华北地区煤层含气性影响因素探讨

煤层含气性是评价煤层气勘探开发前景的决定性因素之一,影响煤层含气性的因素很多,其中较为重要的因素有煤层上覆有效地层厚度、煤的变质程度、断裂构造、盖层条件及煤层厚度等.对此进行了分析探讨,认为影响煤层含气性的主要地质因素为煤层上覆有效地层厚度和煤的变质程度,次要因素为断裂构造、盖层条件及煤层厚度.     

河南胡襄煤田煤层赋存特征及控气因素

以河南胡襄煤田为研究区,通过定性分析和定量研究,探讨了煤层厚度、煤层埋深、上覆基岩厚度、地质构造、顶底板岩性以及变质程度等因素对煤层气富集的控制作用.通过数理统计方法,得出了煤层厚度、埋深、上覆基岩厚度与煤层含气量的回归方程,并进行了显著性检验.研究结果表明,随着煤层厚度的增加,含气量有着增大的趋势,两者之间具有线性正相关关系;随着埋深和上覆基岩厚度的增加,含气量都有着先快速增大而后缓慢增大的趋势,且具有对数正相关关系;煤变质程度是二1煤层和二2煤层含气量变化的影响因素之一,且含气量随Ro,max的增加而增大;次级褶曲向斜翼部和背斜轴部富气,且向抬升区域运移;断层或煤层露头线附近,含气量较小;断层的上升盘含气量明显小于下降盘;断层尖灭端附近,含气量大;煤层顶底板岩性对含气量有一定的影响.     

左权高家庄煤矿煤层气开发前景

以左权县高家庄煤矿煤层气普查区内3#和15#煤层为研究对象,研究了该区煤层特征和煤级变化特征,并对煤储层含气性及储层特征进行了分析。结果表明,该区含煤地层地质条件简单,可采煤层厚度大、分布稳定;3、15#为贫煤～无烟煤,变质程度高,煤的变质程度自上而下随煤层层位的降低逐渐增大,煤层生气量大,煤的吸附能力较强;煤层含气量、渗透率等主要储层参数值较高,煤层含气饱和度接近饱和。     

控制平顶山矿区煤层气赋存的构造与热演化史

在一定条件下,构造演化和有机质热演化史,控制着煤层气的生成、富集和保存特征.在其它控气地质因素相似的前提下,有效生气阶段和有效阶段生气率控制着煤层含气量的高低.通过分析平顶山矿区构造特征及演化史,恢复了主要煤层上覆地层原始厚度,对煤层热演化史进行了模拟,进而确定了煤层的有效生气阶段.     

控制平顶山矿区煤层气赋存的构造与热演化史

在一定条件下,构造演化史和有机质热演化史,控制着煤层气的生成、富集和保存特征。在其它控制气地质因素相似的前提下,有效生气阶段和有效阶段生气率控制着煤层含气量的高低。通过分析平顶山矿区的构造特征及演化史,恢复了主要煤层上覆地层原始厚度,对煤层热演化史进行了模拟,进而确定了煤层的有效生气阶段。     

华北盆山演化对深部煤与煤层气赋存的制约

深部煤和煤层气的聚集及赋存与盆山演化有着密切的关系.在对华北陆块中新生代盆山演化过程与特征研究的基础上,以其主要含煤区为研究区域,探讨了华北陆块盆山演化对其含煤区深部煤和煤层气的制约作用.结果表明:华北不同地区盆山演化特征不仅导致了含煤盆地结构的复杂多变,也使煤层埋深及煤的储层物性发生了不同程度的变化.渤海湾盆地,受挤压和伸展控制作用,其煤层埋藏深;煤层气沿断裂运移至上覆岩层中,形成常规天然气藏,但仍有部分煤层气赋存于深部煤层中,形成煤层气富集层.鲁西含煤区以伸展滑脱作用为主,煤层埋深增加;由于张性断裂作用,煤层含气量降低.两准含煤区以逆冲推覆作用为主,使煤层埋深增加;淮北煤田岩浆-热作用相对淮南煤田强烈,煤层含气性局部变好,渗透率也有所增高.豫西含煤区重力滑动产生的牵引褶皱区,煤层埋深增加,煤层气保存较好.沁水盆地以挤压复向斜构造为主,使煤层埋深增加,且岩浆-热作用明显,煤层含气性较好,而叠加后期形成的构造裂隙,渗透率较好.鄂尔多斯盆地受沉积厚度的影响而煤层埋深增加;由于煤中内生裂隙较多,渗透性也较好.     

