Coal gasificatiom a source of CO2 for enhanced oil recovery? Synfuel plants could supply about 75% of the needed C02 Kit R. Krickenberger Stephen € LI u. ke The MITRE Corporation McLean, Va. 22102 Atmospheric levels of carbon dioxide have been rising in recent years, and many scientists claim that the increase is at least parthlly attributable to the combustion of fossil fuels. Ex-
tensive increases in the use of fossil fuel-either in direct combustion or in the manufacture and combustion of synthetic fuels-may lead to even higher carbon dioxide levels. Several models have been developdto predict the climatic consequences. Although there are a number of uncertainties associated with these models, all of them forecast significant warming. The most realistic models predict a
doubling of the COz content of the atmosphere leading to a 2-3 "C rise in global mean temperatures, with larger increases in the polar regions. Associated with these higher temperatures would be climatic shifts in rainbelts and in the amount of precipitation and evaporation (I, 2 ) . The nation is embarking upon a synthetic fuels program that aims to utilize its massive coal reserves. Al-
FIGURE l
Reposed syngas plant locations and oil fields mosrt amenable to CO. misclbk flooding
1418 EnvironmentalS c l a C ~6 Technologl
-
-
0013-938X1811M)15-141~01.25/0@ 1981 A m e r i m Chemical Society
though, on an end-use energy equivalency basis, high-Btu coal gasification (including product gas combustion) emits up to 27%less C02 to the atmosphere than an equivalent coal-fired electric power generation process, C02 emissions are still considerable. A 250 million cubic feet per day (MMcf/d) coal gasification plant may emit over 19 000 short tons/d of C02 from process vents and 7000 short tons/d from boiler flues; another 18 OOO short tons would he released by the combustion of the produced oil and gas ( 3 , 4 ) . The object of this study isto present a preliminary analysis of the feasibility of reducing COz emissions from
high-Btu coal gasification plants by capturing and transporting the C02 to areas that require it for enhanced oil recovery. This study determines how suitable the emitted C02 is for oil recovery, estimates the cost of C02 capture and transportation, and hypothesizes a pipeline network that would be the most economical. We ascertained the purity of the C 0 2produced by coal gasification by examining plant design data for several proposed high-Btu plants. We extrapolated costs from the costs of operating existing C02 pipeline and re covery systems. The out-of-kilter network flow algorithm described by Ford
and Fulkerson is used to identify minimal-cost flow patterns on the basis of source production levels, line flow capacities, costs of transport, and receptor capacities ( 5 ) . This algorithm is widely employed to solve problems related to transportation.
Sources of carbon dioxide High-Btu coal gnsifmtion (HBG) plants. The American Gas Association (AGA) estimates that, given vigorous support, there could be as many as 33 250 MMcf/d high-Btu coal gasification plants in operation by the year 2000. Possible locations for these plants are shown in Figure 1.
Volume 15. Number 12, December 1981 1418
The high-Btu coal gasification process produces several gaseous waste streams containing COX. These are emitted from gas turbines, steam superheaters, fuel gas heaters, the sulfur plant vent, the sulfur plant incinerator, the emission stream lock, and the residual COz vent. The carbon dioxide content of these streams ranges from 10% to nearly 100% by weight. Because carbon dioxide miscible flooding for enhanced oil recovery requires a COz stream that is at least 90% pure, it is assumed for the purposes of this analysis that only those streams with an estimated CO2 composition equal to or in excess of 90% will be considered as sources (6). It is further assumed that the COz streams produced by the high-Btu coal gasification process are of sufficient purity so as not to require further treatment. Table 1 presents thequantity and composition of COZ-rich gases available from typical Lurgi high-Btu coal gasification plants. The data in
erating in the US. The average daily production of high-quality (290%) COz is estimated to be 300 MMscf/ syngas plant. Daily COz production from 33 svngas Dlants would be 9.9 Bcf. AssumiG a jO-year plant life, the total available CO2 would be 98 Tcf. Naturally occurring sources. Carbon dioxide occurs naturally, and many of these deposits are being considered as sources of COz for enhanced oil recovery. These are shown in Figure 1 and listed in Table 2. The total COz reserve, excluding West Virginia (currently unknown), is 13-21 Tcf-l3-21% of that potentially available from the HBG plants. To transport naturally occurring COz to the Permian Basin in Texas, three pipeline routes have been proposed. Shell Oil has suggested building a 490-mi pipeline from the McElmo Dome area near Cortez, Cola., to the Wasson field in San Andres, Tex. A R C 0 has proposed that a 4 2 0 4 , 20-in. pipelinr "'0 M?"''?
