高煤级煤储层条件下的气体扩散机制

为了研究高煤级煤储层煤层气排采中气体的扩散行为,采用扫描电镜和压汞法对不同煤级煤的孔隙进行了观测和测试,根据气体分子运动理论和扩散理论,探讨了沁水盆地无烟煤储层煤层气排采的不同阶段气体扩散模式的动态演化.研究表明,煤层气排采过程中,孔隙内气体的扩散模式是动态变化的:相同排采阶段,同一孔径范围内的孔隙的扩散方式因压降不同而存在差异.不同排采阶段,同一孔隙可能会经历不同的气体扩散模式.对于无烟煤储层,Knudsen型扩散很弱,过渡型扩散贯穿于排采的整个过程.Fick型扩散主要发生排采初期,在排采末期主要出现在距离井筒较远地段.     

刘家勘探区煤储层特征及煤层气开发条件研究

研究了刘家勘探区煤储层特征及煤层气开发条件，认为研究区煤储层的煤级，孔隙性和渗透性相对较低，但地质构造简单，煤层气资源丰度高，煤储层厚度，含气量，含气饱和度，甲烷浓度，临储压力比，临界解吸压力等都较高，压力梯度基本正常，可采性以及煤层气开发和利用前景条件较好。并已被煤层气井排采试验结果所初步证实，同时，中也就区内今后的煤层气开发工作提出了某些建议。     

潘庄区块煤层气排采过程中水压传播数值模拟

以潘庄区块煤层气直井勘探开发资料为基础,运用对比分析法,采用Visual Modflow 4.2软件分别模拟了原始渗透率与改造后渗透率差别较大的7号井、差别不大的14号井以及群井排采时的水压传播规律.结果表明,单井排采时,当煤储层原始渗透率较差,且与改造后渗透率差别较大时,受煤储层非均质性以及最大水平主应力的影响,水压传播轨迹形成以井筒为中心的椭圆形,且随着排采时间的增长,椭圆的长短半径比例逐渐增大;当原始渗透率较好,且与改造后渗透率差别不大时,则形成以井筒为中心的近似圆形;群井排采时,初始阶段受煤储层的非均质性影响,区域地下水降低不具规律性.随着排采的进行,地下水势具有整体下降趋势,形成井间干扰,成为该地区高产的关键因素.     

高煤级煤储层水力压裂裂缝扩展模型研究

为了研究煤层气井水力压裂后的裂缝扩展规律,以沁水盆地南部煤层气井为例,基于区内煤储层的物性特征和水力压裂工程实践,根据水力压裂原理,采用数值分析的方法,探讨了研究区的煤层气井水力压裂后的裂缝形态与裂缝展布规律,提出了研究区煤层气井压裂过程中的综合滤失系数计算方法,构建了高煤级煤储层水力压裂的裂缝扩展模型,并进行了验证.研究结果表明:区内煤层气井压裂后形成的裂缝一般扩展到顶底板的泥岩中,且以垂直缝为主,裂缝形态符合KGD模型.区内常规压裂井的裂缝长为47.8～177.0m,平均90.6m.裂缝缝宽为0.013～0.049m,平均0.028m.模型计算结果与实测值、生产实践较为吻合.     

沁南地区潘庄区块煤层气井产能主控因素研究

研究煤层气井产能的主控因素对煤层气高效开发具有重要意义.以潘庄区块煤层气勘探开发资料为基础,从资源条件、水文地质条件、钻完井工艺和排采工作制度4个方面对煤层气井产能的影响进行分析,得出了在资源丰度差别不大的情况下,煤储层含气饱和度和临储压力比对该区煤层气井产能贡献大,其中临储压力比贡献最大,煤储层含气饱和度次之,而水文地质条件以及排采工作制度对煤层气井产能影响不明显.     