沙曲矿井瓦斯地质规律研究

运用地质构造控制理论分析了沙曲矿井的瓦斯赋存特征,初步总结了沙曲矿井的瓦斯地质规律.针对矿井4号煤层瓦斯含量高、平面上具有从东向西逐渐增大的特点,从瓦斯地质学的角度指出一定的地质构造条件、煤层上覆基岩厚度差异大、致密的顶底板岩性、复杂的水文地质条件及煤的变质程度是沙曲矿井煤层瓦斯赋存规律的主控因素.并利用数值回归分析的方法,建立了上覆基岩厚度与瓦斯含量的数学预测模型,为预测深水平的瓦斯含量奠定了基础,为瓦斯防治工作提供了依据.     

煤层气生成及含气量控制因素

利用EASY%Ro数值模拟法,对峰峰东部矿区2号煤煤层热演化史进行模拟及恢复,探讨了峰峰东部矿区2号煤煤层气的生成和演化特点,认为峰峰东部矿区受构造运动及岩浆活动的影响,经历二次生气阶段,早期以区域深成变质作用为主,煤中有机质在深成变质作用下发生一次生气;晚期受岩浆活动的影响,促使该区的煤层进一步变质及煤层气第二次生成。在此基础上分析了研究区含气性及含气性的主要控制因素,包括煤储层顶底板岩性、分布特征、地质构造、岩浆侵入及水文地质条件等引起本区煤层甲烷含量在平面及剖面上分布的不均一性。     

焦作矿区山西组二1煤层含气量的控制因素探讨

分析了焦作矿区煤层气含量的分布规律 ;探讨了断块构造、煤层埋深、上覆岩层厚度等对煤层气的控制作用 .结果表明 :焦作矿区山西组二1煤煤层气含量较高 ,最高达 3 2 .7m3 /t(daf) ,平均为 1 6 .7m3 /t(daf) ;由于煤变质及其演化、煤层的有效埋藏深度、抬升剥蚀作用和地质构造等因素对煤储层特性产生显著的影响 ,使本区煤层气含量分布具有明显的规律性 ,从西部断块至东部断块煤层气含量由高到低变化 ,且各断块内由浅部向深部逐渐增高 .     

新景矿3号煤层瓦斯赋存的主控因素研究

运用地质和瓦斯地质相关理论,结合勘探和矿井生产、取样实验、现场实测及大量井下煤壁观测等资料对影响新景矿3#煤层的瓦斯赋存规律的主控因素进行研究。结果得出:煤的变质作用程度和含煤岩系沉积环境为3#煤层瓦斯提供了良好的"生"、"储"条件,而井田构造、煤系盖层、水文地质特征为3#煤层瓦斯提供了有利的保存条件,同时主控因素间的耦合关系亦共同控制着煤层瓦斯的赋存规律。研究结果有助于提高矿井瓦斯防治的针对性和有效性。     

沁水盆地山西组煤储层含气性及控制因素分析

依据实测资料,在统计分析研究区３号煤层含气性特征的基础之上,对控气地质机理进行了探讨,总体上来看,研究区甲烷含量较高高及甲烷浓度较大,而含气饱和度偏低。在埋深１０００ｍ以浅,向盆地内部方向以及随煤层埋深加大,甲烷含量,甲烷浓度和含气孢和度具有增大趋势,显示出埋探控气以及次级向斜相对富气的特点,这种特征可以起源于地质历史时期中煤层抬升卸压过程所导致的煤层气解吸扩散作用。因此,进一步查明次级构造的发育     

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．     

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。     

基于灰色关联与神经网络的瓦斯含量预测研究

为了解各影响因素对煤层瓦斯赋存规律的影响,准确预测煤层瓦斯含量,在分析潘一东勘探钻孔资料的基础上,基于灰色关联分析了影响13-1煤层瓦斯含量的各因素,确定了煤层埋深、顶板岩性、煤层厚度和地质构造是影响煤层瓦斯含量的主要因素;利用神经网络方法建立了煤层瓦斯含量预测模型,结合实际数据,对预测模型进行训练与检验。结果表明：预测精度较高,验证了基于灰色理论与神经网络预测模型的可靠性。     

The impact of depositional environment and tectonic evolution on coalbed methane occurrence in West Henan,China

