Application of Decline Curve Analysis to Estimate Recovery Factors for Carbon Dioxide Enhanced Oil Recovery

Application of Decline Curve Analysis To Estimate Recovery Factors for Carbon Dioxide Enhanced Oil Recovery

By Hossein Jahediesfanjani

Chapter C of Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery Mahendra K. Verma, Editor

Scientific Investigations Report 2017–5062–C

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior RYAN K. ZINKE, Secretary U.S. Geological Survey William H. Werkheiser, Acting Director

U.S. Geological Survey, Reston, Virginia: 2017

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Suggested citation: Jahediesfanjani, Hossein, 2017, Application of decline curve analysis to estimate recovery factors for carbon dioxide enhanced oil recovery, chap. C of Verma, M.K., ed., Three approaches for estimating recovery factors in carbon dioxide enhanced oil recovery: U.S. Geological Survey Scientific Investigations Report 2017–5062, p. C1–C20, https://doi.org/10.3133/sir20175062C.

ISSN 2328-0328 (online) iii

Contents

Background...... C1 Basis for Decline Curve Analysis...... 1 Case Study...... 2 Discussion...... 5 References Cited...... 5 Appendix C1. Decline Curve Analysis of Selected Reservoirs...... 9

Figures

C1. Semi-log plot of the oil production rate versus the oil production time for the San Andres Limestone in the Sable oil field in the west Texas section of the Permian Basin Province, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery

(CO2-EOR) phases...... C3 C2. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Sable oil field, Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced

oil recovery (CO2-EOR) phases...... 4 C3. Bar graph showing the number of studied reservoirs having values of additional oil recovery factors due to carbon dioxide enhanced oil

recovery (CO2-EOR) in five different ranges...... 4 C1–1 to C1–15. Graphs of the oil production rate versus the cumulative oil production showing the decline trends for both the waterflood and the carbon

dioxide enhanced oil recovery (CO2-EOR) phases for the— C1–1. San Andres Limestone in the Sable oil field, Texas...... 13 C1–2. Weber Sandstone in the Rangely oil field, Colorado...... 14 C1–3. Tensleep Formation in the Lost Soldier oil field, Wyoming...... 14 C1–4. Madison Formation in the Lost Soldier oil field, Wyoming...... 15 C1–5. San Andres Limestone in the Wasson oil field, Texas...... 15 C1–6. Clear Fork Group in the Wasson oil field, Texas...... 16 C1–7. Thirtyone Formation in the Dollarhide oil field, Texas...... 16 C1–8. Clear Fork Group in the Dollarhide oil field, Texas...... 17 C1–9. “Canyon-age reservoir” in the Salt Creek oil field, Texas...... 17 C1–10. San Andres Limestone in the Seminole oil field, Texas...... 18 C1–11. Sandstone of the Ramsey Member of the Bell Canyon Formation in the Twofreds oil field, Texas...... 18 C1–12. San Andres Limestone in the Vacuum oil field, New Mexico...... 19 C1–13. San Andres Limestone in the Cedar Lake oil field, Texas...... 19 C1–14. San Andres Limestone in the North Hobbs oil field, New Mexico...... 20 C1–15. San Andres Limestone in the Yates oil field, Texas...... 20 iv

Tables

C1. Best match values of the initial oil production rate, the initial decline rate for oil production, and the corresponding coefficient of determination (R2) values

for both waterflood and carbon dioxide enhanced oil recovery (CO2-EOR) decline periods of the studied reservoirs...... C6 C2. Additional oil recovery factors estimated by using decline curve analysis for

carbon dioxide enhanced oil recovery (CO2-EOR) projects in 15 selected reservoirs...... 7 Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for Carbon Dioxide Enhanced Oil Recovery

By Hossein Jahediesfanjani1

1 − Background q b =+()1 bDi t (C1) qi In the decline curve analysis (DCA) method of estimating where recoverable hydrocarbon volumes, the analyst uses historical production data from a well, lease, group of wells (or pattern), q is the time-dependent oil production rate,r or reservoir and plots production rates against time or cumu- in barrels per day (bbl/day); lative production for the analysis. The DCA of an individual qi is the initial oil prroduction rate, in barrels well is founded on the same basis as the fluid-flow principles per day; that are used for pressure-transient analysis of a single well in a reservoir domain (Fetkovich, 1987; Fetkovich and others, Di is the initial declinne rate per year; 1987) and therefore can provide scientifically reasonable and b represents the degree of curvature of thhe accurate results. However, when used for a group of wells, a shape of the decline trend, lease, or a reservoir, the DCA becomes more of an empirical which is dimensionless; andd method. Plots from the DCA reflect the reservoir response to the oil withdrawal (or production) under the prevailing t is the oil production time, in years. operating and reservoir conditions, and they continue to be Theoretically, the parameters, such as qi , Di , and b, have good tools for estimating recoverable hydrocarbon volumes defined meanings only if equation C1 is applied for a single and future production rates. For predicting the total recov- well that produces from a single reservoir under appropri- erable hydrocarbon volume, the DCA results can help the ate fluid-flow conditions. However, if equation C1 is applied analyst to evaluate the reservoir performance under any of the to larger entities such as a number of wells, a reservoir, or a three phases of reservoir productive life—primary, secondary field, these parameters are only empirical and are obtained by (waterflood), or tertiary (enhanced oil recovery) phases—so a curve-fitting process. Practically, this equation represents long as the historical production data are sufficient to establish three different types of declines depending on the value of b; decline trends at the end of the three phases. namely, an exponential decline for b = 0, a hyperbolic decline for b > 0 and b < 1, and a harmonic decline for b = 1. On the basis of the explanations above and for the sake of simplicity, Basis for Decline Curve Analysis in many of the industrial applications of evaluating reservoir oil production decline, the value of b is often assumed to be The DCA method is used to predict the future oil pro- zero, and, hence, equation C1 takes the form: duction rate of an oil-producing well or reservoir. Theoreti- cally, according to this method, the oil production rate for qq=−iiexp(Dt ) (C2) a given entity will first reach its maximum output and then decline according to the following generalized relationship (Fetkovich, 1987):

1Lynxnet LLC, under contract to the U.S. Geological Survey. C2 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

Equation C2 is rewritten in terms of cumulative oil pro- For a technically recoverable hydrocarbon volume, desig- duction in the following form: nated as Qmax , the recovery factor (RF) under current production conditions is estimated from the following: ()qq− Q = i (C3) Q (C8) Di RF =×max 100 where OOIP Q is the cumulative oil production, in barrells. where

These two equations, C2 and C3, were used for the analy- Qmax is the maximum cumulative oil sis of oil production decline in this current study to determine produuction, in barrels (bbl); the values of constants “D ” and “q ” in the above equations. i i OOIP is the original oil in place, in stock tank For this purpose, these equations can be written as: barrels (STB); and RF is the recovery factorr, expressed as a ln()qq=−ln()iiDt (C4) percentage.