基于灰色预测模型的煤层气储层产气量动态变化预测研究

以沁水盆地某研究区的排采资料为基础,围绕煤层气储层产气量动态变化预测技术开展研究.煤层气开采过程是一个非常复杂的系统,其产气量受煤层气储层自身特性和排采制度等多种因素的影响,是各种影响因素综合作用的结果,是开采过程中系统内在变化的反映.可以通过研究煤层气产量的历史数据,挖掘产气量随时间变化的内在规律,并对未来的产气量进行预测.基于煤层气储层产气量的历史数据,通过建立灰色预测模型预测煤层气储层产气量的动态变化,并通过实际产气量数据验证,对于产量波动小、峰值明显、稳产时间长的煤层气储层,灰色预测模型在对产气量进入递减阶段的动态变化进行预测时效果较好.     

滇东黔西老厂矿区雨汪区块煤层气井产能特征及其影响因素

为研究多煤层发育区影响煤层气井产能的主要因素,以滇东黔西老厂矿区雨汪区块为研究对象,基于区内煤层气地质及气井排采资料,分析区内煤层气井产气、产水特征,探讨影响煤层气井产能的关键因素。研究结果表明,雨汪区块中-低产煤层气井数量占总井数的73%,影响气井产能的主要包括地质和排采因素,其中,地质因素主要为地应力和渗透率,排采因素主要为产水速率和停井次数。建议本区煤层气勘探开发应首选中-低地应力、渗透率较高的部位或层段,气井排采初期产水量需控制在1.5～3 m~3/d,见气后产水量控制在1～1.8 m~3/d,排采期间尽量减少停井次数。     

非低阶煤煤层气解吸关系式研究

煤层气的解吸作用的研究可以较好的预测产气量和气量持续的周期。通过对数个地区煤储层的较为活跃煤层气进行了吸附解吸实验,其结果表明煤层气的降压解吸的数学表达式服从 的数学模型,在煤层气井排水降压过程中,采用此模型对煤层气解吸量的计算,揭示了降压解吸滞后是由于剩余含气量c的存在,解吸量与最大含气量a线性相关,最大解吸率为c/a,生产上要提高解吸量只能通过改变b值。通过两口垂直井、两口水平井的排采实践得到验证。     

煤层气成藏的构造应力场研究

构造应力场是控制煤层气成藏极为重要的因素，深入探讨不同性质构造应力场对煤储层的改造及控制机理，将会为煤层气勘探前景评价提供重要的理论基础．本文在区域构造应力场研究的基础上，分别探讨了不同性质构造应力场的作用特征及其对构造发育、构造展布、构造组合及构造变形的控制作用；分析了不同性质构造及其组合、应力-应变环境对煤储层的改造作用，探讨了不同变形机制和不同结构构造煤在不同构造应力场中的发育及展布规律．研究表明，挤压应力场作用下，在强变形带的中心及其附近，可以形成糜棱煤类构造煤，但糜棱煤分布较为局限；在较大范围内形成脆性变形系列的构造煤，是煤层气勘采的有利区带；拉张构造应力场中，大部分区域内有利于煤层裂隙的形成和渗透率的提高，但易造成煤层气的散失，含气量降低，应重视有利的储气构造的研究．剪切构造应力场中，以平移断层为界，煤层的赋存状态、煤体结构和煤储层物性都会存在一定的差异，应对不同的构造单元分别研究其煤储层特征．     

陆相盆地低煤级煤储层特征研究—以准噶尔、吐哈盆地为例

研究了准噶尔、吐哈盆地低煤级煤储层的特征,结果表明：该储层几何形态复杂,且受成煤环境的控制,表现出显著的规律性变化。煤体形态可归纳为与成煤环境对应的4种类型,其中形成于湖成三角洲的朵状、舌状煤体成藏规模最大,浅部煤储层以含气量低、甲烷浓度低、含气饱和度中等、含气强度大为特征;但在构造相对简单的盆缘斜坡深部具有很好的勘探开发潜力,煤储层孔容及比表面积都很大且变化范围也大;中值孔径、孔隙率的变化特征与孔容一致,预示了低煤级煤储层较高的基岩渗透率,兰氏体积和兰氏压力都显著低于中、高煤级煤储层,煤储层达到饱和的机率更大,更容易解吸。古构造应力场控制着煤储层割理裂隙系统的发育程度和分布规律,现代构造应力场特征影响煤储层割理裂隙系统的开合程度,盆缘斜坡多为高渗区。     

