孔隙流体压力与流体排驱的关系

本文讨论了在压实作用下孔隙流体压力的形成以及与流体排驱的关系，指出异常孔隙流体压力是因岩石渗透率变化引起毛细管力增加而产生的，且二者之间在流体压力孕育过程中一直维持一个动态平衡状态。对于连续沉积的盆地，只有当异常孔隙流体压力增加到超过岩石的抗剪强度时，因岩石发生剪切破裂导致毛细管力降低，流体才被排出；对于强烈构造变动的盆地，因地层大量剥蚀引起负荷压力降低，其降低幅度达到或超过岩石的抗张强度时，岩石     

明格布拉克油田超压流体封存箱特征

费尔干纳盆地明格布拉克油田属于超深层油气藏,油气层普遍存在超压异常,压力系数可达2.0以上,地层发育盐岩、膏盐层,低孔隙储层中裂缝发育,油田的这些特征与流体封存箱的形成和存在有很大关系。通过研究认为,不均衡压实及构造挤压环境是新近系地层形成超压的宏观成因机制,而发育岩盐层且累积厚度达到了200 m以上是现今油田保存超压的重要条件;古近系及新近系下部地层中存在两个超压流体封存箱,上部封存箱的地层压力系数略大于下部封存箱,上、下超压封存箱内流体性质存在较大的差异,是两个相对独立的成藏系统。上部封存箱又被2个岩盐封隔层分隔为3个次一级的、呈阶梯式的超压箱。封存箱内的超压、微裂缝以及岩盐层是钻探过程中发生井涌、井漏及卡钻等钻井事故的主要原因;除已发现的下部封存箱和上Ⅲ次级封存箱油气藏外,上Ⅱ次级封存箱的底部具有一定的勘探潜力;超深层的高密度原油与超压流体封存箱的存在有关,封存箱内的超高压使油气藏储层裂缝处于开启状态,有利于形成高产油气流,但同时也易于早期见水。     

构造应力对裂缝形成与流体流动的影响

裂缝是低渗透储层流体流动的主要通道,控制了低渗透油气藏的渗流系统。低渗透储层裂缝的形成与流体密切相关,高流体压力引起岩石内部的有效正应力下降,导致岩石剪切破裂强度下降,使岩石容易产生裂缝。高孔隙流体压力还造成某一点的应力摩尔圆向左移动,可以使其最小主应力(σ3)由压应力状态变成拉张应力状态,从而在岩石中形成拉张裂缝。裂缝的渗透性受现今应力场的影响,通常与现今应力场最大主压应力近平行分布的裂缝呈拉张状态,连通性好,开度大,渗透率高,是主渗透裂缝方向。构造应力对沉积盆地流体流动的影响主要表现在三个方面:(1)构造应力导致的岩石变形,不仅提供了流体流动的通道,而且还改变了岩石的渗透性能;(2)在构造强烈活动时期,构造应力的快速变化是流体流动的重要驱动力;(3)岩石中应力状态影响多孔介质的有效应力,从而影响介质中的渗流场。当作用在含流体介质上的构造应力发生改变时,岩石孔隙体积变小,构造应力首先由岩石的骨架来承担;当岩石孔隙体积减小到一定程度时,构造应力由孔隙流体来承担,从而影响岩层渗流场的变化。     

岩石变形、流体压力与热液成矿关系的研究现状

地壳中岩石的变形模式受构造应力、流体压力和上覆岩层重力共同作用的影响。岩石组成和构造应力的大小、方向决定着岩石的变形过程,同时岩石的破裂还受先存断裂构造的影响。流体压力增大,岩石可以发生水力破裂,而引起水力引张破裂的条件是σ1-σ3<4T和Pf=σ3+T。随着深度的增加,受地温梯度的影响,岩石由脆性变形向韧性变形转变。在无流体超压影响的情况下,脆韧性转换的温度在300~450℃之间,大约在地壳15km处。当流体压力和应变速率增大时,韧性条件下的岩石变形行为由韧性向脆性变化,脆韧性转变的深度随之增大。从构造角度探讨热液成矿作用,热液矿床形成的深度与流体压力、应变速率、裂隙的发育、介质的渗透率、温度变化等相关。岩石断裂的类型和方向影响岩石的渗透率,提供流体运移的通道和聚集场所,控制矿床形成的深度、位置和矿体产状。     

