The Shale Oil-forming Condition And Resource Evaluation Of Yanchang Formation Chang 7 In Southern Ordos Basin

The geochemical characteristics and potentials for hydrocarbon generation of hydrocarbon resource rocks from Yanchang Formation Chang 7 in southern Ordos Basin have been discussed base on the analyses of different types of hydrocarbon source rock samples and organic petrology tests.Then we established the correlative evaluation criteria and summarized the formed environment difference between various source rocks.Eventually basin simulation technology have been used to simulate the hydrocarbon source rock thermal evolution history and hydrocarbon generation history and calculated hydrocarbon generating quantity of each work area.In the south of Ordos Basin,dark mudstones,carbonaceous mudstones and shales are high-quality hydrocarbon source rocks according to the researches.Furthermore,shales and part of dark mudstones are high grade hydrocarbon source rocks of shale oil.This part of the hydrocarbon source rocks rich in organic matter,organic matter types of shales are mainly belong to?₁,just part of them belong to I.organic matter types of dark mudstone are mainly belong to?₂ and a small amount of them belong to?_1.A new correlative evaluation criteria of the research area have been established.According to this criteria we have done the grading and prediction researches.Shales belong to grade A hydrocarbon source rock,their sedimentary environment is reduction-weak oxidizing and fresh-brackish water environment.Dark mudstones divided to three types.Grade A is reduction-weak oxidizing and fresh-brackish water environment,grade B is mainly belongs to reduction-weak oxidizing and fresh-brackish water environment.The researches of hydrocarbon source rock thermal evolution history and hydrocarbon generation history show that the source rocks generate a great deal of hydrocarbons since early Cretaceous and they are staying in the hydrocarbons generation stage even to this days.The total amount of oil generation of Bingchang area is 20.19×108 t and 17.82×10⁸ t in Xunyi—Yijun area,34.24×10⁸ t in Fuxian area.