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1.
页岩气在储层中主要以游离气和吸附气的形式存在,其含气量主要通过现场解吸和测井方法计算.由于页岩储层十分致密,并且常伴有微裂缝发育,这就造成了页岩储层的储集空间从纳米级孔隙到微米-毫米级的微裂缝并存的特殊情况.针对微孔和介孔段(50nm以内)的等温吸附方法,以及针对宏孔(50nm以上)的高压压汞方法在表征页岩孔隙结构上都存在着局限性.而核磁(NMR)T2分布本身虽然能够表征孔径分布,但是需要精确刻度横向弛豫时间与孔径的关系.本文在现有方法的基础上,结合上述方法的优势,采用拼接的方式表征页岩整体孔径分布,并将核磁T2分布刻度为孔径分布.基于横向弛豫时间和孔径的关系,结合T2-I转换模型,采用动态参数计算页岩储层含水饱和度和含气量,这为页岩储层含气量评价提供了新的可靠的方法. 相似文献
2.
如何提高煤层气渗透率是目前煤层气开采研究中的重要课题。基于煤层瓦斯渗流规律数学模型,利用COMSOL Multiphysics软件,对流-固-热耦合条件下的非等温煤层气解吸、渗流变化规律进行了数值模拟。结果表明,在注热条件下,煤层气渗流压力随着温度的增加而下降,且下降速度加剧,压力差越大,气体从高压区域流向低压区域的渗流速度越快。气体在煤层中径向流向井口,井口附近压力的梯度增大,气体渗流速度较快;在未受到加热影响的区域,煤层气不受外加热量影响,煤层气解吸速率保持不变;注热后煤层温度升高,可以加快煤层气渗流速度、提高渗透率、增加煤层气产量。研究成果可为煤层中注热开采煤层气的工程实践提供相应的理论依据。 相似文献
3.
超短半径径向水平井抽采煤层气渗流规律的数值模拟 总被引：3，自引：0，他引：3
为得到超短半径径向水平井开采煤层气过程中的气体渗流规律以及进行产量预测,在基本假设条件下,建立了径向水平井开采煤层气的固流耦合渗流数学模型;在一定的边界条件及初始条件下,利用Matlab软件进行编程计算后,得到直井和不同数目分支径向水平井开采煤层气1000天后的压力场、速度场和气产量变化规律。数值模拟结果表明,在一定的生产区域和开采时间,随着径向水平井分支数目的增加,煤储层压力下降范围更广,气体流速场干扰加强,压力漏斗降大面积扩展,煤层气有效供气区及解吸面积大幅增长,煤层气解吸能力及稳产能力加强,煤层气产量大幅度增加;同时,气产量增幅随着井筒分支数目的增加而下降,分支井数目理论上应存在一个最优值。模拟结果显示了超短半径径向水平井技术开采煤层气的有效卸压作用,对煤层气工业增产技术的选择和钻孔方案的布置具有重要的理论指导意义。 相似文献
4.
不同掘进工艺煤与瓦斯流固耦合数值模拟研究 总被引：1，自引：0，他引：1
井下瓦斯事故严重威胁着煤矿的安全,研究煤与瓦斯耦合作用规律并采取相应措施可以有效地防止事故发生。考虑瓦斯气体的可压缩性和吸附、解吸特性,假设瓦斯气体在煤体孔隙中的流动遵循D arcy定律,建立了考虑爆破因素的煤与瓦斯流固耦合数学模型,并利用com so l对其求解。结果表明：炮掘对煤体的破坏能力大于机掘;炮掘工艺下,爆破应力对煤体应力、位移的作用大于应力耦合的作用,机掘工艺应该考虑应力耦合的作用;煤层瓦斯压力随着煤壁暴露时间的增加而发生改变,整个巷道附近的瓦斯压力有降低的趋势,呈现漏斗状分布;煤层上表面煤体竖向位移边界呈以巷道顶端为中心的＂O＂型分布,且以＂O＂型中心处的位移值最大。 相似文献
5.
