CO2 sequestration in coals and enhanced coalbed methane recovery: New numerical approach

Mixed gases injection into a large coal sample for CO₂ sequestration in coals and enhanced coalbed methane recovery was investigated using a new numerical approach. A dynamic multi-component transport (DMCT) model was applied to simulate ternary gas (CH₄-CO₂-N₂) diffusion and flow behaviors for better understanding and prediction of gas injection enhanced coalbed methane (ECBM) recovery processes. Several cases were designed to analyze the effects of injection gas composition and pressure on gas displacement dynamics in a large coal sample. The calculated results suggest that mixed gas injections have similar profiles of methane recovery as pure N₂ injection, and mixtures of N₂ and CO₂ reduce the ultimate methane recovery compared to pure CO₂. The breakthrough time of pure CO₂ injection is longer than mixed gas injections. Injection gas composition has significant effect on produced gas composition.     

间接压裂技术在阜新煤层气开发中的应用

水力压裂是低渗透煤层中实现煤层气商业化开采的关键,也是我国煤层气开发的瓶颈之一。本文探讨了间接压裂技术的机理和适用煤层条件,通过在阜新现场的应用,充分证实该项技术在煤层气开发中的可行性。     

Assessment of energetic heterogeneity of coals for gas adsorption and its effect on mixture predictions for coalbed methane studies

This study explains the single-component and binary mixture adsorption studies on two different coals from the Zonguldak Basin (Northwestern Turkey). Assessment of energetic heterogeneity of coal surface and its effect on the equilibrium binary gas adsorption are discussed. Single component adsorption tests were performed using methane and carbon dioxide at 30°C. Binary mixtures prepared with 10, 15 and 20% carbon dioxide were also tested at the same temperature. Various single-component adsorption isotherms were fitted to the experimental data of single gases. The data obtained from these models were interpreted to determine the energetic heterogeneity of the coals towards adsorption of methane and carbon dioxide. Ideal adsorbed solution (IAS) theory was used to predict the data and discrepancies between experimental data, and the model predictions were interpreted. Results showed that coals exhibit a heterogeneous behavior in gas adsorption. This heterogeneity can be different for each coal–gas pair and the extent of the heterogeneity makes the binary gas predictions differ from the experimental data. The deviations between IAS and experimental data increase as the amount of gas, to which the coal shows high heterogeneity, increases in the mixture.     

煤层气成藏机理及气藏类型划分——以鄂尔多斯盆地东缘为例

随着我国煤层气勘探开发工作的不断深入,定义和归纳赋存状态多样化的煤层气藏,并据此指导煤层气有利勘探目标优选就显得愈发重要。为此,在系统梳理国内外煤层气富集成藏理论的基础上,结合鄂尔多斯盆地东缘煤层气勘探开发的地质规律,借鉴常规油气藏按照圈闭成因进行分类的方法,提出了煤层气圈闭的概念和煤层气藏类型的划分方案。研究成果包括:①结合煤层、砂岩、泥岩和石灰岩在垂向上的组合关系,刻画了"泥裹藏、砂通煤、水包气"的气体封闭样式,"泥裹藏"即以泥岩等致密岩层封闭煤储层而成藏,"砂通煤"即上覆砂岩与煤层连通而与煤层统一形成气藏,"水包气"即在水力封闭和水力封堵作用下,气体在煤层中富集而成藏;②阐释了物性封闭、气压封闭、水压封闭和吸附封闭在煤层气藏形成过程中的作用,指出气藏开发的上、下限分别为风氧化带和地应力转折带;③提出了以构造、岩性、水动力和复合型圈闭为主导的气藏类型划分方案,并分别解剖了背斜、断层、向斜、地层—岩性、水力封堵和水力辅助型煤层气藏。     

平顶山煤田东段深部煤层气赋存特征及影响因素分析

在系统分析研究本区地质资料的基础上,再结合相邻生产矿井瓦斯资料,讨论平顶山煤田东段深部矿区二1煤煤层气赋存规律。分别从煤岩成分、变质作用、埋藏深度、岩浆热作用、地质构造条件、煤层厚度、煤层顶底板岩性及水文地质条件等方面探讨对煤层气赋存的影响和控制因素。经分析认为本区地质构造和埋藏深度是影响煤层气富集的关键因素,其它因素也有重要影响。正是由于诸多有利因素的有机结合．使得本区煤层气较为富集,对未来矿井开采有重大的影响。     

中国煤层气资源类型与递进开发战略

将中国煤层气资源从开采技术条件的角度划分为主从四类，主类为压力气和应力气，从类为压力作用型应力气和应力作用型压力气。以此为基础，分析了我国当前煤层气商业开发进步缓慢的主要原因，提出了针对不同类型资源的适应开发技术方向和开发技术战略。建议目前的煤气之争和矿权纠纷需要采用资源四分法原则确立开发主从关系来得到根本解决。     

煤层气井生产曲线的拟合和产量预测

本文根据煤层气井的储层参数和水文地质数据，通过计算排采在煤层中形成的压力降，再结合兰氏方程、临界解吸压力等参数，进一步计算出煤层气井的产水量和产气量，并与实际的生产曲线相比较，进行拟合校正，建立合理的预测模型，用于煤层气井未来的产水量和产气量的预测。该方法回避了以往数值模拟的解吸、扩散、气水两相流运移的复杂计算。     

CO2增产技术改造煤层的可行性探讨

本文通过对煤层CH4脱附原理和CO2基本特性的介绍，结合国内设备配套和施工能力，经过分析和推理，提出利用CO2吞吐、CO2增能压裂和CO2泡沫压裂的可行性。根据我国目前煤层改造的现状，进一步阐述了应用CO2泡沫压裂对煤层实施强化改造的重要性。建议尽早开展专题研究，对煤层实施CO2泡沫压裂改造，以提高煤层气产量。     

煤层气开发利用现状与发展方向

为了进一步开发利用煤层气资源,分析了国内外煤层气开发利用历史与现状。与美国相比,中国煤层气开发利用比较落后,中国煤层气基础工作应当首先进行煤层气地质特征研究,进而找到适合中国煤层气地质条件的开发利用方法。     

煤层气注入增产法的探讨

煤层气储集层具有构造复杂、含气量低、渗透率低、原始储层压力低等特点，注入增产法（ECBM）是当前提高煤层气采收率的主要方法之一，也是目前国内外煤层气开发单位集中力量重点研究的驱替增产技术。本文在石油系统相关经验的基础上，主要从注入增产机理、注气井网类型、地面设备流程、注采动态分析模式等四方面较综合地阐述了注入增产的方式方法。