If an incremental recovery factor is required for any qq=−DQ (C5) ii phase (that is, primary, secondary, or tertiary), it is determined as the total calculated RF at phase i minus the total calculated On the basis of equation C4, plotting the oil production RF at the previous phase (i – 1): rate (q) versus production time (t) on a semi-log graph will result in a straight line having an intercept equal to ln(qi) and RFIncrementali=− RF RFi−1 (C9) a slope equal to Di . Alternatively, on the basis of equation C5, plotting the oil production rate (q) versus cumulative oil production (Q) will result in a straight line having an intercept where i is 1 for primary, 2 for seconddary, and 3 for and slope equal to qi and Di , respectively. After values are determined for Di and qi , equations C4 and C5 are used to pre- tertiary production. dict the future oil production rate and the cumulative amount of recoverable oil, respectively. The current assessment meth- For example, if the reservoir is currently under CO2-EOR, odology is designed to assess only the technically recoverable which was initiated after a waterflood, the calculatedRF at hydrocarbon for the carbon dioxide enhanced oil recovery the current stage represents the total recovery, including all (CO -EOR) application, implying no economic limit. If an 2 three stages of primary, waterflood, and CO2-EOR. Therefore, economic evaluation is required in the future, first an appropri- on the basis of equation C9, the additional recovery factor ate economic hydrocarbon production rate (q ) in reservoir ec due to CO2-EOR is obtained by subtracting the calculated RF barrels per day (bbl/day) needs to be defined below which values of the waterflood from theRF value calculated for the hydrocarbon production from a given reservoir is considered CO2-EOR. to be uneconomic. The magnitude of the introduced value of qec depends on each project configuration and specifications and external factors such as hydrocarbon prices that vary from Case Study one project to another. After the value of qec is chosen, the field’s productive life ()t and total economically recoverable ec The Oil and Gas Journal’s 2012 survey of EOR projects hydrocarbon volume ()Q can be calculated by applying the ec (Koottungal, 2012; Kuuskraa, 2012) indicated that about following equations: 123 CO2-EOR projects were active within the United States in 2012. Twenty-four fields (28 reservoirs) of these projects   1 qec were initially selected for DCA. However, after the initial tec =− ln   (C6) Di  qi  investigation, almost half of these projects were excluded from the DCA because they either did not develop long enough CO -EOR decline periods appropriate for the DCA or were not 1 2 Qec =− ()qqie− c (C7) in their decline phases yet. Data for the DCA were obtained D i from the comprehensive resource database (CRD), which was described by Carolus and others (in press); the CRD was developed from two proprietary databases by Nehring Associ- ates Inc. (2012) and IHS Inc. (2012) and provided adequate injection and production data for only 12 fields containing 15 reservoirs. Therefore, the DCA was successfully applied Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C3

only on these fields that have established a good CO2-EOR The oil production data for DCA are from IHS Inc. decline trend. The results of DCA on 15 reservoirs from (2012), and the calculated OOIP values are from the CRD these 12 fields are summarized in table C1 (tables follow the (Carolus and others, in press), which is based on data from the “References Cited”). The DCA for the Sable oil field in the Nehring Associates Inc. database (2012) and IHS Inc. (2012). west Texas section of the Permian Basin Province is presented Because the OOIP values from the CRD are proprietary, the here to show the procedure, and the details of the DCA for all OOIP values of reservoirs are reported qualitatively in table the 15 reservoirs are provided in appendix C1. It is important C2 and appendix C1 as small, medium, and large: a small to note that the Sable oil field was under a CO2-EOR opera- OOIP is less than or equal to 100 MMbbl, a medium OOIP tion from 1984 to 2001 and hence was not an active CO2-EOR is between 100 and 1,000 MMbbl, and a large OOIP is larger project in 2012. However, because it makes a great example than or equal to 1,000 MMbbl. The OOIP of the San Andres of the application of DCA, this field is being analyzed and Limestone of the Sable oil field was estimated volumetrically presented herein. to be less than 100 MMbbl, thus classifying the reservoir in In order to present the DCA procedure and demonstrate the Sable field as a small reservoir. By applying equation C8, its applicability in modeling both waterflood and CO2-EOR the calculated recovery factors are 27.2 and 36.2 percent for decline periods for the Sable oil field, two figures were gener- waterflood and CO2-EOR, respectively (table C2). On the ated and are discussed. Figure C1 shows the semi-log plot of basis of equation C9, the additional recovery-factor value oil production rate versus production time for the Sable oil due to CO2-EOR is 9.0 percent. A similar process has been field. This graph shows that the oil production decline during repeated for the selected 14 reservoirs located in Colorado, waterflood that began in 1976 continued until 1984, when the Wyoming, and the Permian Basin of Texas and New Mexico

CO2-EOR project was initiated. Because of CO2-EOR, the that were under CO2-EOR in 2012. field production remained stable until 1993, when the produc- The additional recoverable oil volumes for CO2-EOR in tion decline started again. 15 selected reservoirs were estimated by using DCA. Recov- Figure C2 shows the oil production rate versus the cumu- ery factors were calculated by dividing the recoverable oil vol- lative oil production for the Sable oil field. As shown in the umes at the end of the waterflood and at the end of CO2-EOR figure, the technically recoverable oil volume has increased by the OOIP of the individual reservoirs. from 9.85 million barrels (MMbbl) for the waterflood phase to

13.1 MMbbl for the CO2-EOR phase.

Date EXPLANATION 1958 1978 1998 2018 2038 2058 2078 2098 Historical oil production 10,000 Beginning of waterflood decline: 1976 Waterflood decline trend—Dashed where extended Beginning of CO2-EOR: 1984 y a Beginning of CO2-EOR decline: 1993 CO -EOR decline trend—Dashed

d 2 r

e 1,000 where extended p s l e r r

a CO -EOR Decline

b 2

n ln(q) = ln(5,580) − 0.0627t i

, 100 2

e R = 0.992 t

a q = 5,580 bbl/day r i

Di = 0.0627/year o n i

c t Waterflood Decline u ln(q) = ln(12,100) − 0.108t

o d 10 r R2 = 0.990 p il qi = 12,100 bbl/day O Di = 0.1080/year

1 0 20 40 60 80 100 120 140 Oil production time, in years

Figure C1. Semi-log plot of the oil production rate versus the oil production time for the San Andres Limestone in the Sable oil field in the west Texas section of the Permian Basin Province, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms used in the decline equations on the graph: Di = initial decline rate per year; q = oil production rate, in barrels per day (bbl/day); qi = initial oil production rate, in barrels per day (bbl/day); R2 = coefficient of determination; t = oil production time, in years. C4 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

