The Sealing And Forming Effect Of The Mud-stone Of Buried Hills Cover In The Bozhong Depression

To study the typical accumulation mechanism of the mud-stone of Buried Hills cover in the Bozhong Depression.The greatest possible use of drilling,logging,core test,seismic interpretation,to comprehensive evaluation the mud-stone cap-rock sealing performance of buried hill in the studied area.Firstly,the macroscopic distribution characteristics of buried-rock mud-stone cap-rocks were studied in a layered manner.Both the Dongying Formation and the Shahejie Formation of the Paleogene area in the study area developed mud-stones of a certain thickness,of which a set of massive mud-stones developed mainly in the east of the area.The thickness of the perimeter of the depression is more than 150m,and the mud-to-land ratio in the areas of Bodong,Bonan and Shadongnan is all above 0.6.Secondly,to study the microscopic sealing ability of the cover layer,Combined with the the pressure analysis was carried out in research area,the Eaton method is used to predict the pressure coefficient of the study area.It was found that the paleogene of the study area was over pressure divide E₃d₁.The pressure coefficient is generally between 1.2and 1.6.From the convex to the depression,the prediction of over pressure development gradually increased.Then,completing the comprehensive evaluation of the cap.Then,it analyzes many factors that affect the micro-encapsulation ability of the capping layer,formulates the criteria for the evaluation of the shaly cap rock,classifies the grades according to the degree of influence of the selected parameters on the capping ability,and assigns weights.Combined with the sealing effect of the mud-stone cap rock in actual exploration and development,the weights for assigning various evaluation parameters are determined.According to the actual exploration conditions of each buried hill oil and gas field,combined with the forecast reserves and proven actual reserves and other indicators,the capping grade is divided.Evaluation result display:The prediction values of various indicators in Bozhong depression of the research area are high and the evaluation is good.The peripheral region,most areas in the E₃d₂show apical ability.The partial areas of E₃d₃and E₃s₃are good.The cover layer of E₃d₁E₃s₁and E₃s₂is mostly of medium sealing ability.Finally,The author completed the research on the reservoir effect.The cover layer is controlled by the spatial distribution of the oil and gas reservoir:the large and thick mud-stone developed in the E₃d₂^Lin the study area,coupled with the high displacement pressure and over-pressure development characteristics,provides the capping conditions.The main distribution of oil and gas in paleogene is mainly distributed in the E₃d₂^Lin dongying group and shahejie formation.Fracture in the studied area has carried on the qualitative analysis,the fracture in this area can be divided into two kinds,named oil source faults and non-oil source faults,identify oil source faults and cap matching closure is dying and inheritance-shaped fracture.The influence of over-pressure on the dynamics of reservoir formation in the study area was analyzed.The gathering fluid dynamics of each raised zone mainly consisted of converging flow and parallel flow forces.