接触变质作用条件下无机天然气成藏模型——以郯庐断裂带南段双山为例

Reservoir formation model for inorganic natural gas under contact metamorphism: Exemplified as Shuangshan area in the south of Tanlu fault belt

系统地研究了接触变质作用条件下二氧化碳释放规律,模拟计算了二氧化碳气的释放量。以郯庐断裂带南段双山地区接触变质带大理岩为实例,研究了碳酸盐岩变质条件下二氧化碳释放的围岩和侵入体条件。结果表明:二氧化碳释放与围岩性质关系密切,包括围岩的热传输性质、岩石渗透率、孔隙度和连通性等。接触变质作用条件下侵入体成分、深度、规模和产状等要素对二氧化碳释放有一定的影响,岩体侵入导致围岩破裂并产生大量孔隙,这有利于流体运移和汇聚,接触变质条件下产生的二氧化碳在一定条件下具有形成工业二氧化碳气藏的可能。在理论和实验研究的基础上,提出了接触变质作用条件下二氧化碳释放的圆台型模型,据此提出找寻二氧化碳气藏不一定只集中在含油气盆地中,还应该扩大到盆地以外的接触变质带地区的新认识。

The releasing rules of carbon dioxide under the condition of contact metamorphosis were systematically studied,and the releasing amount of carbon dioxide was calculated by modeling. Taking marble of Shuangshan area in southern Tanlu fault belt as an example, the surrounding rocks and intrusive body for controlling carbon dioxide releasing under the condition of carbonate rock metamorphism were investigated. The results show that the releasing amount of carbon dioxide has close relation with the characteristics of the surrounding rock including thermal conductivity of surrounding rock as well as permeability,porosity and connectivity of rock. The compositions of intrusive body, intrusive depth,scale and occurrence under the action of contact metamorphism of surrounding rock have the important influences on carbon dioxide releasing. The occurrence of the intrusive body resulted in a great deal of fractures in the surrounding rocks and thus made fluid flowing and accumulation easily. The full evidence proved that the carbon dioxide produced under contact metamorphism condition could form an industrial-scale inorganic natural gas reservoir in some conditions. On the basis of theoretical and practical study,a circular cylinder model for determining carbon dioxide releasing amount under the contact metamorphism was proposed. It is suggested that the exploration of carbon dioxide reservoir should also be paid attention to the outside oil-and-gas bearing basins.