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A Comprehensive Study on Prediction and Inhibition of Calcium Sulfate Scale Formation in Oil ReservoirsNormal access

Authors: A. Khormali and D.G. Petrakov
Event name: Saint Petersburg 2018
Session: Reservoir Modelling
Publication date: 09 April 2018
DOI: 10.3997/2214-4609.201800117
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 495.94Kb )
Price: € 20

The deposition of inorganic salts in the bottomhole formation zone and on the surface of the oilfield equipment causes a reduction in the well production rate, service life and the rock permeability. The precipitation of calcium sulfate often occurs when mixing incompatible waters during waterflooding of reservoirs. In this work, conditions for the precipitation of calcium sulfate were determined depending on the reservoir conditions and the volume ratio of the injection and formation waters. The effects of reservoir temperature and pressure on the formation of calcium sulfate scale were studied. The results of scale prediction showed that with increasing temperature and decreasing pressure, the amount of forming calcium sulfate is significantly increased. To analyze the inhibition efficiency of calcium sulfate under static conditions, five different scale inhibitors were used. Results of studies on the evaluation of the efficiency of the developed scale inhibitor and industrial scale inhibitors under static and dynamic conditions were presented. The developed scale inhibitor has the highest efficiency for preventing the calcium sulfate scale formation at a concentration of 30 mg/L. Despite the decrease in solubility of calcium sulfate with increasing temperature, the effectiveness of the developed inhibitor does not significantly decrease with increasing temperature.

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