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1.
通过理论研究分析了采动区煤层裂隙特征、煤层气赋存特征和煤层气运移特征,揭示了煤矿采动影响下上覆被保护煤层产气机理。分析认为采动区煤层产气机理与常规煤层气产气机理不同,一是采动区煤层基质孔隙大、内部裂隙多、离层裂隙发育。二是采动区煤层气解吸快、解吸量大、水中溶解气少。三是采动区煤层气运移以气体单向流为主,评价渗透性指标为透气性系数。在收集大量采动区煤层气井产气数据的基础上,研究了产气机理对产气规律的影响。采动区煤层气井产气规律与常规煤层气井相比,具有产量提升快、产气峰值高的特点,整体呈现先迅速增大后逐渐减小趋于平稳的规律。结合采动区煤层产气机理研究,分析认为气产量提升速度快是由于煤层裂隙迅速增多且气体在裂隙中以气相单相流运移为主,产气峰值高是由于储层压力快速下降使煤层气加速解吸,短时间内在井筒附近聚集大量游离气。 相似文献
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深部煤储层处于高地应力环境中,其渗透率变化特征与浅部存在较大差异,为研究有效应力对深部煤储层渗透率的差异性影响,以及应力敏感性各向异性特征,以沁水盆地横岭区块15号煤层为研究对象,采样深度1 200~1 700 m,采用覆压孔渗实验,开展平行层理和垂直层理样品在不同有效应力下的渗透率变化规律研究,探究其应力敏感性特征及其对煤层气产能的影响。结果表明:渗透率随有效应力的增加呈幂指函数降低,平行层理面渗透率总体高于垂直层理面,且在2个方向上渗透率变化规律呈正相关性。选取储层孔裂隙压缩系数、渗透率损害率和渗透率曲率3个参数作为煤储层应力敏感性评价指标,其中,孔裂隙压缩系数随有效应力增加,以5 MPa为界限先后呈现正相关性和负相关性,渗透率损害率和渗透率曲率分别与有效应力呈指数上升和下降的规律。基于应力敏感性参数,推导出煤层气井产能模型,模型显示,不考虑应力敏感性的气井产量高于考虑应力敏感性,揭示了应力敏感性对煤层气产量的影响程度,即在5 MPa生产压差下,气井的产量降低幅度随应力敏感性系数的增大整体呈增高趋势。针对应力敏感性的阶段划分,研究区目标煤层在煤层气排采过程中应采用小–中–大的排采方案来控制生产流量。 相似文献
3.
柳林地区是我国煤层气勘探开发的热点地区之一,初步实现了煤层气商业化开发。根据柳林地区煤层气井生产数据,对气井产气动态进行了分析,按产量大小进行了气井统计,中产气井比例较高,为42.9%,高产气井占28.6%,低和极低产气井比例为28.5%。分析煤层气井排采曲线特征,总结归纳气井的产气模式有单峰式、高峰-稳定式和低峰-高峰-稳定式三类。从影响煤层气产能的构造、气含量、渗透率、煤层厚度、煤层埋深、水文地质条件等地质因素入手,分析了各地质因素对气井产能的影响,并建立各类因素与煤层气井产能的关系。研究认为:柳林地区煤层气井的高产条件并非受单一因素的控制,而是主要取决于多种有利地质主控因素的有机匹配、共同作用的结果。 相似文献
4.
煤储层裂隙是煤层气渗流的主要通道,决定了煤储层的渗透性及煤层气产能,研究裂隙结构特征与煤储层渗透性的关系对准确预测煤层气产能具有重要理论及实践意义。基于经典立方定律渗透率模型,同时考虑分形理论、裂隙网络结构特征及有效应力,构建包含复杂弯曲裂隙特征的分形渗透率模型,将分形渗透率模型与S&D(Shi-Durucan)模型相结合,建立真三轴应力作用下的裂隙煤渗透率模型。开展真三轴应力条件下的气体渗流实验,将构建的渗透率模型与试验结果及S&D模型拟合数据对比,该渗透率模型与实验结果具有良好的一致性,能够体现出三向应力加载条件下应力对渗透率变化的影响趋势,与S&D模型相比更能反映煤岩渗透率的各向异性特征。基于该渗透率模型,定量分析了煤岩裂隙结构参数对其渗透率的影响。结果表明,煤岩渗透率与孔隙率φ(0.05～0.41)、分形维数Df(2.37～2.81)、最大裂隙长度l(max3.5～8.0 cm、比例系数β(0.010～0.065)呈正幂律关系;与迂曲度分形维数DTf(2.005～2.... 相似文献
5.
