PUBLICATION RIGHTS RESERVED PUBLICATION RIGHTS RESERVED THIS PAPER IS TO BE PRESENTED AT THE INTERNATIONAL TECHNICAL MEETING JOINTLY HOSTED BY THE PETROLEUM SOCIETY OF CIM AND THE SOCIETY OF PETROLEUM ENGINEERS IN CALGARY, JUNE 10 TO 13, 1990. DISCUSSION OF THIS PAPER IS INVITED. SUCH DISCUSSION MAY BE PRESENTED AT THE MEETING AND WILL BE CONSIDERED FOR PUBLICATION IN CIM AND SPE JOURNALS IF FILED IN WRITING WITH THE TECHNICAL PROGRAM CHAIRMAN PRIOR TO THE CONCLUSION OF THE MEETING.

Abstract

This paper examines the feasibility of cyclic natural gas injection for the enhanced recovery of light oil from waterflooded fields. Approximately 40 percent of waterflood residual oil was recovered in corefloods using two huff 'n' puff cycles at immiscible conditions. Gross gas utilizations were as low as 3 MSCF/STB. Response to cyclic injection contrasted favorably with immiscible WAG displacement. Coreflood results and numerical simulation indicated that incremental oil was not highly sensitive to remaining oil saturation. Predicted field recovery could be improved by managing offset wells. Response to cyclic gas injection was mostly dependent upon the amount of gas injected. suggesting that there will be a maximum economic slug size in field applications. Results indicated that repressurization and gas relative permeability hysteresis are the major oil recovery mechanisms.

Introduction

Single-well, cyclic injection/production processes are characterized by low initial capital outlay and rapid payout, offering a timely alternative to fullscale tertiary payout, offering a timely alternative to fullscale tertiary flooding. The literature explores cyclic gas injection using rich gas, exhaust gas, and CO2. These processes were introduced for the stimulation of viscous-oil reservoirs. While cyclic CO2 injection was originally proposed as an alternative to cyclic steam for heavy oil proposed as an alternative to cyclic steam for heavy oil recovery, it is now finding wide application in light-oil reservoirs.

This study was undertaken to encourage exploitation of natural gas huff n puff. By analogy to other cyclic gas injection processes, especially cyclic CO2. an immiscible process using natural gas seemed feasible for enhanced recovery of light oil from waterflooded fields.

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