Theoretical aspects of cap-rock and fault seals for single- and two-phase hydrocarbon columns   总被引：6，自引：0，他引：6  

N.L. Watts   《Marine and Petroleum Geology》1987,4(4)

Cap-rock seals can be divided genetically into those that fail by capillary leakage (membrane seals) and those whose capillary entry pressures are so high that seal failure preferentially occurs by fracturing and/or wedging open of faults (hydraulic seals). A given membrane seal can trap a larger oil column than gas column at shallow depths, but below a critical depth (interval), gas is more easily sealed than oil. This critical depth increases with lower API gravity, lower oil GOR and overpressured conditions (for the gas phase). These observations arise from a series of modelling studies of membrane sealing and can be conveniently represented using pressure/ depth (P/D) profiles through sealed hydrocarbon columns. P/D diagrams have been applied to the more complex situation of the membrane sealing of a gas cap underlain by an oil rim; at seal capacity, such a two-phase column will be always greater than if only oil or gas occurs below the seal.These conclusions contrast with those for hydraulic seals where the seal capacity to oil always exceeds that for gas. Moreover, a trapped two-phase column, at hydraulic seal capacity will be less than the maximum-allowed oil-only column, but more than the maximum gas-only column. Unlike membrane seals, hydraulic seal capacity should be directly related to cap-rock thickness, in addition to the magnitude of the minimum effective stress in the sealing layer and the degree of overpressure development in the sequence as a whole.Fault-related seals are effectively analogous to membrane cap-rocks which have been tilted to the angle of the fault plane. Consequently, all of the above conclusions derived for membrane cap-rocks apply to both sealing faults sensu stricto (fault plane itself seals) and juxtaposition faults (hydrocarbon trapped laterally against a juxtaposed sealing unit). The maximum-allowed two-phase column trapped by a sealing fault is greater than for equivalent oil-only and gas-only columns, but less than that predicted for a horizontal membrane cap-rock under similar conditions. Where a two-phase column is present on both sides of a sealing fault (which is at two-phase seal capacity), a deeper oil/water contact (OWC) in one fault block is associated with a deeper gas/oil contact (GOC) compared with the adjacent fault block. If the fault seal is discontinuous in the gas leg, however, the deeper OWC is accompanied by a shallower GOC, whereas a break in the fault seal in the oil leg results in a common OWC in both fault blocks, even though separate GOC's exist. Schematic P/D profiles are provided for each of the above situations from which a series of fundamental equations governing single- and two-phase cap-rock and fault seal capacities can be derived. These relationships may have significant implications for exploration prospect appraisal exercises where more meaningful estimates of differential seal capacities can be made.The membrane sealing theory developed herein assumes that all reservoirs and seals are water-wet and no hydrodynamic flow exists. The conclusions on membrane seal capacity place constraints on the migration efficiency of gas along low-permeabiligy paths at depth where fracturing, wedging open of faults and/or diffusion process may be more important. Contrary to previous assertions, it is speculated that leakage of hydrocarbons through membrane seals occurs in distinct pulses such that the seal is at or near the theoretically calculated seal capacity, once this has been initially attained.Finally, the developed seal theory and P/D profile concepts are applied to a series of development geological problems including the effects of differential depletion, and degree of aquifer support, on sealing fault leakage, and the evaluation of barriers to vertical cross-flow using RFT profiles through depleted reservoirs. It is shown that imbibition processes and dynamic effects related to active cross-flow across such barriers often preclude quantitative analysis and solution of these problems for which simulation studies are usually required.  相似文献   

A higher-order σ-coordinate non-hydrostatic model for nonlinear surface waves     

Chih-Chieh Young  Jan-Tai Kuo 《Ocean Engineering》2007,34(10):1357-1370

A higher-order non-hydrostatic model in a σ-coordinate system is developed. The model uses an implicit finite difference scheme on a staggered grid to simultaneously solve the unsteady Navier-Stokes equations (NSE) with the free-surface boundary conditions. An integral method is applied to resolve the top-layer non-hydrostatic pressure, allowing for accurately resolving free-surface wave propagation. In contrast to the previous work, a higher-order spatial discretization is utilized to approximate the large horizontal pressure gradient due to steep surface waves or rapidly varying topographies. An efficient direct solver is developed to solve the resulting block hepta-diagonal matrix system. Accuracy of the new model is validated by linear and nonlinear standing waves and progressive waves. The model is then used to examine freak (extreme) waves. Features of downshifting focusing location and wave asymmetry characteristics are predicted on the temporal and spatial domains of a freak wave.  相似文献   

龙口港湾大振幅假潮的成因分析     

刘赞沛  陈则实  宋万先  邹娥梅 《海洋学报》2001,23(1):120-126

龙口湾位于山东半岛北部,莱州湾东北隅,为莱州湾的一个附属海湾.海湾湾口朝向西南,湾廓近似半圆形,属半封闭海湾.龙口验潮站位于湾顶(图1),水深7m.  相似文献   

Instrumentation and Numerical Analysis of Cylindrical Diaphragm Wall Movement During Deep Excavation at Coastal Area     

Dong Soo Kim  Byoung Chul Lee 《Marine Georesources & Geotechnology》2005,23(1):117-136

The lateral deflection of a cylindrical diaphragm wall and the associated ground movement induced by deep excavation are analyzed by performing site instrumentations and numerical analyses in the coastal area of Korea. Wall lateral deflection, rebar stress, and pore water pressure were measured and analyzed in eight directions. Variations of soil properties with the decrease of confining pressure are compared by performing various in situ tests before ad after excavation. To calculate the wall lateral deflection accurately, the effects of small strain nonlinearity, confining pressure, and the hysteresis loading/unloading loop developed during excavation are considered in the proposed numerical analysis. By comparing numerical results with measured ones, the importances of considering small strain nonlinearity and confining pressure reduction in the nonlinear (FEM) are emphasized. Also, the effects of wall stiffness on the performance of cylindrical diaphragm walls are studied for future similar excavation in the coastal area.  相似文献   

