中国科学院地球物理研究所地球动力学高温高压实验室介绍

中国科学院地球物理研究所地球动力学高温高压实验室是以高温高压岩石三轴流变实验研究为主要方法.其工作范围是岩石介质在相应的温压范围(常温,32MPa 围压;200℃、500MPa 围压;400℃,800MPa 围压;1500℃,3GPa 固体围压)内的物理性质,力学性质     

冲击载荷下岩石压胀对其性质的影响

采用落锤动态加载岩石实验系统,通过调节落锤质量、下落距离及活塞杆垫板材料,记录岩石瞬间形成冲击压力脉冲,研究压胀对不同岩石性质影响的规律.实验结果表明,压胀产生后岩石的性质发生了改变,岩石的渗透率有不同程度的增加,且岩石越致密,渗透率增加倍数越大;岩石的弹性模量和弹性极限随岩石体积的增加而降低;压胀产生后纵波和横波在岩...     

煤系地层岩石渗透特性试验研究

基于MTS815.02型岩石伺服渗透试验系统,应用两种实验方法测定了岩石的渗透特性,给出煤系地层中多种岩石全应力-应变过程中渗透率变化范围,对几种岩石的渗透特征进行了分析和讨论。研究表明:1)煤系地层岩石全应力-应变过程的渗透率通常在10-9到10-4Darcy量级之间;2)不同岩石在应力峰值前后其渗透性呈现不同的变化趋势;3)岩石渗透率的离散性很大,即使在相同的试验条件下,渗透率变异系数大多在0.65以上,其离散性按粗砂岩、泥岩、砂质页岩、中砂岩、细砂岩、砾岩、石灰岩顺序逐渐增大;4)在MTS815.02系统上,当所测岩样渗透率小于10-4Darcy量级时,应采用瞬态法,当渗透率量级大于10-4Darcy时,可改用稳态法测定。岩石变形过程中应力场和渗流场的耦合作用十分复杂,渗透率受孔隙压力、围压、试件尺寸、饱和程度等因素影响。     

裂缝性低渗透油藏流-固耦合理论与数值模拟

根据裂缝性低渗油藏的储层特征,建立适合裂缝性砂岩油藏渗流的等效连续介质模型。将渗流力学与弹塑性力学相结合,建立裂缝性低渗透油藏的流-固耦合渗流数学模型,并给出其数值解.通过数值模拟对一实际井网开发过程中孔隙度、渗透率的变化以及开发指标进行计算,并和刚性模型以及双重介质模型的计算结果进行了分析比较.     

静水压力对岩石在等离子体冲击下压裂效果的影响

为了了解与掌握深井下水中放电冲击波对岩石的破碎作用规律，建立了静水压力高达35 MPa的电脉冲压裂装置，可模拟深井近3 000 m下的围压，并进行了不同静水压下等离子体冲击压裂实验。电脉冲压裂装置最高工作电压20 kV，最大储能40 kJ。在0~25 MPa的静水压力条件下，对6块砂岩岩样进行了冲击压裂实验。实验结果表明，随着静水压力的升高，相同放电条件下压裂产生的裂缝长度和宽度明显降低。所以静水压力的升高将使得岩样损伤范围减小，孔隙度以及渗透率提升幅度下降。静水压力对冲击压裂后裂缝的形成、分布、生长具有明显的影响。与常压下形成的裂缝相比，施加围压后裂缝多集中在电极处，数量多，但是长度较短，存在不同程度的弯曲，甚至局部区域出现了环形裂缝。     

真三向应力作用下深部储层砂岩渗透率各向异性实验研究

渗透率各向异性是沉积岩层理结构中一个非常典型的现象,一方面它由原生沉积结构决定,即原生各向异性,另一方面它受到总应力和孔隙压力影响,即诱发各向异性.为研究真三向应力条件下储层砂岩渗透率原生与诱发各向异性,以中国东北部S6储气库储层砂岩为研究对象,采用东北大学自主研制的硬岩真三轴应力-渗流耦合装置对储层砂岩进行渗流实验,通过稳态法完成同一砂岩3个相互垂直方向的渗透率测试.实验结果表明:储层砂岩在施加的应力和孔隙压力范围内,平行层理方向的渗透率k x为100.94～113.98 m D,k y为98.34～111.41 mD,垂直层理方向的渗透率k z为54.98～63.29 mD;储层砂岩3个正交方向渗透率均随主应力增加而减少,随孔隙压力加载而递增;与气体渗流方向垂直的应力对渗透率的影响大于与气体渗流方向平行的应力对渗透率的影响;当外部应力方向都垂直于气体渗流方向时,与层理垂直的应力对渗透率的影响大于与层理平行的应力对渗透率的影响;孔隙压力对储层砂岩渗透率的线弹性响应并不是各向同性的,孔隙压力对水平层理方向所产生的渗透率增量超过了垂直层理方向.研究结论为地下储气库储层砂岩渗透率准确预测提...     

