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1、随钻地层压力的预测与评价 王志战胜利地质录井公司地质研究解释中心胜利地质录井公司地质研究解释中心目 录前言一、孔隙压力术语二、温压场的划分三、国内外研究现状四、异常压力预测的发展趋势五、异常高压的成因机制前 言 异常压力与油气的生成、运移和聚集关系密切。据 Hunt(1990)统计，世界上已发现180个超压盆地，其 中有160多个为富油气盆地，其中多数为超压。在油气 生成方面，异常高压可降低烃源岩的成熟度，延缓烃源 岩热演化的进程，当地层压力超过一定门限时，压力对 成烃有明显的抑制甚至是阻止作用，表现为压力系数与 烃源岩生烃门限深度、石油窗下限深度的正相关。在油 气运移和聚集方面，异常高压具有
2、建设和破坏双重作用 ：发育异常高压的泥岩可作为良好的盖层，尤其是作为 良好的区域性盖层，有利于油气成藏；异常高压可以成 为泥岩排水、排烃的动力，产生的裂缝既可作为良好的 油气运移通道，也可能导致油气盖层的破坏，促使油气重新分布，导致幕式成藏。前 言 针对胜利地质录井公司而言，由于它是一个 集钻前地质设计、随钻地质录井、钻后研究 、解释、评价于一体的综合服务机构，因 而异常地层压力预测与监测技术贯穿于公司 各个主营环节，搞好这项工作有助于提高地 质设计水平、提高随钻监测精度、提高地质 研究深度、提高解释评价水准，从而提高公 司的整体技术势力，为油气勘探、开发提供 更深入、更准确、更优质的服务。前
3、 言 研究异常地层压力的成因、分布及其与油气藏的形 成及分布之间的关系是成藏动力学的核心内容，是 成藏动力学系统研究和划分的依据。在油气田的滚 动勘探开发过程中，准确的压力预测及细致而系统 的油气层压力分布规律研究，一方面，可以帮助我 们认识和发现新的油气层，对于了解地下油气层的 能量，控制油气层压力变化，并合理地利用油气层 能量以最大限度地采出地下油气具有十分重要的意 义；另一方面，对于做好钻井、地质设计，在施工 过程中保障钻井安全、提高钻探效率、降低钻井成 本及合理保护油气层具有重要的指导意义。一、孔隙压力术语 静水压力(normal or hydrostatic pressure) 斜率
4、(slope)纯水(1.0g/cm3)：0.433psi/ft盐水(1.07g/cm3) ：0.465psi/ft地层水：0.450.465psi/ft1g/cm3 = .433 pst/ft 开放系统(open system)a column of waterl压力值随深度而增加压力变化率只依赖于水的密度变化代表压力增加最大速率的方向向量是垂 直的压力深度的关系与流体容器的形状完 全无关静水压力的性质一、孔隙压力术语 上覆应力/静岩压力/地静压力（overburden stress) 固体+流体美国海湾盆地水饱和的沉积 岩密度为2.3g/cm3，静岩压 力梯度为：.433psi/ft2.3g
5、 /cm3=1.0psi/ft异常高压发生在静岩 压力梯度线和清水静 压梯度线之间的区域静岩压力的性质 决定静岩压力的三个变量 与盐度有关的地层水密度 各种岩性的净厚度 各种岩性的孔隙度PG=岩柱的重量+水柱的重量PG=m（1-）d+wdl静岩压力梯度的变化原因 岩石体积密度随压实作用的增大而增加 地层水密度的增加（溶解在水中的固体总量（TDS)随深度而增加一、孔隙压力术语 孔隙压力（pore pressure）PressureDepthThe “pore pressure” is the pressure of the fluid in the pore space of the rock.
6、The point at which pore pressures exceed hydrostatic pressures is the “top of overpressures.”In overpressure, fluids are trapped in the pores and bear part of the weight of the overlying solids.Any pressure over the hydrostatic pressure is overpressure（超压）. The amount of pore pressure exceeding the
7、hydrostatic line.Effective stress（有效应力） is the amount of overburden stress that is supported by the rock grains.Another concept implied in the figure is that pore pressure does not reach overburden stress. As pore pressure approaches overburden stress, fractures in the rock open and release fluids a
8、nd pressures.一、孔隙压力术语一、孔隙压力术语Typical trend curves for resistivity, sonic velocity, and density. Blue curves denote normal compaction trends. Arrows indicate deviations due to overpressure.一、孔隙压力术语Cross-section of hypothetical reservoir unit. In the absence of fluid flow, the difference in pore press
9、ure between points A and B is simply the weight of the fluid in the vertical reservoir column.一、孔隙压力术语一、孔隙压力术语 压力梯度（Pressure gradients) A local pressure gradient defines how pressure varies over small depth ranges. At the smallest scale, it equals the slope of a pressure versus depth curve. The most
10、 basic pressure gradient that we use is equivalent mud weight (EMW).Pressure profile for hypothetical reservoir unit一、孔隙压力术语Its utility is that for any depth below the surface, we can derive the pressure of the borehole fluids by drawing a line from the origin through the appropriate mud weight to t
11、he depth and get the pressure for that depth.Pressure plotted against depth with mud weight scale added1 lb/gal = .0519 psi/ft静水压力梯度的性质 控制流体密度的因素温度压力流体成分（包括溶解气和固体）流体相态气体或液体l流体密度和梯度变化范围流体正常密度范围（ g/cm3）梯度范围（psi/ft ） 气体（气态*）0.0070.300.0031.130 气体（液态）0.2000.400.0900.174 油0.4001.120.1740.486 水1.0001.150.
12、4330.500*气体=84.3%C1+14.4%C2+0.5%CO2+0.8%N2一、孔隙压力术语Diagram illustrating pore pressure between hydrostatic gradient and fracture gradient一、孔隙压力术语Using mud weight changes pressure axis to gradient axis.This is the view preferred by drillers.一、孔隙压力术语Casing points and mud weight profile for hypothetical
13、situation一、孔隙压力术语 质心（centroid)Because overpressure of a sand is constant, pore pressure must follow a hydrostatic gradient. Shale pore pressure does not. The sand acts as a conduit to transfer pressures updip. At depth shale pore pressures exceed sand pore pressures but shallow sand pore pressures e
14、xceed shale pore pressures. The centroid is the depth at which sand and shale pore pressures are equal.The value of the centroid concept is that it emphasizes the difference between sand and shale pore pressures. Most pore-pressure prediction techniques emphasize shale properties such as velocity an
15、d resistivity but do not address this essential mismatch of the shale and sand pore pressures. This concept also points out that sands provide a mechanism for vertical and lateral transfer of pressures. As basins subside and dewater, the sands provide the mechanism for fluid escape including hydroca
16、rbons.一、孔隙压力术语Simple illustration of lateral transfer when one side of a basin subsides and fills with shale. Overburden in the subsided portion is higher and, if burial is sufficiently fast that the shale cant dewater quickly enough, it becomes overpressured. This is known as disequilibrium compaction.二、温压场的划分压力场压力系数（pressure coefficient）是地层某处的 地层压力相对于该点正常压力的偏离程度，是该点 实际地层压力和静水压力的比值，无量