上新世——早更新世青藏高原北缘隆升的磁性地层学证据   总被引：9，自引：0，他引：9  

郑洪波  陈惠忠  靳鹤龄  李孝泽  董光荣 《海洋地质与第四纪地质》2002,22(2):57-62

对新疆叶城剖面西域砾岩及下伏第三纪地层的磁性地层学研究表明 ,西域砾岩的沉积时代为晚上新世至早更新世 ,磁性地层年龄为 3.5至 <1.8Ma。阿图什组沉积于早上新世 ,古地磁年龄为 4 .6～ 3.5 Ma。阿图什组以砂岩和粉砂岩为主夹薄层砾岩 ,为河流相及冲积扇前缘相。西域砾岩以厚层砾岩为主夹风成粉砂岩 ,为典型洪积—冲积扇堆积。西域砾岩的沉积反映了青藏高原北缘晚上新世至早更新世强烈的隆起和剥蚀  相似文献   

高精度CTD剖面仪研制过程中的专用设备   总被引：1，自引：1，他引：1  

王欣 《海洋技术学报》2001,20(1):140-142

本文介绍了“油水分离压力罐”的主要理论依据及该设备采用的特殊的机械结构，实践证明，利用该设备实现了在实验室条件下，模拟深海重力场检测CTD剖面仪中的某些关键传感器的目的。  相似文献   

旧路改建高速公路中地基强夯效应测试与工艺参数分析   总被引：2，自引：1，他引：1  

吕国仁  崔新壮 《岩土力学》2008,29(9):2542-2546

旧路改建高速公路遇到的最主要的问题是地基的不均匀沉降。数值分析表明,对新的天然地基进行处理是解决这一问题的关键。强夯是加固地基的一种有效措施,为了对强夯工艺参数进行优化研究,对夯锤冲击地面过程中产生的动孔隙水压力、动土应力以及夯后超静孔隙水压力的消散过程进行了跟踪测试与分析。结果表明,对以风化料为主的地基,最大夯击数不宜超过4击,而且铺底夯完成2d后就可进行满夯。  相似文献   

智能全站仪在大型压力容器焊接变形监测中的应用     

CHEN Ji-hua  JIANG Yan-yun  HUANG Jian-hua  CHU-hu 《测绘学院学报》2008,(3)

在大型压力容器的部件焊接过程中,由于预热、焊接等工艺流程会导致各部件产生变形,从而引起部件之间的位置关系产生变化。为保证压力容器成品满足设计要求,必须在制造过程中实施变形监测,依据变形数据适当调整焊接工艺流程,控制变形量。提出采用智能全站仪配以自动变形监测软件对大型压力容器焊接变形进行实时监测,并应用于生产实践中,监测结果表明该方法自动化程度高、实时性好,能同时给出位置和姿态变形数据。  相似文献   

岩石圈深部温压条件下萜烷演化的实验研究     

王传远  杜建国  段毅  周晓成  陈志 《矿物岩石》2008,28(2):76-80

在密闭体系中700℃、压力高达3 GPa条件下进行褐煤加水的模拟实验,分析实验产物中的萜烷的变化规律,进而对高压高温下有机质演化进行研究.实验结果表明,相同压力条件下,温度升高有利于有机质的成熟演化;压力增加会抑制或延迟油气的生成和有机质成熟;五环三萜烷ββ生物构型转化为αβ地质构型所需能量比烯烃双键加氢饱和更高.高温超高压条件下,研究样品中C24四环萜烷存在4种同分异构体,含量由高到低依次包括10β(H)-降A-羽扇烷、10p(H)-降A-奥利烷、C24-17,21-断藿烷和10β(H)-降A-乌散烷.高碳数烷烃在地幔高压力条件下仍可以存在,这为认识超压盆地的油气资源与深层油气成藏及保存提供了新的思路.  相似文献   

全程注浆在隧道穿越既有建筑物中的试验研究   总被引：6，自引：0，他引：6  

逢铁铮 《岩土力学》2008,29(12):3451-3458

厦门市成功大道工程是福建省2005年重点建设项目,项目由多座立交和两条特长城市隧道组成,其中莲前至梧村山隧道里程长度为3 700 m,采用双洞双向6车道标准.隧道在埔南工业区的685 m段采用跨度达34 m的浅埋连拱结构穿越地面67栋密集建构筑物.洞项至地表的覆盖层只有7～24 m,水文、地质较差,洞顶基本为杂填土和残积亚黏土层,洞底多为全、强风化花岗岩,地下饱和水位高(局部洞身地处海平面以下20 m左右),施工风险极大.为了保证既有地面建构筑物的安全,提出了以过程控制和过程恢复为核心的全过程注浆方案,并预留104#和105#拆迁房为试验楼,采取地面注浆和洞内注浆的方法来进行过程控制和房屋抬升的试验.在现场试验中,根据全过程注浆的思路,提出了建筑物安全风险控制标准.通过室内试验比较了不同浆液的注浆效果,分析实际施工中房屋摹础改造和地基注浆加固、动态跟踪注浆以及工后房屋恢复抬升的特点和效果.在注浆过程中进行实时的信息反馈和分析,进而了解注浆工艺和参数与地层加崮效果和建筑物抬升效果之间的关系,得出了一系列有意义的结论.试验结果为隧道后续穿越建构筑物施工提供经验和指导,研究思路可为类似的隧道穿越工程提供一定的参考.  相似文献