Hydraulic fracturing during the formation and deformation of a basin: A factor in the dewatering of low-permeability sediments
Hydraulic fracturing during the formation and deformation of a basin: A factor in the dewatering of low-permeability sediments
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DOI：
10.1306/8626c997-173b-11d7-8645000102c1865d
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发表时间：
2001-04
期刊：
影响因子：
3.5
通讯作者：
J. Cosgrove
中科院分区：
文献类型：
--
作者：
J. Cosgrove
水力压裂的地质表现形式是多种多样的，主要受差应力大小和岩石的内在性质控制。盆地内发育的裂缝的方向和类型由应力状态决定，而应力状态又受地质边界条件控制。在埋藏和成岩作用的早期阶段，水力裂缝的形成被认为是流体在低渗透性半石化沉积物中运动的重要因素。不幸的是，这些裂缝一般不会被保存下来，一旦流体压力被释放，这些裂缝就会愈合。然而，英格兰西南部布里斯托海峡盆地的低渗透性麦西亚泥岩中含有砂体，在盆地打开期间，这些砂体沿着泥岩中的一些水力裂缝注入，将其作为沉积岩脉和岩床保存下来。现场观察表明，在盆地反转期间，麦西亚泥岩内的流体压力也非常高，水力压裂提供了瞬时渗透性，缓解了这种过度压力。裂缝在大多数泥岩中不可见，但作为缎纹晶石脉的网络保存在富钾长石层位内。因此，沉积岩脉和缎晶岩脉的偶然保存表明，在盆地演化的不同时期，流体通过低渗透单元沿着水力裂缝的瞬态网络迁移。此外，这些裂缝的方向和空间组织反映了盆地历史上不同阶段的边界条件。
The geological expression of hydraulic fracturing is varied and is controlled primarily by the magnitude of the differential stress and the intrinsic properties of the rock. The orientation and type of fractures that develop within a basin are determined by the state of stress, which in turn is controlled by the geological boundary conditions. During the early stages of burial and diagenesis the formation of hydraulic fractures is thought to be an important factor in the movement of fluids through and out of low-permeability, semilithified sediments. Unfortunately, these fractures are not generally preserved and are presumed to heal once the fluid pressure is relieved. The low-permeability Mercia Mudstones of the Bristol Channel Basin, southwest England, however, contain bodies of sand that, during the opening of the basin, were injected along some of the hydraulic fractures in the mudstones, preserving them as sedimentary dikes and sills. Field observations indicate that fluid pressures within the Mercia Mudstones were also very high during basin inversion and that hydraulic fracturing provided a transient permeability that relieved this excess pressure. The fractures are not visible in most of the mudstones but have been preserved within evaporite-rich horizons as a network of satin spar veins. Thus, the chance preservation of the sedimentary dikes and satin spar veins shows that at different times during the evolution of the basin, fluids migrated through low-permeability units along transient networks of hydraulic fractures. In addition, the orientation and spatial organization of these fractures reflect the boundary conditions operating at various stages in the basin history.