首先研究了天然气AVO技术的岩石物理基础--Gassmann方程和Biot理论(以下统称为"Gassmann-Biot理论")--对煤层气AVO技术的适用性.根据该理论创始人在建立其理论时的假设条件、煤层气储层的双相孔隙特征、煤层气的双相赋存特征,本文推理认为,由于煤层气储层的基质型孔隙体系的连通性差,裂隙性孔隙在宏观上是非均质的,并且是各向异性的,因此,总体上来说,Gassmann-Biot理论不完全适用于煤层气储层.特别地,当煤层的水饱和状态保持不变而煤层的含气量变化时,因为煤层中孔(裂)隙中流体的体积压缩模量不变或基本不变,即使煤层的弹性参数发生变化,Gassmann-Biot理论也不可能预测其变化趋势.因此,天然气AVO技术的岩石物理基础完全地不适用于水饱和煤层气储层.研究发现,煤层气储层含气量与其密度、纵波速度、横波速度之间存在负相关关系,即含气量高,密度小、纵波速度小、横波速度小;含气量低,密度大、纵波速度大、横波速度大.但是,这些负相关关系不是现有岩石物理理论能够预测或能够解释的.依据煤层气地质学理论以及负相关关系与现有岩石物理理论的一致性,本文提供了对某勘探区A号煤层含气量与其密度、纵波速度、横波速度之间负相关关系的解释,并认为煤层气储层的含气量与其弹性参数之间的负相关关系可能是这类储层内在的固有的规律性的关系.本文证明含气量与其密度、纵波速度、横波速度之间负相关关系可以作为煤层气AVO技术的岩石物理基础,建立了AVO异常与煤层气储层"甜点(即富集高渗部位)"之间的关系,从而能够使用AVO异常探测煤层气富集高渗部位. 相似文献
6.
We conducted a laboratory study of the joint elastic‐electrical properties of sixty‐three brine‐saturated sandstone samples to assess the likely impact of differential pressure (confining minus pore fluid pressures) in the range 8–60 MPa on the joint interpretation of marine seismic and controlled‐source electromagnetic survey data. The samples showed a wide range of petrophysical properties representative of most sandstone reservoirs. We found that a regression equation comprising both a constant and an exponential part gave a good fit to the pressure dependence of all five measured geophysical parameters (ultrasonic P‐ and S‐wave velocity, attenuation and electrical resistivity). Electrical resistivity was more pressure‐sensitive in clay‐rich sandstones with higher concentrations of low aspect ratio pores and micropores than in clean sandstones. Attenuation was more pressure‐sensitive in clean sandstones with large open pores (macropores) than in clay‐rich sandstones. Pore shape did not show any influence on the pressure sensitivity of elastic velocity. As differential pressure increases, the effect of the low aspect ratio pores and micropores on electrical resistivity becomes stronger than the effect of the macropores on attenuation. Further analysis of correlations among the five parameters as a function of pressure revealed potentially diagnostic relationships for geopressure prediction in reservoir sandstones. 相似文献
7.
针对电化学作用能够显著增强煤中甲烷解吸渗流特性,但对其电极材料的选择缺乏依据的问题,采用实验的方法研究了铝、铁、铜和石墨四种电极材料对电化学改性无烟煤甲烷吸附解吸特性的影响．结果表明：（1）未改性自然煤样的甲烷饱和吸附量a为39.92mL·g~(-1),由铝、铁、铜和石墨四种电极材料进行电化学改性后阳极区域煤样的甲烷饱和吸附量a分别降低了5.22%、8.48%、9.24%和11.33%,阴极区域煤样的甲烷饱和吸附量a分别降低了9.53%、4.97%、6.25%和4.97%;(2）未改性自然煤样在300min的甲烷解吸率为83.17%,经铝、铁、铜和石墨四种电极材料改性后阳极区域煤样的甲烷解吸率分别提高了9.50%、7.10%、8.36%和15.75%,阴极区域煤样的甲烷解吸率分别提高了1.76%、1.12%、6.10%和16.23%;(3）采用石墨作为电极的电化学对无烟煤甲烷解吸的影响效果最为明显,原因在于石墨阳极处电解反应生成较多的H~+离子,一方面对煤表面进行酸化,抑制了煤甲烷的吸附,另一方面更多地溶蚀煤中的碳酸盐和硫酸盐矿物,增加了煤中的孔隙,使得甲烷最终解吸率有所升高．本文的研究结果可为电化学强化煤甲烷解吸电极材料的优选提供基础依据． 相似文献
8.
