岩石渗透率三维指示条件模拟方法

根据指示条件模拟的基本原理 ,以单井小层渗透率数据为基础 ,提出了不同等级渗透率空间分布的三维指示条件模拟方法 ,它是一种非参数条件模拟方法 ,不要求模拟参数符合特定的概率分布模型 ,特别适合于岩石渗透率这样的具有特异值的数据。并以大庆长垣北部喇嘛甸油田北实验区为例 ,给出了渗透率指示变异函数的计算方法和渗透率分布的三维指示条件模拟步骤 ,给出了各小层不同等级渗透率储层平面分布 。

不同围压作用下川西高原地区岩石渗透率变化特性试验研究——以巴郎山隧道为例

为量化和研究不同围压作用下川西高原地区深埋隧道岩石渗透率的变化规律,进一步评价隧道涌水对工程与环境的影响,基于STY-2型气体渗透率仪和YKS-II型智能型覆压岩心孔渗联测系统仪器,采用常规岩石渗透性测试和不同围压下岩石渗透率测试相结合的方法,对川西高原地区巴郎山隧道钻孔岩样进行了应力-渗流耦合试验研究。结果表明:(1)在室内常规的岩石渗透性测试中,不增设围压时,钻孔深度和岩性(砂岩、板岩)的变化对于岩石渗透系数的影响很小,出现岩样渗透系数异常增大的突变点主要是受巴郎山隧道隧址区夹金山倒转向斜褶皱带和断裂带的影响,地质构造是巴郎山隧道在施工、运行和维护时应该考虑的重点;(2)在不同围压下岩石渗透率测试中,同一钻孔ZK02的不同岩样(砂岩、板岩)和不同钻孔ZK02、ZK03的同一岩样(砂岩)在围压加载过程中,岩石渗透率均逐渐减小且存在一个拐点,而在围压卸载过程中,岩石渗透率缓慢增大,但回升的路径远远低于原始路径,即在围压加、卸载之后,岩石中的孔隙、裂隙发生了挤压和破坏,其渗透率恢复不到最初的水平;(3)在围压加、卸载过程中,采用不同函数关系式来拟合应力-渗流耦合的规律,发现拟合曲线的拟合精度最高的是幂律函数关系式,其拟合优度R~2>0.9,说明拟合曲线与试验数据的吻合度较高,可直观地反映岩石渗透率随围压的变化规律。

不同渗透率储层超临界CO_(2)改造模拟研究

水力压裂是非常规能源开发中的一种高效储层改造方法,近年来超临界二氧化碳(S-CO_(2))被认为是一种很有前景的压裂液,相比于水基压裂液由于其具有更高的压裂能力而备受关注。但在基质渗透率(RMP)相对较高的储层岩石中,将超临界二氧化碳用于压裂会出现较高的滤失。本文通过离散裂缝网络(DFN)方法对考虑天然裂缝系统的不同储层进行了模拟,对用水压裂(WF)和用S-CO_(2)压裂(SCF)在不同岩石基质渗透率储层中的适用性及压裂能力进行了模拟研究。与常用的水基压裂液相比,在等同条件下S-CO_(2)的黏度和密度较低,更容易使储层岩石破裂并生成更为复杂的裂缝网络。但是在岩石基质渗透率相对较高的储层中,裂缝不断扩展会导致S-CO_(2)滤失量的不断加剧,严重影响裂缝流体压力的提升,并进一步影响到裂缝的扩展。数值模拟结果也呈现了压裂期间裂缝长度增长趋势出现近水平发展拐点,而这一现象恰恰反映流体滤失对裂缝扩展的影响。在这种情况下继续提高压裂液注入速度可以缩短压裂时间,从而有效降低滤失对压裂的影响。计算结果清楚地表明了岩石基质渗透率的重要性,这一结果可以直接用于S-CO_(2)压裂适用性及生产能力的理论指导。

低孔隙度低渗透率岩石孔隙度与渗透率关系研究

为了能够更好的掌握岩石渗透率同孔隙度间的规律,本文就低孔隙度低渗透率岩石孔隙度与渗透率关系进行一定的研究。

渗透率测试标样标定器的研制

分析了岩石渗透率测试仪器标定技术的现状,介绍了自行设计研制的全直径岩石渗透率测试标样标定器及该标定器的量值溯源标定技术。指出,全直径岩石气体渗透率测试仪标定器适用于目前各种规格岩石渗透率测试仪器的标定。

异常高压气藏岩石应力敏感性及其对产能的影响

文章具体实测了克拉2异常高压气藏岩样不同覆压下的渗透率,根据其实测结果拟合出渗透率的应力敏感性幂函数表达式,总结了岩石渗透率随气藏压力或有效覆压的变化规律。考虑渗透率变化对气藏产能的影响,推导出新的产能方程。研究表明:克拉2气藏岩样应力敏感性高于大庆油田岩样,具有异常高压气藏岩石欠压实的特点。岩样的应力敏感性使产能降低,在克拉2 气藏的条件下,考虑应力敏感时的绝对无阻流量是渗透率为常数时的70%左右。该研究对深入了解异常高压气藏的产能及预测异常高压气藏的开发动态和采收率有一定意义。

