Impact of physical phenomena and cyclical reinjection in miscible CO 2 -WAG recovery in carbonate reservoirs
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ORIGINAL PAPER--PRODUCTION ENGINEERING
Impact of physical phenomena and cyclical reinjection in miscible CO2‑WAG recovery in carbonate reservoirs Marcio Augusto Sampaio1 · Samuel Ferreira de Mello2 · Denis José Schiozer2 Received: 28 January 2020 / Accepted: 3 June 2020 © The Author(s) 2020
Abstract Carbonated reservoirs with high percentage of C O2 have been discovered and produced in the Brazilian pre-salt cluster. Recovery techniques, such as CO2-WAG, have hence been evaluated and applied, as in the Lula field. Although studies demonstrate the advantages of this technique, it is still difficult to estimate an increase in oil recovery. Thus, this work presents a methodology to evaluate the impacts of the main phenomena that occur and how C O2 recycling can benefit the management of these fields. The results showed an increase in recovery with the modeling of the main phenomena such as relative permeability hysteresis and aqueous solubility of CO2, accompanied by a significant increase in CO2 injection. However, the recycling of the CO2 produced was shown to be fundamental in the reduction in this injection and to increase the NPV. The results showed a 4% increase in oil production and 9% in NPV, considering a producer–injector pair. Keywords CO2-WAG · Relative permeability hysteresis · Aqueous solubility · Cyclical reinjection
Introduction Recent discoveries of reservoirs with high concentrations of carbon dioxide (CO2) have boosted the research and applications of EOR methods involving this gas. In Brazil, the pre-salt carbonate reservoirs can have up to 50% of the molar fraction of C O2. This high percentage of C O2 in the reservoirs, together with the long distance from the coast, limitations of handling, drainage and storage of the gas produced, as well as the possible environmental impacts caused by the release of this gas into the atmosphere, made the technique of water alternating CO2 injection (CO2-WAG) one of the main special recovery methods to be used in these reservoirs. In fact, this method has already been used by Petrobras in the Lula field, in the Santos Basin, since 2011, but the increase in its recovery factor cannot yet be safely estimated. * Marcio Augusto Sampaio [email protected] 1
Departamento de Engenharia de Minas e de Petróleo, Universidade de São Paulo, USP, Praça Narciso de Andrade S/N, Santos, São Paulo CEP 11.013‑560, Brazil
Faculdade de Engenharia Mecânica, Departamento de Energia, Universidade Estadual de Campinas, UNICAMP, R. Mendeleyev, N.200, C. P. 6052, Campinas, São Paulo CEP 13.083‑970, Brazil
2
In fields with a high percentage of CO2, it is extremely relevant to investigate the best type of recovery, such as continuous gas injection (CGI), injection of water alternated with CO2 (CO2-WAG), simultaneous injection of water and CO2 (SWAG), as well as the reinjection of the natural gas produced (hydrocarbon gas) or other gases. Regarding the miscibility of CO2 in the oil, we can still have immiscible WAG (IWAG) and miscible WAG (MWAG). The
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