The Reservoir Description Of Chang2in Northern Part Of Beigou In Xiasiwan Oilfiled

Since the rolling extension development of northern part of Beigou, there has not toconduct a comprehensive and systematic study working. Mainly depend on the surroundingwell data contrast, and lack of theoretical research guidance. It is necessary to further makeclear the geological characteristics, sedimentary facies, reservoir, hydrocarbon accumulation,and other reservoir characteristics. Providing certain theoretical basis for further exploration ofthe study area and the surrounding.With the guidance of the theory of sedimentology, structural geology, petroleum geology,oil and gas accumulation geology, on the basis of field outcrop, core analysis laboratory testsdata, logging data, test oil and mining information, combining the predecessors’ researchresults, the stratigraphic distribution and correlation, structural features, sedimentarymicrofacies and sandstone distribution, reservoir characteristics, oil reservoir enrichcharacteristics of Chang2oil layer were researched. The research showed that: Chang2formation were separated into three oil sub-layer which including Chang21, Chang22andChang23. The Chang22can be further divided into Chang22-1, Chang22-2and Chang22-3. Thetop of Chang22-1was incised denudation by the ancient river and distribution range limited;The top structure of Chang2oil layer was overall performance of west pour monoclinic,locally developed multiple nose-shaped uplift structures; Chang22oil layer belong to riversedimentation, Chang22-2and Chang22-3are belong to braided river sedimentation and widthof channel is about2～4km. Chang22-1is belong to meandering river deposition. The channelextends from the northeast to the southwest. The skeleton sand body is channel sand damdeposits, the single sand layer thickness is8～18meters and show a zonal distribution on theplane; The Chang2reservoir rock type is mainly fine-grained feldspar sandstone, with averageporosity13.6%and average permeability4.9×10-3um2.Comprehensive evaluated the reservoiris medium-low porosity and low permeability reservoir. The main pore throats combinationare miniature holes with micro throats. The main pore types are intergranular dissolved poreand intragranular dissolved pore. The intrastrata, interstrata, and plane of the reservoir have amedium heterogeneous reservoir sands. Reservoir sensitivity with “three low, two medium”characteristic, namely the weak velocity sensitivity, weak salt sensitivity, weak alkali sensitivity, medium and weak water sensitivity, moderate acid sensitivity.According to hydrocarbon accumulation, the main type of Chang2is lithologic-structuralreservoir, affected by structure, side sealing by lithology; Hydrocarbon richly accumulated aremainly controlled by “Optimal phase, High permeability”; Cap formation is another importantfactor of controlling hydrocarbon accumulation, mudstone of Chang22-1and the dense layer atthe bottom of channel are the direct cap formation. On the basis of comprehensive evaluationof Chang2, two Ⅰclass building production areas and two Ⅱclass replacement areas wereoptimum selection.