this table are based on actual plant designs for five proposed projects. More accurate estimates cannot be made until a number of commercial HBG ~ l a n t are s constructed and OD-
TABLE 2
Areas naturally producing 60
?eservoirs
amenable t
brmlan Ba8h WSWVOlW 'oienlial recoverableoil :02required per barrel 'Otal coprequired
iouthern Mlsslsdppl~ w e w d = 'otenlial recoverableoil
.oulslana S a l Dom 'otential recoverab :02required per banel -0tai CO? required
Avg hiiverabalk
wave Dome area Reserve
1Hm.t
Avg. deliverabiity
4
Fields amenable to 8.d"
McElmo Dome m a
new
fieserve Bend Arch
Avg. dellverability North Park
1.3-2.5 Tcf 97-99s
4500 n 3-12 MMcfdlweil 250 MMcfd
Paradox Permian SanJUan Sweatgrass Arch Williston Total swrCe:
1420 Environmental Science 8 Technology
from Heurfano County, Colo. (Sheep Mountain), to Yoakum and Gaine Counties, Tex. Amoco has also suggested that a pipeline be built from the Bravo Dome area in southeast New Mexico (Quay, Harding, and Union Counties) to west Texas (7,8). Industrial Sources. In addition to being a byproduct of coal gasification, CO2 is also a byproduct of several other industrial processes, including many of the petrochemical industry. One 200-mi pipeline (SACROC) has been constructed to transport 220 MMcf/d of waste COz from a natural gas processing plant in the Val Verde Basin, Tex., to Scurry County, Tex. The CO2 is transported at pressures greater than 1400psi, in a supercritical state with properties similar to those of the gaseous phase. Oil fields amenable to COz flooding In 1979,385 000 barrels of oil were produced daily in the U S . as a result of enhanced recovery methods. COz miscible flooding was responsible for the production of 21 500 barrels per day, 6%of all enhanced oil production (7). The use of COz for enhanced recovery has been steadily increasing. In 1974, there were six COz recovery projects: there are now 17, including pilot projects, and 20 additional
projects are planned for the future. The U S . Department of Energy is now sponsoring research to ascertain those areas most amenable to COz flooding, the amount of additional oil that might be recovered, and the amount of CO2 required to effect that recovery. Although conclusive data are not yet available, preliminary reviews have been made. Based on field and laboratory tests, reservoirs having the following characteristics are considered to be the k t candidates for CO2 miscible flooding (9). Reservoir characteristics
Value
Depth (ft)
2000+
Thickness (ft) Not critical Permeability (millidarcy) 5+ Homogeneity G d Oil saturation (%) 25+ Oil viscosity (centipose) 5+ Oil gravity (deg API) 35+ Bottom water Not critical Temperature Not critical Using these criteria, three major areas have been identified: the Permian Basin reservoirs.in Texas, which will require 8-96 Tcf of CO2; the Louisiana Salt Dome reservoirs, which will require approximately 0.3-1.8 Tcf of
CO2: and southern Mississippi reservoirs, which will need 1 Tcf of CO2 (Table 3) (IO).In all, 292 individual fields have been identified throughout the continental U S . as targets for CO2 miscible flooding (Table 4) ( 1 1 ) . These target areas and ongoing CO2 miscible projects are shown in Figure 1. Many of the projects coincide with the target areas, but several do not. In view of these discrepancies, the target areas and their characteristics are assumed, for the purposes of this analysis, to be those identified in Table 5. Out-of-kilter algorithm The out-of-kilter algorithm, based on network flow theory, determines transportation networks that are the most economical. A network is comprised of a set of nodes and a set of connecting arcs. An arc represents the flow pathway between two nodes. In this problem, flow is directional and finite, and nodes are of two typasources and sinks. A simplified pictorial representation of these terms is shown below.
Source,.
