Wettability Alteration to Increase Deliverability of Gas Production Wells

TitleWettability Alteration to Increase Deliverability of Gas Production Wells
Publication TypeConference Paper
Year of Publication2008
AuthorsXie, X., Y. Liu, M. M. Sharma, and W. W. Weiss
Conference NameSPE Eastern Regional/AAPG Eastern Section Joint Meeting
Date Published10/2008
PublisherSociety of Petroleum Engineers
Conference LocationPittsburgh, Pennsylvania, U.S.A., October 11-15, 2008
ISBN Number978-1-55563-200-7
Other NumbersSPE 117353-MS
KeywordsChemical Well Stimulation: Solvents and Surfactants, Condensate Banking / Productivity of Gas Condensate Wells, Water Blocking in Low Permeability Gas Sands, Wettability Alteration
Abstract

More than 17,000 gas storage wells in the U.S. annually lose about 5% of their deliverability (i.e., injectivity and productivity).  A common problem is believed to be water blockage around the wellbore.  For strongly water-wet gas reservoirs, capillary forces promote the retention of water in pore spaces, which in turn curtails the flow of gas in and out of the storage wells.  This paper reports the use of surfactants to change the water-wetness of a gas reservoir in order to increase gas deliverability.  Surfactant treatment can alter the strong water-wetness of the rock around wellbore to a neutral-wet condition, thus reducing water retention and improving gas flow.  The objective of this laboratory study was to demonstrate improved gas deliverability by altering the wettability of core samples with proper chemicals from strongly water-wet to neutral-wet.  Seven chemicals were screened for efficacy of changing the wettability of strongly water-wet glass capillary tubes.  Following the capillary rise tests two surfactants were selected for the core sample experiments.  Rock samples and water from the St. Peter formation, a sandstone aquifer gas storage reservoir, have been tested.  Spontaneous imbibition tests of reservoir cores were used to evaluate the wettability before and after surfactant treatment.  The cores were saturated with either initial formation water or surfactant solutions were displaced with wet nitrogen gas. Gas relative permeability was measured.  A decrease in the trapped water saturation caused an increase in gas permeability.  This increase indicated improved gas deliverability that resulted from wettability alteration away from very strongly water-wet conditions. Laboratory results demonstrated that reducing the water-wetness increased permeability and improved the deliverability of gas from the cores.  This technique provides a cost-effective method to increase gas deliverability in fields where water blocking is a major factor in decreased gas deliverability.

DOI10.2118/117353-MS