库车坳陷古流体动力与天然气成藏特征分析

doi:10.11743/ogg20070616

摘要/Abstract

摘要：

根据库车坳陷超压的成因分析结果,将其分为沉积型超压和构造挤压型超压。利用实测压力、包裹体形成压力和最大埋深时期的古压力等直接证据作为约束条件,根据所建立的流体压力演化数学模型,恢复出不同地质时期的沉积型超压;基于构造压实作用机理,评价了喜马拉雅期构造型超压的形成幅度。将二者加以叠合,获得了目的层的压力演化历史,并恢复出气势的演化历史,分析了流体动力对天然气运移、成藏的影响。研究认为,目的层在库车组沉积前处于沉积型超压阶段,而库车期以来则属沉积型超压的萎缩和构造挤压型超压的发育阶段;侏罗系烃源岩与下白垩统储层之间过剩压力的大小对比关系,形成了天然气的持续充注、早期充注晚期停滞、早期充注早期停滞等3种运移类型;不同时期的气势梯度分布表明,库车组沉积以后的侧向运移、成藏作用最为活跃;第四纪以来的构造运动促成天然气的运移、聚集强度增大,是造成天然气晚期成藏的主要原因。

关键词: 超压, 过剩压力, 气势梯度, 流体动力, 油气运移, 成藏特征, 库车坳陷

Abstract:

Analysis of the causes of overpressure in the Kuqa depression reveals that there are two types of overpressure:the depositional overpressure and the tectonic compressive overpressure.Constrained by such direct evidences as measured pressure,forming pressure of fluid inclusions,and palaeo-pressure during the epoch with the maximal burial depth,the depositional overpressure in different geologic periods are reconstructed in accordance with the mathematical model of fluid pressure evolution.On the basis of mechanism of structural compaction,the amplitude of tectonic overpressure in the Himalaya period is evaluated.The evolution history of fluid pressure in target strata is obtained and the development of gas pressure potential is restored by combining these two kinds of overpressures.The impact of hydrodynamic force upon gas migration and pooling is also studied.The results show that the target was under depositional overpressure before the deposition of Kuche Formation,and since then went through the decline of depositional overpressure and rising of tectonic overpressure.Three modes of gas migration including continuous charging,early charging with later standstill and early charging with early standstill are recognized based on analyses of the pressure relationship between the Jurassic source rock and the lower Cretaceous reservoir rock.Gas pressure potential gradients in different geologic periods show that the lateral migration and accumulation was most active after the deposition of Kuche Formation.The major cause of the late accumulation of gas was the intensifications of gas migration and accumulation by tectonic movement since the Quaternery period.

Key words: overpressure, excess pressure, gas potential gradient, hydrodynamic force, hydrocarbon migration, hydrocarbon accumulation characteristic, Kuqa Depression

中图分类号:

TE122.3

王震亮. 库车坳陷古流体动力与天然气成藏特征分析[J]. 石油与天然气地质, 2007, 28(6): 809-815. doi: 10.11743/ogg20070616 Wang Zhenliang. Analysis on paleohydrodynamic force and gas accumulation characteristics in the Kuqa Depression,the Tarim Basin[J]. Oil & Gas Geology, 2007, 28(6): 809-815. doi: 10.11743/ogg20070616

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