Improvement of Thermal Heavy-Oil Recovery in Sandstone and Carbonate Reservoir Using Hydrocarbon Solvents
本文针对碳酸盐岩裂缝性油藏重油开采难题，提出蒸汽 - 溶剂交替注入（SOS - FR）新技术。通过大量静态、动态实验及数值模拟，研究多种因素对采收率影响，结果表明该技术在不同条件下均能有效提高采收率且溶剂回收良好，同时降低二氧化碳排放，具有良好应用前景。静态实验方面，探究了基质润湿性、溶剂类型、初始含水饱和度、基质边界条件和尺寸等参数对采收率的影响，发现油湿基质中存在复杂渗吸 - 驱替过程，沥青质沉淀会影响渗透率，且水在油湿基质中对扩散和驱油有不同作用，不同流向实验显示过程受交互作用性质影响大。动态实验表明，过程存在最优注入速率，注入方案影响采收率，溶剂可因油收缩进入基质并引发对流增强驱油，大岩心受边界条件和尺寸影响大，沥青质沉淀在不同速率下对采收率影响不同，溶剂回收速度快是重要成果。可视化实验揭示，水平和垂直 Hele - Shaw 模型中溶剂扩散方式不同，边界条件对两种模型采收率影响显著，温度加速溶剂扩散，溶剂回收与温度和基质形状因子有关，并引入相关系数和特征长度描述扩散与采收率关系。
数值模拟中，提出实验室数据放大到现场数据的方法，研究了机械弥散与分子扩散关系，确定大基质块溶剂注入速率规律，表明该方法在大基质规模下有效且经济环保，裂缝密度是关键参数，确定了主要控制物理过程及循环溶剂刺激的效果。
CMG 软件应用情况
在数值模拟部分使用了 CMG STARS 软件，构建了二维单孔隙度和渗透率模型进行模拟研究，包括设置模型参数如网格属性、基质和裂缝属性、流体属性等，模拟不同注入阶段（蒸汽注入、溶剂注入、蒸汽再注入）的过程，分析不同工况下的采收率、溶剂饱和度、压力等变化情况，通过历史拟合获取相关系数用于模型优化和放大研究，为研究裂缝性油藏中 SOS - FR 技术的应用提供了重要的模拟分析工具。
作者单位：Al Muatasim Mohammed Hamood Al Bahlani 阿尔伯塔大学
Abstract
This thesis introduces a new approach for heavy-oil recovery from fractured reservoirs: Steam-Over-Solvent Injection in Fractured Reservoirs (SOS-FR). The SOS FR technique is a new technology proposed as an alternative method to the sole injection of steam or solvent and consists of three phases; Phase 1 produces heavy oil by thermal expansion and conditions the oil for Phase 2, which is solvent injection, and Phase 3 is applied mainly to retrieve the solvent.
Extensive experimental evidence and analysis were provided through static and dynamic laboratory scale experiments. Static experiments were conducted to test four parameters: (1) Matrix wettability, (2) solvent type, (3) initial water saturation, and (4) matrix boundary conditions and size. This was followed by dynamic experiments to test the effect of solvent injection rate on the process. Experiments were conducted using heavy-crude oil samples obtained from a field in Alberta on either wettability-treated sandstone (to mimic oil-wet behavior), or cleaned carbonate cores.
Visualization experiments were also performed on 2.5 cmx7.5 cm Hele-Shaw cells with different boundary conditions to gain an insight into fluid-fluid interaction between oil in the matrix and solvent in the surrounding fracture. Interaction between oil saturated 2-D models and the hydrocarbon solvent surrounding it was analyzed qualitatively. Two new dimensionless numbers were introduced as functions of fluidproperties (viscosity, density, and diffusion coefficient) and matrix boundary conditions, and the numbers were correlated to oil recovery rate.
Finally, numerical simulations were conducted using a commercial software package for two main purposes; (1) history matching and obtaining an insight into the upscaling procedure from lab to larger scales, and (2) examining the efficiency of the process at the field scale (mainly large matrix sizes).
The importance of this work is that it provides a novel perspective on the interaction between steam/solvent and heavy oil in the matrix, and presents an alternative technique for heavy-oil recovery from deep natural fractured reservoirs with tight and oil-wet matrix.
