Preliminary Laboratory Evaluation of Cold and Post-Cold Production Methods for Heavy Oil Reservoirs Part B: Reservoir Conditions

Abstract

Abstract The problem of cold and post-cold production for conventional heavy oil (Lloydminster type) reservoirs is addressed. First, a brief overview of cold production-related material is presented. Primary production experiments are run in laboratory models of different geometries. Then, several post-cold production experimental methods for additional heavy oil recovery are attempted. The methods tested include water flooding, gas pressure pulsing, and polymer flooding. The effect of sand production is evaluated. The results are very preliminary, but encouraging. This work is offered as a challenge for the industry to consider the state of all cold produced heavy oil reservoirs and focus on the possible alternatives for this significant Canadian reserve. Introduction The heavy oil and oil sand deposits of western Canada represent one of the largest hydrocarbon accumulations in the world, with a resource base of nearly 1.7 trillion bbls(1). This is 1.5 times larger than the proven reserves of the entire Middle East. The bulk of the reserves are contained in three major geologically distinct regions. These areas are the conventional heavy oil of Lloydminster area, the Carbonate Triangle, and the oil sands deposits. Enhancement of primary production of conventional heavy oil through the so-called cold production mechanism has been a popular topic in the heavy oil industry for the past 15 years. However, cold production alone cannot produce more than an estimated 10 - 15% of the original oil in place (OOIP). This paper addresses the issue of post-cold production or, in general, post-primary production of heavy oil via different injection techniques that include: water flooding, polymer flooding, and pressure pulsing/shut-in. Several independent sets of experiments were run that include one cold production experiment in a large cylindrical model with a central production well (radial production geometry), two linear core floods, and six experiments at reservoir conditions in rectangular geometry physical models (one including sand production). In a companion paper(2), comparative experiments at ambient conditions are described. Those experiments(2) were used as a starting point for the experimental work presented here. The following questions summarize the objectives of this work:How does linear geometry single perforation compare to radial geometry multiple perforations when dealing with sand production?;Can recovered unconsolidated core be useful for laboratory core floods?;Is there some hope for gas injection to be used in heavy oil reservoirs?;How does water flooding and polymer flooding at ambient conditions compare to the same tests post-cold production?;Does flow pattern modification improve heavy oil recovery?; and,Do wormholes pose a support or an obstacle in post-cold production? Literature Survey A large variety of heavy oil EOR methods are proposed in the literature(3). Earlier work on non-thermal recovery of heavy oil(2, 3) did not take into account cold production mechanisms and thus it is questionable how such work applies to the current state of the Canadian heavy oil fields. Some recent work(4–19) is listed below.