Characteristics Of Reservoir And Prediction Of Favorable Areas Of Lower Yanchang Formation In Xiasiwan Oil Field

Xiasiwan oil field is the main area of the research,and the development zone is upper combination reservoir of chang2-chang6. As the increasing actual need of production and decreasing yield of old formations, it needs to extend the lower part of yanchang group to find resources. Because of the less attention under the combination of the reservoir in the past and uneven distribution of exploratory wells and appraisal wells in the lower combination drill, therefore the sedimentary characteristics, depositional system, rule of sedimentary sequence change and provenance direction system on reservoir were not understood adequately.In the thesis.using black shale as the main mark layer and several auxiliary mark layers, methods of layer uniform thickness,sedimentary cycle and contrast of adjacent well were used to divide chang7-chang10into chang71, chang72, chang73,chang81, chang82, chang91,chang92and chang101et.al.through contrasting large section first and single layer then.Based on the outcrop,rock type,log facies and facies marker of sedimentary tectonics combining with regional geological background and provenance analysis, the sedimentary facies of chang7was recognized as half deep-deep lake subfacies,chang8and chang9as delta front subfacies and the depositional microfacies were subsea distributary channel, interdistributary bay, estuary dam and flood plain, while chang10as delta plain subfacies and the depositional microfacies were distributary channel of delta plain, flood plain and natural levee.Through identification of thin section, data of mercury injection curve, reference of scanning electron microscopy (sem) and identification of mineral composition, characteristics of reservoir pores, diagenesis and physical property were conluded to classify the sandstone of each layer in low combination into feldspar sandstone and lithic feldspar sandstone.Type of the rock pores were main intergranular pore and intragranular dissolved pore, and main pore throat combination for fine holes and micro-fine throat. Reservoir physical property of low combination was poor and porosity ranged from5-10%, permeability was0.1-0.2mD,which was low porosity-low permeability reservoir. The reservoir was mainly ultra-low permeable zone (Ⅲ class) and dense reservoir (IV class).According to characteristics of sedimentary facies, sand distribution,structure, ancient fluid potential and reservoir analysis as well as production performance data, favorable areas of layers in low combination are predicted and3-4favorable target areas are selected, which could provide basis on further exploration and development.