H₂S formation and enrichment mechanisms in medium to large scale natural gas fields (reservoirs) in the Sichuan Basin

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• 作者：Liu Wenhui ; Tenger ; Gao Bo ; Zhang Zhongning ; Zhang Jianyong ; Zhang Dianwei ; Fan Ming ; Fu Xiaodong ; Zheng Lunju ; Liu Quanyou
• 关键词：northeastern Sichuan ; H₂S ; TSR ; enrichment mechanism ; highly sour gas field
• 刊名：Petroleum Exploration and Development
• 出版年：2010
• 出版时间：October 2010
• 年：2010
• 卷：37
• 期：5
• 页码：513-522
• 全文大小：477 K

文摘

A comprehensive study on the temporal and spatial distribution of H₂S accumulations and the geochemical characteristics of sour gas fields (reservoirs) in the Sichuan Basin has been conducted. It has been followed by a series of carefully designed simulation experiments to elucidate an H₂S formation mechanism which is able to predict the distribution of H₂S. In some reservoirs, for example P₂ch(T₁f, have sufficient magnesic SO₄²⁽ and abundant hydrocarbons (palaeo pools) present at sufficiently high temperatures to cause thermochemical sulfate reduction (TSR). This is the major origin of abundant H₂S in large to medium scale gas fields. The formation mechanism of highly sour gas fields (reservoirs) is an in-situ reaction under conditions where sufficient source, enough energy supply, suitable reservoir volume and severely reducing environments occur. However, in some areas or strata, such as slope belts or on continental shelf deposits, or formations such as the Jialingjia and Leikoupo Formations, which are dominantly compact carbonatite and have contemporaneously different facies, it is difficult to form abundant H₂S. These formations lack a source of sulphur and energy compared to the P₂ch(T₁f reef flat facies reservoirs. Even though highly sour natural gas migrating from the P₂ch(T₁f reservoirs is present, H₂S is often consumed due to long distance migration and results in hydrocarbon-rich sweet natural gas. This study predicts that the Heichiliang reef flat facies sedimentary zone in northeastern Sichuan to have highly sour natural gas reservoirs.