砂岩峰后卸除围压过程的渗透性试验研究

为了探讨煤层开采引起的围岩卸除围压过程中砂岩渗透性的变化规律,本文用数控瞬态渗透法在电液伺服岩石力学试验系统MTS815.02上进行了砂岩试样的渗透特性试验。得出了试样峰前渗透系数-应变与应力-应变的关系曲线,以及在峰后保持轴向应变一定卸除围压过程中试样的渗透系数-围压与主应力差-围压的关系曲线;对试验砂岩在变形破坏过程中渗透性变化规律进行了总结,重点分析了其峰后卸除围压过程中渗透性的变化规律;并对试验砂岩峰后渗透系数与有效围压关系进行了拟合,得出了拟合方程式,为煤层开采引起的围岩体应力场与渗流场耦合问题提供参考。     

动力荷载对围压卸载下岩石动态变形模量的影响

利用SHPB岩石动静组合加载实验系统,研究在不同轴压水平下围压以1 MPa/s速率卸载至预加值50%时矽卡岩受频繁冲击作用的动态变形模量变化规律。实验结果表明:高轴压促使岩石内部微裂纹萌发与扩展,降低了岩石抵抗外部冲击的能力。围压的侧向约束阻碍岩石内部裂纹的横向扩展,但在围压卸载时会加剧岩石内部的损伤,这是由于高轴压下,围压卸载导致岩石内部应力重新分布。轴压与围压卸载共同影响着冲击作用下的岩石动态变形模量,通过岩样在冲击荷载下的能量耗散分析岩石动态变形模量的变化规律,有助于了解深部岩体开挖的破坏机制。     

人工砂岩物理力学性质的实验研究

在40MPa的成型压力下,选用环氧树脂作为粘结剂,采用不同配比的石英砂、粘土为材料制作了37个直径25mm、高度50mm的泥质人工砂岩。通过声波测量实验与单轴压缩实验得到其力学性质:人工砂岩的动静弹性模量测量结果均随粘土质量分数的增加而降低,其中动态弹性模量的测量结果相对较高。通过CT扫描实验得到其结构性质:人工砂岩中石英砂与粘土分布均匀,石英砂颗粒作为岩体的骨架结构,粒间存在丰富的孔隙空间,粘土则以填充的形式分布在粒间孔隙中。当粘土质量分数大于10%时,部分粘土将代替石英砂成为岩样骨架的一部分。通过覆压渗透实验得到其孔隙及渗透性质:人工砂岩渗透性质近似满足Poiseuille等效管道渗流模型。孔隙度及渗透率均与粘土质量分数呈负相关,其中孔隙度与粘土质量分数符合线性关系,渗透率与粘土质量分数满足负指数关系。     

卸压开采损伤煤岩气体渗透率试验研究

我国煤系地层的煤岩体渗透率普遍较低,直接影响煤矿瓦斯抽采效果。卸压开采使采场围岩受采动应力作用具备了峰后力学行为,其渗透率也大幅度增加,有助于瓦斯的高效抽采。本文基于MTS815.02型电液伺服岩石渗透试验系统,对卸压开采后损伤煤岩的气体渗透率进行了测试。研究表明:(1)卸压损伤煤岩石的渗透率在10-5～10-4 m2之间,较受采动影响前要大107～108倍;(2)卸压过程中,煤样的气体渗透率与围压近似呈线性关系,与岩样呈双曲线关系;(3)卸压损伤煤岩逐渐加围压,气体渗透率近似为线性下降,卸压阶段,其渗透率增加;(4)加卸围压对煤岩的气体渗透率有很大影响。研究结果可为卸压瓦斯高效抽采提供理论依据。     

Experimental Study and Fractal Analysis of Heterogeneity in Naturally Fractured Rocks

Capillary pressure curves of six low porosity and low permeability core samples from The Geysers geothermal field were measured using the mercury-intrusion approach to characterize the heterogeneity of rock. One high permeability Berea sandstone core sample was analyzed similarly, for comparison. The maximum pressure of mercury intruded into the rock was about 200 MPa to reach the extremely small pores. Experimental data showed that the capillary pressure curves of The Geysers rock are very different from that of the Berea sandstone. It was found that the frequently used capillary pressure models could not be used to represent the data from The Geysers rock samples. This might be because of the fractures in the rock. To this end, a fractal technique was proposed to model the features of the capillary pressure curves and to characterize the difference in heterogeneity between The Geysers rock and Berea sandstone. The results demonstrated that the rock from The Geysers geothermal field was fractal over a scaling range of about five orders of magnitude. The values of the fractal dimension of all the core samples (six from The Geysers and one Berea sandstone) calculated using the proposed approach were in the range from 2 to 3. The results showed that The Geysers rock with a high density of fractures had a greater fractal dimension than Berea sandstone which is almost without fractures. This shows that The Geysers rock has greater heterogeneity, as expected.     