Permeability Estimation of Shale Oil Reservoir with Laboratory-derived Data: A Case Study of the Chang 7 Member in Ordos Basin

The shale oil reservoir within the Yanchang Formations of Ordos Basin harbors substantial oil and gas resources and has recently emerged as the primary focus of unconventional oil and gas exploration and development.Due to its complex pore and throat structure,pronounced heterogeneity,and tight reservoir characteristics,the techniques for conventional oil and gas exploration and production face challenges in comprehensive implementation,also indicating that as a vital parameter for evaluating the physical properties of a reservoir,permeability cannot be effectively estimated.This study selects 21 tight sandstone samples from the Q area within the shale oil formations of Ordos Basin.We systematically conduct the experiments to measure porosity,permeability,ultrasonic wave velocities,and resistivity at varying confining pressures.Results reveal that these measurements exhibit nonlinear changes in response to effective pressure.By using these experimental data and effective medium model,empirical relationships between P-and S-wave velocities,permeability and resistivity and effective pressure are established at logging and seismic scales.Furthermore,relationships between P-wave impedance and permeability,and resistivity and permeability are determined.A comparison between the predicted permeability and logging data demonstrates that the impedance–permeability relationship yields better results in contrast to those of resistivity–permeability relationship.These relationships are further applied to the seismic interpretation of shale oil reservoir in the target layer,enabling the permeability profile predictions based on inverse P-wave impedance.The predicted results are evaluated with actual production data,revealing a better agreement between predicted results and logging data and productivity.

欠平衡钻井井壁失稳和储层损害的最大负压差确定研究

确定合理的井底负压差值对于欠平衡钻井至关重要。如果负压值过大,地面设备控制和处理困难,并可能导致地层坍塌、出砂,造成地层渗透率严重下降。因此,如何准确确定井壁失稳和储层损害的最大负压差,关系到欠平衡钻井工程的成败。文章根据岩石力学和渗流力学理论对井壁失稳的力学机理进行了分析,并基于摩尔—库仑准则建立了欠平衡钻井井壁失稳极限压差的数学模型。同时,针对欠平衡钻井储层伤害的问题,着重分析了储层应力损害的机理,首次提出并引入了井壁岩石破坏比的概念,通过大量岩心实验,得出井壁岩石渗透率与其所受应力之间的数学回归关系式和相应的极限压差数学模型。并结合新疆呼图壁气田呼3 井和石南4003 井2口井现场数据和相应地层层位的岩心力学实验数据,进行了实例计算模拟,此2 口井的钻井实践证实了文章中欠平衡钻井井壁失稳和储层损害的最大负压差确定的理论方法和数学模型的正确性,表明该数学模型对欠平衡钻井设计具有重要的实用意义。

环抱式密封岩心夹持器的设计与研制

岩心夹持器是一种用于夹持和密封岩心,完成各种岩石物理性质测试及相关实验的装置。文章介绍的岩心夹持器采用气压密封方式,夹持器上端设有一密封气体入口,支撑杆置于密封套内,密封气体进入夹持器缸套与岩心密封套之间的腔体,对待测岩石样品侧表面施加均匀围压,确保测试流体通过岩心样品前后两端时无测试流体渗漏。该岩心夹持器具有密封效果好,装取样品方便,结构简单,安全防爆且使用寿命长的特点。

多层合采用工作液对储层伤害程度的计算方法

1.目的目前常用的利用工作液伤害前、后岩石渗透率的变化来评价工作液引发储层伤害程度的方法,用岩心柱塞表征整个油气藏,仅适用于单个均质的油气藏。纵向上发育多个储层或者单个储层具有强非均质性的油气藏,如果沿用上述方法来评价工作液对储层的伤害程度,由于多个储层整体渗透率涉及多个柱塞长度无法选取,致使渗透率无法计算得到或单一柱塞难以表征纵向上多个强非均质性储层在同一条件下受伤害的程度,也就不能准确表征储层伤害的整体程度,由此造成了无法计算多层合采用工作液对储层伤害程度的难题。

煤岩气储层滑脱效应实验研究

岩石的孔隙度与岩石的渗透率成正相关。岩石的气透测渗率高于液测渗透率,且具有压力依赖性,该现象被称作滑脱效应或Klinkenberg效应。气测渗透率的压力依赖性是由于在计算渗透率时气体黏度取值不当所致,气体黏度在低压下随压力变化很大,但计算渗透率时却选用了定值。滑脱效应将使气体的黏度无法测量,从而出现测试悖论。气体分子每时每刻都在做不规则的热运动,会不停地与孔隙壁面发生碰撞,致使气体无法出现滑脱。岩石渗透率的气测值高于液测值,是测试介质的分子尺度与孔隙尺度对比的结果。

