Hamaker, R.J., Member SPE-AIME, Production Operators, Inc. Production Operators, Inc. This paper was presented at the 1979 Production Operations Symposium of the Society of Petroleum Engineers of AIME, held in Oklahoma City, Oklahoma, February 25–27, 1979. The material is subject to correction by the author. Permission to copy is restricted to an abstract of not more than 300 words. Write: 6200 N. Central Expy., Dallas, Texas 75206.
With the increase in enhanced recovery projects, it is helpful for all operators to have the benefit of the experience obtained to date in order that future projects may proceed as smoothly as possible. It is the intent of this paper to review some of the history and design criteria employed in this miscible recovery project. Further, the experience obtained during the first year of operation along with associated problems are reviewed. Future field performance and its relation to the existing facility performance and its relation to the existing facility is included to cover the full scope of projects of similar nature.
The Marchand Sands formation in Caddo County, OK, were established as a significant producing zone in the first half of 1975. Based on preliminary reservoir analysis and history of the nearby Norge Field, it became evident that some type of pressure maintenance program was required and detailed reservoir studies were authorized to establish the best method of production. Primary production, waterflood, natural gas injection, and inert gas injection were the production techniques investigated over the next 12 to 18 months.
The reservoir oil has an API gravity of approximately 42 SSU at 60 degrees F having an intermediate hydrocarbon content (C2 – C6) of 30%. The producing formation is tightly packed sandstone with an average permeability of less than 1.0 md. These hydrocarbon and geological considerations are similar to Arco's Block 31 in Crane County, TX. Research of this project along with the laboratory test on the efficiency of the recovery techniques previously mentioned indicated that a miscible gas drive would be the most effective recovery mechanism.
Natural gas was eliminated as a reinjection media based on its current value and, therefore, a substitute inert gas was selected. Flue gas, nitrogen, and CO2 were investigated with flue gas offering the most attractive economic alternate after consideration of all applicable operating and investment parameters.
Concurrent with the evaluation as to the method of production, unitization formulas were developed, discussed, and finally agreed upon with approval of the unit by the majority of the operators in Jan. 1977. The Oklahoma Corp. Commission approved the unit in July and flue gas injection began in September of that year (Fig. 1).
In March 1977, an order was given to proceed with design and construction of a facility to deliver 30 MMscf/D (24 MMscf/D on a long-term contract and 6 MMscf/D on a 3-year contract) at a plant discharge pressure of 4500 psig. Many factors plant discharge pressure of 4500 psig. Many factors were to be considered in the design of this facility with two basic requirements establishing the general plant configuration:earliest possible injection date to allow increased production without further pressure decline in the reservoir, andflexibility in capacity to provide for possible changes in flow requirements.
To meet the early onstream date, the contractor elected to move to the plant site two existing 3-MMscf/D modules that had been in operation at another location. Necessary revisions were made to these modules, and they were installed and placed in operation by Sept. 1977, 6 months after approval to proceed (Fig. 2). proceed (Fig. 2).The principle of plant design for this project is to take the exhaust gas generated by the gas engine driver of the injection compressor, catalytically treat this exhaust gas to remove O2 and NOx, dehydrate the gas, and perform the injection compression. (See Fig 3.) By use of this technique approximately 7.5 to 8:0 MMscf/D of dry inert exhaust gas can be delivered at injection pressures for every 1 MMscf/D of fuel consumed. It is helpful also to note that 500 hp will generate about 1 MMscf/D of dry exhaust gas (15,000 hp giving 30 MMscf/D).