煤层剩余气液成因机制及有效动用地质约束

Horizontal and vertical variations of coal rank, coal facies, and structure cause strong heterogeneity in coalbed methane reservoirs, resulting in uneven disturbance f coalbed methane production and thus uneven enrichment of residual coalbed methane (CBM), which affects CBM recovery and even selections of stimulation treatment and stable production technology. Aiming at the scientific problem as genesis of residual CBM and water in coal seam and geological constraints on recovery, based on similarity of pore network and related physical properties controlled by coal facies, coal rank, and structure, micro reservoir type will be classified; characteristics and influencing factors of gas-water two-phase flow in coal will be analyzed, and the mathematical model of relative permeability under controls of multi-physics and micro reservoir type will be established; characteristics of residual CBM and water will be quantitatively delineated, and genesis of residual CBM and geological constraints on effective recovery will be elaborated, and the mathematical model of residual gas and water flow under the constraints of multi-physics and reservoir types will be established; The refined geological model for typical CBM block will be constructed, and distribution of residual CBM and recovery potential under geological constraint will be evaluated through numerical simulation. The above achievements will further enrich theory of CBM development geology, and provide scientific support for remaining CBM production both in high-yield and low-yield blocks.

煤阶、煤相及煤体结构纵向或横向变化造成煤储层强非均质性，导致煤层气生产波及程度不均匀，剩余煤层气非均匀富集，影响煤层气采收率乃至稳产增产技术选择。本项目针对煤层气剩余气液成因机制及有效动用地质约束这一科学问题开展研究，基于煤相-煤阶-煤体结构控制下储层孔隙网络结构及相关物性相似性，划分微观储层类型；采用物理模拟分析典型结构类型煤在多物理场下气液两相流动特征及影响因素，建立多物理场和储层类型约束下相对渗透率数学模型；定量描述剩余气液赋存特征，阐释剩余气成因机制及有效动用地质约束，建立多物理场和储层类型约束下剩余气液启动数学模型；构建典型区块精细地质模型，通过数值模拟研究剩余气分布规律及地质约束下有效动用潜力。上述成果将进一步丰富煤层气开发地质理论，为高产区剩余煤层气生产挖潜与低产区剩余煤层气盘活工程措施提供科学支撑。

我国煤层气勘探开发多年，现今的产量仍然难以满足国家需求，大量低产低效井的治理依然是困扰行业的难题。究其原因是多物理场与煤阶-煤相-煤体结构共同约束下煤层气液流动规律以及煤层剩余气液成因机制及有效动用地质约束等关键科学问题限制了老气田剩余煤层气资源的有效释放。结合煤层气综合勘探和开发工程，采用物理模拟和数值模拟相结合方法，项目研究了不同宏观煤岩类型煤裂隙发育特征，建立了不同类型煤多尺度离散裂隙网络，阐明了煤中不同孔裂隙发育类型，划分了储层类型，揭示了组分对煤中连通孔裂隙发育的控制作用；查明了不同宏观煤岩类型煤中剩余水体积和形状因子的分布规律，划分了煤中剩余水类型，阐释了不同类型剩余水的形成控制因素，揭示了流态与宏观煤岩类型造成的剩余水形成差异性。分析了不同作用力对煤储层微观剩余水的作用机制，建立了不同类型剩余水动用临界数学模型，阐明了裂隙开度、裂隙交角和气体速度等因素对煤层剩余水动用的影响；构建了以宏观煤岩类型为岩相约束的研究区精细三维地质模型，预测了剩余煤层气的三维空间分布规律，厘清了煤层剩余含气量的地质控制因素，评价了煤层剩余气量的有效动用潜力。上述成果丰富了煤层气开发地质理论，为高产区剩余煤层气生产挖潜与低产区剩余煤层气盘活工程提供了科学支撑。