Screening of WAG Injection Strategies for Heterogeneous Reservoirs

Surguchev, L.M.; Korbøl, Ragnhild; Haugen, Sigurd; Krakstad, O.S.

doi:10.2523/25075-ms

Cited by 29 publications

(25 citation statements)

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“…The water alternating gas injection (WAG) scheme is a combination of two traditional techniques of improved hydrocarbon recovery⎯waterflooding and gas injection. 9 The first field application of WAG is attributed to the North Pembina field in Alberta, Canada by Mobil in 1957. 10 Whether injectivity abnormalities developed was not reported.…”

Section: Overview Of Wag Injection Processmentioning

confidence: 99%

A Literature Analysis of the WAG Injectivity Abnormalities in the CO2 Process

Grigg

2000

SPE/DOE Improved Oil Recovery Symposium

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TX 75083-3836, U.S.A., fax 01-972-952-9435. 3. 3 nitrogen-miscible projects 4. 1 hydrocarbon-immiscible 5. 1 nitrogen-and hydrocarbon-immiscible 6. 6 nitrogen-immiscible CO 2 projects continue to grow in numbers. Immiscible CO 2 projects have dropped to zero while ten new miscible CO 2 projects were planned as of January 1998. Brock and Bryan 2 presented a summary of CO 2 EOR projects and reviewed the performance of 30 full-scale field projects and field pilots up to 1987. In 1992 there were 45 active CO 2 projects in the U.S. 3 Initially the industry outlook was pessimistic; however, by 1992 most projects had been shown to be technically and economically successful. In a number of projects, the production performance has been better than was anticipated. 3 At the beginning of 1998 and based on 1997 production figures, the U.S. production from gas injected EOR was estimated at 307,544 b/d or approximately 4.7% of the total oil production in the US. Oil production from CO 2 activity alone contributed nearly 179,000 b/d, which is an increase of 4.9% over 1996 production attributable to CO 2 production and represents 2.8% of the 1997 US oil production of 6.4 MM bopd. 1 The Permian Basin of west Texas and southeastern New Mexico remains a very active area for CO 2 projects. Eight of the ten planned projects are in the Permian Basin. 1 However, new CO 2 EOR projects are possible for areas of California,

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Section: Overview Of Wag Injection Processmentioning

confidence: 99%

A Literature Analysis of the WAG Injectivity Abnormalities in the CO2 Process

Grigg

2000

SPE/DOE Improved Oil Recovery Symposium

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“…Declining CO 2 and water injectivity while on a tapered WAG schedule has been noted on numerous injection wells since the early 2000's. A literature review on the critical factors, reasons, and remedies to injectivity loss are summarized below [12,13,14]. …”

Section: Injectivity Lossmentioning

confidence: 99%

Overview of CO2 Injection and WAG Sensitivity in SACROC

Ghahfarokhi

Pennell²,

Matson³

et al. 2016

SPE Improved Oil Recovery Conference

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This paper presents an overview of the SACROC Unit's activity focusing on different CO 2 injection and WAG projects that have made the SACROC Unit one of the most successful CO 2 injection projects in the world. The main objective of this work was to review CO 2 injection and injection rate losses due to the CO 2 /WAG miscible displacement process in the SACROC Unit and recommend an injection strategy for WAG-sensitive patterns.Two types of pattern CO 2 /WAG injection rate performance were observed, 1) WAG-sensitive and 2) WAG insensitive. WAG-sensitive patterns displayed loss of CO 2 injectivity, exceeding 80% in some patterns, during water-alternating-gas (WAG) injection, and an apparent reduction in water injectivity during the follow-up brine injection. This injectivity loss was observed in over 150 injection patterns. Over time, CO 2 injectivity tended to return to prior-to-WAG values. WAG-insensitive patterns suffer from these injectivity losses and were characterized by differences in 1) injectivity profiles, 2) Dykstra-Parsons coefficients, and 3) injectivity indexes.In the majority of WAG-sensitive patterns, injectivity profiles redistributed after CO 2 injection, while WAG-insensitive patterns did not show a significant change in their injectivity profiles over time. In a limited data set, the mean Dykstra-Parsons coefficient calculated for WAG-sensitive patterns was 0.83, while for WAG-insensitive patterns the mean Dykstra-Parsons coefficient was 0.76. However it was observed that in the lower Dykstra-Parsons patterns (WAG-insensitive patterns) much larger injectivity indexes were also observed; 19.5 bbl/day/psi, compared to 8.5 bbl/day/psi for higher Dykstra-Parsons patterns. This suggests that the WAG-insensitive patterns were dominated by fracture flow rather than matrix flow. These observations indicate that the WAG injection process in these heterogeneous SA-CROC wells is successful in diverting the injected fluids from zones with higher permeability to zones with lower permeability.For wells with injectivity values of less than 10 bbl/day/psi it is recommended to begin CO 2 /WAG injection with a long CO 2 cycle since they are likely to show sensitivity to WAG.A simulated 5-spot pattern was used to study the injection schedule for WAG-sensitive patterns. Longer CO 2 cycles and shorter water cycles improved the injectivity and pattern production. Most importantly, it was observed that increasing producing BHP to MMP resulted in significantly lower GOR.