水敏指数变化规律研究

探寻水敏指数变化规律 ,可有效指导油田开发调整方案。作者通过统计文南油田的水敏试验资料 ,找出了水敏指数与岩石空气渗透率和注入水矿化度的关系。结果表明 ,其关系式相关程度很高 ,利用该式可预测这一地区不同岩石、不同注入水的潜在水敏性。该方法对其它油田或其它方面实验资料的应用具有重要的借鉴作用。

Effect of Freeze-Thaw Cycles on Mechanical Properties and Permeability of Red Sandstone under Triaxial Compression

Geological disasters will happen in cold regions because of the effects of freeze-thaw cycles on rocks or soils, so studying the effects of these cycles on the mechanical characteristics and permeability properties of rocks is very important. In this study, red sandstone samples were frozen and thawed with o, 4, 8 and 12 cycles, each cycle including 12 h of freezing and 12 h of thawing. The P-wave velocities of these samples were measured, and the mechanical properties and evolution of the steady-state permeabilities were investigated in a series of uniaxial and triaxial compression tests. Experimental results show that, with the increasing of cyclic freeze-thaw times, the P-wave velocity of the red sandstone decreases. The number of freeze-thaw cycles has a significant influence on the uniaxial compressive strength, elastic modulus, cohesion, and angle of internal friction. The evolution of permeability of the rock samples after cycles of freeze-thaw in a complete stress-strain process under triaxial compression is closely related to the variation of the microstructure in the rock. There is a highly corresponding relationship between volumetric strain and permeability with axial strain in all stages of the stress-strain behaviour.

Creep properties and permeability evolution in triaxial rheological tests of hard rock in dam foundation

Triaxial creep tests were carried out under seepage pressure by using rock servo-controlled triaxial rheology testing equipment. Based on experimental results, rock rheological properties influenced by seepage-stress coupling were studied, and variations of seepage rate with time in complete creep processes of rock were analyzed. It is shown that, when the applied stress is less than failure stress level, the creep deformation is not obvious, and its main form is steady-state creep. When applied stress level is greater than or less than but close to fracture stress, it is easier to see the increase of creep deformation and the more obvious accelerative creep characteristics. The circumferential creep deformation is obviously higher than the axial creep deformation. At the stage of steady-state creep, the average of seepage flow rate is about 4.7×10-9 rn/s at confining pressure （tr3） of 2 MPa, and is about 3.9×10-9 m/s at a3 of 6 MPa. It is seen that the seepage flow rate at or3 of 2 MPa in this case is obviously larger than that at tr3 of 6 MPa. At the stage of creep acceleration, the seepage flow rate is markedly increased with the increase of time. The variation of rock permeability is directly connected to the growth and evolution of creep crack. It is suggested that the permeability coefficient in complete creep processes of rock is not a constant, but is a function of rock creep strain, confining pressure, damage variable and pore water pressure. The results can be considered to provide a reliable reference for the establishment of rock rheological model and parameter identification.

Experimental Study into Permeability of Broken Mudstone

Much attention should be paid to the permeability of broken rocks in goafs for the sake of water preservation in mining and to prevent disasters. Using a special device together with the MTS815.02 Rock Mechanics Test System,we tested the permeability of broken mudstone during its compacting process,and obtained the relations between axial stress and differential seepage pressure and between the pressure gradient and the seepage velocity. The effect of axial stress,grain size,and seepage velocities on the permeability coefficient is analyzed. The results show that 1) permability varies abruptly when the load reaches the compressive strength of rock samples,2) for a constant seepage velocity,the differential seepage pressure and the axial stress can be expressed by an exponential function,3) for a constant axial stress,the pressure gradient and the seepage velocity can be also expressed by an exponential function and 4) the permeability coefficient of broken mudstone of different sizes is closely related to its compaction state and will decrease with the increase of axial stress,expressed as a logarithmic function.

Numerical modeling of permeability evolution based on degradation approach during progressive failure of brittle rocks

The permeability evolution of rock during the progressive failure process is described. In combination with the strength degradation index, the degradation formulas of s and a, which are dependent on the plastic confining strain component, the material constants of Hock-Brown failure criterion are presented, and a modified elemental scale elastic-brittle-plastic constitutive model of rock is established. The rela- tionship between volumetric strain and permeability through tri-axial compression is investigated. Based on the above, a permeability evolution model is established. The model incorporates confining pressure- dependent degradation of strength, dilatancy and corresponding permeability evolution. The model is implemented in FLAC by the FISH function method. The permeability evolution behavior of rock is inves-tigated during the progressive failure process in a numerical case. The results show that the model is cap- able of reproducing, and allowing visualization of a range of hydro-mechanical responses of rock. The effects of confining pressure on degradation of strength, dilatancy and permeability evolution are also reflected.

