Rigorous Computer Simulation Of CO2 Dehydration Facilities

Abstract

Best, Jim W., Amoco Production Company (USA) Abstract The possible development of the Bravo Dome Carbon Dioxide (CO2) Gas Field located in northeastern New Mexico has led to a detailed study of CO2 dehydration design using computer simulation. Two Commercially available computer programs from the ChemShare Corporation were used to simulate actual CO2 dehydration test results. Amoco is currently in the process of using these programs to aid in preliminary design of a full-scale dehydration facility. Introduction In the early 1970's, Amoco Production Company (USA) and others were successful in leasing CO2 rights underlying more than a million acres of land in northeastern New Mexico in an area called Bravo Dome. The Bravo Dome CO2 Gas Field is the largest known concentration of CO2 anywhere in the world and is located approximately 100 miles northwest of Amarillo, Texas. The field encompasses parts of three New Mexico counties: Union, Harding, and Quay. Carbon dioxide is one of several gases that can be used for enhanced oil recovery of oil bearing formations. The approximately 99 percent pure CO2 in the Bravo Dome Field has potential application in tertiary recovery of oil in the Permian Basin oil fields of West Texas and eastern New Mexico. Therefore, the possible development of this CO2 resource has led to the need for designing facilities to process CO2. The facilities required include CO2 gas gathering, compression, and dehydration. Dehydration of the CO2 with triethylene glycol (TEG) is the subject of this paper. EXPERIMENTAL LABORATORY DATA The first step in developing an economic process design is to obtain thermodynamic data on process design is to obtain thermodynamic data on the components involved. To that end, experimental CO2 dehydration data was obtained from a lab analysis conducted at a major southwestern university. The experimental data collected was vapor-liquid equilibrium (VLE) data for the CO2-TEG-H2O ternary system and the binary CO2-H2O system. Some data on the CO2- TEG system already exists in the literature. DEHYDRATION FIELD TEST Although laboratory data is of interest and value, Amoco has always preferred to verify lab data with actual field data, if at all possible. Because of the importance of this facility to our overall CO2 induced oil recovery process, our management chose to have an actual field test of TEG dehydration of CO2. The field test conducted at the Bravo Dome CO2 Field for six months in 1979, was used to obtain operational, corrosion, and production data. The test consisted of producing one well into a 2" and 4" O.D. pipeline, compressing and dehydrating the CO2 at the test facility approximately 1 1/2 miles away, then injecting the high pressure CO2 into a well near the test facility. Figure 1 shows schematically the test facility. Figure 2 shows partial data obtained from the dehydration part of partial data obtained from the dehydration part of the field test. COMPUTER SIMULATION TECHNIQUE For verification, the laboratory vapor-liquid equilibrium (VLE) data for the CO2-TEG-H2O ternary system was input into ChemShare Corporation's CHEMTRAN program. CHEMTRAN is a computer program for prediction and correlation of physical properties for chemicals and chemical mixtures. CHEMTRAN has the capability to regress tabular multicomponent VLE data to unique binary pair interaction parameters for the Peng-Robinson equation of state. The equation of state approach for regressing VLE data relies on the fundamental relationship shown in Table 1. The resultant Peng-Robinson equation of state's enthalpy prediction was also used. The liquid density values were generated by the Yen Woods correlation, ChemShare's standard estimation technique for liquid densities. These systems among others are readily available when using ChemShare's programs. programs.