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“…The Minimum Miscibility Pressure (MMP) is commonly defined as a pressure of maximum curvature when recovery of oil is plotted against pressure (Surguchev, 1992). If sight glass observation is available, there should be no two-phase flow observed in the sight glass (Yellig, 1978;Sebastian, 1984).…”

Section: Mmp and Miscibility Studiesmentioning

confidence: 99%

The Influence of O2 Contamination on MMP and Core Flood Performance in Miscible and Immiscible CO2 WAG

Jiang¹,

Nuryaningsih

Adidharma

2012

SPE Improved Oil Recovery Symposium

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For a given oil and reservoir temperature, the CO2 Minimum Miscibility Pressure (MMP) is largely affected by the CO2 purity. A commonly found contamination gas in CO2 EOR is O2, the existence of which will influence the MMP and thus influence the CO2 Water Alternating Gas (WAG) performance.Slim tube tests and core flood experiments are conducted in order to study the influence of O2 on the MMP and CO2 WAG performance. Both experiments utilize crude oil from South Slattery Field in Wyoming. The mole concentration of O2 in CO2 gas varies from 0 mol% to 5 and 10 mol% and the experimental temperature is set at 57 ˚C to mimic the reservoir condition. In the slim tube tests, the oil recoveries at gas breakthrough are used to interpret the MMP. All core flood experiments utilize Berea sandstone cores and synthetic brines. A pressure of 20% higher than the pure CO2 MMP is used to ensure miscible condition and a pressure of 50% of the pure CO2 MMP is used for the immiscible study. WAG is injected in the tertiary recovery mode and its parameters include a WAG ratio of 1:1, a half cycle slug size of 0.1 PV, and a total slug size of 2.0 PV. WAG performance, i.e., percent oil recovery, tertiary recovery factor, and CO2 utilization factor are determined.Slim tube results show that the existence of O2 increases the CO2 MMP significantly. Five mol percent of O2 in CO2 gas increases its MMP by 20.88%, while 10 mol% of O2 increases it by 61.92%. Core flood results show that the existence of O2 in CO2 gas adversely influence the WAG performance. For miscible CO2 WAG flooding, the higher the O2 content, the lower the incremental recovery and tertiary recovery factor (TRF). The same results are also found in immiscible CO2 WAG with less significant effects.Similar studies have been mainly focused on N2 and CH4, while the influence of O2 has never been experimentally investigated. This study is essential for better understanding the influence of CO2 contamination on WAG performance, which is a major concern in CO2 EOR utilizing unpurified CO2 gas sources.

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Screening of WAG Injection Strategies for Heterogeneous Reservoirs

Cited by 29 publications

References 0 publications

A Literature Analysis of the WAG Injectivity Abnormalities in the CO2 Process

A Literature Analysis of the WAG Injectivity Abnormalities in the CO2 Process

Overview of CO2 Injection and WAG Sensitivity in SACROC

The Influence of O2 Contamination on MMP and Core Flood Performance in Miscible and Immiscible CO2 WAG

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