/
‘=.Sink,
Arcs, therefore, become equivalent to CO2 pipelines: sources and sinks are analogous to locations of high-Btu coal gasification plants and areas amenable to CO2 miscible recovery, respectively. For each possible directed arc, five input parameters must be defined. The source and the sink must be numerically designated; the maximum flow from the source and the receiving capacity of the sink must be identified; and the cost of transportation along the pathway must be quantified. For example, in central North Dakota (Source #I), it is estimated that there may be six 250-MMcf/d syngas plants in existence by the year 2000. Each of the syngas plants will produce 300 MMcf/d of COz, resulting in a total CO2 flow of 1800 MMcf/d from location No. 1 . This flow may be transported to the Williston Basin (Sink #2), which has a receiving capacity of 1429 MMcf/d. The cost of transporting the COz is calculated to be 17$/ Mcf. Associated with each of the 12 locations shown in Figure 1, there is a maximum flow equal to the product of the number of plants designated at that location and 300 MMcf/d of C 0 2 . from each plant. That flow or some Volume 15, Number 12, December 1981 1421
Example of cost data sYrru.l plaw
Mlon
E011
-
Mi
(hp)
1
loo 120
2 2
1 . 0 2 ~105
1.23X IOs 8 . 3 7 ~105 1.37X I O 8
portion of it may go to any or all of the 13 areas amenable to COz miscible flooding. The capacity of these areas or sinks is the daily requirement designated in Table 6. The cast associated with each of the possible 156 pathways is unique and is based on the length of the pipeline and compression requirements. The method of determining these costs is detailed in the following section. Costs of CO2 delivery
Costs were estimated in such a way that they are compatible with the out-of-kilter algorithm and are expressed in Q/Mcf. Capital, operating, compression, and maintenance costs were derived for every possible pipeline route connecting each syngas plant
527 862
with each enhanced oil recovery area. A summary of a few of these cost estimates is shown in Table 6. The following sections describe the baseline data from which these casts were derived. CO2 purification. As previously discussed, C 0 2 emissions from syngas prpcesses may not be suitable for direct injection into a pipeline. It may first be necessary to treat the emissions in order to make the CO2 content greater than 90%. This may be accomplished by methanol amine absorption or hot potassium carbonate removal processes. The former is used at the Val Verde natural gas processing plant, which vents C 0 2in concentrations of 10-13%. To process 25 MMcf/d at this plant, capital costs are $4 000 000
FIGURE 2
Leastcost COI transportaaion network solution to out-of-kilter algorithd
Possible pipelines 0 Existing COI miscible floodingprojects COZ
Oil reserves currently amenable to co2 flooding Oil reserves which may be amenable to COI flooding in the future A Hypothetical locations of HEG plants in 2000
1422
Envlronmental Science 8 Technology
(1975$); operating and maintenance casts are 10$/Mfc (12).Other sources report an investment of $1 5 800 000 (1979$) for CO2 purification and compression to provide a 20 MMcf/d flow. Because of the uncertainty concerning direct utilization of COz, the absence of scale-up factors, and the disparity of existing data, we decided that the costs of C 0 2treatment would not be included in this analysis. This omission does not affect the relative ranking of plants as indicated by the out-of-kilter algorithm. However, if we had decided that other sources of C02 should be considered as competitors with the syngas plants and associated data consequently entered into the algorithm data base, we would have to develop cost data for purification
processes. COz compression. In order for COz to flow through a pipeline in the super-critical phase, pressures in excess of 1200 psi must be maintained. In the SACROC pipeline system, the pressure is held at 1700 psi en route and hwsted to 2400 psi for injection. Compression is accomplished in four stages. The total horsepower required is approximately 81 000. We calculated horsepower/Mcf/mi to be 1690. For purposes of this analysis, we assumed that $630/hp are required for construction. Operating and maintenance costs are assumed to be 7.2$/ Mcf [escalated on the basis of inflation rates reported by the Oil and Gas Journal (Aug. 13, 1979) ( 1 3 ) from 6$/Mcf estimated by the National Petroleum Council, 19761 ( 1 2 ) . pipelining. The National Petroleum Council reports a cost of $330 000/mi for a 200 MMcf/d capacity C02 line ( 1 2 ) .In this analysis, weassumed that a single 20-in. pipeline with a 300 MMcf/d capacity will be built from each syngas plant. Construction costs are estimated at $330 000/mi (1979$), and operating and maintenance costs are estimated at 1.56$/ Mcf/100 mi [escalated on the basis of inflation rates reported by the Oil and Gus Journal (Aug. 13, 1979) (13) from 1.3Q/Mcf/100 mi estimated by the National Petroleum Council, 19761 ( 1 2 ) .
