The Application of Fluid Injection To Mitigate Coning

Abstract

As an oil zone thins during the mature stages of a vertical miscible or immiscible flood, oil production becomes dominated by coning of water, gas and / or miscible solvent. This results in lower revenues and increased operating costs which in turn accelerates well abandonment. In contrast to the early operations of a pool, the remaining oil volumes which are increasingly at risk have access to only limited capital. Coning therefore is controlled by conventional techniques such as re-completions, choking back oil production or intermittent operation. As the effectiveness of these techniques becomes reduced, other less conventional approaches are sought. Such techniques as the placement of polymeric agents or the injection of oil or water to divert the coning fluids, are becoming attractive because of their low capital requirements. In support of the present work, scaled laboratory experiments and numerical simulation studies have demonstrated the recovery benefits using fluid injection as a way to maintain production from a thinning oil sandwich. Currently, Imperial Oil is developing oil re-injection technology to increase recoveries by 1.5 to 3 percent of the original oil-in-place (OOIP) by reducing solvent coning in a number of their vertical miscible flood pools located in the Pembina Nisku area. A pilot project evaluating this technology has been in operation for nearly a year. After overcoming a number of start-up and other operational problems, the pilot has demonstrated that oil re-injection can successfully control GOR. History matching the pilot performance has confirmed the design approach and performance expectations. Based on the encouraging results, four more projects have been planned for start-up in 1994.