Experimental study on influence of coal structural anisotropy to gas permeation

Based on ＂true triaxial coal rock permeability of coal sample test system , the permeability under different gas pressure to coal specimen in bedding plane and the vertical bedding directions are tested. The results show that coal structural anisotropy has a greater impact on gas permeability properties, differences in experimental coal permeability are roughly one order of magnitude. In view of the differences of the gas flow characteristics in the coal bedding plane and vertical bedding, established series and parallel choked flow model of coal sample gas seepage, and made a theoretical analysis to the influences of the bedding structure to gas permeability properties.

Seismic Signatures of Rock Pore Structure

Rock pore structure is one of the important parameters in controlling both seismic wave velocity and permeability in sandstones and carbonate rocks. For a given porosity of two similar rocks with different pore structures, their acoustic wave speeds can differ 2 km/s, and permeability can span nearly six orders of magnitude from 0.01 mD to 20 D in both sandstone and limestone. In this paper, we summarize a two-parameter elastic velocity model reduced from a general poroelastic theory, to characterize the effect of pore structures on seismic wave propagation. For a given mineralogy and fluid type of a reservoir, this velocity model is defined by porosity and a frame flexibility factor, which can be used in seismic inversion and reservoir characterization to improve estimation of porosity and reserves. The frame flexibility factor can be used for quantitative classification of rock pore structure types (PST) and may be related to pore connectivity and permeability, using both poststack and prestack seismic data. This study also helps explain why amplitude versus offset analysis (AVO) in some cases fails for the purpose of fluid detection: pore structure effect on seismic waves can mask all the fluid effects, especially in carbonate rocks.

低渗透储层水锁效应的解除

解除生产压力接近毛管吸入压力的低渗透气藏的水锁要花费相当长的时间。气井水锁效应的解除发生在两个区域：通过流动气体蒸发，将流体从地层中驱替出；地层流体随压力下降变成欠饱和流体。在盐水饱和的岩心上进行了气体驱替实验。随着室温下长时间的气体注入(高达100000PV)，气体相对渗透率增加。在注入50～100PV的气体后加入甲醇，可提高温度及孔隙渗透率从而加快水锁的解除。岩石润湿性的改变从水湿到油湿同样促使气体相对渗透率的快速恢复。通过实验发现，以下措施可改进水锁解除的进行：①影响盐水驱替，如改变润湿性；②加快蒸发速度，加入类似甲醇之类的挥发性溶剂。已经发现改变岩石润湿性同样会影响盐水及甲醇的蒸发速率。该项研究对影响气体相对渗透率的诸多因素进行了量化，如岩石渗透率、润湿性、表面张力、温度。该项研究结果有助于选择一种合理的方案解除在钻井、酸化、压裂过程中造成的水锁效应，并且推荐了向地层注入表面活性剂或溶剂来解除水锁的几种方法。

应力-损伤-渗流耦合下采动弱胶结覆岩渗透性演化规律

应力-损伤-渗流耦合作用下弱胶结地层采动覆岩渗透性演化是影响矿井保水开采的重要因素。以新疆伊犁四矿21103工作面弱胶结地层条件为背景,选取侏罗系弱胶结泥岩、砂岩,在分析全应力应变过程中弱胶结岩石渗透率变化规律的基础上,明确了弱胶结岩石孔隙结构、矿物组成对其渗透性的影响机理,建立了弱胶结岩石应力-损伤-渗流耦合模型,研究了采动弱胶结覆岩渗透性演化规律。结果表明:围压5 MPa内,弱胶结岩石初始渗透率高,压密阶段渗透率大幅下降,最大降幅达91.5%,这与其初始孔隙率高、孔径大直接相关。同时,弱胶结岩石最大渗透率及残余渗透率与初始渗透率相比增幅较小,最大比值分别为4.51和4.17,这与岩石中高岭石、蒙脱石等水敏矿物遇水膨胀泥化造成部分导水裂隙弥合有关;基于弱胶结岩石基质可压缩融合、破裂等假设,定义了损伤变量D,建立了弱胶结岩石应力-损伤-渗流耦合模型,有效表征了弱胶结岩石初始渗透率高而残余渗透率增幅较小的渗透特性;工程尺度下,弱胶结地层采空区在工作面回采后快速压实闭合,出现渗透率恢复区,且该区域渗透率仅为初始地层的1.1~1.2倍。当工作面连续推进长度大于面长时,覆岩渗透率增高区由“马鞍形”演化为“双V形”,并集中分布于开切眼前方及工作面后方25~30 m范围。研究结果可为弱胶结地层保水开采提供指导。