致密油藏水平井-直井双向示踪动力学模型研究

The water injection of volume fracturing horizontal well-vertical well combined well pattern is an important technology of tight reservoir development. Extensive natural fracture and artificial fracture of tight reservoir causes the water channeling and flooding of horizontal well. The key of effective implementation of water controled measures is quantitatively describing the fracture and water flooded condition from the plane and the section of combined well pattern systematically and accurately. Therefore, based on the limitations of interwell tracer and slow-release tracer, a bi-directional tracer method of horizontal well-vertical well in tight reservoirs is proposed, and the dynamic model of bi-directional tracer is researched basically by the theory of percolation mechanics, dissolution and transportation of solute. The dynamical model of interwell tracer transportation with natural fracture and artificial fracture is researched, and the influence law of the output concentration of interwell tracer by fracture system is revealed. The dynamical model of slow-release tracer is researched with the consideration of scouring velocity, and the influence law of the output concentration of slow-release tracer by scouring velocity is revealed. The aforementioned dynamical models and the percolation model of tight reservoir are combined to establish the integrative interpretation method of the bi-directional tracer. The results of the project provide the theoretical basis for the application of the bi-directional tracer method. A new approach is provided to solve the systematic monitoring and quantitative characterization of water channeling in tight reservoirs in China.

体积压裂水平井-直井联合井网注水是致密油开发的重要手段，水平井经大规模改造后会形成人工裂缝与天然裂缝相沟通的复杂缝网结构，在注水开发中后期易水淹，如何准确的从平面和剖面上实现对水淹状况的系统监测与水窜裂缝系统的定量表征已成为后续有效实施控水措施的关键。因此，本项目从井间示踪与缓释型示踪监测技术的局限性出发，提出了一种致密油藏水平井-直井双向示踪方法，并利用渗流力学、溶质溶解及运移等理论对其动力学模型开展以下基础研究：研究含天然裂缝及人工裂缝的井间示踪剂运移动力学模型，揭示水窜裂缝系统对示踪剂产出浓度的影响规律；研究考虑流体冲刷速度的缓释型示踪剂缓释动力学模型并揭示其对释放浓度的影响规律；通过以上两个动力学基础模型与致密油藏渗流模型的耦合，建立双向示踪一体化解释方法。项目研究成果可为该方法先导矿场应用提供理论基础与依据，为有效解决我国致密油藏水窜水淹特征的系统监测与定量表征提供一种新思路。

针对致密油水平井-直井井间水窜裂缝系统与水平井产液剖面监测的问题，提出了一种致密油藏水平井-直井双向示踪方法，根据致密油藏体积压裂裂缝展布及水窜水淹特征，基于连续性方程、示踪剂运移方程、状态方程、辅助方程、裂缝与井筒之间运移方程、裂缝与基质之间运移方程及流线分布方程，建立了致密油藏水-直联合注采井网井间示踪剂运移动力学模型，利用有限差分对该模型进行数值求解，并分析了窜流通道突进系数、窜流通道厚度、窜流通道长度、储层渗透率、储层孔隙度、储层含油饱和度、后期注水速度、示踪剂注入初始浓度、示踪剂注入总量、注示踪剂前储层压力等因素对示踪剂曲线产出特性的影响规律；由于国外技术封锁，样品难以获取，基于自制的缓释示踪剂，开展了缓释型示踪剂宏观静态非冲刷实验、宏观动态冲刷实验和CT扫描微观缓释动力学实验，明确了温度和冲刷流量均对缓释型示踪剂释放有较大影响，其示踪剂释放浓度曲线均表现为开始快速下降，随后缓慢下降的趋势，温度和冲刷流量越大释放速率越高，微观释放实验表明缓释型示踪剂的释放是一由外向内且存在明显动界面的逐步溶解扩散释放的过程，且分界面随着示踪剂的不断释放向内部迁移并基于微观缓释实验认识，基于其缓释动力学过程，建立了缓释型示踪剂一维缓释动力学模型，通过参数敏感性分析表明其释放速度随时间的增加而变慢，且受冲刷速度和温度的影响，其释放速率是非等速释放的。基于建立的便于耦合的水-直井间水窜裂缝系统示踪剂运移解析模型和水平井缓释示踪剂稳态模型，利用冲刷速度将上述2个模型进行耦合，采用遗传算法，建立了水平井-直井双向示踪“双控”拟合方法及解释流程，实现了系统精细的刻画出水平井-直井联合注采井网内水窜位置、水窜裂缝系统参数并确定水平井水淹井段来水的详细参数。项目技术及研究成果可为致密油水平井段出水状况及各水平段来水通道参数及来水方向识别提供可靠监测手段，为致密油水平井有的放矢的靶向封调，延长水平井长期持续稳定开发提供重要保障。