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Emmons, Fred R., Phillips Petroleum Company; Phillips Petroleum Company; Hudspeth, Lon D., Phillips Petroleum Company; Phillips Petroleum Company; Clancy, James P., Niject Services Company; Zornes, David R., Phillips Petroleum Company; Phillips Petroleum Company; Philcox, John E., Philcox, John E., Niject Services Company Abstract The East Binger Field located in Caddo County, Oklahoma had an expected primary recovery of only 10.7%. After extensive reservoir, laboratory, and model studies, a plan of unitization was approved an inert gas miscible displacement project was initiated in 1977. Unanticipated operational problems, such as leaks in casings, tubing and packers, plugging of low permeability sand, and other problems were analyzed and solved. Oil and gas production to date is consistent with the production to date is consistent with the predictive models. An anticipated predictive models. An anticipated problem of inert gas breakthrough has been problem of inert gas breakthrough has been handled to date by planned interim methods. In 1984, as a result of engineering and economic studies of several viable alternatives, a decision was made by the East Binger Unit (EBU) to switch to a nitrogen management concept. Under construction, with a late 1986 startup date, is a nitrogen management facility which will replace the existing inert gas supply system as well as replace the interim method of handling produced gas. The facility which is integrated to reduce capital, energy and other operating costs, will provide cryogenically-produced nitrogen from both nitrogen rejection and air separation, 985 Btu/SCF [3.48 × 10(4) MJ/m3] residue gas, pipe-line quality natural gas liquids and pipe-line quality natural gas liquids and 18,000 MSCFD (thousand standard cubic feet per day) [5.1 × 10(5) m3/D] of 5,000 psig [3.45 mPa] nitrogen. With nitrogen management, higher hydrocarbon recoveries and lower lifting costs are expected. Introduction The EBU is located in Caddo County near Binger, Oklahoma. See Figure 1. In 1986, nine years after unitization and initiation of a miscible inert gas EOR project in the EBU, an average of 13,300 project in the EBU, an average of 13,300 MSCFD [3.8 × 10(5) m3/D] of inert gas, obtained from engine exhaust gas, has been injected into the Marchand Sand reservoir. The inert gas consists of about 85% nitrogen, 12% carbon dioxide, 3% carbon monoxide, and a trace of other components. When nitrogen breaks through to a production well, it reduces the heating value production well, it reduces the heating value of the produced gas, eventually rendering it unmarketable. An operator has to consider the alternatives of reinjection of the diluted gas resulting in a loss of income from the unrecovered hydrocarbons versus the installation, of facilities to separate (reject) the nitrogen from the produced gas. Brown and Aberle give produced gas. Brown and Aberle give a good overall discussion of nitrogen rejection facilities. Price, et al. and also Looney, et al. specifically describe the nitrogen rejection facility designed to handle the separation of nitrogen from the produced gas, and installed at the University Block 31 Field in Crane County, Texas, a nitrogen/ hydrocarbon miscible displacement project.

The rapid growth of Carbon Dioxide (CO2) and/or Nitrogen (N2) Enhanced Oil Recovery (EOR) projects has resulted in the need for efficient low cost rejection technology. This is particularly true if the Nitrogen or Carbon Dioxide is produced with a natural gas that has an existing market. Basic rejection cycles are described and compared. Key process and mechanical design considerations, especially those unique to Nitrogen and Carbon Dioxide, are emphasized. The Carbon Dioxide or Nitrogen content in the produced gas increases with time over the life of a project, so the rejection equipment must perform satisfactorily over a broad range of feed compositions. Recycling the rejected Carbon Dioxide or Nitrogen is a cheaper source of injection gas than its original source. A rejection unit can be designed as an add-on unit to existing natural gas processing facilities in which much of the stabilization, pretreatment, and liquid recovery already exists. A sample application for nitrogen rejection is presented including process performance and simple economics for a "typical" case. Introduction The Cryogenic Rejection of Nitrogen or Carbon Dioxide from natural gas has become extremely important to the oil producer. It is customary for produced wellhead gas to be processed to recover the natural gas liquids, often including ethane as well as heavier hydrocarbons. However, "typical" produced gas has only a small percentage of Nitrogen or Carbon Dioxide. Therefore, it can be returned to the reservoir or sold as a product natural gas. Nitrogen and Carbon Dioxide are defined as "inert gases", and their inclusion in the residue gas reduces the heating value, and thus the value of the gas. Many pipeline contracts specify minimum heating value for sales gas. With the advent of EOR projects, Nitrogen and Carbon Dioxide gases are showing up in increasing amounts as these projects mature. Therefore, it becomes essential that the operator prepare for the "break-through" of the gases, and economically handle them. In either case (Carbon Dioxide or Nitrogen) the rejected gas can best be utilized by reinjecting the gas back into the reservoir, and in substance "re-using" the rejected gas. If a produced gas slated for market has a "high" Nitrogen and Carbon Dioxide content, whether it is the result of injecting the inert gas into the reservoir or it is a naturally occurring inert gas, it must be removed. At this point in time, cryogenic separation is the most economically viable and proven method to accomplish this task. APPLICATIONS For this presentation, rejection applications can be divided into three broad categories. Since there are more Nitrogen rejection applications than Carbon Dioxide rejection applications at this point in time, attention will be directed toward the former. Although the equipment and conditions are somewhat different for Carbon Dioxide and Nitrogen, basic cryogenic principles and design criteria are similar. The nitrogen rejection separation process must reach temperature levels of -250F, while the CO2 rejection process must stay above CO2 freezing temperature of -70F. P. 225^