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COBEM 2021
26th International Congress of Mechanical Engineering
EVALUATION OF OIL RECOVERY BY LOW SALINITY WATER INJECTION (LSWI) ON OIL-WET CARBONATES FROM PRE-SALT
Submission Author:
Taciana Cristina Clemente , SP , Brazil
Co-Authors:
Taciana Cristina Clemente, Alexandre Vidal, Eddy Ruidiaz, Alessandra Winter Spagnol, Paulo Ramos
Presenter: Taciana Cristina Clemente
doi://10.26678/ABCM.COBEM2021.COB2021-0323
Abstract
Considering the challenges present in the oil and gas industry, reservoir engineering seeks to develop and optimize techniques that effectively increase hydrocarbon recovery. The LWSI is an enhanced oil recovery method that has been gaining prominence over the years. For carbonate reservoirs, defined by having complex characteristics and intermediate or preferential wettability to oil, this technique is even more attractive, resulting in wettability alteration, an important factor in increasing oil recovery. Thus, the objective of this research was to evaluate the recovery of oil in carbonate reservoirs by reducing the concentration of sodium chloride in the injection water under pre-salt reservoir conditions. Coreflooding tests were conducted on four rock samples, with experimental conditions of 8230 psi and 69°C. The stages for rock preparation involve: core cleaning, saturation and wettability restoration. The tests were divided into two series. Three different brines concentrations are used in each test. The injection waters analyzed were: formation water (FW), seawater (SW), desulfated seawater (SWDs), seawater depleted in NaCl (SW0NaCl), desulfated seawater depleted in NaCl (SWDs0NaCl), seawater depleted in NaCl spiking with sulfate ion (SW0NaCl+SO_4^(2-)) and desulfated seawater with a 50% reduction of NaCl (SWDs0.5NaCl). The first series of tests analyzed FW as the first injected water and the second evaluated SW. Also a mixture of oil with a simplified gas composition was used to represent the condition of the fluid in the reservoir. The results obtained present that the most promising injection waters were: SWDs0NaCl (tertiary recovery), which resulted in total increases of 5.6% in production, and SW0NaCl (final recovery), which resulted in total increments of 3.5%. The influence of the sulfate ion could also be observed. SW0NaCl+SO_4^(2-) was not effective, a fact that may indicate that the concentration of sulfate present in seawater is already enough to allow the wettability alteration and that the proposal to increase the amount of sulfate is not valid for this type of lithology and operational conditions. In this case, FW and SW are good options. The use of SW resulted in tertiary recovery. However, it was possible to observe that the amount of oil produced with few porous injected volumes of FW is much greater than with SW, which indicates faster oil production and less fluid injection. Using either FW or SW will depend on operational factors, such as economic evaluations and increased recovery potential. In conclusion, the LSWI is efficient in increasing oil recovery in carbonate reservoirs.
Keywords
Low salinity water injection, Carbonate reservoirs, Enhanced oil recovery, sodium chloride, Sulfate