扩散是煤层甲烷运移的关键环节之一,而目前有关煤层中甲烷扩散特征的认识并不充分.以沁水盆地南部高煤阶煤层气藏为例,应用微纳渗流力学理论分析了煤基质中气体扩散模式及定量表征参数;应用Simed软件开展了扩散性能对不同煤体结构煤层气排采规律的影响数值研究.结果表明:煤层甲烷的扩散受化学势梯度的驱动,产气过程中体相扩散、努森扩散和构型扩散模式并存且呈动态变化;甲烷扩散性能受气体温度、压力、气体种类、水分以及基质孔隙结构共同影响,基质孔隙吸附甲烷会改变微孔孔径并影响扩散路径的空间形态;煤基质中甲烷的扩散是非热力平衡过程,扩散系数是吸附量的函数.基于拟稳态扩散的数值研究表明,扩散性能强弱对于长期累计产气量几乎没有影响,而对短期产气速率具有较大的影响;扩散性能弱的,产气速率峰值较低,但峰值之后的一段时间内产气速率相对较高;与高渗煤层相比,低渗构造煤层的产气速率对吸附时间常数更敏感. 相似文献
6.
考虑基质收缩效应的煤层气应力场-渗流场耦合作用分析 总被引：2，自引：0，他引：2
在煤层气的初级生产过程中,为了获取较高的生产率,需要降低储层压力,储层压力下降对于煤层气的渗透率具有两个相反的效应：（1）储层压力下降,有效应力增加,煤层裂隙压缩闭合,渗透率降低;（2）煤层气解吸,煤基质收缩,煤层气流动路径张开,渗透率升高。Shi和Durucan、Palmer-Mansoori以及Gray等都建立了包含了基质收缩效应以及有效应力的影响的渗透率模型,其模型都基于以下两个关键假设：煤岩体处于单轴应变状态以及竖向应力恒定。为了检验上述两个假设的合理性,建立了一个考虑基质收缩效应以及渗流场-应力场耦合作用下的煤层气流动模型,对煤层气初级生产过程中渗透率的变化进行了耦合分析。分析结果表明：单轴应变的假设具有合理性,而竖向应力是随指向生产井的应变梯度的变化而变化的,其对于渗透率的变化具有重要影响,因此,竖向应力恒定的假设可能导致渗透率预测出现误差;上述渗透率模型都可能低估煤层气初级生产过程中渗透率的变化。 相似文献
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8.
煤层气开采过程中储层渗透率的变化对产气量影响较大,通过引入S＆D渗透率变化模型,建立了考虑渗透率变化的煤储层三维气水两相渗流数学模型,完成模型检验后应用所编制软件研究了煤储层参数、吸附参数及渗透率模型特征参数对开发效果的影响。结果表明,煤层气产量随着初始含气量、煤层有效厚度、裂缝渗透率和Langmuir压力的增大而增大,随储层原始压力、裂缝孔隙度和Langmuir体积的增大而减小,而解吸时间对产气量影响不大;裂缝渗透率随着杨氏模量和基质收缩/膨胀系数的增大而增大,随泊松比和裂缝压缩系数的增大而减小。引入S＆D模型后计算的累积产气量要比常规模型低1.3%,因此不可忽视煤层气产出过程中渗透率的变化。 相似文献
9.
元素硫从含硫天然气中析出沉降会影响流体流动,常规的水平井产量预测模型无法用于高含硫气藏水平井非稳态产量预测。本文基于非稳态椭圆流理论,耦合基质内的椭圆流动和裂缝内的非达西流动,考虑元素硫沉积及缝间干扰效应的影响,建立了适用于酸化水平井与酸压水平井的非稳态产量预测模型。分析了硫沉积对渗透率、孔隙度的影响,计算了不同裂缝参数对产能的影响,该模型适用于变井底流压生产条件。计算结果表明：科学准确的元素硫溶解度模型能较好地预测高含硫气藏水平井产量。酸压改造后缝间干扰现象会降低气井产能,且随着时间逐渐增强。硫沉积会降低储层渗透率和孔隙度,使得产量下降。增大裂缝导流能力,增加裂缝半长或者裂缝数量都能有效提高水平井产量,与裂缝导流能力相比,裂缝半长和裂缝数量对产量的影响更大。 相似文献
10.
