Paradis CO2 Flood Gathering, Injection, and Production Systems

Abstract

Summary Texaco U.S.A. has constructed a CO2 gathering and distribution system along with injection and production facilities for use in the Paradis field CO2 flood. The facilities were constructed concurrently and efficiently. They can be used readily for expansion of the injection into additional Paradis reservoirs. The systems have provided the operational reliability required for long-term projects. Modifications and maintenance have been minimal. The paper describes each system and discussesequipment and reasons for its selection andoperations history. Introduction CO2 injection began in Feb. 1982 in two reservoirs in the Paradis field, St. Charles Parish, LA (Fig. 1). However, the screening, planning, and design of the flood began in May 1979. The initial screening process to identify candidate reservoirs that were amenable to CO2 flooding required three months (Fig. 2). The reservoirs' producing histories and properties were reviewed and compared with guidelines for applying various EOR processes. Laboratory experimentation with reservoir fluid samples was begun. The planning and construction phases of project implementation required 30 months. The main objective of the planning phase was to determine the economic viability of the project. Estimates of equipment and operating cost were prepared. Actual bids for equipment and facility construction were received during project construction. The economics were updated as actual costs became available. Long-lead-time items for the various facilities, such as air emission permits, were applied for during the planning phase to avoid delays in construction. Frequent reviews of the project status were conducted to ensure that the project implementation went smoothly. Any commercial application of CO2 injection requires the securing of a long-term CO2 supply. The identification of such a source for the Paradis CO2 flood was conducted during the screening phase. The two sources were natural deposits in the Jackson Dome area of Mississippi and waste by product from industrial plants along the Mississippi River between Baton Rouge and New Orleans. The source selected was the by product from Monsanto Co. ammonia plants near Luling, LA. Equipment purchase and facilities construction did not begin until a purchase agreement was executed. CO2 Gathering System The CO2 gathering system consists of a gathering line, compression, dehydration, and metering facilities (Fig. 3). The system was constructed within the Monsanto Co.'s facility. Monsanto has two ammonia plants in operation that produce the CO2 as a waste by product. The flow data and an analysis of the gas produced by each plant are listed in Table 1. Plant 1 is 2,000 ft [610 m] from the compressor station site and Plant 2 is approximately 600 ft [183 m] away. To minimize Plant 2 is approximately 600 ft [183 m] away. To minimize the pressure drop, the gathering lines from each of the two plants are 24 in. [61 cm] in diameter. At the intersection plants are 24 in. [61 cm] in diameter. At the intersection of the two lines, the gathering line diameter increases to 30 in. [76 cm]. The gathering line is constructed of carbon steel pipe, which has the best structural attributes. Existing pipe supports and road crossings within the plant were used. pipe supports and road crossings within the plant were used. To protect the gathering line from the extremely corrosive wet CO2 and water that drops out in the line, the pipe was sandblasted internally and coated with an inorganic zinc primer and two epoxy top coats. The weld joints were primer and two epoxy top coats. The weld joints were wire-brushed and sealed with two brush-applied coats of coal tar epoxy. The piping system has not experienced any corrosion problems although it has only been in operation for a little problems although it has only been in operation for a little over 1 year. Stainless steel pipe was considered because of its corrosion resistance but was rejected because of its cost. Plastic pipe also was considered, but it is not structurally Plastic pipe also was considered, but it is not structurally strong enough for the required route through the plant. At the facility inlet, the saturated CO2 goes through a shell and tube inlet heat exchanger to cool the CO2 and knock out entrained water vapor. The heat exchanger was designed to provide a maximum temperature drop and be cost-efficient. It produces 30F [16.7C] temperature drop, which produces a corresponding drop in water content. From the heat exchanger, the CO2 passes to the inlet separator, which collects the water that falls out in the gathering line and heat exchanger. From the inlet separator, the CO2 goes to the suction manifold where it is picked up by the compressors. The suction pressure at the first stage cylinders on each unit is approximately 6 psig [41 kPa]. psig [41 kPa]. JPT p. 1312