Steam Injection Strategies for Thin, Bottomwater Reservoirs

Abstract

ABSTRACT This paper presents the results of thirty-nine scaled model experiments which were conducted to study variations of steamflooding in thin, heavy oil formations, with bottom water present in many instances. The work primarily addresses Lloydminster, Saskatchewan, type reservoirs which are characterized by a viscous oil (1275 mPa·s at reservoir temperature) and a thin pay (6 − 13 meters). Reservoirs of this type are common in Saskatchewan and eastern Alberta; thus it is imperative to develop recovery strategies which are likely to succeed in the field, which was the objective of this research. Experiments of many types were conducted, many of which gave favorable results. Eight of the thirty-nine experiments were conducted with bottom water models, using strategies based on steamflooding experience gained from the homogeneous model experiments. It was found that by injecting an inert gas into the model, prior to steamflooding, the effect of thick bottom water zones can be minimized. Temperature profiles indicate that the injected gas creates a flow channel away from the water zone, and that the injected steam tends to follow this path of least resistance, rather than channeling directly into the bottom water zone. Injecting gas into a bottom water model, prior to steamflooding improved the oil recovery from 16.79% to 20.66% of the original oil in place. The experimental results suggest that there is some minimum bottom water thickness (approximately 10% of the gross pay thickness), below which the effect of bottom water is small.