深层超稠油油藏注多元热流体降粘增效机制
Mechanism of Viscosity Reduction and Efficiency Enhancement by Injection of Multi-Component Thermal Fluid in Deep Ultra-Heavy Oil Reservoirs

针对深层超稠油油藏，常规蒸汽热采难以有效动用是面临的主要问题。运用油藏工程方法、物理模拟实验和数值模拟方法相结合的方法，采用商业软件PVTsim计算地层温度、压力下注入多元热流体后超稠油的粘度变化，评估注入多元热流体后的产能和采出情况。研究表明在地层压力30 MPa下，注入多元热流体后，在100？C、二氧化碳溶解度80，120？C、二氧化碳溶解度50时，超稠油的粘度分别从18,000 mPa？s下降到622.8 mPa？s和709.4 mPa？s，温度和气体的综合效应下形成以温度、溶解度和粘度划分的高、中、低三个不同区域。根据动用的直井段长度，其产能可达7~34 m³/d。针对深层超稠油油藏采用多元热流体热采，相比常规的蒸汽吞吐该技术可充分发挥气体溶解降粘、增能保压、提升举升效率等优势，为深层超稠油油藏的高效开发探索了一条新路径。
Aiming at the deep ultra-thick oil reservoir, it is difficult to use effectively conventional steam thermal recovery to extract heavy oil. It was studied by using a combination of reservoir engineering methods, physical simulation experiments and numerical simulation methods. By using the commercial software PVTsim to calculate the viscosity change of ultra-thick oil after injection of multi-component thermal fluid under formation temperature and pressure, it can be evaluated the production capacity and recovery after injection of multi-component thermal fluid. The study shows that the viscosity of ultra-thick oil decreases from 18,000 mPa？s to 622.8 mPa？s and 709.4 mPa？s at 100？C, CO₂ solubility of 80 and 120？C, CO₂ solubility of 50 respectively, under the formation pressure of 30 MPa, after the multi-component thermal fluid is injected. The three different zones are formed under the combined effect of temperature and gas, which are classified by temperature, solubility and viscosity. In the end, the production capacity can be up to 7~34 m³/d depending on the length of the straight well section. Multi-component thermal fluid thermal recovery for deep ultra-thick oil reservoirs can make full use of the advantages of gas dissolution to reduce viscosity, increasing the energy to maintain pressure and improving the lifting efficiency compared with the conventional steam throughput, which has explored a new way for high-efficiency development of deep ultra-thick oil reservoirs.