吐哈盆地沙尔湖地区煤层气钻完井适用技术探讨

在剖析美国圣胡安盆地煤层气空气钻井、裸眼洞穴完井技术及优势的基础上,确定了低煤阶煤层气钻井及裸眼洞穴完井的煤储层条件等,并以吐哈盆地沙尔湖地区低煤阶煤层气为主要研究对象,利用类比法及地质统计法,具体分析了吐哈盆地沙尔湖地区的煤储层厚度、含气量、渗透率、井壁稳定性及储层压力条件等．研究表明,沙尔湖地区煤层厚度大,储层物性好,井壁稳定性好,可采用低成本空气钻井及裸眼完井技术提高钻井效率,保护煤储层,提高煤层气采收率．     

Coal reservoir characteristics and their controlling factors in the eastern Ordos basin in China

In the eastern Ordos basin, due to the diversity of the tectonic setting, coal rank, gas content and permeability, coal reservoirs have differing characteristics. In this paper, based on coal reservoir geometry, gas content, adsorption capacity, pores and fissures developments and permeability data, the coalbed methane(CBM) reservoir characteristics and their controlling factors in the eastern Ordos basin is discussed. The results show that, due to undergoing different paleo-temperatures in the geological history,coal rank has a higher trend from the north part to the south and from the shallow part to the inward basin, which determines CBM distribution and recoverability. In the north, although having large coal thickness and high permeability, Zhungeer-Xingxian coal rank is low, and gas content is small. In the central part, with medium rank, higher gas content and relatively high permeability, and the Wubao-Liulin area is the most favorable area in the eastern Ordos basin. In the southern part, medium and high metamorphism coal occurs, and although having the highest gas content, the permeability in the Hancheng area is low due to the development of sheared coal.     

煤岩气藏开发分类探讨

煤岩气藏在孔隙结构、天然气赋存方式和产出机理方面均表现出区别于其它气藏的特殊性。已经形成的关于煤岩气藏分类主要用于指导勘探和选区评价，随着国外煤层气开发成功的气藏类型逐渐增多，特别是我国开发试验区规模和数量的扩大，综合各类气藏的主要特征和影响开发效果的主控因素，提出区别于选区评价及勘探的煤岩气藏开发分类具有重要的意义。主要考虑煤层厚度、渗透率、含气饱和度和裂隙含水状况等因素，对煤岩气藏进行分类。实例分析表明，类似圣胡安、黑勇士盆地的中、高渗煤岩气藏的开发问题已基本解决，低渗、致密煤岩气藏开发是今后的主攻方向，仍存在一些关键理论和技术难题尚待解决。     

中国煤储层岩石物理学因素控气特征及机理

基于全国主要矿区或勘探区统计资料,总结了煤级、煤岩类型、显微组分组成等煤的岩石物理学因素与煤层含气量、吸附性、渗透性等之间的关系,探讨了煤储层岩石物理学特征的控气作用机理．发现煤级－含气量的“包络线”具有阶段性演化规律,最大含气量的显著变化与煤化作用阶跃高度一致,煤储层含气量较高的地区沿纬向等间距展布且与较高煤级煤分布区吻合,煤的兰氏体积与镜质组含量关系中存在一个镜质组含量临界值．指出不同煤化作用阶段控气作用的实质在于煤物理结构和化学结构的演化,沉积作用控气的思路对煤储层渗透率非均质性预测具有一定实践意义．     

Mechanism of CO2 enhanced CBM recovery in China: a review

Permeability of coal reservoirs in China is in general low. Injection of CO2 into coal seams is one of the potential ap-proaches for enhancing coalbed methane (CBM) production. The feasibility of this technology has been investigated in China since the 1990s. Advances in mechanism of CO2 enhanced CBM recovery (CO2-ECBM) in China are reviewed in light of certain aspects,such as the competitive multi-component gas adsorption, sorption-induced coal swelling/shrinkage and its potential effect on CBM production and numerical simulation for CO2-ECBM recovery. Newer investigations for improving the technology are discussed. It is suggested that a comprehensive feasibility demonstration in terms of geology, technology, economics and environment-carrying capacity is necessary for a successful application of the technology for CBM recovery in China. The demonstration should be car-ried out after more investigations into such facets as the control of coal components and structure to a competitive multi-component-gas adsorption, the behavior and essence of super-critical adsorption by coal of gas, environmental and safe feasi-bility of coal mining after CO2 injection and more extensive pilot tests for CO2-ECBM recovery.     