only 7.0 Bcf (70%) could be supplied out of a daily demand of 10.1 Bcf. The Permian Basin-by far the largest sink-could absorb the total quantity of available C02 from the 33 HBG plants. However, the minimal-cost network would require it to claim only 70% of the C02 produced by the 33 facilities.
Summary This paper presents a preliminary analysis of how the concentrated carbon dioxide stream produced by the high-Btu coal gasification process might be used for enhanced oil recovery. Because power plant stack gases are not amenable to C02 recovery and utilization, this concept offers synfuel production a significant advantage over coal electrification by minimizing C02 emissions to the atmosphere. The major findings of the study include the following: High-Btu coal gasification plants would he a source of inexpensive, high quality CO2. Through use of this C02 for enhanced oil recovery, approximately 6.8 billion barrels of oil, which would not otherwise be recovered, could be extracted over a IS-year period (1.24 million barrels per day).
The added cost per barrel would be $5.36. Including pipeline construction, compression, operating, and maintenance costs, the average cost of transporting CO2 to oil fields amenable to C02 miscible flooding is estimated to he $0.67/Mcf of C02. The tdtal C02 available from the 33 HBG plants that could be operating by the year 2000 would be a cumulative 100 Tcf over a 30-year period, two to four times that available from naturally occurring sources. Assuming a IS-year lifetime per well, the daily COZdemand for enhanced oil recovery is estimated to he approximately 13 Bcf. The potential daily C02 supply of 9.9 Bcf from the 33 potential HBG plants could meet 76% of this demand. According to this analysis, only 70% (7 Bcf/d) of the IO Bcf/d total C02 needed by the Permian Basin could he supplied, while the demand for C02 at all other oil field locations (2.9 Bcf/d) would he fully met.
.
Acknowledgment This work was funded by the American Gas Association. The authors would like to thank Dr. Benjamin Schlesinger and MI.
Use of out-of-kilter algorithm The least-cost transportation network calculated from the out-of-kilter algorithm is shown in Figure 2. Out of a possible 156 pipeline routings, the out-of-kilter algorithm identified 23 that comprise the most economical network. The total length of the hypothetical network is 14 845 mi. Over a IS-year period, the total cost to construct and operate the pipeline in the network is estimated at $32.7 billion, and the average cost per Mcf is computed to be 67$. Assuming that 8 Mcf are required for each barrel of oil recovered (Table 3). the added cost per barrel would be $5.36, and approximately 6.8 billion barrels of oil could be recovered over the IS-year period. This amounts to 1.24 million barrels of oil per day or approximately 20% of the 6.3 million barrels now being imported each day (14). By employing this network, all the available COz from the 33 potential syngas plants (9.9 Bcf/d) would be used (Table 7). The syngas operations would supply the full amount of COz needed by every enhanced oil field except for those in receptor 10, the Permian Basin in west Texas, where volume 15. Number 12, December 1981
14239
Nelson Hay ofthat organization as well as Dr. Milton Beychok for their invaluable suggestions. Before publication. this feature article was read and commented on for technical accuracy by Dr. Charles C. Coutant, Oak Ridge National Laboratory. Oak Ridge, Tennessee 37830. References (I) US.Department of Energy”Workshop on the Global Effectsof Carbon Dioxide from Fossil Fuels”. CONF-770385: 1979. (2) The National Research Council “Carbon Dioxide and Climate: A Scientific Arsessment”; 1979. (3) American Gas Association “Energy Analysis: Carbon Dioxide Emissions from Fossil Fuel Combustion and from Coal Gasification”; Sept. 2, 1917. (4) Beychctk. Milton R., report to the American Gas Association: July 11. 1980. (5) Ford, L. R.; Fulkerson, D. R. “Flows in Networks”; Princeton Univ. P m : Princeton, N.J.. 1962. (6) Holm, L. W. “Status of COz and Hydracarbon Miscible Oil Recovery Methcds”, J. Per. Technoi. 1976 Jan. 76-84. (7) “EOR Methods Help Ultimate Recovery”. .OiiCorJ. 1980.Mar.31.79-121. (8) Rcnfro. J. J.“Colorado’s Sheep Mountain CO2 Project Moves Forward”. Oil Cos J. 1979, Dee. 17.51-56. (9) McRee. Boyd C. T O z : How It Works. Where I t Works”, Pet. Eng. 1977, Noo.. 52-63. (10) Zimmerman. F. “Naturallv &urrinQ Carbon Dioxide Sources in ‘the U n d S131C1”. Fifth Annual DOE Symposium Enh i n d 0 1 1 md Car Recovery and Improved D r t l h Tcr.hnaloev. ~ Volume 2.011. . .COKF79080j.~2; 1979.-. (11) Pease.R.W.;Hartsock.J.H.:Goodrich.
