The Geochemistry Characteristics Of Source Rock And Analysis Of Petroleum Resource Potential Of Paleogene In Liaozhong Depression

Liaozhong sag has a high amount of oil and gas resources.The systematic evaluation of source rock in each stratum and each section,along with the calculation of petroleum resources,can provide more reliable geochemistry basis for further exploration in Liaozhong sag.In this paper,the Paleogene of Liaozhong sag is considered as main research object by means of organic geochemical research method,the abundance,type,and maturity of organic matter in source rock are studied.Besides,the influence of tectonic background and sedimentary environment on the organic matter abundance and kereogen type in source rocks is analysed by using the characteristics of biomarker,algae content and the mudstone content in stratum.This paper combine geology and geochemistry charactors to simulate the process of the evolution of geology and thermal history and hydrocarbon generation,therefore calculate the petroleum resources in different stratum and section in the studied area and thus guiding the work of petroleum exploration.The main conclusions of this study are as follows.1.There are 3 groups of main source rocks in the studied area,which are sha 3 segment,sha 1 segment and dong 3 segment.All of them have high abundance of organic matter and a good type of kereogen,but the maturity is low.Sha 2 segment and dong 2 segment are not so well as sha 3 segment,sha 1 segment and dong 3 segment.The middle parts of Liaozhong sag has higher abundance of organic matter and a better type of kereogen,but a lower stage of maturity compared to the northern parts of Liaozhong sag.2.The intensive extensional riftogenesis in Sha3 period and the strike slip pull apart in Dong3 period of Tanlu Faulted Zone caused two times of rapid subsidence in Liaozhong Sag,which formed deep-water environment,and thus a large number of fine clastic materials are sedimented.These conditions,along with the warm humid weather,made a large number of organic matter which is hydrogen-rich sediment and keep well in the reductive environment,so the mud content and the algae content are high while the Pr/Ph value is low,and thus the TOC,which represent the abundance of organic matter,and KTI,which represent the kerogen type,are high.3.The source rocks of LiaoZhong Sag can be roughly divided into two-stage,the late of Dongying formation?30²5Ma?is the first stage with higher hydrocarbon production;the end of Neogene to Quaternary system is the second stage,which has a lower rate of hydrocarbon production.The rate of hydrocarbon production of Es₄ is also high,which can be the key point in further exploration.The rate of hydrocarbon production is also controlled by Tanlu Faulted zone.4.The denudation thickness and restored the burial history is caculated.The ancient and modern geothermal flow to restore its thermal history are combined and then the process of hydrocarbon generation is simulated,based on which the petroleum resources in Liaozhong Sag can be calculated.5.The resource potential of Liaozhong Sag is huge,and the resource extent of its source rocks that finally calculated is 14.76×10⁸T.The resource extent of source rocks in Ed₃ is2.90×10⁸T,Es₁ 0.82×10⁸T,Es₃ 11.04×10⁸T.The resource extent of source rocks in southern part of Liaozhong Sag is 8.06×10⁸T,middle part 3.52×10⁸T,northern part 3.18×10⁸T.The key stratum of further exploration is Es₃,then comes Ed₃ and Es₁.The key section of further exploration is southern part,then comes middle part and northern part.6.Based on the inspiration of new discovery in Tuquan Basin,Es₄ and Ek and the deep subtle reservoirs of those two stratum,the reservoirs in Liaozhong Sag,the activity of Tanlu Faulted zone and“old oil and new storage”,the exploration in vocanic area,as long as the exploration in the Mesozoic source rocks deserve more study.