青海省木里地区天然气水合物构造成藏机制——来自物理模拟实验的启示

发布时间：2019-02-08 21:06

【摘要】：青海省木里地区,2008年钻探岩心中首次钻取天然气水合物实物样品,从而引起了地质学家们越来越多的关注。以木里地区聚乎更矿区为例,结合分析该区域的钻井资料以及断裂分布特征,发现天然气水合物的成藏分布存在一定的规律,即该区天然气水合物主要集中于一条先存深大断层F1的两侧,而邻近区域在具有相似物化条件下却并未发现天然气水合物的存在。因此在前人研究基础上,结合区域地质构造特征,设计了3组物理模拟沙箱实验,试图从构造的角度来阐述研究区天然气水合物可能的构造成藏机制及其影响因素。实验模拟结果表明,先存断层和区域滑脱层对木里地区构造演化具有明显的控制作用。先存断层属于区域性深大断裂,其在后期应力作用下再活化,形成切割地层深部的运移通道;而区域性滑脱层的分布则造成挤压应力作用下区域性薄皮滑脱断层的广泛发育,这些断裂的根部主要集中到区域性滑脱层之上,滑脱层之下地层则基本未被断裂切穿。对比分析物理模拟实验结果及研究区构造特征,结合研究区天然气水合物的分布特征,提出了木里地区天然气水合物可能的区域性"断裂运移、下生上储"成藏模式,即深部热解气沿着深大先存断层运移至冻土层下有利位置富集成藏,并在有利的物化条件下形成天然气水合物,而在研究区其他区域,深部运移通道不发育,则在浅部地层未见天然气水合物的富集成藏。
[Abstract]:Natural gas hydrate samples were drilled for the first time in the core of Muli region of Qinghai Province in 2008, which has attracted more and more attention from geologists. Taking Juhugan mining area in Muli area as an example, combined with the analysis of drilling data and fault distribution characteristics in this area, it is found that there are certain laws of gas hydrate accumulation and distribution. That is to say, the gas hydrate in this area is mainly located on both sides of a pre-existing deep fault F1, but no gas hydrate is found in the adjacent area under similar physicochemical conditions. On the basis of previous studies and combined with the characteristics of regional geological structure, three sets of physical simulation sandbox experiments were designed to explain the possible structural reservoir formation mechanism and its influencing factors of natural gas hydrate in the study area from the point of view of structure. The experimental results show that the preexisting faults and regional slip beds play an important role in controlling the tectonic evolution of Muli area. The pre-existing fault belongs to the regional deep fault, which is reactivated under the late stress to form the migration channel in the deep part of the cutting strata. The distribution of regional slip layer causes the extensive development of regional thin skin detachment fault under the action of compression stress. The roots of these faults are mainly concentrated on the regional detachment layer, but the strata under the detachment layer are basically not cut through by the fracture. By comparing and analyzing the results of physical simulation experiments and the structural characteristics of the study area, combined with the distribution characteristics of natural gas hydrate in the study area, a possible regional "fault migration, lower generation and upper reservoir" reservoir formation model of gas hydrate in Muli area is proposed. That is, the deep pyrolysis gas migrated along the deep and large pre-existing faults to the favorable position under the permafrost, and formed natural gas hydrate under favorable physical and chemical conditions, while in other areas of the study area, the deep migration channels did not develop. There is no rich and integrated reservoir of gas hydrate in shallow formation.
【作者单位】：南京大学地球科学与工程学院;中国地质科学院地质研究所;江苏省地震局;
【基金】：中国地质调查水合物专项项目(编号:GZHL20110313) 国家自然科学基金项目(编号:41272227;41572187)联合资助
【分类号】：P618.13

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