Surfactant-induced spreading and wettability effects in condensate reservoirs

Document Type

Conference Proceeding

Publication Date

1-1-2010

Abstract

Condensate blockage is known as a serious problem in gas condensate reservoirs due to the depletion of reservoirs to pressures below the dew point. It reduces gas phase relative permeability and consequently results in the loss of gas productivity. The objective of this study was to identify and attempt to remedy this blockage problem through reservoir wettability determination and wettability alteration by using surfactants in the condensate buildup regions. Experiments were performed at ambient conditions by using stock tank condensate sample, methane, synthetic reservoir brine, and quartz substrate. In this study, both the spreading coefficient and wettability were measured to characterize the influence of anionic and nonionic surfactant on interfacial behavior. The contact angles were experimentally measured using Dual-Drop-Dual-Crystal (DDDC) technique. The Drop Shape Analysis (DSA) and capillary rise technique were used for measuring oil-water, water-gas and gas-oil interfacial tensions. An advancing angle of 152° obtained from the experiments indicated that this sandstone condensate reservoir had a strong oil-wet nature. Anionic and nonionic surfactants at the concentration levels of 500, 1500, and 3000 ppm were tested in the experiments. Results showed that although spreading coefficients were all positive for the condensate-brine system with/without surfactants, they decreased after the surfactants application. This implies that oil recovery is still enhanced from surfactants usage in this strongly oil-wet system. Also, all three concentrations of anionic surfactant were shown to alter the wettability of quartz surface from strongly oil-wet to intermediate-wet or weakly oil-wet. However, no wettability alteration was found after nonionic surfactant usage. The key finding from the ambient condition experiments is that the sandstone reservoir wettability is altered from strongly oil-wet to intermediate-wet or weakly oil-wet by using an anionic surfactant. Copyright 2010, Society of Petroleum Engineers.

Publication Source (Journal or Book title)

Proceedings - SPE Symposium on Improved Oil Recovery

First Page

335

Last Page

355

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