大牛地下古生界气藏天然气原生含硫成因研究

Study on the origin of primary sulfur in natural gas of Daniudi gas reservoir

关键词:  H₂S  天然气  含硫成因  下古生界  大牛地气田

Key words:  H₂S  natural gas  sulfur formation reason  lower Paleozoic  Daniudi gas reservoir

摘要:

大牛地下古生界气藏多口气井在生产过程中始终伴有H₂S,但含硫成因问题一直认识不清。首先对气藏含硫的全部成因进行全面分析和逐一排查。在确认为热化学成因的基础上,采用δ³⁴S同位素分析,明确了大牛地下古气藏H₂S为热化学成因中的硫酸盐热化学还原TSR成因。然后通过开展还原反应模拟试验,结合气相色谱分析、全岩XRD扫描、剩余有机质检测等手段,对下古气藏H₂S的生成机理、反应条件、控制因素等进行的系统研究,结果表明,大牛地下古气藏硫酸盐热化学还原TSR反应是在富含石膏、烃类气体充足、密闭的还原环境、温度超过200 ℃和有地层水参与的条件下而进行的。 

Abstract:

H₂S has always been found in the long-term production process in multi-gas wells of Daniudi lower Paleozoic gas reservoir, but the cause of sulfur formation has been unclear. In this paper, the whole causes of sulfur in gas reservoir were comprehensively analyzed and investigated one by one. On the basis of confirming the origin of thermochemistry, δ³⁴S isotope analysis was used to determine the H₂S of Daniudi gas reservoir as the thermochemical reduction TSR of sulfate. Then through the reduction reaction simulation test, full-rock XRD scanning, residual organic matter detection, etc., the formation mechanism, reaction conditions and control factors of H₂S in lower Paleo gas reservoir were ensured. It is revealed that the necessary conditions for the formation of TSR reaction of sulfate thermochemical reduction are rich gypsum, enough hydrocarbon gas, closed reduction environment, over 200 ℃ and the participation of formation water.