J. H.; Lohse. E. A. “Carbonate Target Rerervoirs for COz Miscible Flooding”. Fifth Annual DOE Symposium Enhanced Oil and Gas Recovery and Improved Drilling Technology. Volume 2, Oil. CONF-790805-P2: 1979. (12) . . National Petroleum Council “Enhanced Oil Recovery: An Analysis of the Potential for Enhanced Oil Recoveiy from Known Fields in the United States--1976 to 2000”; 1976. 4 13) “Pioeline Buildine Costs Continue Steeo Climb. Oil Cor 1.fi79, Aug. 1 3 . 6 i - 8 2 . ~ r (14) U.S. Department of Energy. Monthly Energy Review. DOE/EIA-0035 (81/08), Aug. 1981.p.32. Additional reading American Gas Association “Fact B w k Synthetic Pipeline Gas from Coal”; 1979. Amr. A. T. “Potential Impacts of Carbon Dioxide Emissions from the Coal Fuel Cycle” The MITRE Corporation, WP-7dWOOl30 1979. Best. C. N.; Schurger, M. L.; Smith, E.; Szurgat. A. “Hygas Demonstration Plant Project. Process Baseline Report Initial Process Trade-off Studies Environmental Inventory Report, Revision 0.PROCON Project W-2174”; May 1978. Best, C. H.; Schurger, M. L.; Smith, E.; Szurgat, A., Hygas Conceptual Design Report, PROCON; June 19,1979. Crockett. D. H. “COT Profile Control at SACROC“, Per. Eng. 1975, Nou. 44-52. DeBerry, D. W. “Survey and Analysis of Corrosion Problems Caused by C 0 2 Injection for Enhanced Oil Recovery”, 1424 Envlrmmmal Science h Teclmology
Fifth Annual DOE Symposium Enhanced Oil and Gas Recovery and Improved Drilling Technology, Volume 2, Oil, CONF-790805-P2; 1979. Dicharry, R. M.;Perryman, T. L.; Ronguill, J. D. “Evaluation and Design of a C02 Miscible Flood ProjectSACROC Unit, Kelly-Snyder Field”, J. Per. Technol. 1973, No”., 13091318. Ford, H. J.; Grange. F. E.; Erbar, J. H. “Alternative Methods of Supplying C02 for Enhanced Oil Recovery”, Fifth Annual DOE Symposium Enhanced Oil and Gas Recovery and Improved Drilling Technology, Volume 2. Oil, CONF-790805-P2; 1979. Glazer. F.; Hershaft, A,; Shaw, R. “Emissions from Processes Producing Clean Fuels”, EPA-450/3-75-028; 1974. “Growth Marks Enhanced Oil Recovery”, OilGas J. 1978, Mar., 113-140. Hare, M, Perlich, H.; Robinson, R.; Shah, M.; Zimmerman, F. “Sources and Delivery of Carbon Dioxide for Enhanced Oil Recovery”, Pullman Kellogg for U S . Department of Energy. FE2515-24; Dec. 1978. Hardy. J. H.; Robertson, N. “Miscible Displacement by High-pressure Gas at Block 31”, Per. Eng. 1975, Nov., 2428. Herbeck. E. F.; Hientz, R. C.; Hastings, J. R. “Fundamentals of Tertiary Oil Re-very, Part 5, Carbon Dioxide Miscible Process”, Per. Eng. 1976, M a y . 114120. Holm, L. W.; Josendal, Y.A. “Mechanisms of Oil Displacement by Carbon Dioxide”, J. Per. Technol. 1974, Dee., 1427-1438. Kane. A. Y.“Performance Review of a Large-Scale COz-Wag Enhanced Recovery Project, SACROC Unit-KellySnyder Field”, J. Per. Techno/. 