Fluids in the Upper Continental Crust: Static or Dynamic?

[90927]在我们的地壳流体动力学知识中，一个主要的不确定领域涉及大陆地壳超压产生、维持和消散的时间和空间尺度。目前，学术界和工业界对几个基本问题都没有达成共识。在数亿年没有经历活跃沉积的较老的沉积盆地中，是什么原因导致了超压？是否存在压力密封？如果它们存在，那么岩石渗透率要多低才能形成密封？如果存在压力密封，它们是由成岩蚀变造成的，还是实际上是气毛管密封？俄克拉荷马州西南部的阿纳达科盆地将被用作自然实验室，研究可能产生和控制高压的条件。阿纳达科盆地是异常的，因为它包含了大面积的异常高压流体，但它在100多Ma的时间里一直处于构造静止状态。这个问题将从假定地壳水文地质学的两个端元概念的概念框架来处理。静态假说解释了地壳中存在高流体压力，通过调用压力密封，在适当的时间尺度上基本上是不渗透的岩石单元。动态假说将地壳中超压的存在解释为地质过程（例如，碳氢化合物的生成）造成的一种短暂的不平衡，这种不平衡产生的超压比它们从低渗透岩石中消散的速度快。为了区分这些不同的假设，或者确定它们是否实际上是连续统的末端成员行为，将收集测井和岩心数据，并用于表征盆地的热、水文和地质性质。然后，压力产生和消散模型将用于检验不同的假设，并区分不同的盆地流体状态。了解超压是如何在上大陆地壳中形成和消散的，可以更好地理解大陆地壳中发生的许多重要的物理、化学和机械过程（例如，成岩作用、压实作用、油气生成和运移、地震活动），以及地壳岩石的物理性质（例如孔隙度、渗透率）如何在时间、空间和规模上变化。

9909277DemingA major area of uncertainty in our knowledge of crustal hydrodynamics concems the temporal and spatial scales over which overpressures in the continental crust are generated, maintained, and dissipated. At the present time there is no consensus in either academic or industry circles to several fundamental questions. What is the cause of overpressuring in older sedimentary basins which have not undergone active sedimentation for hundreds of millions of years? Do pressure seals exist? If they exist, how low must rock-permeability be to form a seal? If pressure seals exist, are they created by diagenetic alteration, or are they in fact gas capillary seals?The Anadarko Basin in southwestem Oklahoma will be used as a natural laboratory to study the conditions under which high fluid pressures may be generated and contained. The Anadarko Basin is anomalous, because it contains extensive areas of abnormally high fluid pressures, yet it has been tectonically quiescent for more than 100 Ma. The problem will be approached from a conceptual framework which postulates two end-member conceptions of crustal hydrogeology. Static hypotheses explain the existence of high fluidpressures in the crust by invoking pressure seals, rock units that are essentially impermeable over an appropriate time scale. Dynamic hypotheses explain the existence of overpressures in the crust as a transient imbalance caused by a geologic process (e.g., hydrocarbon generation) creating overpressures faster than they may be dissipated from low-permeability rocks. To distinguish between these alternative hypotheses, or to determine if they are in fact end-member behaviors of a continuum, well log and core data will be gathered and used to characterize the thermal, hydrologic, and geologic nature of the basin. Models of pressure generation and dissipation will then be used to test different hypotheses and discriminate between contrasting visions of basinal fluid regimes.Obtaining an understanding of how overpressures form and dissipate in the upper continental crust could lead to a better understwiding of many important physical, chemical, and mechanical processes (e.g., diagenesis, compaction, hydrocarbon generation and migration, seismicity) that take place in the continental crust as well as an understanding of how the physical properties (e.g. porosity, permeability) of crustal rocks vary in time, space, and scale.