煤储层应力敏感性是影响煤层气井产能的地质因素,以鄂尔多斯盆地东南缘高煤级煤储层为对象,通过煤样的应力敏感性实验和现场测试,建立了高煤级煤储层渗透性与应力之间的相关关系和模型;探讨了渗透性变化的控制机理.研究结果表明, 煤储层渗透率随应力的增加按负指数函数规律降低.在应力小于5 MPa时,煤储层渗透率随应力增加快速下降,应力敏感性最强;应力在5~10 MPa时,渗透率随应力增加而较快下降,应力敏感性较强;而当应力大于10 MPa后,渗透率随应力的增加下降速度减缓,应力敏感性减弱.与沁水盆地南部高煤级煤样实验结果对比认为,鄂尔多斯盆地东南缘山西组2煤层应力敏感性要小于沁水盆地南部山西组3煤层的应力敏感性.煤储层渗透性是在应力作用下煤储层中裂隙产生压缩(压密)变形,裂隙开度急剧减小的结果.因此在煤层气开发过程中控制排采速度,尤其是排采早期降液速度,对于防止煤储层应力敏感性,提高采收率具有实际意义. 相似文献
9.
建立能够反映储层孔隙结构、流体特征的逾 渗网络模型,通过数值模拟研究了储层孔隙尺寸、 孔隙形状、连通性、微孔隙的发育状况等对I-Sw曲 线影响的定性规律,研究了地层水矿化度对岩石电 阻率的影响。分析讨论了不同因素对电阻率影响的 相对强度。最后,通过曲线拟合定量地研究了不同 因素对I-Sw曲线的影响规律。研究表明,在上述影 响因素中连通性和微孔隙对I-Sw曲线的影响很大, 其它因素的影响强度较小。地层水矿化度对岩石电 阻率绝对值的影响很大。“非阿尔奇”现象普遍存在, 在低渗透(低连通性)储层岩石中更为明显。 相似文献
10.
Desorption-diffusion model and lost gas quantity estimation of coalbed methane from coal core under drilling fluid medium 总被引：1，自引：0，他引：1
Geoff WANG 《中国科学:地球科学(英文版)》2010,(4)
The differences of coalbed methane(CBM) desorption-diffusion from coal drilling-core under various drilling fluid medium are not considered in the present calculating methods of lost CBM quantity,which leads possibly to the inaccuracy of CBM quantity in coal seam.Here we took the desorption of CBM from coal core under drilling fluid medium as a pressure-swing process,and based on the Langmuir equation and Fick-first law,established the desorption-diffusion model and numerical modeling method of lost gas(inc... 相似文献
11.
