The Research Of Sandstone Reservoir Petrology Characteristics Of Well Qing 36 Of YanChang Formation, Triassic, Ordos Basin

The South of Ordos basin is the major oil-producing areas, and Yanchang Formation of Upper Triassic is its major hydrocarbon-bearing strata.Most test data of casting thin sections, SEM, particle size analysis, X-ray diffraction of clay minerals have been used; the thesis evaluated the YanChang Formation reservoir of Well Qing 36 in Ordos basin being guided by the new achievements of sedimentary theory, clastic reservoir research and international oil-gas field exploration.That is of significance in petroleum exploration in the south of Ordos Basin.The reservoir Petrology types of Well Qing 36 include feldapar quartz sandstone,arkose,lithic arkose,feldspathic litharenite. Among the four types of sandstone, arkose and lithic arkose are the main rock types. The structural maturity of sandstones is low and the componential maturity is low.The cement formed maily by carbonate,silicon,siderite etc; the carbonate cement of each oil group formed maily by ferrocalcite. From upper oil reservoir group to the lower, the dolomite content have a decreasing trend.The porosity of Well Qing 36 is between 1.6%-23%, the effective porosity is 7.61%, and effective permeability is 0.56×10-3um2, the reservoirs overall belong to low prosity and low to extra-low permeability. The porosity and permeability of Chang 2 to Chang 9 have gradually reduced.It's because the YanChang Formation reservoir of Well Qing 36 lies beneath the unconformity at the base of the Jurassic section.The origin of secondary pores is related to the leaching by meteoric water during the time of subaerial exposure.The reservoirs in the upper member of Yanchang Formation near the unconformity, such as Chang 2 and Chang 3, have higher porosity and permeability.