Increasing total prodn. from oil reservoir by injecting - gas rich in ethane and heavy components, followed by water (HU 28.03.81)

摘要

The yield of crude oil from a reservoir is increased by: (i) injecting from an injection well a gas contg. a high concn. of ethane and heavy components, so as approximately to restore the reservoir's initial pressure, until the injected gas appears at the prodn. well; and then (ii) injecting water instead of gas, while maintaining nearly constant pressure. The gas injected in phase (i) contains at least 30-40% heavy components, the mole ratio (ethane: heavy components) being pref. 2.5:1: it can be extracted from associated gas or natural gas. The increase of oil yield (e.g. 10%) is higher than by known processes. Investment costs are low. The gas used is pref. to CO2 because it does not ppte asphaltenes in the rock, has low water-solubility and corrosivity, and does not contaminate the prod. ().