利用CBM-SIM煤层气数值模拟软件,以焦坪矿区低阶煤层为例,研究了煤层厚度、渗透率、含气量、吸附性、储层压力、含气饱和度和临储比等煤储层因素对煤层气井产量的影响。结果表明:气井产量随煤层厚度、渗透率、含气量、Langmuir压力、含气饱和度和临储比的增大而增大,随Langmuir体积的增大而减小;储层压力不影响产气量大小,只改变气井的产气时间;含气饱和度和临储比能更好地反映多个因素变化时的产气量变化。 相似文献
11.
Charles J. Moon 《Journal of Geochemical Exploration》1999,65(2):365
The quantitative relation between point source soil geochemical anomalies and their response in stream sediments is linked through the concept of productivity (area × concentration). The equation proposed by Hawkes in 1976 is shown to be a subset of a wider range of equations proposed by Russian workers. These workers introduced two coefficients to account for the contrasting behaviour of different elements and the position of the soil anomaly within the drainage catchment. The calculation of these coefficients requires a series of samples downstream from the ending of anomalous soil input. The concept of productivity has particular application where multiple samples and anomalies are present in catchments. Plotting of productivity allows the discrimination of anomalous areas not detectable from raw element concentrations. The usefulness of these techniques is demonstrated from a small detailed stream sediment survey in NW Scotland. Dispersion from a gossan shows deviation from the Hawkes equation with the result that detailed sampling is required to detect soil anomalies. Plotting productivity allows the detection at the base of major slopes of anomalies that are diluted by upslope sediment. 相似文献
12.
A coupled physical-biological-chemical model has been developed at C-MMACS. for studying the time-variation of primary productivity
and air-sea carbon-dioxide exchange in the Indian Ocean. The physical model is based on the Modular Ocean Model, Version 2
(MOM2) and the biological model describes the nonlinear dynamics of a 7-component marine ecosystem. The chemical model includes
dynamical equation for the evolution of dissolved inorganic carbon and total alkalinity. The interaction between the biological
and chemical model is through the Redfield ratio. The partial pressure of carbon dioxide (pCO2) of the surface layer is obtained from the chemical equilibrium equations of Penget al 1987. Transfer coefficients for air-sea exchange of CO2 are computed dynamically based on the wind speeds. The coupled model reproduces the high productivity observed in the Arabian
Sea off the Somali and Omani coasts during the Southwest (SW) monsoon. The entire Arabian Sea is an outgassing region for
CO2 in spite of high productivity with transfer rates as high as 80 m-mol C/m2 /day during SW monsoon near the Somali Coast on account of strong winds. 相似文献
13.
对于Biot固结方程中的连续性方程形式,不同的研究者存在分歧。在详细分析了Biot推导固结方程的过程后,发现其在推导固结方程时用到的弹性应变能密度函数存在错误。为了得到正确的连续性方程,采用两种思路进行了分析：①通过对土体单元变形的分析,得到了考虑土体颗粒和流体可压缩性的连续性方程;②按照Biot推导固结方程的思路,通过修正推导过程中用到的弹性应变能密度函数得到了连续性方程。上述两种思路得到的连续性方程是等价的,同时将上述连续性方程和其他研究者通过质量守恒得到的连续方程进行了对比,结果是一致的,从而确定了连续性方程的正确形式,并澄清了目前在Biot固结方程中的连续性方程上存在的分歧,所得结论可为固结方程的解析或数值计算提供依据。 相似文献
14.