CO_2-盐水相对渗透率影响机制研究进展

将CO2封存于地下深部含水层,是减轻碳排放压力的有效手段之一。CO2-盐水相对渗透率是影响地层中CO2迁移、捕获的最重要参数之一。在借鉴油气资源领域渗透率研究成果的基础上,详细论述了影响CO2-盐水相对渗透率的因素,包括流体性质、流体饱和历史和岩石结构,认为流体性质对相对渗透率的影响主要体现在界面张力、黏度比和毛管数的大小;不同流体饱和历史的相对渗透率曲线存在明显滞后性;岩石结构通过矿物润湿性和孔隙结构差异影响相对渗透率大小;最终得到的相对渗透率曲线是各因素叠加的综合结果。     

低渗致密砂岩渗透率应力敏感性试验研究

储层岩石中孔隙流体压力的变化会引起有效应力发生变化,进而导致渗透率的改变,引发储层岩石渗透率应力敏感现象。以试验研究了不同围压下渗透率随孔隙流体压力的变化规律,试验包含了老化处理和升降内压4个回路,每个回路是在围压不变降低和增加孔隙流体压力下实现的,采用稳态法采集每个测试点的数据。试验结果表明,渗透率随着孔隙流体压力的降低而减小,随着孔隙流体压力的增加而增加;在低围压下渗透率的变化幅度较大,在高围压下,则变化幅度较小;在不同围压回路下,净应力相等的点对应的渗透率不相等;渗透率在随孔隙流体压力的变化中呈现出“台阶式”变化。根据Bernabe的模型计算了渗透率有效应力系数,结合Bernabe的观点分析计算结果发现渗透率呈“台阶式”变化是微裂缝随应力的变化而发生变形的表现。对试验岩样进行了储层岩石应力敏感性评价,结果表明,该低渗致密砂岩储层表现为中等应力敏感。     

超压封存箱的压力封闭机制研究进展综述

超压封存箱的封闭机制研究是封存箱研究中的难点之一,倍受许多专家学者关注。深入研究和揭示封隔层的封存机制和异常高压的保存时间对超压成因和油气成藏条件诸多方面的研究都非常重要。已有的关于异常高压的封闭机制研究可分为静态和动态两种观点。静态观点认为:极低渗透率(渗透率10-11μm2)的致密岩层可作为封闭层阻止流体流动,如蒸发岩或经历强烈碳酸盐矿化作用的碎屑岩可形成近于非渗透性岩层从而形成有效封闭;在砂泥岩频繁互层的地层中,气-水两相界面可产生足够大的毛细管压力,而且毛细管压力具有可叠加性,进而形成有效封闭。动态观点认为:在封存箱和封闭层处于连续水相的地质环境中,剩余压力将通过低速扩散方式逐步同其环境压力达到平衡,但由于异常高压通过低渗透岩层(渗透率10-8~10-10μm2)的扩散速度极其缓慢,从而也可使封存系统长期保持超压状态。超压封闭机制的静态和动态两种观点都各自具有事实依据,但具有普遍意义的封存机制可能是气-水两相界面毛细管压力封闭和低速扩散机制。     

构造成矿非线性动力学:1.递增应力流变学模型

本文提出了构造成矿作用动力学研究的递增应力流变学方法。利用该方法将构造变形、应力、流体流动、地球化学反应及成岩成矿作用等多过程耦合起来，可以从多种地质过程的耦合与反馈作用对构造成矿的动力学演化过程进行１～３维数值模拟。模拟的主要内容是在各种过程耦合作用下，以下描述构造成矿体系的主要变量的时空演化：（１）与成矿流体的形成和性质有关的变量，如地层中矿物（包括成矿物质）的溶解速率、流体中各组分的浓度与饱和度、流体温度、压力、离子强度等；（２）与构造变形和流体运移有关的各变量，如应力与变形速率、岩石孔隙度、构造（断裂）渗透率等；（３）与沉淀成矿有关的变量，如矿物（金瞩矿物和脉石矿物）的成核速率、各矿物的沉淀量等；（４）上述各有关变量间的时空耦合关系，如断裂渗透率时空演化与流体流动、汇聚和成矿的耦合关系等。     

