Some mature fields in Ecuador produce with a water cut greater than 90%, and CaCO3 scaling is a common problem. Scale buildup adversely affects the performance and run life of both the ESPs and production.
To remove the CaCO3 scale, operators routinely perform small matrix acid treatments or inhibitor squeezes. Both options result in deferred production and substantially increase lifting costs, especially in fields where treatments must be performed every 6 months or less to maintain production.
The production of a PetroEcuador well completed in the Basal Tena, producing 550 bbl/d of crude with 40% basic sediment and water (BS&W), had declined to less than 300 bbl/d. This production decline was due to the onset of CaCO3 scaling.
Stimulating production and eliminating scale
A matrix stimulation treatment including ScaleMAT acid-compatible scale inhibitor was performed on the well. The inclusion of the ScaleMAT inhibitoreliminates at least one inhibitor squeeze treatment with every acid treatment, and the workover cost savings can be considerable. ScaleMAT treatments can prevent the deposition of scale for more than a year in many cases, thus extending the economic production of the well.
For the Basal Tena well, the ScaleMAT treatment consisted of a solvent stage followed by a 10% HCl stage, pumped through CT to clean the ESP and near-wellbore matrix. Following a 6-hour
shut-in to allow the ScaleMAT inhibitor to adsorb onto the rock matrix, the well was put on production.
Sustained production increase
The ScaleMAT treatment recovered the production lost due to scaling, with the well producing more than 500 bbl/d of crude with 40% BS&W. After more than 6 months, the well is still producing more than 500 bbl/d of crude, indicating effective scale inhibition. Meanwhile, production in offset wells treated conventionally declined by more than 50%.