Improved Oil Recovery by Chemical Flood from High Salinity Reservoirs-Single-Well Surfactant Injection Test

Abstract

Reservoirs containing very high total dissolved solids and high hardness make the design of a surfactant polymer (SP) flood extremely difficult because surfactant tends to precipitate and separate under these conditions. Beside divalent ions, Ca2+and Mg2+, the presence of iron in the brine can be a challenging issue. Different surfactant formulations incorporating cosurfactants and co-solvents are studied. These formulations minimize viscous macroemulsions, promote rapid coalescence under Winsor Type III conditions, and stabilize the chemical solution by reducing precipitation and phase separation. The optimal surfactant formulations are further studied in one-dimensional sand packs and coreflood tests using Berea sandstone, reservoir oils, and brines at 42°C. Using similar injection protocols, 0.5 PVs surfactant/polymer, oil recoveries ranging from 50 % to 70% of the residual oil (Sor) after waterflooding are observed. The level of surfactant loading is less than 0.6 wt%. A single-well test is conducted to confirm laboratory results in situ in the presence of high-salinity formation water containing 165,000 mg/L total dissolved solids (TDS). The test is considered to be a technical success and confirms the effectiveness of a high-salinity surfactant-polymer formulation composed of 0.23 wt% of surfactant and 1,800 ppm of polymer loading. Approximately 87% of the residual oil was mobilized.

Design of an optimal middle phase microemulsion for ultra high saline brine using hydrophilic lipophilic deviation (HLD) method

“…Most of the suggested formulations for high salinity brines are developed either for brines up to 21 wt % NaCl without hardness [19] or brines containing hardness up to 8,500 mg/l with a total TDS of 165,000 mg/l [23]. In this work, surfactant formulations for reservoir brine having total TDS of over 300,000 mg/l with the total hardness of about 13,000 mg/l are reported.…”

Modeling and Interpretation of Single Well Chemical Tracer Tests (SWCTT) for pre and post Chemical EOR in two High Salinity Reservoirs

“…The surfactant formulation optimization and column test results for Stewart Fee has been reported elsewhere (Hsu, et al 2012). Two ternary surfactant systems which create a middle phase microemulsion with crude oil and formation brine were formulated for each field.…”

“…And the formulation details are summarized in Table 2. The stability test method has been reported in a published paper (Hsu, et al 2012), and all formulations past the stability tests. A biopolymer CPXG was added for Stewart Fee test.…”