1,800 EXPLANATION Historical oil production 1,600 Waterflood decline trend—Dashed

ay 1,400 where extended d

CO2-EOR decline trend—Dashed 1,200 where extended

Beginning of CO2-EOR: 1984 1,000

CO2-EOR Decline 800 y = −182.4x + 2,390 R2 = 0.99 q = 2,390 bbl/day Waterflood Decline i 600 D = 182.4/year y = −299.8x + 2,950 i R2 = 0.99

production rate, in barrels per barrels in rate, production il 400 q = 2,950 bbl/day

O i

Di = 299.8/year 200 Q@(q=0) = Q@(q=0) = 9.85 MMbbl 13.1 MMbbl 0 0 2 4 6 8 10 12 14 Cumulative oil production, in millions of barrels

Figure C2. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Sable oil field,

Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms used in the decline equations on the graph: Di = initial decline rate per year; q = oil production rate, in barrels per day (bbl/day); qi = initial oil production rate, in barrels per day (bbl/day); Q = cumulative oil production, in millions of barrels (MMbbl); R2 = coefficient of determination; x = cumulative oil production in the trendline equation, in millions of barrels; y = oil production rate in the trendline equation, in barrels per day.

7 6 5 4 3 2 1 Number of studied projects studied of Number 0 ≥ 5 to 10 ≥ 10 to 15 ≥ 15 to 20 ≥ 20 to 25 ≥ 25

Ranges of additional recovery-factor values for CO2-EOR, in percent

Figure C3. Bar graph showing the number of studied reservoirs having values of additional oil recovery factors due to carbon dioxide enhanced oil recovery (CO2-EOR) in five different ranges. Recovery-factor values estimated by decline curve analysis are from table C2. Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C5

Discussion From the lithology point of view, the majority of the studied reservoirs (12 out of 15) are carbonates and only 3 are Generally speaking, the DCA is utilized in this study as sandstone reservoirs. This small sample size of sandstone reservoirs makes the comparison of the CO -EOR performance in a method that enables calculating both current and projected 2 values of reservoir oil recovery-factor values at the end of a these two lithological classes practically impossible. waterflood period and a subsequent CO2-EOR period. Table C1 summarizes the best match values of the initial oil production rate (qi) and the initial decline rate for oil production (Di) References Cited and the corresponding values of the coefficient of determination (R2) values in the DCA equation for both waterflood Carolus, Marshall, Biglarbigi, Khosrow, Warwick, P.D., and CO -EOR decline periods of the studied reservoirs. As 2 Attanasi, E.D., Freeman, P.A., and Lohr, C.D., in press, explained above, the q and D values are empirical match- i i Overview of a comprehensive resource database for the ing parameters and do not carry any physical meanings. For assessment of recoverable hydrocarbons produced by car- comparison purposes, it can be observed from this table that bon dioxide enhanced oil recovery: U.S. Geological Survey the overall average values of q and D are 72,500 bbl/day and i i Techniques and Methods, book 7, chap. C16. 360.7/year for the waterflood period and 125,400 bbls/day and

190.5/year for the CO2-EOR period, respectively. It is impor- Fetkovich, M.J., 1980, Decline curve analysis using type tant to note that the overall average values of R2 are 0.951 and curves: Journal of Petroleum Technology, v. 32, no. 6 (June 0.952 for the waterflood and CO2-EOR periods, respectively, 1980), p. 1065–1077, paper SPE–4629–PA. indicating a good to excellent match for the waterflood and Fetkovich, M.J., Vienot, M.E., Bradley, M.D., and Kiesow, CO2-EOR periods. This observation highlights an important point that the basic DCA method as it has been routinely U.G., 1987, Decline curve analysis using type curves—Case applied to model waterflood decline in performance analysis histories: SPE (Society of Petroleum Engineers) Formation Evaluation, v. 2, no. 4 (December 1987), p. 637–656, paper can also be utilized to model the CO2-EOR decline period with similar accuracy. SPE–13169–PA. The calculated recovery factors for the technically recov- Holm, L.W., and Josendal, V.A., 1974, Mechanisms of oil erable oil volumes for the waterflood and CO -EOR phases 2 displacement by carbon dioxide: Journal of Petroleum Tech- and the additional oil recovery for the CO -EOR phase for all 2 nology, v. 26, no. 12 (December 1974), p. 1427–1438, paper 15 studied reservoirs are reported in table C2. The results of SPE–4736–PA. this table indicate that the incremental oil recovery factor by

CO2-EOR ranges from 6.6 percent for the Weber Sandstone in IHS Inc., 2012, PIDM [Petroleum Information Data Model] the Rangely field to 25.7 percent for the San Andres Lime- relational U.S. well data [data current as of December 23, stone (dolomite) in the Wasson field, whereas the average 2011]: Englewood, Colo., IHS Inc. overall calculated recovery factor for the studied reservoirs is 13.2 percent. The ranges of the additional recovery factor Koottungal, Leena, ed., 2012, 2012 worldwide EOR survey: Oil and Gas Journal, v. 110, no. 4 (April 2, 2012), p. 1–4, due to CO2-EOR from DCA along with the values from the accessed in 2014 at http://www.ogj.com/articles/print/vol- review of literature on CO2-EOR in chapter D are utilized to substantiate the estimated values from the reservoir modeling 110/issue-4/general-interest/special-report-eor-heavy-oil- as described in chapter B. survey/2012-worldwide-eor-survey.html. Data from table C2 reveal that the average additional Kuuskraa, Vello, 2012, QC updates carbon dioxide projects in recovery factor with CO -EOR from the seven dolomite res- 2 OGJ’s enhanced oil recovery survey: Oil and Gas Journal, ervoirs producing from the San Andres Limestone is around v. 110, no. 7 (July 2, 2012), p. 1–4, accessed [in 2014] at 13.5 percent, whereas the other five carbonate reservoirs have http://www.ogj.com/articles/print/vol-110/issue-07/drilling- an average additional recovery of 14.3 percent. The aver- production/qc-updates-carbon-dioxide-projects.html. age additional recovery factor for the 3 clastic (sandstone) reservoirs is 10.9 percent, which is lower than the 13.8 percent Nehring Associates Inc., 2012, Significant oil and gas fields for the 12 carbonate reservoirs. However, the data are limited of the United States database [data current as of December in terms of samples and, therefore, it is hard to make any 2012]: Colorado Springs, Colo., Nehring Associates Inc. conclusive observations. In figure C3, the reservoirs that were evaluated for DCA are grouped according to their RF values for CO2-EOR, and the graph shows that most of them are in the lower range (13 out of 15 are less than 20 percent)—6 are in the range of ≥5 to 10 percent, 4 are in the range of ≥10 to 15 percent, and 3 are in the range of ≥15 to 20 percent. C6 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

Table C1. Best match values of the initial oil production rate, the initial decline rate for oil production, and the corresponding 2 coefficient of determination (R ) values for both waterflood and carbon dioxide enhanced oil recovery (CO2-EOR) decline periods of the studied reservoirs.

