Oil Yeild Heterogeneity Characterization Of Paleogene Lacustrine Shales,Eastern China

This thesis focused on the underlying scientific problem related to the characterization of oil yield heterogeneity in lacustrine shales.Investigations were carried out in three facets,geological analog analysis,method development and application in the resolution of real exploration problems.There is little previous attempt in the methodology development for the characterization of oil yield heterogeneity in lacustrine shales.Sediments in Chinese nonmarine basins exhibit strong heterogeneity in the sedimentology and oil yields,which makes the development of tools and protocols for the oil yield characterization a prerequisite for the classified evaluation of shale oil resource.Key innovations include analytical methodologies and protocols for the characterization of oil yield heterogeneity in lacustrine shales:(1)a generation kinetics based method to characterize heterogeneous lacustrine source rocks: Rock-Eval pyrolysis data of core samples collected from Luo 69 well,Zhanhua Depression,was employed to study the impact of shale lithofacies and migrated oil on pyrolysis data.Estimated onset and offset temperatures for the oil window vary up to 15? for the relatively “homogeneous” shale intervals,indicating the importance for considering shale heterogeneity in shale oil resource evaluation.(2)a numerical method that utilizes the full pyrogram of a single run pyrolysis,in order to overcome the shortcomings of oil content estimation from whole rock pyrolysis before and after solvent extraction.The Rock-Eval pyrogram on temperature domain is transformed into activation energy domain.The proposed method was applied to the source rock samples from Shahejie Formation,Dongying Depression,and found to be equally effective to the traditional two step pyrolysis method but more cost and time efficient.(3)a hydrocarbon generation kinetics based method is proposed to recognize,quantitate and remove the impact of migrated oil,respectively.Analysis of core samples from two shale oil exploration wells in Jianghan Basin allows the recognition of migrated hydrocarbons from the Rock-Eval pyrolysis data.The method was validated using extensive data set of Rock-Eval pyrolysis on the studied samples before and after solvent extraction.(4)an innovative methods for resolving free hydrocarbon composition and free versus non-mobile oils in shale based on Rock-Eval data.Shale oil resources are defined into three categories in relation to oil mobility,adsorbed,restricted and moveable oils.Results from Jiyang Superdepression indicate that the distal facies contains more shale oil potential with higher mobility than that in the transitional faces;fresh core samples from the BYY2 well in the Jianghan Basin were used to develop a numerical method to infer the free oil composition in shale from the Rock-Eval pyrolysis S1 response.It was observed that within a single evaporative cycle intra-salt shales contain little volatile and light oils,whereas,the free oils in the inter-salt shales are dominated by light components.Therefore,de-convolution of Rock-Eval S1 potentially provides vital information on oil mobility in shale oil resource evaluation.Results obtained from the innovative methods have provided sound geochemical basis for constraining the hydrocarbon generation models,prolific lithofacies identification and favorable shale oil play definition.