Reservoir Study Of The Chang4+5and Chang6Oil Layer Of Yanchang Formation In City Zone Of Wayaobao Oilfield

The Triassic Yanchang formations4+5and6in Wayaobu Oilfield area arethe typical low permeability clastic reservoirs. Its reservoir heterogeneity isserious. It is still in the natural energy exploration period. In order to meet thefoundation of efficient exploration in this type of reservoir, this thesis uses thereservoir geology theory and modern reservoir description method andtechnology to do comprehensive study and classification evaluation in thesereservoirs.The oil-bearing formations in this oilfield block are4+5and6in Yanchangformation. The main reservoir61in Yanchang formation is divided into61-1and61-2two small layers. The reservoir structural characteristic is a gentlewest-dipping monocline. It developed two east-west nose uplift rows. The maingenetic type of the reservoir sand is underwater (water) distributary channel. Inthis area its sedimentary facies control the reservoir sand distribution, lyingmostly in northeast-southwest direction. Reservoir rock is mainly fine-grainedfeldspathic sandstone, which is in the late diagenetic stage A. Laumontite cementation anddissolution is the main diagenetic event, which affecting reservoir performance.Residual intergranular pore is the main reservoir space type, secondly is thezeolite dissolution pores and intergranular dissolution porosity, which aremedium and small micro throat. The average porosity is9.33%. The averagepermeability is1.02×10-3μm2.. Reservoir interlayer and flat non-homogeneousare strong. Natural fractures are developed, mainly in north-east. Reservoirsensitivity contradictions are focus on the stress sensitivity and acid sensitivitydamage. The contradictions are mainly in matrix porosity and cracks-matrixpores flooding, with low flooding efficiency. The reservoirs mainly are the lowpermeability class III and ultra-low penetration class IV. Reservoir is a typicalelastic solution gas drive lithologic reservoir.