1979, Feb.. 217-231. Kastrop, J. E. “Potential Impact of Tertiary Oil Recovery”. Pet. Eng. 1975, Nou., 21-23. Maskowitz, P. D.; Morris, S. C.; Albanese. A. S. “The Global Carbon Dioxide Problem: 1mpacuofU.S. Synthetic Fuel and Coal-Fired Electricity Generating Plants”, J. Air Pollur. Control Assoc. 1980,30(4),353-357. Office of Technology Assessment “Enhanced Oil Recovery Potential in the United States”: 1978. Peddycoart. L. R. “Water Control for ER Production Improvement”, Oil Gas J . 1980, Feb., 52-54. Perry. G. E.; Kedwill, C. M.; “Weeks Island S Sand Reservoir B Gravity Stable Miscible COZDisplacement Iberia Parish. LA”, Fifth Annual DOE Symposium Enhanced Oil and Gas Recovery and Improved Drilling Technology, Volume 2, Oil, CONF-790805-P2: 1979. San Filippo, G. P. “Progress of the Pilot Carbon Dioxide Flood in the Rock. Creek-Big lnjun Field, Roane County, West Virginia”. Fifth Annual DOE Symposium Enhanced Oil and Gas Re-
covery and Improved Drilling Technology, Volume 2. Oil, CONF-790805-P2: 1979. Schumacher, M. M. Enhanced Oil Recovery, Secondary and Tertiary Methods. 1978. SERNCO, Applicant’s Environmental Assessment for a Proposed Gasification Project in Campbell and Converse Counties. Wyo.. Oct. 1974. Shah, M. H.; Cover. A. E. “Sources and Delivery of Carbon Dioxide for Enhanced Oil Recovery“. Fifth Annual DOE Symposium Enhanced Oil and Gas Recovery and Improved Drilling Technology, Volume 2, Oil, CONF790805-P2; 1979. U S . Department of Energy, Enhanced Oil Recovery and Improved Drilling Technology, Progress Review, DOE/ BETC-80/I. 1980. U S . Department of Energy, Carbon Dioxide Research Progress Report, BY1979. DOE/EV-0071,1980. U S . Department of Interior, Bureau of Reclamation, El Paso Coal Gasification Project San Juan County, N. M., Final Environmental Statement, FES77093, Feb. 1977. “US Enhmced Recover) Marked by Unccrtdintiev”. Oti Gas J 1978,.Yepr , 35-39 Warner, H. R. “An Evaluation of Miscible C02 Flooding in Water-flooded Sandstone Reservoirs”, J. Per. Technol. 1977, 29, 1339-1437. West. J. “Line Will Move 240 MMcfd of COT. Oii Gas J. 1971. Nou., 53-56. White. T. M.; Lindsay, R. F. “Enhanced Oil Recovery by CO2 Miscible Displacement in the Little Knife Field Billings County, North Dakota”, Fifth Annual DOE Symposium Enhanced Oil and Gas Recovery and Improved Drilling Technology, Volume 2, Oil, CONF-790805-P2; 1979.
Stephen H. h b o r e ( l e f r ) IJ an associare department head in rhe Enoironmenr Division of rhe M I T R E Corporation, where he has been since 1964. He has direcred numerous enuironmenral impocr assessmenr and modelingprojecrs in supporr of federal sponsors. He received his Ph.D. in Operations Researchfrom Johns Hopkins. Universiry in 1969.
Kit R. Krickenberger (righr) is rhe associare deparrmenr head of the Enuironmental Engineering and Hazardous Waste Departmenr in rhe Enuironmenr Division ofrhe M I T R E Corporalion. She has been wirh M I T R E since 1976. She received her Ph.D. in geochemistry in 1977 from fhe Uniuersiry of Maryland.
