Progress and prospects of EOR technology in deep, massive sandstone reservoirs with a strong bottom-water drive

Abstract

The Triassic massive sandstone reservoir in the Tahe oilfield has a strong bottom-water drive and is characterized by great burial depth, high temperature and salinity, a thin pay zone, and strong heterogeneity. At present, the water-cut is high in each block within the reservoir; some wells are at an ultra-high water-cut stage. A lack of effective measures to control water-cut rise and stabilize oil production have necessitated the application of enhanced oil recovery (EOR) technology. This paper investigates the development and technological advances for oil reservoirs with strong edge/bottom-water drive globally, and compares their application to reservoirs with characteristics similar to the Tahe oilfield. Among the technological advances, gas injection from the top and along the direction of structural dip has been used to optimize the flow field in a typical bottom-water drive reservoir. Bottom-water coning is restrained by gas injection-assisted water control. In addition, increasing the lateral driving pressure differential improves the plane sweep efficiency which enhances oil recovery in turn. Gas injection technology in combination with technological measures like channeling prevention and blocking, and water plugging and profile control, can achieve better results in reservoir development. Gas flooding tests in the Tahe oilfield are of great significance to identifying which EOR technology is the most effective and has the potential of large-scale application for improving development of deep reservoirs with a strong bottom-water drive.

Keywords

• Edge water
• Bottom water
• Water coning
• Massive reservoir
• Water injection
• Gas injection