Biogenic production of hydrogen sulfide in gas storage reservoirs is increasing as storage fields age ~). Attempts to mitigate this phenomenon have been primarily limited to treatment of the injected gas with organic biocides or periodic downhole treatments with organic biocides ~2). These treatment attempts have resulted in only limited success at decreasing the rate of reservoir souring ¢~). 9,10-anthraquinone (anthraquinone) has been shown to inhibit biogenic production of sulfides in oilfield water systems for extended periods of time 13). Anthraquinone functions as a sulfide inhibitor by forming insoluble, sub-micron sized particles that become incorporated into the biofilm. Subsequent to incorporation into the biofilm, the anthraquinone is transported into the cells of sulfate reducing bacteria (SRB) where it blocks production of ATP and ultimately reduction of sulfate to sulfide t4). Studies to determine applicability of this chemistry for inhibition of sulfide production in gas storage fields are presented in this paper. Sulfide inhibition studies were conducted in formation material to determine if anthraquinone was capable of inhibiting biogenic sulfide production in a high surface area environment. Positive results from the sulfide inhibition studies required that sandpack flood and core flood experiments be conducted to verify that anthraquinone could be safely squeezed into a gas storage field formation. Anthraquinone is soluble in high pH water in anaerobic conditions. However, in the presence of oxygen or neutral pH, anthraquinone will form colloidal particles ~5~. The sandpack and core flood experiments demonstrate that anthraquinone may be applied by squeeze techniques into the formation material with acceptable loss of injectivity. Appropriate squeeze designs for field trials in gas storage fields were developed using data from this study.
Biogenic production of hydrogen sulfide (H2S) in gas storage fields results when sulfate-reducing bacteria (SRB) in the formation metabolize sulfate to sulfide. This phenomenon results in sweet gas that is injected into the storage reservoir during the storage season becoming contaminated with H2S prior to withdrawal and transportation to the consumer. Due to the toxicity and potential to promote corrosion, H2S must be reduced to pipeline specifications (typically 4 ppm) prior to transportation m. In many cases, gas must be treated to meet pipeline specifications prior to transportation to the storage field. In these cases biogenic souring in the storage field results in the requirement to treat this gas to remove sulfides twice prior to transportation to the final consumer. Biogenic production of hydrogen sulfide in gas storage reservoirs is increasing as storage fields age and SRB populations increase. In some storage fields, this increased SRB activity results in HzS concentrations in the withdrawn gas that gradually increase from season to season. The current approach to treatment of biogenic sulfide production in gas storage fields focuses either on treatment of the symptoms (i.e. the sulfide) by using sulfide scavenging technology or treatment of the source of the souring (i.e. the sulfate reducing bacteria). H2S scavenger treatments are continuous process that will only increase in scale and cost as the HzS concentrations in the withdrawn gas continues to increase. Attempts to mitigate biogenic sulfide production at the source by controlling the SRB populations in the reservoir have been primarily limited to treatment of the injected gas with organic biocides or periodic downhole treatments with organic biocides. These treatment attempts achieved only limited success at decreasing the rate of reservoir souring. Bacte
