly high angle oblique fractures and vertical fractures.The fracture width in the study area is mainly concentrated in the range of 0~1mm,and the structural fracture length is mainly within the range of 0~50cm.The average fracture line density of the whole core is 0.68 per m,and the average structural seam density of the imaging identification is 0.12 per m.Secondly,based on the core fracture and imaging fracture data,the corresponding response characteristics of conventional logging fracture were extracted by contrasting logging at the core.The effective fractures on single well section are comprehensively identified by BP neural network and probabilistic stepwise discrimination method in the study area,and the effective fracture development index was calculated,and fracture development characteristics of single well were defined.The anastomosis rate between conventional logging and core fracture is 81%,and that between conventional logging and imaging fracture is 70%.The average effective fracture development index of a single well in the study area was 0.12,and the effective fracture development index was in good agreement with the core and imaging fracture linear density.Thirdly,based on the study of fracture development characteristics,in order to determine the formation period and development factors of structural fractures in the study area,various experiments and methods are used for research in this paper.Such as isotope test and analysis of structural fractures backfill,inclusion analysis,rock mechanics parameter test,stress simulation and structural curvature.The tectonic fractures with large scale,long extension and good effectiveness in the study area were mainly formed in the middle to late period of Longjing movement,which played an important role in oil and gas migration and dredging.Development of structural fractures are mainly comprehensive influenced by lithology,physical properties of rock,monolayer thickness,structural deformation and fault development,and fractures are the main factors affecting the development of fractures in the study areaFourthly,considering the influencing factors of fracture development,the fracture development model in the study area was established.The distribution evaluation method suitable for reservoir effective fractures in H group in X area was established,focusing on the evaluation indexes parameters such as fault development,rock layer thickness and tectonic deformation.The evaluation results have a good positive correlation with the effective fracture development index,and the favorable fracture development area was determined finally.In the study area,the basic characteristics of fractures were defined,and the effective fracture identification method was established,and the influencing factors of fracture development were revealed,and the main fracture development area were identified,which can provide reference for further exploration and development of the study area in this paper.