[The selection of the 15 studied reservoirs and the sources of data are described in chapter C of this report. Fourteen of the reservoirs had active CO2-EOR proj-

ects in 2012. The reservoir in the Sable oil field did not have an active CO2-EOR project in 2012, but it is included because it is a good example. The values in this table were determined by decline curve analysis. Each reservoir is described as a case study in appendix C1. State abbreviations: CO, Colorado; NM, New

Mexico; TX, Texas; WY, Wyoming. Variables: Di , initial decline rate per year in oil production; qi , initial oil production rate, in barrels per day (bbl/day)]

Case study Waterflood CO -EOR Stratigraphic unit 2 number in Oil field State containing the q D q D appendix i i 2 i i 2 reservoir R R C1 (bbl/day) (/year) (bbl/day) (/year) 1 Sable* TX San Andres Limestone 2,950 299.8 0.99 2,390 182.4 0.99 2 Rangely CO Weber Sandstone 89,500 215.9 0.98 88,000 169.9 0.92 3 Lost Soldier WY Tensleep Formation 18,000 427.8 0.95 23,000 314.3 0.96 4 Lost Soldier WY Madison Formation 6,900 497.9 0.98 8,500 329.9 0.96 5 Wasson TX San Andres Limestone 421,000 300.9 0.98 120,000 43.1 0.95 6 Wasson TX Clear Fork Group 26,000 279.3 0.99 20,000 65.0 0.93 7 Dollarhide TX Thirtyone Formation 23,000 405.9 0.89 11,000 87.6 0.85 8 Dollarhide TX Clear Fork Group 7,500 426.8 0.95 9,000 213.3 0.97 9 Salt Creek TX “Canyon-age reservoir” 49,000 154.3 0.94 116,000 295.1 0.96 10 Seminole TX San Andres Limestone 106,000 232.3 0.87 97,000 129.4 0.96 11 Twofreds TX Ramsey Member 6,000 1,042.5 0.91 2,400 176.1 0.96 12 Vacuum NM San Andres Limestone 61,000 271.6 0.96 44,000 132.7 0.97 13 Cedar Lake TX San Andres Limestone 14,000 217.6 0.99 14,500 94.8 0.96 14 North Hobbs NM San Andres Limestone 1,200 387.3 0.97 1,900 402.6 0.96 15 Yates TX San Andres Limestone 256,000 250.2 0.91 244,000 221.7 0.98 Average 72,500 360.7 0.951 125,400 190.5 0.952

* The Sable oil field was under a CO2-EOR operation from 1984 to 2001 and hence is not included in the list of CO2-EOR projects that were active in 2012. Because it makes a great example of the application of decline curve analysis, this field is being analyzed and presented in chapter C and appendix C1 of this report. Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C7

Table C2. Additional oil recovery factors estimated by using decline curve analysis for carbon dioxide enhanced oil recovery

(CO2-EOR) projects in 15 selected reservoirs. [The selection of the 15 studied reservoirs and the sources of data are described in chapter C of this report. Each reservoir is described as a case study in appendix C1. Reservoirs are classified on the basis of the estimated original oil in place OOIP( ) as small, medium, or large; a small reservoir has less than or equal to100 million barrels (MMbbl) of OOIP, a medium reservoir has between 100 and 1,000 MMbbl of OOIP, and a large reservoir has more than or equal to 1,000 MMbbl of OOIP. State abbreviations: CO, Colorado; NM, New Mexico; TX, Texas; WY, Wyoming. Terms: RF, recovery factor; WF, waterflood; %, percent]

Case study Additional Stratigraphic unit Reservoir RF after number in RF after WF RF due to Oil field State containing the Lithology size CO -EOR appendix (%)* 2 CO -EOR reservoir classification (%)* 2 C1 (%) 1 Sable** TX San Andres Limestone Dolomite Small 27.2 36.2 9.0 2 Rangely CO Weber Sandstone Sandstone Large 26.2 32.8 6.6 3 Lost Soldier WY Tensleep Formation Sandstone Medium 17.7 30.0 12.3 4 Lost Soldier WY Madison Formation Limestone- Medium 8.6 16.2 7.6 dolomite 5 Wasson TX San Andres Limestone Dolomite Large 26.2 51.9 25.7 6 Wasson TX Clear Fork Group Dolomite Large 9.3 30.0 20.7 7 Dollarhide TX Thirtyone Formation Dolomite Medium 14.8 31.9 17.1 8 Dollarhide TX Clear Fork Group Dolomite Medium 11.4 27.7 16.3 9 Salt Creek TX “Canyon-age reservoir” Limestone Large 21.4 31.2 9.8 10 Seminole TX San Andres Limestone Dolomite Large 18.9 31.0 12.1 11 Twofreds TX Ramsey Member Sandstone Small 12.4 26.2 13.8 12 Vacuum NM San Andres Limestone Dolomite Large 19.5 28.9 9.4 13 Cedar Lake TX San Andres Limestone Dolomite Medium 19.5 27.9 8.4 14 North Hobbs NM San Andres Limestone Dolomite Small 15.2 33.2 18.0 15 Yates TX San Andres Limestone Dolomite Large 19.7 31.6 11.9 Average for clastic (sandstone) reservoirs 18.8 29.7 10.9 Average for carbonate (mostly dolomite) reservoirs 17.6 31.4 13.8 Average for all 15 reservoirs 17.9 31.1 13.2

* The obtained recovery factors are based on the projection that both waterflood and CO2-EOR continue until oil production of zero (q = 0 barrels). ** The Sable oil field was under a CO2-EOR operation from 1984 to 2001 and hence is not included in the list of CO2-EOR projects that were active in 2012. Because it makes a great example of the application of decline curve analysis, this field is being analyzed and presented in chapter C and appendix C1 of this report.

