塔中奥陶系储层硫化氢成因及主控因素

Origin of hydrogen sulfide and the main control factor of its distribution in Ordovician carbonate reservoirs of Tazhong area

塔中奥陶系储层内硫化氢广泛分布,由于其剧毒、易溶于油水中、腐蚀性强,给勘探开发工作带来一定难度。为了弄清奥陶系储层的硫化氢成因及分布规律,在分析现有关储层中H_2S来源研究成果的基础上,结合塔中地区奥陶系碳酸盐岩中的矿物组分、H_2S及其硫碳同位素分析来探讨其H_2S原因。结果表明:三期方解石交代硫酸盐矿物,且硫酸盐未被TSR还原;奥陶系内硫化氢硫同位素普遍比寒武系内硫化氢硫同位素低;奥陶系内硫化氢硫同位素和地层水硫酸根硫同位素具有伴生关系,TSR发生在烃水过渡带;TSR反应物与硫化氢含量无相关关系,并出现了沥青质碳同位素值的负偏;甲烷碳同位素值与硫化氢含量无相关关系,甲烷并未参与TSR。奥陶系与寒武系内硫化氢为不同阶段各自的产物;硫化氢生成时期为奥陶系良里塔格组(O_3l)和鹰山组(O_(1-2)y)内TSR发生在晚燕山期-喜山期,寒武系内TSR发生在晚海西期和晚燕山期-喜山期。总体上,奥陶系内硫化氢为原地TSR成因,受控于走滑断裂注入寒武系高矿化度、富镁地层水和油气,以及沿I号断裂运移的贫硫化氢干气稀释作用。

Hydrogen sulfide is widely distributed in Ordovician reservoir of Tazhong area. The gas is soluble in oil water fluid, poisonous and corrosive and brings difficulty for the exploration and development. In order to define its origin and distribution in the reservoir analysis of its source, mineralogy of Ordoviclan carbonate rocks and chemical analysis of S, C isotopes and the gas were conducted and the result shows that calcite of the third stage replaces sulfide minerals and the sulfide is not reduced by TSR and that S isotopes of the hydrogen sulfide of the Ordovician system is generally lower than that of Cambrian system and that company relation of isotopes exists between the Ordovician hydrogen sulfide and SO42- of the formation water and that TSR occurs at transitional zone of hydrocarbon and water and that reactants of TSR is not correlated with content of hydrogen sulfide and C isotopes of bituminous material is biased toward negative values and that C isotope value of methane is not correlated with content of hydrogen sulfide. Thus methane is not incorporated with TSRo Hydrogen sulfide of Ordovician system is the product different from that of Cambrian system and was formed in Lianglitage formation （O3l） and Yingshan formation （O1-2y） of Ordovician system and TSR occurred in Yanshan -Himalaya period. TSR of Cambrian system occurred in Late Hercynian period and Late Yanshanian -Himalayan period. In general hydrogen sulfide in Ordovician system is generated from the autochthonous TSR that is controlled by filling of highly mineralized and Mg-rich formation water and oil along the strike sliding fault and dilution of dry hydrogen sulfide- poor gas along faut I.