Evaluation of a Nonionic Surfactant Foam for CO2 Mobility Control in a Heterogeneous Carbonate Reservoir

Abstract

Summary In this paper, we describe a laboratory investigation of a nonionic surfactant for carbon dioxide-(CO2-) foam mobility control in the East Seminole field, a heterogeneous carbonate reservoir in the Permian Basin of west Texas. A method of high-performance liquid chromatography-evaporativelight-scattering detector (HPLC-ELSD) was followed for characterizing the surfactant stability. The foam transport process was studied in the absence and the presence of East Seminole crude oil, with test results showing that strong CO2-foam forms in either a bulk-foam test or foam-flow test. An oxygen scavenger, carbohydrazide, was found effective for controlling the stability of the surfactant up to 80°C and total dissolved solid of ∼34,000 ppm. Moreover, a phosphonate scale inhibitor was investigated and found to be compatible with the oxygen scavenger to accommodate a surfactant solution in a gypsum-oversaturated reservoir brine. During the oil-fractional flow test, an emulsion appears to form, causing a noticeable pressure increase; however, emulsion generation failed to cause a significant phase plugging in the test. Also, a STARS™ (Computer Modelling Group Ltd., Calgary, Alberta, Canada) foam model was applied to obtain the foam parameters from the foam-flow experiments at steady-state conditions. The insights from laboratory experiments better enable translation of the foam technology to the field.

CO2 Foam Behavior in Carbonate Rock: Effect of Surfactant Type and Concentration

“…Once the wormhole had been formed, it significantly altered the pressure measurements, due to the increase in permeability along the path of the wormholes, especially at the entrance of the core where there was most damage. Similar problems have also been described by Gland et al 23 and Jian et al 27 It was observed that the most significant damage (as observed from the pressure traces) often occurred during the transition from one foam quality to another, i.e., when switching from a high CO 2 fraction to a high water fraction or vice versa. The reason for this is not known.…”

“…The oxygen scavenger used for all the core flood tests was 100 ppm of carbohydrazide, as there are known issues (possible gypsum formation) when using the sodium sulphite in a carbonate core. 27 Between five and seven pore volumes of the solution were injected at 1 mL/min (equivalent to 1.47 × 10 −5 m/s or 4.2 feet/day). The effluent was captured in the fraction collector with a sample size of 4 mL (∼0.1 PV) each.…”

“…The recommendation is therefore to use nonionic or amphoteric surfactants with carbonate rocks. 26,27 The current core floods were carried out in the highest permeability cores available, to reflect the fact that some reservoirs contain medium to high permeable carbonates due to diagenesis. Previous work has tended to focus on lowpermeability chalks or fractured limestones, 28−31 and it is only recently that researchers have considered slightly higher permeability carbonate cores.…”

“…They also tend to exhibit high toxicity for aquatic organisms, so they are not recommended for use in the subsurface. The recommendation is therefore to use nonionic or amphoteric surfactants with carbonate rocks. , …”

Nonylphenol Ethoxylate Surfactants Modified by Carboxyl Groups for Foam EOR at High-Salinity Conditions

“…Depending on the hydrophilic-lipophilic balance and length of an ethoxylated group [13], nonionic surfactants can have good solubility and stability in high-salinity water. However, nonionic surfactants showed low foaming ability, compared to ionic type surfactants [14][15][16][17]. Comparison made by Li et al [18] of three types of surfactant: nonionic, anionic and anionic-nonionic, showed that anionic-nonionic surfactant created foam with higher stabilized pressure during filtration tests and higher foam elasticity than others.…”