Modified EOR Screening Criteria as Applied to a Group of Offshore Carbonate Oil Reservoirs

Abstract

This screening study has been applied on a group of offshore carbonate oil reservoirs. The methodology is based on the EOR screening criteria set forth by Taber et. al. 1,2 enriched with additional screening criteria. The EOR techniques screened included solvent flooding (miscible, immiscible hydrocarbon and CO2 Gas flooding), chemical flooding (Polymer flooding, and Surfactant and Polymer flooding), as well as Thermal flooding (Steam injection and In-situ combustion) techniques. The screening study investigated the challenging and the killing parameters of each technique if any, indicating the most applicable EOR technique.By comparing the depth and API gravity data of the reservoirs under study to that of the worldwide producing EOR projects, it was possible to define at a glance which EOR methods have been already experienced for the same conditions of reservoir depth and API oil gravities. Furthermore, by considering the relatively high pressure and temperature of the heterogeneous carbonate reservoirs under study, with its low viscosity oil, and the associated high salinity formation water, several EOR methods can be discarded including: Steam Injection, In Situ Combustion, and Polymers. Two methods were found to be most suitable for most of the reservoirs: Miscible Hydrocarbon and CO2 Gas injection. Minimum Miscibility Pressure (MMP) has been estimated using correlations. A miscible gas injection could be achieved in most of the reservoirs by adding 2 to 13% C3-C4 to processed gas. CO2 mimimum miscibility pressure, MMP, is expected to be about 1000 psi lower than most of the reservoir pressures, making CO2 miscible flooding to be easily achieved.Surfactant Polymers flooding could reduce Remaining Oil Saturation in reservoirs with more than 50mD permeability. This technology is less mature, than other EOR technologies. It is yet too challenging due to the high salinity, high temperature and carbonate formation.

Review on Polymer Flooding: Rheology, Adsorption, Stability, and Field Applications of Various Polymer Systems

“…Other important parameters of consideration in designing polymer flood are reservoir temperature (<90 • C), salinity (<40 g/L), and permeability (>50 mD). 32 High permeability reservoirs are better candidates as low permeability reservoirs have injectivity and excess retention issues. 33 Core flood data also help in predicting the efficiency of polymer at reservoir conditions.…”

Experimental evaluation of low concentration scleroglucan biopolymer solution for enhanced oil recovery in carbonate

“…Polymer flooding is an option to overcome heterogeneity issues, but the technique presents additional challenges associated with some carbonate reservoirs such as high reservoir temperature and high salinity/ hardness injection and formation water. These characteristics lead authors to discourage the implementation of polymer floods in naturally fractured carbonates (Al-Adasani and Bai, 2010;Boekhout, 2015;Bourdarot and Ghedan, 2011;Carcoana, 1982;Chang, 1978;Kang et al, 2016;Littmann, 1988;de Melo et al, 2002;Meyer et al, 2007;Sorbie, 1991;Taber et al, 1997).…”

Novel fluorinated surfactants for enhanced oil recovery in carbonate reservoirs

“…Thermal, miscible, and chemical methods are the three main EOR approaches . The nature of the reservoir, temperature, salinity, oil viscosity, permeability, and economics determine which EOR method is most suitable for a particular reservoir …”

“…[2][3][4] The nature of the reservoir, temperature, salinity, oil viscosity, permeability, and economics determine which EOR method is most suitable for a particular reservoir. [5][6][7] Chemical EOR (cEOR) is a promising method to increase oil recovery from a given reservoir. In cEOR, higher recovery factors are achieved by altering the fluid properties within the reservoir using chemicals [8] such as surfactants, polymers, and alkalis.…”