Heavy oil is an important part of unconventional resources. Many great breakthroughs have been made in heavy oil EOR mechanism of thermal methods. With the unprecedented development of technology, Super-critical Water Coupled with Toe-point Injection Technique is entering people’s view.
Compared with previous thermal methods, the reservoir can be heated to a higher temperature by injecting supercritical water, obtaining a larger heated radius. Meanwhile, toe-point injection could abate the problem of early channeling and unequal steam absorption caused by heel injection in extremely long horizontal wellbore or reservoir of serious heterogeneity, which results in a higher recovery rate.
In this paper, a novel topic is discussed on the effect of different parameters on oil productivity during the single horizontal well production process, using discrete horizontal well model. The recovery process is completed through a single horizontal well--the supercritical water is injected into the reservoir through the tubing, while oil is produced to the surface through the annulus. Some meaningful conclusions are listed below.
(a) Under the same production policy, the recovery ratios of supercritical water are generally higher than those of steam, indicating that, besides its chemical reactions with heavy oil and rock minerals and fracture initiation ability, the effect of physical properties (high pressure and high temperature) on oil recovery efficiency also play an important role in the usefulness of supercritical steam in heavy oil recovery. (b) The relative well height in the reservoir has significant influence on the production performance, whose impact varies as the production methods change. Consequently, the optimum well position ns under diverse production methods are different. (c) The direction of oil recovery is from toe point to the heel point. The matching between well height and the growth of steam chamber and water puddle decides the production performance.