Zama Acid Gas Disposal/Miscible Flood Implementation And Results
Authors: Davison R.J. , Mayder A. , Hladiuk D.W. , Jarrell J. 
Published: March 2010

During 1994, Pennzoil Canada, Inc. entered into an agreement with Novagas Clearinghouse Ltd. (NCL) to re-inject the waste gas produced at their newly constructed Zama gas compression/ processing facility. Figure 1 highlights the project location.

This paper will provide a general overview of the design, implementation, operation, and available results of this acid gas disposal/miscible flood project. Approval to inject 70 103m3/day waste gas was received from the EUB in March 1995. Injection limits were increased (August 1995) to 120 103m3/day which made the Zama acid gas system the largest in Canada. The acid gas (60% CO2 and 40% H2S) is being injected into the Zama Keg River "X2X" Pool (a previously waterflooded reef). Reinjecting the acid gas has several significant upsides. The immediate benefit is reduced atmospheric emissions. This one project is a significant contributor to CAPP's Climate Change Voluntary Challenge Committee. Additional benefits include tertiary crude oil reserves, subsurface sulphur storage and a more effective use of capital (i.e., compression versus sulphur recovery unit). The acid gas stream (based on theoretical and laboratory work) is miscible under achievable operating conditions. Unfortunately, the use of acid gas as a miscible product has not been widely published. Laboratory work has been required to refine our understanding of the process. The key results are included. Zama has not been an area where miscible flooding was considered an economic alternative (i.e., the reefs are relatively small and isolated). The construction of NCL's plant provided an inexpensive miscible solvent to test the process. The concept has broad applications to other reefs in the Zama area and elsewhere in Alberta.

Introduction

The oil industry as a whole is working towards a more responsible and proactive attitude towards the environmental issues. Pennzoil Canada, Inc. stepped forward to implement a very effective method of dealing with the waste gas produced at NCL's Zama facility (13-12-116-06W6M). The general benefits as outlined previously can be applied at many existing facilities and should be given consideration during the construction of new facilities.

Potential miscibility was another key factor in Pennzoil's decision to participate in the acid gas disposal scheme. The Zama Basin contains a significant number of Keg River reefs with overlying Zama carbonates. Most of the larger pools were found during the early exploration phases and are now in various stages of depletion. Secondary recovery methods (waterflood, pressure maintenance) have met with mixed success. Tertiary recovery methods (gas injection, fireflood, etc.) have been attempted with no success reported to date. Pennzoil had considered miscible flooding as a potential recovery method in the Zama Basin (based on the process's application in the Rainbow Basin). Smaller reef size and miscible solvent availability made the option impractical. When NCL approached Pennzoil with the acid gas disposal concept, it was recognized as an opportunity to test the process and make available a long-term inexpensive, miscible solvent.

The discussion will be organized into three general categories.Non-time specific informationThe pre-gas injection period (Data up to April 30, 1995)