南祁连盆地木里坳陷中侏罗统烃源岩原始有机碳含量恢复及与微孔隙演化的相关性  

Restoration of“original organic carbon content”and its relationship with micropore evolution of the Middle Jurassic source rock in the Muli Depression,Southern Qilian Basin

作　　者：刘世明 谭富荣 唐书恒[1] 王金喜 王伟超 李永红 Shi-ming LIU;Fu-rong TAN;Shu-heng TANG;Jin-xi WANG;Wei-chao WANG;Yong-hong LI(School of Energy Resource,China University of Geosciences,Beijing 100083,China;Shaanxi Mineral Resources and Geological Survey,Xi’an 710068,China;Key Laboratory of Resource exploration Research of Hebei Province,Handan 056038,China;China National Administration of Coal Geology,Beijing 100038,China)

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]陕西省矿产地质调查中心,陕西西安710068 [3]河北省资源勘测研究重点实验室,河北邯郸056038 [4]中国煤炭地质总局,北京100038

出　　处：《天然气地球科学》2021年第7期982-992,共11页Natural Gas Geoscience

基　　金：国家自然科学基金(编号:41702144);中央高校基本科研业务费专项资金(编号:2652018234)联合资助

摘　　要：泥页岩有机质碳含量(TOC)是页岩油气评价的重要参数之一。然而,受有机质热演化生排烃影响,利用现今TOC评价与预测页岩油气资源时会出现一定的偏差。因此,进行烃源岩原始有机碳恢复对油气资源评价具有重要意义。木里坳陷位于南祁连盆地东北部,陆相中侏罗统广泛分布。中侏罗统为一套湖泊—三角洲相沉积的细粒碎屑岩,发育多套厚层富有机质暗色泥页岩,生烃潜力巨大。该层段内油气资源丰富,页岩有机质从低成熟到高成熟阶段均有分布,为原始有机碳含量的恢复提供了必要条件。以木里坳陷中侏罗统富有机质页岩为研究对象,利用岩石热解数据,采用物质平衡法有机碳恢复模型,对中侏罗统页岩原始有机碳含量进行了恢复。结果表明,中侏罗统页岩原始TOC含量与现今TOC含量的比值介于1.04~1.62之间,且随着热演化程度增高,比值变大。现今TOC含量与有机质孔隙发育之间没有必然的联系,然而,原始TOC含量与现今TOC含量之间的比值可以间接判断页岩有机质微孔隙发育情况。木里坳陷侏罗系页岩有机质类型以Ⅱ型和Ⅲ型为主,热演化参数(T_(max))大于440℃时,烃类转化率和排烃率都大于40%。相比样品矿物(石英和黏土矿物)含量、T_(max)参数和现今TOC含量,原始TOC含量与页岩兰氏体积拟合性更好,结合热解参数T_(max),可以更好地判断页岩油气的吸附能力。因此,开展木里坳陷中侏罗统烃源岩原始有机碳含量恢复的研究,可以为木里坳陷烃源岩评价提供理论基础;同时对木里坳陷油气资源勘探提供新的思路。Organic carbon content(TOC)of shale is one of the significant parameters for shale oil and gas assessment.However,the generation and expelling of hydrocarbons in shale was influenced by thermal evolution of organic matter,and a certain deviation occurred using present TOC to evaluate and predict shale oil and gas resources.Therefore,the restoration of original organic carbon from source rocks is of great significance for the evaluation of oil and gas resources.The Muli Depression,located in the northeast of the Southern Qilian Basin,was widely developed the Middle Jurassic continental shale.The Middle Jurassic is composed of a set of fine clastic rocks deposited in the lacustrine and delta setting.Multiple sets of thick dark organic-rich shales were developed,which have great hydrocarbon generation potential,and are found with abundant petroleum resources,and the thermal maturity of organic matter was from low maturity to high maturity,which provides the necessary conditions for the restoration of the original organic carbon content.In this paper,the original organic carbon content of Middle Jurassic shale in Muli Depression was calculated by material balance method using rock pyrolysis data.The results suggest that the ratio of original to present TOC content of the Middle Jurassic shale is between 1.04 and 1.62,and increases with the higher thermal maturity.No obvious relationship between the present TOC content and the pore development of organic matter in the Middle Jurassic shale.However,the difference between original and present TOC content could effectively assess the development of the micropores of organic matter in shale.The organic matter is mainly typesⅡand Ⅲ with thermal evolution(T_(max))greater than 440℃,and the transform and expulsion of hydrocarbons is greater than 40%.Compared with the minerals content(quartz and clay minerals content),T_(max) and present TOC content,the original TOC content has a better correlation with the shale Langmuir volume,which combined with T_(max),could be more

关 键 词：木里坳陷 原始有机碳含量 有机质孔 中侏罗统 烃源岩 

分 类 号：TE122[石油与天然气工程—油气勘探]