以鄂尔多斯盆地X地区长6储层为研究对象,利用多尺度CT成像技术、聚焦离子束扫描电镜技术,结合Avizo软件的强大数据处理和数值模拟功能,对研究区目的层岩石样品进行不同尺度孔喉分维数重构,建立三维超低渗透砂岩储层纳米级孔隙结构模型.研究表明,微米尺度下,超低渗透砂岩储层孔喉形态呈点状、球状和条带状及管状.储集空间类型以溶蚀微孔为主且多孤立分布,局部孔隙为片状,连通性较差.纳米尺度下,超低渗透砂岩储层孔喉系统整体较发育,孔喉形态呈球状、短管状.远离裂隙处多为孤立状,连通性较差,仅具有储集能力.微裂缝、粒间缝发育部位多为短管状,有一定连通性,相当于喉道.微观非均质性较强,岩样整体较致密,局部相互连通,溶蚀孔及裂隙对储集能力、渗滤能力具有控制作用.数值计算求得目的层A、Y、C三个样品的孔隙度分别为6.95%、5.55%、4.44%,渗透率分别为0.828×10^-3μm^2、0.115×10^-3μm^2、0.00065×10^-3μm^2.聚焦离子束扫描电镜与多尺度CT成像技术相结合能够定量表征超低渗透砂岩储层微、纳米级孔隙结构. 相似文献
12.
Ultrasonic elastic characteristics of five kinds of metamorphic deformed coals under room temperature and pressure conditions 总被引：3，自引：0，他引：3
The calibration of the elastic characteristics of deformed coals is essential for seismic inversion of such units, because the prediction of coal deformation is essential for both mining safety and methane production. Therefore, many samples of broken and mylonitic deformed coal were tested with ultrasonic waves in the laboratory. These samples came from four mining areas: the Huainan, Pingdingshan, Hebi and Jiaozuo coal mines, which present five different metamorphic ranks shown as cylinders striking across circular limits of steel. Under normal pressures and temperatures, ultrasonic P- and S-wave tests show that the velocities, quality factors, and elastic moduli of the deformed coals were greatly reduced compared with undeformed coals. Also, some correlation was found between the P- and S-wave velocities in the deformed coals. However, there is no evidence of linear correlations between velocity and density, velocity and quality factor, or the quality factors of P- and S-waves. Compared with the elastic characteristics of undeformed coals, such as P- and S-wave velocity ratios or Poisson’s ratio, those of deformed coals generally decrease and the P-wave quality factors are less than those of S-waves. Moreover, the analysis of the relationship between pore structure and elastic modulus shows a better correlation between the P- and S-wave velocities and effective porosity, pore volume and specific surface area. Also, there are similar relationships between the pore structure and the Young’s and shear moduli. However, there are no such correlations with other moduli. Correlations between these elastic moduli, pore structure, coal rank and density were not found for the various samples of deformed coals, which is consistent with only structural destruction occurring in the deformed coals with other physical properties remaining unchanged. The experimental results show that it is possible to predict the deformation of coals with multi-component seismic elastic inversion. 相似文献
13.
《Marine pollution bulletin》2014,78(1-2):69-76
Reactivation and chemical modification were used to obtain modified activated carbons with different pore structure and surface chemical properties. The samples were characterized by nitrogen absorption–desorption, Fourier transform infrared spectroscopy and the Bothem method. Using mercury chloride as the target pollutant, the Hg2+ adsorption ability of samples was investigated. The results show that the Hg2+ adsorption capacity of samples increased significantly with increases in micropores and acidic functional groups and that the adsorption process was exothermic. Different models and thermodynamic parameters were evaluated to establish the mechanisms. It was concluded that the adsorption occurred through a monolayer mechanism by a two-speed process involving both rapid adsorption and slow adsorption. The adsorption rate was determined by chemical reaction. 相似文献
14.
碳酸盐岩储层孔隙类型多样,各种孔隙的尺寸变化范围可以跨越几个数量级,孔隙结构非常复杂,这种复杂孔隙结构和不均匀分布的多元孔隙空间使得储层电性呈现明显非阿尔奇特性.为了了解影响电阻率变化的控制因素,本次研究选取中三叠世雷口坡组的8块全直径碳酸盐岩岩样,开展了核磁共振、岩电实验、孔渗实验、压汞实验及薄片等实验,并利用数字图像分析法定量分析了孔隙结构特征.研究结果表明：①孔隙度是影响电阻率高低的重要因素,但并非唯一因素,除孔隙度以外,孔隙尺寸和数量、孔隙网络复杂程度远比吼道大小对电阻率的影响大;②在孔隙度一定的条件下,胶结指数m随储层中孤立大孔隙占比的增多而增大,当孔隙度增大到一定程度后,胶结指数m又随大孔隙占比的增多而减小,微裂缝起重要沟通作用;③在给定孔隙度时,以简单大孔隙为主的岩样表现为胶结指数m值较大,而以复杂孔隙网络、细小孔隙为主的岩样表现为胶结指数m值较小,具分散、孤立大孔隙的岩样,胶结指数m值最高;④依据孔隙几何参数与电阻率和胶结指数之间的关系,可以利用测井资料间接判别储层类型,从而提高储层有效性和含水饱和度评价精度. 相似文献
15.