上部地壳岩石流动与显微构造演化--天然与实验岩石变形证据

岩石流动性和变形显微构造的发育直接受温度、压力、应变速率和流体相等制约 ,致使在不同地壳层次岩石的流动性表现出很大的差异。对上部地壳环境条件下天然和实验变形岩石的显微构造分析揭示出一系列具有不同特点以及由不同的成核、扩展和联合方式形成的破裂与微破裂型式的存在。讨论了在上部地壳环境中 ,温度与围压的变化对岩石破裂的影响 ,并阐述了高压破裂与低压破裂及其力学、流变学和显微构造特点 ,提出高压破裂对应于天然变形环境下出现的剪切 (挤压 )破裂 ,而碎裂岩带是典型的天然低压破裂 ,其低压环境的出现可以是浅部低围压或深部高流体压力所致。流体相的存在不仅可以引起石英 ,也可以引起方解石类碳酸盐岩矿物的水解弱化 ,并进而导致岩石流动机制的转变。岩石变形及流体等因素所致的岩石粒度变化 ,则从另一个方面影响着上部地壳岩石流动性的变化。从变形环境考虑 ,随着深度的加大 ,温度和压力升高 ,导致岩石由脆性向韧性转变 ;转变域内岩石的变形是一个复杂过程 ,是多种不同脆性和晶质塑性机制的综合。     

构造-流体-成矿体系的反应-输运-力学耦合模型和动力学模拟

建立了一个综合的构造流体成矿体系的反应输运力学耦合动力学模型。利用有限元方法求解岩石变形、断裂作用和断裂网络统计动力学、流体流动、有机和无机地球化学反应及成岩成矿作用、压力溶液和其它压实力学、热迁移的方程组 ,可以对构造流体成矿体系的动力学演化过程进行 1～ 3维数值模拟。模拟的主要内容是在各种过程耦合作用下描述构造流体成矿体系的主要变量的时空演化 :( 1)与成矿流体的形成和性质有关的变量 ,如地层中矿物 (包括成矿物质 )的溶解速率、流体中各组分的浓度与饱和度、流体温度、压力、离子强度等 ;( 2 )与构造变形和流体运移有关的各变量 ,如应力与变形速率、岩石孔隙度、构造 (断裂 )渗透率等 ;( 3 )与沉淀成矿有关的变量 ,如矿物 (金属矿物和脉石矿物 )的成核速率、各矿物的沉淀量等 ;( 4 )上述各有关变量间的时空耦合关系 ,如断裂渗透率时空演化与流体流动、汇聚和成矿的耦合关系等。以湖南沃溪金锑钨矿床为例 ,应用该模型和方法对成矿动力学过程和动力学机制进行了初步的模拟与分析。     

Magnetotelluric Constraints on the Occurrence of Lower Crustal Earthquakes in the Intra-plate Setting of Central Indian Tectonic Zone

Lower crustal earthquake occurrence in the Central Indian Tectonic Zone(CITZ) of the Indian sub-continent was investigated using magnetotelluric(MT) data. MT models across the CITZ, including the new resistivity model across the 1938 Satpura lower crustal earthquake epicenter, show low resistive(80 ?m) mid-lower crust and infer small volume(1 vol%) of aqueous fluids existing in most part of lower crust. This in conjunction with xenoliths and other geophysical data supports a predominant brittle/semi-brittle lower crustal rheology. However, the local deep crustal zones with higher fluid content of 2.2%–6.5% which have been mapped imply high pore pressure conditions. The observation above and the significant strain rate in the region provide favorable conditions(strong/moderate rock strength, moderate temperature, high pore pressure and high strain rate) for brittle failure in the lower crust. It can be inferred that the fluid-rich pockets in the mid-lower crust might have catalyzed earthquake generation by acting as the source of local stress(fluid pressure), which together with the regional stress produced critical seismogenic stress conditions. Alternatively, fluids reduce the shear strength of the rocks to favor tectonic stress concentration that can be transferred to seismogenic faults to trigger earthquakes.     

Relationship between porosity and permeability with stress using pore volume compressibility characteristic of reservoir rocks

Effective stress is one of the most important parameters which strongly affects pore volume compressibility curve, which is used in assessing the reservoir rock properties. It causes change in porosity as well as permeability of the reservoir rocks. In the present study, pore volume compressibility characteristics of the reservoir rocks at different effective stresses were used to derive the relationship of porosity and permeability with the effective stress. To this end, analytical processes for deriving the porosity–stress and permeability–stress relationships are discussed in relation to the reservoir rocks. As a result, a porosity–stress formulation is proposed which is in good agreement with the experimental data. Also, two formulas are proposed for permeability–stress relationship; one on the base of Kozeny–Carman permeability–porosity model and the other one is based on a differential form of permeability–porosity relationship. After calibrating the required coefficients for one sandstone and three limestones, it was concluded that the first permeability–stress model is the upper bound correlation while the latter is the lower bound. Furthermore, it is shown that the latter has better agreement to the real experimental data of the sansdstone samples, while the first one is close to the experimental observations from limestone samples. Also, it is concluded that structure of pores is a key factor on permeability–stress relationship, so that there is a significant difference between the experimental data and the proposed relationship for a limestone sample with vuggy pore spaces.     

