Research On Enhancing Recovery Of Super-Heavy Oil Reservoir By Thermochemical Complex System

As to a deep and thin layer of super-heavy oil reservoir, the conventionalrecovery technologies, such as steam huff and puff and SAGD, can not develop iteffectively due to different reasons. Fortunately, a ternary thermal chemical compositehuff and puff technique combining with horizontal well (HDCS Technology) isinvented by Shengli Oilfield. This technique can develop an super-heavy oil reservoirwith1500m in-depth and less10m of layer thickness effectively. However, as thecyclic numbers increase, the problem that how to enhance the recovery of super-heavyoil reservoir further using thermal chemical composite system is needed to be solved.According to the diffusion rule of CO2in the process of thermochemicalcomplex system huff and puff, a mathematical model of CO2diffuse in porous mediawith oil was built. The results showed that in the core saturated by oil, the oil volumeexpansion due to CO2dissolving will lead to the decrease of CO2concentration anddiffusion velocity. A3D physical model is used to stimulate thermal chemicalcomposite system huff and puff. By this stimulation, the diffusion of viscosity reducer,the effect of CO2and steam on the diffusion law of viscosity reducers and the changeof oil property are studied, and the oil produced in the field is also analyzed. Theresults show that the incoming liquid amount of horizontal well heel is a little higherthan that of horizontal well toe when the viscosity reducer is injected into layer. Andthe viscosity reducer can reduce the content and the molecular weight of asphaltene ofultra-heavy oil. The non-uniform distribution of viscosity reducer in space will lead toa big difference in oil property. The injection of CO2can promote the diffusion andeffecting area of viscosity reducer, and uniform the distribution of viscosity reducer inspace. The injection of steam can improve the mobility of oil, which lowers thenon-uniformity of oil property. In the field productive process, the oil viscosityincreases gradually in the same steam soak cycle and the dissociation of viscosityreducer will become weak as the cyclic numbers increase.The compose of thermal chemical composite system in flooding stage was chosen through displacement experiments for parallel cores, and the injectionparameters are also optimized. Steam has the most important impact on ultimaterecovery of thermal chemical composite system flooding, and the optimum injectionvolume of steam, oil soluble dissolver and CO2is2.5PV,1.5%, and0.2PV separately.We also found that the slug injection of oil soluble dissolver can increase the effectingtime, achieving a better viscosity reducing effectiveness. Considering the steambreakthrough confronted with in the later stage of thermal chemical composite systemflooding, the laboratory experiments are conducted to testify the feasibility of foamprofile control technology. The results show that high-temperature foam have anexcellent profile control performance in non-homogeneous layer and increase theconformance efficiency of low-permeability layer significantly, which enhance therecovery of non-homogeneous reservoir largely. The thermochemical compositesystem huff and puff technique have been proved to be in good effect in thedevelopment of Shengli Oilfield super-heavy oil reservoir by production results.