Appendix C1. Decline Curve Analysis of Selected Reservoirs C10 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

Appendix C1. Decline Curve Analysis of Selected Reservoirs

The 15 reservoirs for case studies of decline curve analy- both waterflood and CO2-EOR declines and the relevant DCA sis (DCA) were chosen because adequate geologic, reservoir, equations and parameters are presented in figure C1–1. and production data were available for them. They all possess specific data on reservoir and fluid properties and vary signifi- cantly in terms of (1) size, as is obvious from their reported Case Study 2. Weber Sandstone, Rangely original oil in place (OOIP), (2) rock types, as they contain Oil Field both clastic and carbonate reservoirs, (3) geographical loca- tions, being distributed in different basins throughout Texas, The Weber Sandstone in the Rangely oil field in Colo- New Mexico, Wyoming, and Colorado, and (4) source of car- rado is an oil-bearing sandstone formation that was under bon dioxide (CO ), as they use both natural and industrial CO . CO2-EOR operations in 2012. On the basis of its OOIP, 2 2 the Weber Sandstone in this field is classified as a large oil Miscible carbon dioxide enhanced oil recovery (CO2-EOR) operations were used in 14 reservoirs, and an immiscible reservoir. The waterflood decline of the field started in 1978 operation was used in 1 reservoir (case study 15). Fourteen and continued until 1986, when the CO2-EOR operation started in various sections of the reservoir. As a result of the of the reservoirs had active CO2-EOR projects in 2012. The reservoir in the Sable oil field (case study 1) did not have an CO2-EOR, the field’s oil production rate increased approximately 10 percent over the course of 5 years until 1991, when active CO2-EOR project in 2012, but it is included because it is a good example. The 15 reservoirs all make great examples the decline in production started again. This reservoir was and case studies in demonstrating the applicability of DCA in among the largest clastic reservoirs undergoing CO2-EOR in predicting the behavior of decline periods for both waterflood 2012. The details of both waterflood and CO2-EOR declines and the obtained relevant DCA equations and parameters are and CO2-EOR phases. The DCA was applied to the period of declining produc- presented in figure C1–2. tion of each reservoir separately, and the DCA parameters were obtained by curve fitting. The goodness of the obtained Case Study 3. Tensleep Formation, Lost Soldier fit is presented by values for the coefficient of determination, R2, which are reported separately on the graph for each Oil Field reservoir analyzed (figs. C1–1 to C1–15). The closer the value The Tensleep Formation in the Lost Soldier oil field in of R2 is to 1, the better the quality of the fit. The obtained DCA Wyoming is an oil-bearing sandstone formation that was under parameters were utilized to forecast the cumulative oil produc- CO -EOR operations in 2012. On the basis of its OOIP, the tion when the oil production rates were available over the life 2 Tensleep Formation in this field is classified as a medium- of the reservoir for both waterflood and CO -EOR phases; for 2 sized oil reservoir. The waterflood decline of the field started this study, the economic hydrocarbon production rate (q ) is ec in 1978 and continued until 1988, when the CO -EOR opera- assumed to be 0 reservoir barrels per day. This process also 2 tion started in various sections of the reservoir. As a result of made it possible to estimate the reservoir’s additional oil the CO -EOR, the field’s oil production rate increased approxi- recovery due to the CO -EOR operation that was modeled. 2 2 mately 300 percent over the course of 3 years until 1991, when It is important to note that this study does not present the the decline in production started again. The production profile technical and operational details of reservoirs described in the of this reservoir shows two distinct and classical declines for case studies. Nor does it provide a detailed insight into the both waterflood and CO2-EOR periods. The details of both extent of the CO2-EOR operation for each investigated project. waterflood and CO2-EOR declines and the obtained relevant DCA equations and parameters are presented in figure C1–3. Case Study 1. San Andres Limestone, Sable Oil Field Case Study 4. Madison Formation, Lost Soldier The San Andres Limestone in the Sable oil field in Oil Field Texas is an oil-bearing dolomite formation that was under The Madison Formation in the Lost Soldier oil field in CO -EOR operation between 1984 and 2001. On the basis of 2 Wyoming is an oil-bearing carbonate (limestone-dolomite) its OOIP, the San Andres Limestone in this field is considered formation that was under CO -EOR operations in 2012. On the a relatively small oil reservoir. The production decline under 2 basis of its OOIP, the Madison Formation in this field is clas- waterflood started in 1976 and continued until 1984 when the sified as a medium-sized oil reservoir. The waterflood decline CO -EOR operation was initiated in various sections of the 2 of the field started in 1984 and continued until 1989, when the reservoir. As a result of the CO -EOR, the field’s oil produc- 2 CO -EOR operation started in various sections of the reser- tion rate remained stable over the course of 9 years until 1993, 2 voir. As a result of the CO -EOR, the field’s oil production when the oil production began to decline again. The details of 2 rate increased approximately 40 percent over the course of 16 Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C11

years until 2005, when the decline in production started again. clearly the effect of CO2-EOR on a reservoir’s oil production The production profile of this reservoir shows two distinct and rate and cumulative production. The details of both waterflood classical declines for both waterflood and CO2-EOR periods. and CO2-EOR declines and the obtained relevant DCA equa-

The details of both waterflood and CO2-EOR declines and the tions and parameters are presented in figure C1–7. obtained relevant DCA equations and parameters are presented in figure C1–4. Case Study 8. Clear Fork Group, Dollarhide Oil Field Case Study 5. San Andres Limestone, Wasson Oil Field The Clear Fork Group in the Dollarhide oil field in the Permian Basin in Texas is an oil-bearing carbonate (dolomite)

The San Andres Limestone in the Wasson oil field in the formation that was under CO2-EOR operations in 2012. On the Permian Basin in Texas is an oil-bearing carbonate (dolomite) basis of its OOIP, the Clear Fork Group in this field is classi- formation that was under CO2-EOR operations in 2012. On fied as a medium-sized oil reservoir. The waterflood decline of the basis of its OOIP, the San Andres Limestone in this field the field started in 1970 and continued until 1977. On the basis is classified as a large oil reservoir. The waterflood decline of of the available production data, it is not possible to investi- the field started in 1975 and continued until 1983, when the gate what happened between 1977 and 1995, during which

CO2-EOR operation started in various sections of the reservoir. time the reservoir oil production rate stopped declining and

As a result of the CO2-EOR, the field’s oil production decline increased slightly. This change in the oil production decline rate has decreased since. The San Andres Limestone in the could be due to infill drilling and (or) changes in the water- Wasson field is one of the largest carbonate reservoirs under- flood scheme in different sections of the reservoir. In Novem- going CO2-EOR worldwide. The details of both waterflood ber 1995, the CO2-EOR operation started in this reservoir. As a and CO2-EOR declines and the obtained relevant DCA equa- result of the CO2-EOR, the field’s oil production rate increased tions and parameters are presented in figure C1–5. approximately 139 percent over the course of 4 years until 1999, when it started to decline again. The details of both

waterflood and CO2-EOR declines and the obtained relevant Case Study 6. Clear Fork Group, Wasson DCA equations and parameters are presented in figure C1–8. Oil Field

