Reservoir Sedimentology Study Of Carboniferous Huanglong Formation In Longhui-pubaoshan Area,Northeast Sichuan

To meet the needs of the exploration progress of oil and gas resources,further expansion and development the potential of Oil and Gas resources and the risk aversion of prospecting in Northeast Sichuan,and looking at potentially favorable exploration block,this requires conducting new research on the general problems of Carboniferous stratigraphic distribution,sedimentary facies features,reservoir characteristics and the controlling factors,thus providing a theoretical guidance for deepening exploration Carboniferous old gas fields in northeastern Sichuan.Longhui-Pubaoshan area,as an important Carboniferous gas exploration area in northeastern Sichuan,has been gained a new development in Carboniferous exploration at the Longhuichang structure of the low permeability reservoir distribution area,northeastern Sichuan;However,the Carboniferous system in Longhui-Pubaoshan area is affected by multi-episodic tectonism,has the complex denudation residual strata distribution,changeable reservoir distribution character and sedimentary microfacies,and the main controlling factors of reservoirs are not defined,which bring a lot of difficulties for the prediction of Carboniferous reservoir distribution and the optimum selection of exploration targets in this Area.On this basis,this study relies on the scientific research project undertaken by the tutor,regarding the reservoir of Carboniferous Huanglong Formation in Longhui-Pubaoshan Area,Northeast Sichuan as the research object;basing on a detail investigation on the current research status of carbonate reservoirs and the exploration status in the study area here and abroad;guiding by the multidisciplinary theories of stratigraphy,ithofacies and paleogeography,carbonate reservoir sedimentology,petroleum geology;integrating information of geological,logging,core,laboratory analysis and partial seismic data,and combining with existing research results.This paper adopts the global and local analyses,which carried out the research to the reservoir sedimentary characteristics of the Carboniferous Huanglong Formation.The main results are as following:?1?The Carboniferous graphers of stratigraphy thickness of the study area was redesigned,and the distribution characteristics of residual strata in each section of Huanglong Formation in the study area were further analyzed.It is considered that the Huanglong Formation is 25-70m thick and has the characteristics of thin in the west and the north,thick in the east and the south,and the thick areas are mainly distributed in Puxi,Tingzipu and the north of Longhui-Tieshan.?2?It is determined that the Carboniferous in the study area is mainly composed of three sedimentary facies types:Saboha,barrier coast and bay shelf,which are subdivided into eight sedimentary subfacies and many sedimentary microfacies.?3?Isograms of strata,granular carbonate rocks,dolomite and karst breccia have been compiled respectively;Based on the analysis of regional tectonic background,compiled the plane distribution map of sedimentary microfacies;the geometric shape,plane distribution,evolution law and their relationship with reservoir development of different sedimentary facies belts are discussed in depth;there is larger development area of granular beach and clearer distribution law of beach body in the plane,compared with previous studies.?4?Carbonate reservoirs in the study area are mainly developed in?dolomite of?the second set of Huanglong Formation;the reservoir rocks are crystalline dolostones,dolomite karst breccia and grain dolostones;effective reservoir space is intercrystalline solution pores,intergranular solution pores and intragranular solution pores;reservoir types are fracture-pore type II and III reservoirs.Effective reservoir thickness varies greatly,and shows the characteristics of thick in the South and the north,similar to dolomite plane distribution.?5?The occurrence of natural fractures in Huanglong Formation in the study area is mainly low-angle and high-angle oblique,which can be divided into shear and tension fracture,calcite and peat are mainly holes filling materials,higher effectiveness.The degree of development from high to low is as follows:C₂hl²,C₂hl³,C₂hl¹.Fracture development is mainly controlled by faults,tectonic deformation,lithology and rock thickness.It was formed in Indosinian-Early Yanshanian and Late Yanshanian-Early Himalayan periods,and mainly consists of two genetic types:tectonic deformation fracture and fault co-derived fracture.?6?Proposed the main factors controlling reservoir development are tectonism,lithology,sedimentary microfacies and diagenesis;summarized the reservoir development laws of Huanglong Formation:?1?structural fracture effectively improves reservoir porosity and permeability;?2?grain shoal facies zone controls the distribution range and scale of reservoirs;?3?dolomitization is the material basis of reservoir formation;?4?the karstification enlarges the rang of reservoir development and improves the reservoir quality.