Field-Scale Evaluation of Re-Injecting the Associating Produced Gas Through the GDWS-AGD EOR Process
- Watheq J Al-Mudhafar (Basrah Oil Company & The University of Texas at Austin) | Andrew K Wojtanowicz (Louisiana State University)
- Document ID
- Society of Petroleum Engineers
- SPE Europec featured at 81st EAGE Conference and Exhibition, 3-6 June, London, England, UK
- Publication Date
- Document Type
- Conference Paper
- 2019. Society of Petroleum Engineers
- Gas Injection, Gravity Drainage, Enhanced Oil Recovery, Strong Water Aquifers, Downhole Water Sink
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- 56 since 2007
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To date, our feasibility studies [CMTC-502487-MS and SPE-190163-MS] of the Gad and Downhole Water Sink-Assisted Gravity Drainage (GDWS-AGD) process for the South Rumaila oil field have considered using Carbon Dioxide gas injection to enhance recovery from the field. As availibiulity of CO2 is limited and its cost considerable it might be also feasible to use natural gas,, Associated Produced Gas (APG) as an alternative solvent to enhance oil recovery with this process. In the study, efficiency of APG vs. CO2 is compared for the South Rumaila oil field.
In the study, the GDWS-AGD process installation includes 20 vertical APG injection wells are drilled to the top of the reservoir to build a gas cap in the oil pay zone. In addition, eleven horizontal oil-producing wells are placed at the bottom of the oil pay zone with six horizontal water drainage (sink) wells below the oil-water contact (OWC). The two horizontal leg installation may be made from a vertical well with 7-casing dual-completed (from two kick-off points) in the oil payzone and in the bottom water (below OWC) with two horizontal well legs and the two 2-3/8 inch tubings in each well. In a dual-tubing design of the process the two horizontal well legs produce independently. If only one tubing is used production from the water sink well is hydraulically isolated inside the vertical well by a packer. In either design, the water sink well is operated with a submersible pump.
In this study, the GDWS-AGD process with APG is considered for the upper sandstone member/South Rumaila Oil Field, located in Iraq to improve oil recovery. The Rumaila field has an infinite acting-aquifer with very strong edge water drive. In the GDWS-AGD, the bottom water drainage would not only reduce water cut and water cresting, but would also significantly reduce the reservoir pressure, resulting in improving gas injectivity. The study shows considerable improvement with the GDWS-AGD process - oil recovery increased from 76% by CO2 to 83% by APG and water cut was readily controlled resulting in more rapid reduction with APG (from 98% to less than 5%) than that with CO2 in all horizontal oil producers. The results show that the use of APG gas alternative for the GDWS-AGD process not only improves water-cresting control due prompt reduction of water cut, but also enhances gas injectivity and significantly improves oil recovery.
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Al-Mudhafar, W. J. 2016. "Statistical Reservoir Characterization, Simulation, and Optimization Of Field Scale-Gas Assisted Gravity Drainage (GAGD) Process with Uncertainty Assessments." PhD Dissertation. Louisiana State University. http://etd.lsu.edu/docs/available/etd-04072016-165145/
Al-Mudhafar, W. J. 2018. "From Coreflooding and Scaled Physical Model Experiments to Field-Scale Enhanced Oil Recovery Evaluations: Comprehensive Review of the Gas-Assisted Gravity Drainage Process." Energy & Fuels 32(11): 11067–11079. DOI: 10.1021/acs.energyfuels.8b01023
Al-Mudhafar, Watheq J., Wojtanowicz, A. K. and Rao, D. N. 2017. "Hybrid Process of Gas and Downhole Water Sink-Assisted Gravity Drainage (G&DWS-AGD) to Enhance Oil Recovery in Reservoirs with Water Coning." Carbon Management Technology Conference. https://doi.org/10.7122/502487-MS.