The Clear Fork Group in the Wasson oil field in the Case Study 9. “Canyon-age reservoir,” Salt Permian Basin in Texas is an oil-bearing carbonate (dolomite) Creek Oil Field formation that was under CO2-EOR operations in 2012. On the basis of its OOIP, the Clear Fork Group in this field is classi- The “Canyon-age reservoir” in the Salt Creek oil field fied as a large oil reservoir. The waterflood decline of the field in the Permian Basin in Texas is an oil-bearing carbonate started in 1968 and continued until 1984, when the CO2-EOR (limestone) formation that was under CO2-EOR operations in operation started in various sections of the reservoir. As a 2012. On the basis of its OOIP, the “Canyon-age reservoir” in result of the CO2-EOR, the field’s oil production rate increased this field is classified as a large oil reservoir. The waterflood approximately 93 percent over the course of 13 years until decline of the field started in 1972 and continued until 1993,

1997, when it started to decline again. The details of both when the CO2-EOR operation started in various sections of the waterflood and CO2-EOR declines and the obtained relevant reservoir. As a result of the CO2-EOR, the field’s oil produc- DCA equations and parameters are presented in figure C1–6. tion rate increased approximately 38 percent over the course of 4 years until 1997, when it started to decline again. The

details of both waterflood and CO2-EOR declines and the Case Study 7. Thirtyone Formation, Dollarhide obtained relevant DCA equations and parameters are presented Oil Field in figure C1–9.

The Thirtyone Formation in the Dollarhide oil field in the Permian Basin in Texas is an oil-bearing chert and carbonate Case Study 10. San Andres Limestone,

(dolomite) formation that was under CO2-EOR operations in Seminole Oil Field 2012. On the basis of its OOIP, the Thirtyone Formation in this field is classified as a medium-sized oil reservoir. The water- The San Andres Limestone in the Seminole oil field in the flood decline of the field started in 1965 and continued until Permian Basin in Texas is an oil-bearing carbonate (dolomite)

1985, when the CO2-EOR operation started in various sections formation that was under CO2-EOR operations in 2012. On of the reservoir. As a result of the CO2-EOR, the field’s oil the basis of its OOIP, the San Andres Limestone in this field production rate increased approximately 118 percent over the is classified as a large oil reservoir. The waterflood decline of course of 13 years until 1998, when it started to decline again. the field started in 1977 and continued until 1983, when the

This reservoir is one of the best examples to demonstrate CO2-EOR operation started in various sections of the reservoir. C12 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

As a result of the CO2-EOR, the field’s oil production rate The details of both waterflood and CO2-EOR declines and the increased approximately 37 percent over the course of 8 years obtained relevant DCA equations and parameters are presented until 1991, when it started to decline again. The details of both in figure C1–13. waterflood and CO2-EOR declines and the obtained relevant DCA equations and parameters are presented in figure C1–10. Case Study 14. San Andres Limestone, North Hobbs Oil Field Case Study 11. Ramsey Member, Twofreds Oil Field The San Andres Limestone in the North Hobbs oil field in the Permian Basin in New Mexico is an oil-bearing carbon-

The Ramsey Member of the Bell Canyon Formation in ate (dolomite) formation that was under CO2-EOR operations the Twofreds oil field in the Permian Basin in Texas contains in 2012. On the basis of its OOIP, the San Andres Limestone an oil-bearing sandstone that was under CO2-EOR operations in this field is classified as a small oil reservoir. The water- in 2012. On the basis of its OOIP, the sandstone of the Ramsey flood decline of the field started in 2000 and continued until

Member in this field is classified as a small oil reservoir. The 2003, when the CO2-EOR operation started in various sections waterflood decline of the field started in 1967 and continued of the reservoir. As a result of the CO2-EOR, the field’s oil until 1974, when the CO2-EOR operation started in vari- production rate increased approximately 104 percent over the ous sections of the reservoir. As a result of the CO2-EOR, course of 3 years until 2006, when it started to decline again. the field’s oil production rate increased approximately 323 The details of both waterflood and CO2-EOR declines and the percent over the course of 11 years until 1985, when it started obtained relevant DCA equations and parameters are presented to decline again. The details of both waterflood and CO2-EOR in figure C1–14. declines and the obtained relevant DCA equations and parameters are presented in figure C1–11. Case Study 15. San Andres Limestone, Yates Oil Field Case Study 12. San Andres Limestone, Vacuum Oil Field The San Andres Limestone in the Yates oil field in the Permian Basin in Texas is an oil-bearing carbonate (dolo-

The San Andres Limestone in the Vacuum oil field in mite) formation that was under CO2-EOR operations in 2012. the Permian Basin in New Mexico is an oil-bearing carbonate It should be noted that unlike the previous examples, the

(dolomite) formation that was under CO2-EOR operations in CO2-EOR operation in this field is immiscible. On the basis of 2012. On the basis of its OOIP, the San Andres Limestone in its OOIP, the San Andres Limestone in this field is classified as this field is classified as a large oil reservoir. The waterflood a large oil reservoir. The waterflood decline of the field started decline of the field started in 1983 and continued until 1997, in 2000 and continued until 2004, when the CO2-EOR opera- when the CO2-EOR operation started in various sections of the tion started in various sections of the reservoir. As a result of reservoir. As a result of the CO2-EOR, the field’s oil produc- the CO2-EOR, the field’s oil production rate increased approxi- tion rate stayed stable until 2001, when it started to decline mately 48 percent over the course of 2 years until 2006, when again. The details of both waterflood and CO2-EOR declines it started to decline again. The details of both waterflood and and the obtained relevant DCA equations and parameters are CO2-EOR declines and the obtained relevant DCA equations presented in figure C1–12. and parameters are presented in figure C1–15.