A deeper understanding of the mechanisms by which geological factors(depositional environment and tectonic evolution) control the occurrence of coalbed methane(CBM) is important for the utilization of CBM resources via surface-drilled wells and the elimination of coal-methane outbursts, the latter of which is a key issue for coal mine safety. Based on drill core data, high-pressure isothermal adsorption experiments, scanning electron microscopy experiments, mercury intrusion porosimetry, and X-ray diffraction experiments, the impact of the depositional environment and tectonic evolution on CBM occurrence of the II-1 coal seam of the Shanxi Formation in West Henan was analyzed. Results showed that the depositional environment led to the epigenetic erosion of tidal flat coal-accumulating structures by shallow-delta distributary channel strata. This resulted in the replacement of the original mudstonesandy mudstone coal seam immediate roof with fine-to-medium grained sandstones, reducing methane storage capacity. Epigenetic erosion by the depositional environment also increased coal body ash content(from 6.9% to 21.4%) and mineral content, filling the cleat system and reducing porosity, reducing methane storage capacity. The maximum methane adsorption capacity of the coal body reduced from35.7 cm3/g to 30.30 cm3/g, and Langmuir pressure decreased from 1.39 MPa to 0.909 MPa. Hence, the methane adsorption capacity of the coal body decreased while its capacity for methane desorption increased. Owing to the tectonic evolution of West Henan, tectonically deformed coal is common; as it evolves from primary cataclastic coal to granulitic coal, the angle of the diffraction peak increases, d002 decreases, and La, Lc, and Nc increase; these traits are generally consistent with dynamic metamorphism.This is accompanied by increases in the total pore volume and specific surface area of the coal body, further increasing the capacity for methane storage. Increases in micropore volume and specific surface area also increase the ability of the coal body to adsorb methane.     

河南省下二叠统山西组二_1煤煤层气储层描述

从煤厚、煤岩组成、煤级、煤体结构、裂隙系统、渗透性、吸附／解吸特性等方面对河南省的主可采煤层二１煤的煤层气的储层特征进行了详细论述．指出镜质组含量较高、割理比较发育、外生裂隙发育适中的原生结构煤和碎裂煤渗透性最好,是最有利的储层;外生裂隙发育适中的无烟煤是有利储层;碎粒煤为不利储层;糜棱煤为不可开发储层．临界解吸压力较高、含气量较高的中煤级煤分布区是煤层气勘探开发的首选地区．     

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.     

Estimation of correction coefficients for measured coal bed methane contents

Improving the accuracy and precision of coal bed methane (CBM) estimates requires correction of older data from older coal exploration surveys to newer standards. Three methods, the depth gradient method, the contour aerial weight method, and the well-point aerial weight method, were used to estimate the correction coefficient required to predict CBM gas content from coal exploration data. The data from the Nos. 3 and 15 coal seams provided the coal exploration data while the CBM exploration stages within the X1 well block located in the southern part of the Qinshui Basin provided the data obtained using newer standards. The results show the correction coefficients obtained from the two aerial weight methods are similar in value but lower than the one obtained from the depth gradient method. The three methods provide similar results for the Nos. 3 and 15 seams in that the correction factor is lower for the former seam. The results from the depth gradient method taken together with the coal seam burial depth and the coal rank suggest that variations in the correction factor increase linearly along with coal seam burial depth and coal rank. The correlation obtained can be applied to exploration and the evaluation of coal bed gas resources located in coalfields.     

沁水盆地郑庄区块构造演化与煤层气成藏

基于沁水盆地郑庄区块的构造发育特征,研究了自二叠纪煤系形成以来该区域构造应力场演化,分析了其对煤层气藏的控制作用,包括构造-埋藏史、后期成藏演化及成藏控制因素.研究表明:郑庄地区主要经历了印支期、燕山期、喜马拉雅早期和喜马拉雅晚期—现代4个期次的构造应力场演化.在构造控制下,二叠纪煤层经历了印支期和燕山中—晚期两次成烃作用,特别是燕山中、晚期煤层生气量巨大,是煤层气的主要成藏期.此后,随着地壳持续抬升剥蚀,煤层埋藏不断变浅,并发育了多组封闭性较好的节理.受南东侧的寺头断层控制,煤层埋深处于600～1 200m,为煤层气成藏以来的最浅埋藏,虽然本区二叠系煤层气的成藏时间较早,但保留的煤层气含量大,煤储层厚度大,且煤层埋藏适中.