Diagenesis And Its Influence To The Pore Of Sandstone Reservoirs Of The Shahejie Formation In Qinan Sag Of Huanghua Depression

The main exploration area of Dagang oilfield is in the middle-south of HuanghuaDepression,in Bohai basin. The Paleogene Shahejie is one of the major oil producingformation. In this thesis, Based on the theory of sedimentary petrology, petroleumgeology, well logging geology, reservoir geology and sequence stratigraphy etc,combined with the comprehensive research of laboratory tests and analyze, To carry outresearch work on lithology characteristics and diagenesis of sandstone reservoirs andits impact on pore, in Shahejie formation. we should understand the diagenesis type,diagenesis stage and diagenesis sequence, to discusses diagenesis mode. Cleary proetypes and structure of rock, to discusses the rules of porosity evolution, analyze thesecondary porosity of rocks and its control factors. Thereby to analyze the impact ofdiagenesis on reservoir.In lithology, the reservoir rocks in research area were dominated by richfeldspathic and rich lithic greywacke with lower textural maturity and compositionalmaturity. They main have medium degree of sorting and subrounded-subangularpsephicity. It was shown that the primarily rock types of Shaheji formation isfeldspathic litharenite, followed by lithic arkose. The two types of rock accounted for83.5%of all rocks, including feldspar lithic sandstone52.5%, lithic sandstoneaccounted for10.2%. The main grain characteristics of the reservoir sandstone inShahejie formation are rich in debris and feldspar, and quartz content is low. By way ofcore observation, and combining with the comprehensive research of laboratory testsand analyze, such studies were carried as diagenetic stage, diagenetic mode, pore typesand the diagenesis of the reservoir and its influence on the reservoir. The pore typesseen in the reservoir included intergranular pore, intercrystal pore, casting membrane pore, and structural fracture etc. The diageneses of reservoir sandstones were mainlyunderwent comprise compaction, pressolution, cemeniation, metasomatism, anddissolution and so on. The sandstones of Shahejie formation are in the stage ofmiddle diagenesis while part of them are in the late diagenesis. The compaction andcementation are the main reasons of destroying the porosity and permeability, andthe impact of compaction on the influence of reservoir pore is better than cementation,while dissolution is benefieial to improvement of the reservior.