The Forming Mechanism Of Effective Reservoirs Of Es_3-4 In Duzhai-qiaokou Area Of Dongpu Depression

With the observation and description of the core and casting thin section as the main means, and using the collected date about mercury injection, petrophysical property and others, the thesis researched the deep reservoir of Es3-4 in duzhai-qiaokou area, which is also combined with previous research achievements. A comprehensive research including reservoir development characteristics, the identifion of effective reservoir, influencing factors and the forming mechanism were are out, all of which are based on the analysis of regional geological background.The deep reservoir in duzhai-qiaokou area has the following characteristics: (1) arcose and subarkose are the main sadstone style, the secondary emposieu is the main reservoir space, carbonate cement and feldspath are the main material which are dissolved; (2)The diagenetic has been Into the middle diagenetic A period.The diagenetic environment experienced the change from weak-acid-alkaline to caidic. The reservoir was reconducted by multi-phase diagenetic, and it is especially affected by hydrocarbon filling and abnormal overpressure; (3) petrophysical property belongs to the low porosity-permeability type, with the vertical zonation.The limit of the effective properties is achieved by different methods.It is recognized that the limit of effective drainage and permeability porosity is 7.25%⁷.65%, 0.112⁰.126×10^-3μm²,from which four effective reservoirs are identified, with depth ranges:3300³900meters, 4000⁴250meters, 4350⁴550meters,>4800 meters. The evolution of the pore which includes: primary pore formatted→Primary porosity shrink→secondary pore formatted→secondary porosity shrink→residual pore is researched combined with the study of the sequence of diagenesis, the development of hydrocarbon filling and abnormal overpressure.Effective reservoir is the direct production of diagenesis, also affected by the original sedimentary composition, hydrocarbon filling and abnormal overpressure , it is also the comprenhensive effect of these factors. It is recognized that the petrophysical property of braid channel in middle sublacustrine fan,large segment of sand or a larger proportion of sand in Sand-shale Inter bedding are better.The petrophysical property is proportional to the oilsaturation, and the cementing material in oil sandstone is lower than that in oil-free sandstone.These show that the hydrocarbon filling increases the corrosion rate,meanwhile, it also inhibits the conduct of cementation.Abnormal pressure expands the oil-generating window, which conducives to the preservation of porosity inadvance.On the base of making a clear definition of the evolution and influential factors ofthe diagenesis, mechanism of effective reservoir developing in the study area is established which includes organic acid-carbonic acid corrosion, the pore saved by abnormal overpressure and reworked by thermal cycled fluid ,convection and micro-fracture caused by abnormal overpressure in deep reservoir.