Sedimentary Facies And Reservoir Characteristics Of Liangshan Formation In Gongshanmiao Oilfield, Central Sichuan

The Jurassic Lianggaoshan Formation in the central Sichuan is one of the major oil-producing reservoirs in Sichuan Basin.Many wells in this area have good oil indication,which shows good exploration prospects and huge development potential.The thesis takes the Lianggaoshan Formation of Gong 39 well area of Gongshanmiao oilfield,in the central Sichuan Basin,as the object of research.With the core data,logging data and testing data,the sedimentary facies and reservoir of Lianggaoshan Formation,using the theories and technical methods such as sedimentology,petroleum geology,logging geology,reservoir geology and others,are the two important aspects of the thesis,which are aim at formulating reasonable development plan and guiding the deployment of well position.To a certain extent,the thesis lays a good foundation for the formulation of technical countermeasures and technological measures for the reservoir.Base on the regional geological background and achievements of previous research,the sedimentological markers,paleontological markers and logging facies markers of the Lianggaoshan Formation in Gong 39 well area are analyzed and summarized,which are useful to establish the rock-electrical-phase model.After proposing the sedimentary facies division scheme suitable for this area,The sedimentary facies of 16 single wells and 5 even well sections are divided and contrasted in vertical and horizontal respectively,and the sedimentary facies characteristics in this area are analyzed deeply.It is considered that the Lianggaoshan Formation is developed in lakefront subfacies,shallow lake subfacies and semi deep lake subfacies.Lakefront subfacies is dominated by lakefront mud and lakefront sand dam microfacies,while shallow Lake subfacies is mainly consist of shallow lake mud,shallow lake sheet sand and shallow lake beach dam,besides,the semi deep lake subfacies mainly deposit semi deep lake mud microfacies and locally develop turbidite.Combined with the short-term sequence stratigraphy cycle division scheme of high resolution,the plane distribution map of sedimentary facies has been compileted.The feature of sedimentary facies distribution on the plane is carried out,and the model of the Lianggaoshan Formation is finally established.Under the guidance of reservoir geology theory and technical method,the reservoir characteristics of Lianggaoshan Formation in Gong 39 well area are researched.The reservoir is mainly consists of feldspar lithic sandstone and lithic quartz sandstone.The primary pore remains less,and the main reservoir space is secondary dissolution pore and structural fracture.Through the analysis of physical property,the porosity of reservoir in Lianggaoshan Formation is between 0.14%and 6.6%,with an average of 1.75%,and the permeability is between 0.01×10-3?m2 and 0.1×103?m2,which means the reservoir belongs to fracture-pore reservoir.In the light of statistical analysis,the reservoir of Lianggaoshan Formation in the Gong 39 well area is mainly controlled by sedimentary facies,diagenesis,fault and fracture.According to reservoir rock type,pore type,porosity,permeability and pore structure,the reservoirs can be divided into four types and mainly composed of class ? reservoirs,which are mainly developed in SSC3,SSC4,SSC6 and SSC7 vertically.The reservoir of SSC7 is the most developed and better quality.According to the results mentioned above,comprehensive energy storage coefficient,structural characteristics and fracture development,two favorable reservoir development zones are selected in combination with the results of drilling result in the Lianggaoshan Formation,which are the east area of Gong 003-6 well to Gong 58 well area and the Gong 45 area to the Gong 003-12 well area.