Coal measures (coal bearing rock strata) can contain large reserves of methane. These reserves are being exploited at a rapidly increasing rate in many parts of the world. To extract coal seam gas, thousands of wells are drilled at relatively small spacing to depressurize coal seams to induce desorption and allow subsequent capture of the gas. To manage this process effectively, the effect of coal bed methane (CBM) extraction on regional aquifer systems must be properly understood and managed. Groundwater modeling is an integral part of this management process. However, modeling of CBM impacts presents some unique challenges, as processes that are operative at two very different scales must be adequately represented in the models. The impacts of large‐scale gas extraction may be felt over a large area, yet despite the significant upscaling that accompanies construction of a regional model, near‐well conditions and processes cannot be ignored. These include the highly heterogeneous nature of many coal measures, and the dual‐phase flow of water and gas that is induced by coal seam depressurization. To understand these challenges, a fine‐scale model was constructed incorporating a detailed representation of lithological heterogeneity to ensure that near‐well processes and conditions could be examined. The detail of this heterogeneity was at a level not previously employed in models built to assess groundwater impacts arising from CBM extraction. A dual‐phase reservoir simulator was used to examine depressurization and water desaturation processes in the vicinity of an extractive wellfield within this fine‐scale model. A single‐phase simulator was then employed so that depressurization errors incurred by neglecting near‐well, dual‐phase flow could be explored. Two models with fewer lithological details were then constructed in order to examine the nature of depressurization errors incurred by upscaling and to assess the interaction of the upscaling process with the requirement for adequate representation of near‐source, dual‐phase processes. 相似文献
16.
依据密度测井资料评估煤层的含气量 总被引：1，自引：0，他引：1
煤层甲烷长期以来认为是对采煤工作的危害，只是近十多年来才被认为是一种潜在的能源。煤层不仅是甲烷的储层，而且是甲烷的源岩。煤的物理结构是一种双重孔隙结构，即煤层中含有由基质孔隙和裂缝孔隙组成的孔隙系统。煤层中的气（甲烷）主要吸附在基质孔隙的内表面，是吸附气，而不是存在于骨架粒间的孔隙空间内，因而传统的评价天然气储层含气量的方法虽然不能适合于评估煤层的气含量。本文利用密度测井资料和煤样煤质化验资料确定 相似文献
17.
High resolution images acquired from X-ray μ-CT are able to map the internal structure of porous media on which multiphase flow properties can be computed. While the resolution of a few micrometers may be sufficient for capturing the pore space of many sandstones, most carbonates exhibit a large amount of microporosity; pores which are below the image resolution and are not resolved at specific resolution. Neglecting the effect of micropores on fluid flow and transport properties of these rocks can cause erroneous results in particular at partial saturations. Current image-based pore scale models typically only consider macropores for simulating fluid flow. In this paper, we quantify the effect of microporosity on the effective permeability of the wetting phase for heterogeneous model structures with varying amount of micro-to-macro porosity. A multi-scale numerical approach is proposed to couple an average effect of micropores with an explicit representation of macropores. The Brinkman equation is solved using a lattice Boltzmann formulation to facilitate the coupling of Darcy and Stokes equations in micropores and macropores, respectively. The results show good agreement between the fine scale solution and the results of the upscaled models in which microporous regions are homogenised. The paper analyses in particular the choice of the momentum sink parameter at low wetting phase saturations. It is shown that this parameter can be found using either a flux-based calculation of permeability of microporous regions or chosen purely on the basis of the effective permeability of these regions. 相似文献
18.