Reservoir reconstruction technologies for coalbed methane recovery in deep and multiple seams

Multiple coal seams widely develop in the deep Chinese coal-bearing strata. Ground in situ stress and coal seam gas pressure increase continuously with the increase of the mining depth, and coal and gas outburst disasters become increasingly severe. When the coal is very deep, the gas content and pressure will elevate and thus coal seams tends to outburst-prone seams. The safety and economics of exploited firstmined coal seams are tremendously restricted. Meanwhile, the multiple seams occurrence conditions resulted in different methane pressure systems in the coal-bearing strata, which made the reservoir reconstruction of coal difficult. Given the characteristics of low saturation, low permeability, strong anisotropy and soft coal of Chinese coal seams, a single hydraulic fracturing surface well for reservoir reconstruction to pre-drain the coalbed methane(CBM) of multiple seams concurrently under the different gas pressure systems has not yet gained any breakthroughs. Based on analyses of the main features of deep CBM reservoirs in China, current gas control methods and the existing challenges in deep and multiple seams, we proposed a new technology for deep CBM reservoir reconstruction to realize simultaneous high-efficiency coal mining and gas extraction. In particular, we determined the first-mined seam according to the principles of effectiveness and economics, and used hydraulic fracturing surface well to reconstruct the first-mined seam which enlarges the selection range of the first-mined seam. During the process of mining first-mined seam, adjacent coal seams could be reconstructed under the mining effect which promoted high-efficiency pressure relief gas extraction by using spatial and comprehensive gas drainage methods(combination of underground and ground CBM extraction methods). A typical integrated reservoir reconstruction technology, ‘‘One well for triple use", was detailed introduced and successfully applied in the Luling coal mine. The application showed that the proposed technology could effectively promote coal mining safety and simultaneously high-efficiency gas extraction.     

煤基块弹性能及其与地质控制因素之间的关系

煤储层弹性能是联系成藏动力学条件与煤层气藏之间的桥梁和纽带，煤基块弹性能是储层能量的主要组成部分，是煤层气成藏的关键．本文通过煤基块弹性能物理模拟实验，对影响煤基块弹性能的参数进行了研究，分析了其与地质控制因素之间的关系．研究表明：煤基块弹性能受控于煤体自身的岩石力学性质，与地质历史时期的煤储层埋藏深度、煤级演化程度密切相关．煤基块弹性能随着煤储层埋深的增加而降低，随着煤级的升高而增大．     

Interlayer interference mechanism of multi-seam drainage in a CBM well:An example from Zhucang syncline

Based on the characteristics of the strong volatility of physical property in vertical direction, high gas content, high resource abundance and large exploitation potentiality of coal reservoir in Bide-Santang basin of Zhina coal field, we study the generation mechanism of interlayer interference, propagation rules of reservoir pressure drop and influencing factors of gas productivity in CBM multi-seam drainage in the paper. On the basis of the actual production data of X-2 well of Zhucang syncline in Bide-Santang basin,by simulating the gas production process of a CBM well under the condition of multiple seam with COMET3 numerical simulation software, we analyze the influencing factors of gas productivity during the process of multi-seam drainage, and illuminate the interlayer interference mechanism of multiseam drainage. The results show that permeability, reservoir pressure gradient, critical desorption pressure and fluid supply capacity of stratum have great influence on gas productivity of multi-seam drainage while coal thickness has little influence on it. Permeability, reservoir pressure gradient and fluid supply capacity of stratum affect the propagation velocity of reservoir pressure drop and thereby affect the final gas productivity. Moreover, the influence of critical desorption pressure on gas productivity of multiseam drainage is reflected in the gas breakthrough time and effective desorption area.