一种适用于孔隙体积应变的有效应力方程

土力学奠基石Terzaghi有效应力原理被广泛应用于油藏孔隙和渗透率应力敏感研究中,然而其对于岩石孔隙体积应变的适用性存在争议。对颗粒不可压缩和颗粒可压缩的多孔介质分别进行了受力分析,推导了总体积、颗粒骨架、孔隙体积的有效应力表达式,与Biot、Skepmton有效应力方程对比,建立了适用于孔隙体积应变的新型有效应力方程,并进行了试验论证和应用举例。研究表明:在颗粒不可压缩多孔介质中,有效应力为超出平衡孔隙流压之外的颗粒间宏观等效应力;在颗粒可压缩变形多孔介质中,有效应力为其相同应变下的等效应力,有3种有效应力分别适用于总体积应变、颗粒体积应变、孔隙体积应变;新提出的孔隙体积有效应力方程与孔隙度、岩石总体积压缩系数、颗粒压缩系数、总应力和流压相关,4个理论计算式计算结果在3种多孔介质试验测试结果中的偏差均在5%以内;孔隙体积有效应力系数解决了如何定量增总应力来等效模拟储层降流压生产过程这一关键问题,3个压缩系数关系式理论计算准确方便。     

Numerical modelling of fault reactivation in carbonate rocks under fluid depletion conditions – 2D generic models with a small isolated fault

This generic 2D elastic-plastic modelling investigated the reactivation of a small isolated and critically-stressed fault in carbonate rocks at a reservoir depth level for fluid depletion and normal-faulting stress conditions. The model properties and boundary conditions are based on field and laboratory experimental data from a carbonate reservoir. The results show that a pore pressure perturbation of −25 MPa by depletion can lead to the reactivation of the fault and parts of the surrounding damage zones, producing normal-faulting downthrows and strain localization. The mechanism triggering fault reactivation in a carbonate field is the increase of shear stresses with pore-pressure reduction, due to the decrease of the absolute horizontal stress, which leads to an expanded Mohr's circle and mechanical failure, consistent with the predictions of previous poroelastic models. Two scenarios for fault and damage-zone permeability development are explored: (1) large permeability enhancement of a sealing fault upon reactivation, and (2) fault and damage zone permeability development governed by effective mean stress. In the first scenario, the fault becomes highly permeable to across- and along-fault fluid transport, removing local pore pressure highs/lows arising from the presence of the initially sealing fault. In the second scenario, reactivation induces small permeability enhancement in the fault and parts of damage zones, followed by small post-reactivation permeability reduction. Such permeability changes do not appear to change the original flow capacity of the fault or modify the fluid flow velocity fields dramatically.     

Primary Deformation Analyses of High Pressure Metamorphic Rock in Western Dabie Mountain Area

In the western Dabie Mountain area, the eclogites have similar compositions and tectonic environment, which could be contrastively researched. Except for the reservation of the early structural deformation inside and outside of the eclogite lens, there is no obvious difference between the characteristics of the foliation and lineation in the eclogite lens from the one in surroumding region. So this paper concludes that the eclogites or blueschists (high pressure metamorphic rocks, i. e. HPM) are basically situated in the original position. The eclogites are mostly superposed by the ductile shear zone and show the feature of structural displacement, but so far we have not discovered any large-scale structural zone to uplift eclogite return. Based on the analyses of finite strain measure, petrofabric analysis and TEM image for some minerals such as quartz and garnet, we could efficiently know the deforming characteristics of the eclogite in the prophase and anaphase of the main deforming epoch, and finally determine the forming condition of eclogite according to the strain and the differential stress. This paper puts forward preliminary conclusion that some HPM rocks could be formed by the deep-layer embedding and local stress concentration in the process of regional metamorphism.     