A Semi-analytical Model for Pressure-Dependent Permeability of Tight Sandstone Reservoirs

In tight gas reservoirs, permeability is pressure dependent owing to pore pressure reduction during the life of the reservoir. Empirical models are commonly used to describe pressure-dependent permeability. In this paper, it was discussed a number of issues which centered around tight sandstone pressure-dependent permeability experiment, first to apply core aging on permeability test and then to develop a new semi-analytical model to predict permeability. In tight sandstone permeability test experiment, the microinterstice between core and sleeves resulted in over estimation of dependency of permeability on pressure. Then, a new semi-analytical model was developed to identify the relation between permeability and fluid pressure in tight sandstone, which indicates there is a linear relation between pore pressure changes and the inverse of permeability to a constant power. Pressure-dependent permeability of 8 tight sandstone core samples from Ordos Basin, China, was obtained using the modified procedure, and results were perfectly matched with the proposed model. Meanwhile, the semi-analytical model was also verified by pressure-dependent permeability of 16 cores in the literature and experiment results of these 24 cores were matched by empirical models and the semi-analytical model. Compared with regression result of commonly used empirical models, the semi-analytical model outperforms the current empirical models on 8 cores from our experiment and 16 cores from the literature. The model verification also indicates that the semi-theoretical model can match the pressure-dependent permeability of different rock types. In addition, the permeability performance under reservoir condition is discussed, which is divided into two stages. In most tight gas reservoirs, the permeability performance during production is located in stage II. The evaluation result with proposed experiment procedure and the stress condition in stage II will reduce permeability sensitivity to stress.     

A New Method for Calculating Two-Phase Relative Permeability from Resistivity Data in Porous Media

Many resistivity data from laboratory measurements and well logging are available. Papers on the relationship between resistivity and relative permeability have been few. To this end, a new method was developed to infer two-phase relative permeability from the resistivity data in a consolidated porous medium. It was found that the wetting phase relative permeability is inversely proportional to the resistivity index of a porous medium. The proposed model was verified using the experimental data in different rocks (Berea, Boise sandstone, and limestone) at different temperatures up to 300°F. The results demonstrated that the oil and water relative permeabilities calculated from the experimental resistivity data by using the model proposed in this article were close to those calculated from the capillary pressure data in the rock samples with different porosities and permeabilities. The results demonstrated that the proposed approach to calculating two-phase relative permeability from resistivity data works satisfactorily in the cases studied.     

初始压力对多孔介质中气体水合物生成的影响

利用自制的一维天然气水合物生成与开采模拟实验系统,实验研究多孔介质中天然气水合物生成时不同初始压力对生成量、生成时间的影响.分别用相同气水比注入、相同注气量不同注水量、相同注水量不同注气量三种方式来控制初始压力.结果表明:在砂粒粒径300μm～500μm,盐水质量浓度2%,系统温度为2℃、初始压力为5MPa～9MPa的条件下进行水合物的等容生成实验时,初始压力越大,生成的水合物量越多,水合物开始生成的时间越早;但初始压力越大,实验系统中水合物生成最终稳定所需的时间越长.本实验系统采用的三种不同的控制初始压力的方式都可以得到上述结果.由此,可以为今后室内进行天然气水合物的生成实验提供科学指导.     

裂隙岩体渗透系数确定方法研究

裂隙岩体渗透系数以及渗透主方向的确定对研究岩体渗透性大小及各向异性具有重要意义。高放废物地质处置库介质岩体的渗透性能将直接影响其使用安全性。本文运用离散裂隙网络模拟的方法对我国高放废物处置库甘肃北山预选区3#钻孔附近裂隙岩体进行了渗透性质分析。通过对3#钻孔1715～1780m段压水试验数据的反演,标定了离散裂隙网络渗流模型中的裂隙渗透参数(导水系数T)。利用标定的离散裂隙网络模型对场区裂隙岩体进行了渗流模拟,确定了该区域裂隙岩体的渗流表征单元体(REV)的尺寸大小以及渗透主值和主渗透方向。运用离散裂隙网络模型计算得出的渗透主值的几何均值与现场压水试验计算结果较接近,证明了计算结果的有效性。     

Mean field calculation of effective permeability based on fractal pore space

Effective permeability for porous rocks is calculated using mean field theory. We make two simplifying assumptions about the internal conductances in a network representation of the porous rock: (i) Pore space is characterized by a uniform fractal scaling; (ii) the internal conductances depend only on the characteristic pore sizes. Within these approximations, it is possible to derive a simple probability density for the internal conductances which is used for calculating effective permeability. Good agreement between calculations and experimental data of permeability vs. porosity is achieved.     