油藏岩石的孔隙连通性是反映流体渗流难易程度的重要参数,对渗透率、有效孔隙度等岩石物理参数的评价具有重要作用.连通的孔隙中,核磁共振(NMR)弛豫的交换会产生扩散耦合现象,可作为孔隙连通性的表征和探测方法.本文提出利用横向弛豫T 2-T 2脉冲序列测量岩石的扩散耦合现象.运用随机游走方法模拟多孔岩石的核磁共振响应特征,分析扩散耦合的影响因素,推导表征扩散耦合强度的弛豫交换速率计算公式.结果表明:孔隙间的扩散耦合强度与T 2-T 2脉冲序列的混合时间呈正相关性,基于双孔弛豫交换模型推导的弛豫交换速率计算公式能够准确表征双尺度孔隙系统的扩散耦合强度.在孔隙尺寸不满足快扩散条件时,会出现与扩散耦合无关的非对角峰信号.针对含多类型孔隙的碳酸盐岩模型,随混合时间的增加,扩散耦合强度变大,一维T 2谱的形态畸变程度加重,在T 2-T 2二维谱中,代表微裂缝、粒间小孔、溶蚀大孔的信号能量变化趋势不同,反映不同类型孔隙间的连通性存在差异.本文的分析与讨论丰富了核磁共振弛豫在岩石物理性质评价中的应用方向,对利用核磁共振评价复杂孔隙岩石的孔隙结构和连通性提供了新思路和新方法. 相似文献
19.
CAI YiDong LIU DaMeng PAN ZheJun YAO YanBin LI JunQian QIU YongKai 《中国科学:地球科学(英文版)》2014,57(7):1567-1582
Pore structure of Chinese coals with heating and pressurization treatments was studied using small angle X-ray scattering(SAXS),N2adsorption/desorption isotherms and scanning electron microscope(SEM).SAXS was performed for some samples after heat treatment at seven elevated temperatures from 25 to 250°C at 0 MPa and for other samples with hydrostatic pressure treatment at 0,5,10,15 and 20 MPa at the room temperature.The results show that N2adsorption isotherm together with SAXS could be a comprehensive method to evaluate the pore shape and the pore size distribution:the pore shapes are generally spherical for low rank coal and they are mainly ellipsoidal for high rank coal.All these measurements were then interpreted using the fractal theory to reveal relationship between surface fractals and coal rank,and the evolution of surface fractals under heating and pressurization treatments.The results show that surface fractal dimension(Ds)changes with different treating temperature and pressure and maximum vitrinite reflectance(Ro,m).Especially in the bituminous stage,Ds shows an increasing trend with Ro,m under varied temperatures.Moreover,Ds shows an increasing trend with increasing temperature before 200°C,and a decreasing trend after 200°C.Furthermore,the results show that Ds has a more complex relationship with Ro,m under varied treating temperature than that under varied treating pressure. 相似文献
20.
南海琼东南盆地发现的高压泥底辟构造、海底“气烟囱”和天然气冷泉表明该地区可能存在着渗漏系统天然气水合物藏.假定在该区直径为1500 m的甲烷渗漏区内,甲烷渗漏通量为1000 kmol/a,甲烷水合物沉积层的温度范围为3~20 ℃,根据水合物条形移动界面理论建立传热模型,选取0 mbsf、100 mbsf、200 mbsf和425 mbsf分别计算在渗漏和扩散情况下的温度和生长速度变化曲线.结果表明甲烷水合物在沉积层骨架里的固结速度约为0.2 nm/s,经过约35000年后渗漏系统将演变成扩散系统.同时,甲烷水合物在渗漏系统里比在扩散系统里的生长速度快约20～40倍. 相似文献