Case Study 13. San Andres Limestone, Cedar Reference Cited Lake Oil Field IHS Inc., 2012, PIDM [Petroleum Information Data Model] The San Andres Limestone in the Cedar Lake oil field in relational U.S. well data [data current as of December 23, the Permian Basin in Texas is an oil-bearing carbonate (dolo- 2011]: Englewood, Colo., IHS Inc. mite) formation that was under CO2-EOR operations in 2012. On the basis of its OOIP, the San Andres Limestone in this field is classified as a medium-sized oil reservoir. The waterflood decline of the field started in 1983 and continued until

1994, when the CO2-EOR operation started in various sections of the reservoir. As a result of the CO2-EOR, the field’s oil production rate increased approximately 25 percent over the course of 7 years until 2001, when it started to decline again. Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C13

1,800 EXPLANATION Historical oil production 1,600 Waterflood decline trend—Dashed

ay 1,400 where extended d

CO2-EOR decline trend—Dashed 1,200 where extended

Beginning of CO2-EOR: 1984 1,000

CO2-EOR Decline 800 y = −182.4x + 2,390 R2 = 0.99 q = 2,390 bbl/day Waterflood Decline i 600 D = 182.4/year y = −299.8x + 2,950 i R2 = 0.99

production rate, in barrels per barrels in rate, production il 400 q = 2,950 bbl/day

O i

Di = 299.8/year 200 Q@(q=0) = Q@(q=0) = 9.85 MMbbl 13.1 MMbbl 0 0 2 4 6 8 10 12 14 Cumulative oil production, in millions of barrels

Figure C1–1. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Sable oil field,

70,000 EXPLANATION Historical oil production

60,000 Waterflood decline trend—Dashed where extended

CO2-EOR decline trend—Dashed 50,000 where extended

Beginning of CO2-EOR: 1986 40,000

CO2-EOR Decline y = −169.9x + 88,000 R2 = 0.92 30,000 Waterflood Decline qi = 88,000 bbl/day

y = −215.9x + 89,500 Di = 169.9/year R2 = 0.98

20,000 qi = 89,500 bbl/day production rate, in barrels per day per barrels in rate, production il D = 215.9/year

O i

10,000 Q@(q=0) = 414 MMbbl Q@(q=0) = 519 MMbbl

0 0 100 200 300 400 500 Cumulative oil production, in millions of barrels

Figure C1–2. Graph of the oil production rate versus the cumulative oil production for the Weber Sandstone in the Rangely oil field,

Colorado, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1. For completeness, this figure is included in the appendix even though it is also shown as text-figure C2.

14,000 EXPLANATION

Beginning of CO -EOR: 1988 Historical oil production 12,000 2 Waterflood decline trend—Dashed where extended 10,000

CO2-EOR decline trend—Dashed CO -EOR Decline where extended 8,000 2 y = −314.3x + 23,000 R2 = 0.96 6,000 q = 23,000 bbl/day Waterflood Decline i D = 314.3/year y = −427.8x + 18,000 i 4,000 R2 = 0.95

qi = 18,000 bbl/day

Di = 427.8/year production rate, in barrels per day per barrels in rate, production il 2,000 Q@(q=0) = O Q@(q=0) = 42.6 MMbbl 71.9 MMbbl 0 0 10 20 30 40 50 60 70 80 Cumulative oil production, in millions of barrels

Figure C1–3. Graph of the oil production rate versus the cumulative oil production for the Tensleep Formation in the Lost Soldier oil field, Wyoming, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1. Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C15

3,500 EXPLANATION

Beginning of CO2-EOR: 1989 Historical oil production 3,000

ay Waterflood decline trend—Dashed d CO2-EOR Decline where extended y = −329.9x + 8,500 2,500 2 R = 0.96 CO2-EOR decline trend—Dashed

qi = 8,500 bbl/day where extended D = 329.9/year 2,000 i

1,500

Waterflood Decline 1,000 y = −497.9x + 6,900 R2 = 0.98 production rate, in barrels per barrels in rate, production il

O q = 6,900 bbl/day 500 i Di = 497.9/year

Q@(q=0) = 13.8 MMbbl Q@(q=0) = 25.9 MMbbl 0 0 5 10 15 20 25 Cumulative oil production, in millions of barrels

Figure C1–4. Graph of the oil production rate versus the cumulative oil production for the Madison Formation in the Lost Soldier oil field, Wyoming, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1.

300,000 EXPLANATION Historical oil production

ay 250,000 Waterflood decline trend—Dashed

d where extended

CO2-EOR decline trend—Dashed 200,000 where extended Waterflood Decline y = −300.9x + 421,000 R2 = 0.98 150,000 qi = 421,000 bbl/day CO2-EOR Decline Di = 300.9/year y = −43.1x + 120,000 R2 = 0.95

100,000 qi = 120,000 bbl/day D = 43.1/year Beginning of i

CO2-EOR: 1983 production rate, in barrels per barrels in rate, production il

O 50,000 Q@(q=0) = 2,780 MMbbl Q@(q=0) = 1,400 MMbbl 0 0 500 1,000 1,500 2,000 2,500 3,000 Cumulative oil production, in millions of barrels

Figure C1–5. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Wasson oil field, Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1. C16 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

16,000 EXPLANATION Beginning of CO -EOR: 1984 2 Historical oil production 14,000 ay Waterflood decline trend—Dashed d 12,000 where extended CO -EOR Decline 2 CO2-EOR decline trend—Dashed 10,000 y = −65.0x + 20,000 where extended R2 = 0.93 q = 20,000 bbl/day 8,000 i Di = 65.0/year

6,000 Waterflood Decline y = −279.3x + 26,000 4,000 R2 = 0.99 qi = 26,000 bbl/day production rate, in barrels per barrels in rate, production il D = 279.3/year O 2,000 i Q@(q=0) = 93 MMbbl Q@(q=0) = 300 MMbbl 0 0 50 100 150 200 250 300 Cumulative oil production, in millions of barrels

Figure C1–6. Graph of the oil production rate versus the cumulative oil production for the Clear Fork Group in the Wasson oil field,

Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1.

14,000 EXPLANATION

ay Historical oil production d 12,000 Waterflood Decline y = −405.9x + 23,000 R2 = 0.89 Waterflood decline trend—Dashed 10,000 where extended qi = 23,000 bbl/day

Di = 405.9/year CO2-EOR decline trend—Dashed 8,000 where extended CO2-EOR Decline 6,000 y = −87.6x + 11,000 R2 = 0.85 Beginning of qi = 11,000 bbl/day 4,000 CO2-EOR: 1985 Di = 87.6/year

production rate, in barrels per barrels in rate, production il 2,000 O Q@(q=0) = 55 MMbbl Q@(q=0) = 118.9 MMbbl 0 0 20 40 60 80 100 120 140 Cumulative oil production, in millions of barrels

Figure C1–7. Graph of the oil production rate versus the cumulative oil production for the Thirtyone Formation in the Dollarhide oil field,

Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1. Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C17

4,500 EXPLANATION Waterflood Decline Historical oil production 4,000 y = −426.8x + 7,500 2

ay R = 0.95 Waterflood decline trend—Dashed d q = 7,500 bbl/day 3,500 i where extended Di = 426.8/year

3,000 CO2-EOR decline trend—Dashed where extended CO2-EOR Decline 2,500 y = −213.3x + 9,000 R2 = 0.97 q = 9,000 bbl/day 2,000 i Di = 213.3/year 1,500 Beginning of CO -EOR: 1995 1,000 2 production rate, in barrels per barrels in rate, production il O 500 Q@(q=0) = 17.8 MMbbl Q@(q=0) = 42.0 MMbbl 0 0 10 20 30 40 50 Cumulative oil production, in millions of barrels

Figure C1–8. Graph of the oil production rate versus the cumulative oil production for the Clear Fork Group in the Dollarhide oil field,

Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1.

