致密气藏储层干化、提高气体渗流能力的基础研究

Tight gas reservoirs are normally characterized by very small pore diameter, high capillary pressure and various clay minerals, making them more vulnerable to water blocking problems caused by invasion of fluids during well drilling, completion, stimulation and production processes. Experimental studies combined with theoretical modeling will be adopted in this project to try to develop an effective and efficient anhydration method for tight formations. A database for further screening and developing of anhydration agents will first be set up based on the research about water blocking mechanisms and corresponding water blocking removal methods. Based on the database and considering different tight formation types, experimental studies will be conducted to develop and screen formulation system of anhydration agents. Phase equilibrium experiments under high temperature and high pressure condition will be conducted to investigate the phase behavior of anhydration agent and reservoir fluids (tight gas and formation water). Together with phase equilibrium theory, a thermodynamic model for predicting the gas-liquid-solid phase equilibrium behavior of the anhydration agent-gas-formation water system will be established. Various microscopic pore structure characterization methods and core flooding experiments will also be conducted to qualitatively and quantitatively evaluate the ability of the developed anhydration agent's capacity to decrease water saturation as well as increase gas permeability in tight formations. In addition, a seepage model, incorporating corresponding phase transition, change of saturation profile and increase of gas permeability happened during anhydration process, will be established to evaluate and predict gas well deliverability after anhydration treatment. A filed pilot will finally be conducted to examine the effectiveness of the newly developed anhydration agent and corresponding treating procedures. Prospective research results of this project have important theoretical significance and application value in the decrease of water saturation in tight formations and thus efficient development of tight gas reservoirs.

致密气藏具有孔喉半径小、高毛管力、粘土矿物丰富等特征，导致钻完井等过程中各种工作液极易侵入储层造成水锁伤害。本项目拟将室内实验和理论模拟相结合，对致密储层干化机理进行研究。首先基于水锁伤害机理及相关水锁解除方法的研究，建立干化剂配方数据库，结合室内实验研制适用于不同致密储层的干化剂体系。开展高温高压条件下干化剂与储层流体的相态实验，并借助相平衡理论，建立多孔介质内干化剂-烃类气体-地层水体系的相平衡热力学模型，揭示干化剂与储层流体及多孔介质的作用机理。综合利用多种储层微观结构表征手段及渗流实验，对干化前后储层微观特征、渗流特征进行对比分析，并对干化工艺相关参数优选。建立考虑干化效应的渗流数学模型，对储层干化后气井产能动态进行评价和预测，并进行现场试验，最终形成一套系统的致密储层干化工艺方法及配套的效果评价体系。研究成果对于降低致密储层含水、高效开发致密气具有重要的理论意义和应用价值。

致密气藏具有孔喉半径小、高毛管力、黏土矿物丰富等特征，原生水饱和度高、同时钻完井等过程中各种滤失水也会导致近井地带高含水饱和度，这些水极大地阻碍了致密气的流动。本项目针对降低致密气藏含水的干化剂研制、干化反应相态、微观孔喉表征及储层微观条件下的干化渗流、干化产能及干化下微尺度数值模拟等关键科学问题开展研究。取得了如下创新性成果：（1）发明了适用于致密储层的干化剂配方以及干化剂与地层水反应的抗盐配方，揭示了干化反应延迟作用机理，形成了干化剂在致密储层微纳米孔隙中注入方法的基础理论，创建了干化剂-致密气-地层水三相反应相态预测理论与技术。（2）构建了利用核磁共振和激光雕刻孔隙结构模型联合表征干化效果的评价方法，定性定量评价了干化剂对不同产状束缚水的干化效果。（3）创新了乙醇-水混合流体核磁信号分离技术，形成了致密砂岩干化渗流实验方法，揭示了干化作用对储层物性的影响程度，优选了干化剂注入工艺参数。（4）建立了致密砂岩气藏耦合干化效应的产能评价及数值模拟模型，评价了干化强度与气井产能关系、干化效应对气井生产动态的影响，揭示了干化效应对微观孔隙尺度致密气流动能力影响机制。直接相关成果在国内外期刊发表论文54篇，出版学术专著4部（其中Elsevier出版专著2部），申请国家发明专利18项（授权10项）、软件著作权8件，获全国石油天然气标准化技术委员会突出贡献奖1项，中国石油和化工自动化行业协会科技进步二等奖1项，中国石油和化学工业联合会科技进步二等奖1项，四川省人民政府自然科学二等奖1项，四川省人民政府科技进步二等奖1项。