Study The Luminiferous Of The Buqu Formation Oil-bearing Dolomites In Shuanghu Area, Qiangtang Basin

Qiangtang Basin is located in the center of Tibet Plateau. It is a basin with the lowest degree in oil and gas exploration in China and is the most potential target for petroleum exploration in Tethys region. The dolomite from the Shuanghu area of the Qiangtang basin has close relationship with oil reservoirs and is principal reservoirs in this area. At present, The Buqu Formation dolomites is considered the major reservoir layers in South of depression in Qiangtang Basin, surface oil and gas shows were founded mainly in the Buqu Formation. and Qiang D2 Well comprehensive evaluation showed that the Buqu Formation dolomite is an important reservoir. Therefore, determine the distribution of dolomite, diagenesis and understand the filling and migration process of oil and gas in the pores have great significance for Researching on the Qinghai-Tibet region marine strata oil and gas exploration targets.The papers by methods such as ordinary sheet, cast sheet, cathodoluminescence and microscopy fluorescence to study dolomite rock group characteristics, microscopy fluorescence and the reservoir of oil and gas and to compare the dolomite sedimentary diagenetic features of underground and surface profile, and to made the following awareness and conclusions:1 .To compore the thickness of the surface and underground profile oil-bearing dolomite,we know that the thickness of surface profile oil-bearing dolomite from 31.6 m to 48.7m and the Qiang D2 well profile oil-bearing dolomite thickness is more than 223.9 m. The types of oil-bearing dolomite are dominantly composed of Ceramics - powder dolomite, fine-grained dolomite, Crystal dolomite and Coarse-grained dolomite.2. According to researching 64 cast sheets and 79 fluorescence sheets and researching on the oil-bearing dolomites reservoir properties indicates that reservoir space consist of intercrystal gap, intercrystal pore, vug or cave ,intercrystal dissolved pore and Crack, and the face late, the porosity and permeability of dolomites are from10% to 20% , from 0.60% to 17.48% and from 0.0029×10^-3μm² to 271×10^-3μm². According to the Qiangtang Basin carbonate reservoir classification evaluation criteria, the Qiang D2 Well dolomite reservoir belong to type II (good)and type III(middle-bad) and belong to low-permeability, ultra-low permeability reservoir. The Qiang D2 dolomite reservoir porosity wells close to or slightly better than the Sichuan Basin carbonate reservoir, but the penetration rate slightly worse3.To use the luminescence ring researching diagenetic environment and establishing identifier of environmental in favour of further study diagenetic environment .To observe dolomite cathodoluminescence of 64 samples indicate that dolomite mainly have uniform orange-red - red roses color, its edge shallower. The grain around the hole between the dissolution of dolomite often have belt construction. Its reflect the characteristics of the dolomite growth process, the environment changes is relatively stable on the whole,the dolomite dissolution is obvious.4.Microscopy fluorescence can be used to distinguish between different groups of asphalt, judg oil and gas migration, enrichment and so on.The oil-bearing dolomite asphalt in shuanghu area is main component of oil -asphalt ,there is small number of glial asphalt and pitch asphalt .The asphalt is mainly free asphalt and belong to late time. The oil-bearing dolomite in shuanghu area have higher asphalt content, are composite of light asphalt component and were migrated long-distance. The oil and gas of oil dolomite in shuanghu region was have secondary migration and was enrich two times.