断层内破碎岩石渗透性的实验研究

断层破碎带岩石的渗透性是影响地下工程中由渗流失稳而引发灾害事故的重要影响因素之一。利用一种专门的破碎岩石压实渗透仪,在MTS815.02岩石力学伺服试验系统上测试了取自断层内的破碎灰岩、破碎砂岩、破碎泥岩的渗透系数,得到并分析了轴向压力、岩样粒径、水流速度与渗透系数的关系曲线。研究表明:破碎岩石渗透系数与其压实状态密切相关,随着轴压的增加,渗透系数都相应降低;在相同的轴向压力状态下,岩样粒径越小,其渗透系数也越小,因此,挤压程度和充填程度都较低的小断层导水性好,容易导致突水;破碎岩石的渗透系数随着水流速度的增大呈减小趋势,但水流速度对破碎岩石渗透系数的影响程度有限;在相同的压力、粒径情况下,破碎泥岩的渗透系数比破碎灰岩、破碎砂岩的要小1～2个量级,说明当断层上下盘为坚硬岩石时,断层带渗透性好、易导水。研究结果可为采动过程中评价断层的导水性提供参考。     

A Hierarchical Sampling for Capturing Permeability Trend in Rock Physics

Among all properties of reservoir rocks, permeability is an important parameter which is typically measured from core samples in the laboratory. Due to limitations of core drilling all over a reservoir, simulation of rock porous media is demanded to explore more scenarios not seen in the available data. One of the most accurate methods is cross correlation based simulation (CCSIM) which recently has broadly applied in geoscience and porous media. The purpose of this study is producing realizations with the same permeability trend to a real sample. Berea sandstone sample is selected for this aim. Permeability results, extracted from smaller sub-samples of the original sample, showed that classic Kozeny–Carman permeability trend is not suitable for this sample. One reason can be due to lack of including geometrical and fractal properties of pore-space distribution in this equation. Thus, a general trend based on fractal dimensions of pore-space and tortuosity of the Berea sample is applied in this paper. Results show that direct 3D stochastic modeling of porous media preserves porous structure and fractal behavior of rock. On the other hand, using only 2D images for constructing the 3D pore structures does not reproduce the measured experimental permeability. For this aim, a hierarchical sampling is implemented in two and three steps using both 2D and 3D stochastic modeling. Results showed that two-step sampling is not suitable enough, while the utilized three-step sampling occurs to be show excellent performance by which different models of porous media with the same permeability trend as the Berea sandstone sample can be generated.     

岩石蠕变特性试验研究

针对大安山煤矿+550水平西二石门围岩蠕变变形严重的问题,采用室内蠕变试验与理论分析相结合的方法研究岩石蠕变特性。选取泥质粉砂岩作为软岩试样,通过自制三轴蠕变仪对所取岩样进行恒围压分级增轴压的三轴压缩蠕变试验,结果表明:随应力水平的提高,起始蠕变速率增大,进入稳态蠕变阶段用时延长,稳态蠕变速率从0h-1增大到3.12e-4·h-1,瞬时应变以线性关系增加,围压9MPa条件下的起始蠕变应力阈值为6MPa,当应力水平超过岩石长期强度时出现加速蠕变。基于蠕变试验规律,考虑起始蠕变应力阈值,将一种可用阶跃函数表示的开关元件与广义K体并联,并引入损伤元件对CVISC蠕变模型进行改进。采用1st-Opt中的Levenberg-Marquardt+通用全局优化法计算蠕变参数并进行反演。反演结果表明理论曲线与试验曲线的吻合效果较好,证明了所建模型的合理性。上述研究成果可为岩石工程的长期稳定性分析提供试验和理论依据。     

轴、侧向同卸荷下砂岩力学特性影响的试验研究

本文以实际岩体工程为背景,利用WDT-1500 仪器开展了轴向、侧向同时卸荷条件下砂岩的三轴试验. 结果表明:轴、侧向同卸荷这种卸荷路径下,砂岩试样破坏时并没有出现应力峰值,为了定义试样的破坏强度,将最大与最小主应力差随最小主应力的变化关系曲线上应力跌落的拐点处的应力值定义为破坏强度. 砂岩变形初始段发生应力跌落和轴向应变回弹,破坏前无明显的弹性和屈服阶段;试验的过程中,砂岩的侧向变形明显大于轴向变形,其体积应变一直处于膨胀状态;相对于砂岩的常规三轴试验结果,试样破坏时的强度在轴向、侧向同时卸荷条件下有所降低. 初始轴压和初始围压对试样的力学特征有十分显著的影响,但围压的卸荷速率却并不显著. 砂岩的破坏特征主要是以张-拉为主的混合张剪的破坏.