鄂尔多斯盆地彭阳地区侏罗系原油伴生气中H_(2)S成因  

Origin of H_(2)S in Jurassic associated gas in Pengyang area,Ordos Basin

作　　者：李剑锋[1,2] 吴凯[1,2] 刘曼 孔令印 马军[1,2] 刘飞[1,2] Jianfeng LI;Kai WU;Man LIU;Lingyin KONG;Jun MA;Fei LIU(Research Institute of Petroleum Exploration and Development,PetroChina Changqing Oilfield Company,Xi'an 710018,China;National Engineering Laboratory for Exploration and Development of Low?Permeability Oil&Gas Fields,Xi'an 710018,China;Eleventh Oil Production Plan of PrtroChina Changqing Oilfield Compamy,Qingyang 745000,China)

机构地区：[1]中国石油天然气股份有限公司长庆油田分公司勘探开发研究院,陕西西安710018 [2]低渗透油气田勘探开发国家工程实验室,陕西西安710018 [3]中国石油天然气股份有限公司长庆油田分公司第十一采油厂,甘肃庆阳745000

出　　处：《天然气地球科学》2022年第3期472-483,共12页Natural Gas Geoscience

基　　金：国家科技重大专项“大型油气田及煤层气开发”课题“鄂尔多斯盆地致密油资源潜力、甜点预测与关键技术应用”(编号:2016ZX05046-005)资助。

摘　　要：鄂尔多斯盆地彭阳地区侏罗系延安组原油伴生气含有一定量的H_(2)S,其成因研究对预测盆地中生界H_(2)S的分布具重要意义。研究区侏罗系延安组原油主要来自于延长组7段(长7段)主力烃源岩,而具有相同油源的长10段—长3段原油伴生气中均未检测到H_(2)S。因此,延安组原油伴生气中H_(2)S的形成可能与储集和成藏因素有关。分析表明,侏罗系地层水具高矿化度且富含二价硫,抑制了硫酸盐还原菌的发育,因此生物还原硫酸盐生成H_(2)S的可能性较小。延安组原油伴生气中H_(2)S的δ^(34)S值均大于25‰,明显不同于火山热液、有机质及微生物还原生成物的δ^(34)S分布特征,而与地层水中二价硫同位素值相近,比地层水中硫酸根离子的δ^(34)S值偏低约为10‰,具有TSR生成H_(2)S的硫同位素分布和分馏特征。研究区侏罗系延安组储层岩石包裹体测温显示,油气初次充注温度高于100℃,最大成藏温度高达150℃,延安组地层水中含有大量的来自于硬石膏或埋藏时赋存的硫酸根离子,满足了发生硫酸盐热化学还原反应的条件,同时地层水中丰富的镁离子催化了反应的发生。因此,鄂尔多斯盆地彭阳地区侏罗系原油伴生气中H_(2)S为TSR成因。A certain amount of H_(2)S is found in the crude oil associated gas of Jurassic Yan’an Formation in Pengyang area of Ordos Basin.The study of its genesis is important for us to predict the distribution of H_(2)S in Mesozoic in the basin.The crude oil of Jurassic Yan’an Formation area mainly comes from the 7^(th) member of Yanchang Formation(Chang 7 member)source rock of Yanchang Formation.H_(2)S is not detected in the crude oil associated gas from Chang 10 to Chang 3 members of Yanchang Formation.Therefore,the formation of H_(2)S in the crude oil associated gas of Yan’an Formation may be related to reservoir and reservoir forming factors.The analysis shows that Jurassic formation water has high salinity and rich in divalent sulfur,which inhibits the development of sulfate reducing bacteria.The possibility of H_(2)S generation from biologically reduced sulfate is low.The δ^(34)S values of H_(2)S in crude oil associated gas of Yan’an Formation are more than 25‰,which are obviously different from those of volcanic hydrothermal solution,organic matter and microbial reduction products.Theδ^(34)S values are similar to the divalent sulfur isotope value in formation water and about 10‰ lower than that of the sulfate ion in formation water.The H_(2)S has the characteristics of sulfur isotope distribution and fractionation characteristics generated by TSR.The temperature measurement of rock inclusions in Jurassic Yan’an Formation shows that the initial charging temperature of oil and gas is higher than 100 ℃,and the maximum reservoir forming temperature is 150 ℃.The formation water of Yan’an Formation contains a large number of sulfate ions from anhydrite or buried stage.Those rich sulfate ions meets the conditions for sulfate thermochemical reduction reaction.At the same time,the rich magnesium ions in formation water catalyze the reaction.Therefore,H_(2)S in Jurassic crude oil associated gas in Pengyang area of Ordos Basin is of TSR origin.

关 键 词：延安组 原油伴生气 H_(2)S 硫同位素 成因 彭阳地区 鄂尔多斯盆地 

分 类 号：P618.13[天文地球—矿床学]