60,000 EXPLANATION Historical oil production ay

d 50,000 Waterflood decline trend—Dashed

CO2-EOR Decline where extended y = −295.1x + 116,000 40,000 2 R = 0.96 CO2-EOR decline trend—Dashed q = 116,000 bbl/day where extended Beginning of CO -EOR: 1993 i 2 D = 295.1/year 30,000 i

20,000 Waterflood Decline y = −154.3x + 49,000 R2 = 0.94 10,000 production rate, in barrels per barrels in rate, production il qi = 49,000 bbl/day

O Q@(q=0) = D = 154.3/year i Q@(q=0) = 316 MMbbl 386 MMbbl 0 0 100 200 300 400 Cumulative oil production, in millions of barrels

Figure C1–9. Graph of the oil production rate versus the cumulative oil production for the “Canyon-age reservoir” in the Salt Creek oil field, Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1. C18 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

80,000 EXPLANATION Historical oil production 70,000 ay Waterflood decline trend—Dashed d 60,000 where extended CO -EOR decline trend—Dashed Beginning of CO2-EOR: 1983 2 50,000 where extended CO2-EOR Decline y = −129.4x + 97,000 40,000 R2 = 0.96

qi = 97,000 bbl/day D = 129.4/year 30,000 Waterflood Decline i y = −232.3x + 106,000 20,000 R2 = 0.87 qi = 106,000 bbl/day production rate, in barrels per barrels in rate, production il D = 232.3/year O 10,000 i Q@(q=0) = 456 MMbbl Q@(q=0) = 752 MMbbl 0 0 200 400 600 800 Cumulative oil production, in millions of barrels

Figure C1–10. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Seminole oil field, Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1.

3,500 EXPLANATION Historical oil production 3,000 ay Waterflood decline trend—Dashed d where extended 2,500 CO2-EOR decline trend—Dashed where extended 2,000

CO2-EOR Decline 1,500 y = −176.1x + 2,400 2 Beginning of CO2-EOR: 1974 R = 0.96

Waterflood Decline qi = 2,400 bbl/day 1,000 y = −1,042.5x + 6,000 Di = 176.1/year R2 = 0.91 production rate, in barrels per barrels in rate, production il qi = 6,000 bbl/day O 500 Di = 1,042.5/year Q@(q=0) = 5.8 MMbbl Q@(q=0) = 13.6 MMbbl 0 0 2 4 6 8 10 12 14 Cumulative oil production, in millions of barrels

Figure C1–11. Graph of the oil production rate versus the cumulative oil production for the sandstone of the Ramsey Member of the Bell Canyon Formation in the Twofreds oil field, Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1. Chapter C. Application of Decline Curve Analysis To Estimate Recovery Factors for CO2-EOR C19

40,000 EXPLANATION Historical oil production 35,000 ay Waterflood decline trend—Dashed d 30,000 where extended

CO2-EOR decline trend—Dashed 25,000 Beginning of CO2-EOR: 1997 where extended

CO -EOR Decline 20,000 2 y = −132.7x + 44,000 R2 = 0.97 15,000 Waterflood Decline qi = 44,000 bbl/day y = −271.6x + 61,000 D = 132.7/year 2 i 10,000 R = 0.96 qi = 61,000 bbl/day

production rate, in barrels per barrels in rate, production il Di = 271.6/year O 5,000 Q@(q=0) = Q@(q=0) = 223 MMbbl 331 MMbbl 0 0 50 100 150 200 250 300 350 Cumulative oil production, in millions of barrels

Figure C1–12. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Vacuum oil field, New Mexico, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1.

9,000 EXPLANATION Beginning of CO -EOR: 1994 8,000 2 Historical oil production ay

d Waterflood decline trend—Dashed 7,000 where extended 6,000 CO2-EOR decline trend—Dashed where extended 5,000

4,000 CO2-EOR Decline Waterflood Decline y = −94.8x + 14,500 3,000 y = −217.6x + 14,000 R2 = 0.96 R2 = 0.99 qi = 14,500 bbl/day 2,000 qi = 14,000 bbl/day Di = 94.8/year

production rate, in barrels per barrels in rate, production il Di = 217.6/year O 1,000 Q@(q=0) = 63.7 MMbbl Q@(q=0) = 153 MMbbl 0 0 40 80 120 160 Cumulative oil production, in millions of barrels

Figure C1–13. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Cedar Lake oil field, Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1. C20 Three Approaches for Estimating Recovery Factors in Carbon Dioxide Enhanced Oil Recovery

800 EXPLANATION Historical oil production CO2-EOR Decline 700 y = −402.6x + 1,900 ay 2 Waterflood decline trend—Dashed d R = 0.96 600 q = 1,900 bbl/day where extended Waterflood Decline i Di = 402.6/year y = −387.3x + 1,200 CO2-EOR decline trend—Dashed 500 R2 = 0.97 where extended

qi = 1,200 bbl/day D = 387.3/year 400 i

300 Beginning of CO -EOR: 2003 200 2 production rate, in barrels per barrels in rate, production il O 100 Q@(q=0) = 3.2 MMbbl Q@(q=0) = 4.8 MMbbl

0 0 1 2 3 4 5 Cumulative oil production, in millions of barrels

Figure C1–14. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the North Hobbs oil field, New Mexico, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1.

140,000 EXPLANATION Historical oil production 120,000

ay CO -EOR Decline 2 Waterflood decline trend—Dashed d y = −221.7x + 244,000 R2 = 0.98 where extended 100,000 q = 244,000 bbl/day i CO -EOR decline trend—Dashed D = 221.7/year 2 Waterflood Decline i where extended 80,000 y = −250.2x + 256,000 R2 = 0.91 q = 256,000 bbl/day 60,000 i Di = 250.2/year Q@(q=0) = 1,110 MMbbl 40,000 Beginning of CO2-EOR: 2004 production rate, in barrels per barrels in rate, production il

O 20,000 Q@(q=0) = 1,030 MMbbl 0 0 200 400 600 800 1,000 1,200 Cumulative oil production, in millions of barrels

Figure C1–15. Graph of the oil production rate versus the cumulative oil production for the San Andres Limestone in the Yates oil field,

Texas, showing the decline trends for both the waterflood and the carbon dioxide enhanced oil recovery (CO2-EOR) phases. Data are from IHS Inc. (2012). Terms are as defined for figure C1–1.