上明峪金矿地质特征及其与大河南岩体的关系

太行山北部的大河南岩体内部分布有一些金矿床及大量金矿化点,其中最具代表性的是上明峪金矿。大河南岩体侵位之后,遭受了强烈的构造运动,形成了近ＳＮ向和近ＥＷ向的两组断裂构造,断裂构造的活动使岩石强烈破碎形成破碎蚀变岩,岩浆热液萃取了花岗岩中的成矿元素并将其搬运至断裂带内,这种富含成矿元素的岩浆热液在断裂带中与天水混合,导致热液中的成矿元素沉淀形成矿化。上明峪金矿的形成是岩浆热液与天水共同作用的结果。     

黔西比德-三塘盆地煤储层异常高压形成机制

比德-三塘盆地含煤地层的储层压力普遍较高, 压力梯度较大, 异常高压发育.通过研究该盆地现今煤储层压力分布特点, 对煤层异常高压影响因素进行了综合分析, 阐明了其形成机制.结果表明: 构造作用是本区异常高压形成的最主要因素, 煤储层生烃作用和顶板泥岩的封闭性次之.盆地内部断裂较少, 具有良好的圈闭条件, 储层流体富集, 压力增大, 易出现超压地层.研究区煤层生烃能力强, 含气量高, 但渗透率普遍较低, 生成的烃类气体使得储层内部流体孔隙体积膨胀产生高压.同时, 超厚的顶板泥岩封闭性较好, 在沉积过程中极易产生欠压实作用, 进一步促进了异常高压的形成.      

Prediction and analysis of the stimulated reservoir volume for shale gas reservoirs based on rock failure mechanism

The ultra-low-permeability shale gas reservoir has a lot of well-developed natural fractures. It has been proven that hydraulic fracture growth pattern is usually a complex network fracture rather than conventional single planar fractures by micro-seismic monitoring, which can be explained as the shear and tensile failure of natural fractures or creation of new cracks due to the increase in reservoir pore pressure caused by fluid injection during the process of hydraulic fracturing. In order to simulate the network fracture growth, a mathematical model was established based on full tensor permeability, continuum method and fluid mass conservation equation. Firstly, the governing equation of fluid diffusivity based on permeability tensor was solved to obtain the reservoir pressure distribution. Then Mohr–Coulomb shear failure criterion and tensile failure criterion were used to decide whether the rock failed or not in any block on the basis of the calculated reservoir pressure. The grid-block permeability was modified according to the change of fracture aperture once any type of rock failure criterion was met within a grid block. Finally, the stimulated reservoir volume (SRV) zone was represented by an enhancement permeability zone. After calibrating the numerical solution of the model with the field micro-seismic information, a sensitivity study was performed to analyze the effects of some factors including initial reservoir pressure, injection fluid volume, natural fracture azimuth angle and horizontal stress difference on the SRV (shape, size, bandwidth and length). The results show that the SRV size increases with the increasing initial pore reservoir and injection fluid volume, but decreases with the increase in the horizontal principal stress difference and natural fracture azimuth angle. The SRV shape is always similar for different initial pore reservoir and injection fluid volume. The SRV is observed to become shorter in length and wider in bandwidth with the decrease in natural fracture azimuth angle and horizontal principal stress difference.     

Paterson高温高压流变仪及其在岩石流变学的应用

地球作为一个动态体系,其内部岩石在各种物理化学条件下变形,形成各种地质构造.在过去的几十年里,得益于相关测试分析手段的不断发展,地球材料的流变学研究取得了许多实验突破,加深了人类对地壳和上地幔岩石变形行为的理解.本文对实验岩石变形装置的技术发展做了扼要的回顾,重点介绍了Paterson高温高压流变仪(HPT).HPT是...     

美国北加州吉塞尔斯诱发地震与热汽田特征的关系

吉塞尔斯地震活动可能是因蒸汽开发引起的.水在一个承受很高构造剪应力和应变的大范围破裂体中汽化为蒸汽。 汽田地震震源机制解与区域构造应变场几乎一致,并且在该区域范围内汽田地震与别的构造地震不易区分。观测中注意到地震活动与注液历史无关,这表明孔隙水压力增高与注液不可能是吉塞尔斯诱发地震的成因。 相反,所有证据都表明诱发地震与孔隙水压力及温度降低有关。形成机制有两种最大可能:其一,是裂隙排水(汽)导致局部剪应力增加所致,其二,是由稳定滑动转化为不稳定滑动(粘滑)。没有其它记载的诱发地震机制与吉塞尔斯汽田条件相符。