A new site-specific vibration prediction equation was developed based on site measurement performed in a sandstone quarry. Also, several vibration prediction equations were compiled from the blasting literature and used to predict ground vibration for the studied quarry. By this way, site-specific equation created by regression analysis and the equations obtained from the blasting literature were compared in terms of prediction accuracy. Some of the equations obtained from the literature made better predictions than the site-specific equation created for the studied quarry. The prediction equations were grouped, and the effects of the rock formation and mine type on the prediction accuracy were investigated. Suitable error measures for evaluation of ground vibration prediction were examined in detail. A new general prediction equation was created using site factors (K, β) of the examined studies. The general equation was created using 17 prediction equations reported by blast researchers. Prediction capability of the general equation was found to be strong. Diversity of the blast data is one of the strongest features of the general equation. 相似文献
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16.
In this paper, we present a numerical model for simulating two-phase (oil–water and air–water) incompressible and immiscible flow in porous media. The mathematical model which is based on a fractional flow formulation is formed of two nonlinear partial differential equations: a mean pressure equation and a water saturation equation. These two equations can be solved in a sequential manner. Two numerical methods are used to discretize the equations of the two-phase flow model: mixed hybrid finite elements are used to treat the pressure equation, h-based Richards' equation and the diffusion term in the saturation equation, the advection term in the saturation equation is treated with the discontinuous finite elements. We propose a better way to calculate the nonlinear coefficients contained in our equations on each element of the discretized domain. In heterogeneous porous media, the saturation becomes discontinuous at the interface between two porous media. We show in this paper how to use the capillary pressure–saturation relationship in order to handle the saturation jump in the mixed hybrid finite element method. The two-phase flow simulator is verified against analytical solutions for some flow problems treated by other authors. 相似文献
17.
研究了天然河流纵向分散系数理论公式及其参数的确定问题.借助于抛物型断面型态方程确定了河道垂线水深沿河宽的分布及流速分布对断面平均流速的偏离u‘的横向分布,给出了横向混合系数计算方法.在此基础上通过对Fischer的三重积分的直接求解,建立了新的天然河流纵向分散系数计算公式.这一新建立的纵向分散系数计算公式与原有的有代表性的经验公式以及26条美国河流上实测的59组资料进行了比较,比较结果表明,本文建立的纵向分散系数计算公式能给出与实测纵向分散系数最接近的预测值.与现有的其它纵向分散系数计算公式相比,本文建立的天然河流纵向分散系数公式理论上更加合理,机理上更加清楚,并且具有最小的预测误差. 相似文献
18.
岩溶隧道开挖过程中突水发生机制复杂,本文以Darcy定律、Brinkman方程及Navier-Stokes(N-S)等渗流方程为基础,应用多场耦合数值分析工具,在计算模型中耦合Darcy流、Brinkman和N-S等不同的渗流控制方程,将深部含水层、隧道开挖破碎带和隧道临空面整个突水水流路径相连接,实现突水流动的全过程模拟。明月山隧道突水算例表明,在开挖扰动作用下,地下水沿节理裂隙流动导致隧道突水;单一裂隙水流速和水压较大,而多管道溶隙具有分流分压作用;隧道与断层呈小角度相交时流速较小,断层能起到截水的作用,而呈大角度相交时,断层不仅有导水的作用,更加剧了突水的流通。 相似文献
19.
Savithru Jayasinghe David L. Darmofal Marshall C. Galbraith Nicholas K. Burgess Steven R. Allmaras 《Computational Geosciences》2018,22(2):527-542
This paper analyzes the adjoint equations and boundary conditions for porous media flow models, specifically the Buckley-Leverett equation, and the compressible two-phase flow equations in mass conservation form. An adjoint analysis of a general scalar hyperbolic conservation law whose primal solutions include a shock jump is initially presented, and the results are later specialized to the Buckley-Leverett equation. The non-convexity of the Buckley-Leverett flux function results in adjoint characteristics that are parallel to the shock front upstream of the shock and emerge from the shock front downstream of the shock. Thus, in contrast to the behavior of Burgers’ equation where the adjoint is continuous at a shock, the Buckley-Leverett adjoint, in general, contains a discontinuous jump across the shock. Discrete adjoint solutions from space-time discontinuous Galerkin finite element approximations of the Buckley-Leverett equation are shown to be consistent with the derived closed-form analytical solutions. Furthermore, a general result relating the adjoint equations for different (though equivalent) primal equations is used to relate the two-phase flow adjoints to the Buckley-Leverett adjoint. Adjoint solutions from space-time discontinuous Galerkin finite element approximations of the two-phase flow equations are observed to obey this relationship. 相似文献