Reserves Are Added By Re-Thinking a 1983 Steamflood Pilot
Authors: Nelson Donald George , Economides Michael John 
Published: November 2008

A 1983 steamflood pilot project was abruptly terminated in the Edison Field in California. Recently discovered and re-interpreted information suggests that the decision was unjustified. A critical review of the pilot and the original steamflood simulation along with a comparison of actual field measurements make it clear that the steamflood should be reconsidered, and in the process, greatly adding to the field oil reserves.

One of the salient issues is that at the time, reservoir simulation results, which presumed that a fully confined, thermal frontal displacement was occurring did not account for the importance of gravity in steamfloods. This evolution became known after 1983 and available field data were never used which would have demonstrated the inadequacy of the original notions. Remaining oil saturation was determined to be the critical unknown. The surface steam distribution system had vertical T's instead of dead-end T's resulting in poor steam quality distribution.

Revisited down-hole measurements of pressure and temperature showed a critical piece of information: only one of the four injectors was receiving wet steam. The other three took only hot water. Wide ranging flow line temperature and production data showed poor areal conformance and temperatures and rates in many producers were not affected by the four injection wells. A survey run in the updip confined producer several months after the pilot termination showed 400 bbls per day of hot water entering the wellbore 100 ft above the steam flood interval indicating the injected steam was not confined.

Production results were dominated by the low oil saturations in the overlaying wet sands. The pilot project resulted in frontal displacement in a wet sand instead of gravity drainage in an oil sand. Thus, the wrong process in the wrong interval was the key to the pilot results.

The recent study suggests that the Edison Field has excellent potential for major reserves additions via gravity-enhanced steamflooding, similar to the very large neighboring Kern River Field. This work suggests that old conclusions should be questioned when new ideas and/or data emerge. In particular, when steam conformance is favorable, gravity-enhanced steamflood can be viable at relatively low oil saturations. Steamflood projects are of course very complex and a thorough understanding of steam movement through surface lines, down wellbores, and through formation layers is required for successful execution.

Introduction

Thermal Enhanced Oil Recovery (TEOR) is often indicated for heavy oil producers worldwide. Several commercial expansions have followed small pilot projects involving steam injection since the 1950's. An ongoing 'knowledge-evolution' of the complex physics involved in thermal recovery continues to be documented in the technical literature (Kumar et al. 2005). Technology advances have followed activity levels, first centered in California and later in Canada. Unfortunately, there has been very little reporting about failed thermal recovery pilot projects. This is inopportune because critical investigation of failures can lead to profound improvements in knowledge.