MODELING OF NON-THERMAL RECOVERY OF HEAVY OIL BY CYCLIC SOLVENT INJECTION

使用低温室气体（GHG，非蒸汽）工艺开发重油有相当大的推动力。这可以使用溶剂来实现，这对于Alberta和Saskatchewan的稠油油田来说尤其重要，因为这些油田之前已经进行了冷稠油砂开采（CHOPS）。这些油藏的初次采收率为原始油储量（OOIP）的5 - 10%，因此仍有大量的石油存在，并且在chop后油田无法注入蒸汽，这使得它们成为开发非热溶剂采收率的绝佳候选者。******循环溶剂注入（CSI）是单井工艺，通过注入气相溶剂对储层加压。在高压下，溶剂溶解到重油中，降低了稠油的粘度。随后，该井投入生产，因此井压下降，为溶剂稀释油的流动提供了动力。这一过程的几项实地试点研究已经在进行中。CSI面临的挑战是，随着生产井压力的下降，溶剂会从溶液中流出，油的粘度会再次增加。生产是实现流动和保持气体在溶液中的平衡行为。直觉表明，这种方法有可能大幅增加石油产量，但目前还不清楚这种方法是否可以商业化。通过了解CSI的物理特性（即控制石油生产的因素），并能够正确地模拟该过程，这有助于为该过程的未来大规模可行性提供见解。******根据我们过去实验室规模岩心驱油的经验，在初次生产后CSI采收率很低，并且在每个连续周期中压力下降速率都需要增加。在现场，压力下降的速度要比实验室慢得多，因此在实验室研究中还没有捕捉到一些物理现象。这项工作的目的是确定这些物理特性，以及是否存在可以控制的操作参数，以提高CSI的采收率。******本课程的第一部分侧重于了解在重复CSI循环中采油的重要机制。CSI的实验室测试通常在初级产量远高于现场产量之后开始。此外，岩心注水通常不考虑重力对CSI性能的影响。最后，油-溶剂体系的PVT试验不能很好地反映溶剂在油中留下的溶液作为压力和时间函数的非平衡响应。不同的溶剂也可能具有不同的非平衡效应，因此它们在减压（生产）周期中的反应可能不同。该计划将运行实验来研究所有这些参数，并模拟CSI生产，以捕获适当的恢复机制。

There is a considerable push to develop heavy oil using low Green House Gases (GHG, non-steam) processes. This can be achieved using solvent, which may be particularly relevant in the heavy oil fields in Alberta and Saskatchewan that have previously undergone Cold Heavy Oil Production with Sand (CHOPS). Primary production from these reservoirs leads to recovery of 5 – 10% of Original Oil in Place (OOIP) so there are significant volumes of oil still present, and without the ability to inject steam in post-CHOPS fields this makes them excellent candidates to develop non-thermal solvent recovery processes.******Cyclic Solvent Injection (CSI) is a single well process, whereby a vapour phase solvent is injected to pressurize the reservoir. At elevated pressures solvent dissolves into the heavy oil and reduces its viscosity. The well is then placed on production, so well pressure drops and provides a driving force for solvent-diluted oil to flow. Several field pilot studies of this process are already underway. The challenge to CSI is that as the production well pressure drops, solvent comes out of solution and oil viscosity will increase again. Production is a balancing act between achieving flow and keeping gas in solution. Intuition suggests the potential for significant incremental oil production, but what is not defined is whether this process can be commercial. By understanding the physics of CSI (i.e. what controls oil production), and being able to model the process properly, this can help to provide insights into the future viability of this process on a large scale. ******In our past experience in lab-scale core floods, CSI recovery is low after primary production and the pressure decline rate needs to be increased in each successive cycle. In the field, pressure drawdown rates are much slower than in the laboratory, so there are physics present that are not being captured yet in lab studies. The objective of this work is to determine what those physics are, and if there are operational parameters that can be controlled to improve recovery from CSI.******The first part of this program focuses on understanding what mechanisms are important for oil recovery from repeated CSI cycles. Lab tests of CSI generally start after a much higher primary production than what is seen in the field. In addition, core floods generally do not consider the effects of gravity on CSI performance. Finally, PVT tests on oil-solvent systems do not properly represent the non-equilibrium response of solvents leaving solution in oil as a function of pressure and time. Different solvents may also have different non-equilibrium effects, so they may respond differently during depressurization (production) cycles. This program will run experiments to study all of these parameters, and model CSI production capturing the proper recovery mechanisms.