Blast from the Past, Solving Severe Congealed Oil Problems by Combining Existing Solutions

Abstract

A mature field in central Sumatra, Indonesia, has been producing heavy oil for decades, and it has shown decreased production. The ESP, as the main lifting method, needs to be replaced more frequently due to mechanical damage by congealed oil. Many wells in that field were forced to be deactivated because of congealed oil plugging along the wellbore. The conventional method to tackle this issue is to pump hot water. This practice however did not give sustainable results after the treatment. The remedy of coiled tubing (CT) well cleanout with a wash nozzle has also not been considered successful because the congealed oil is too hard to penetrate. Furthermore, using mechanical devices such as CT milling tools has not been effective because the deposits stick to the mill. Considering the low-production-rate wells, high-rate fluid injection was proposed to meet cost criteria. Although the well was able to produce afterwards, production kept declining due to the production of congealed oil from the formation. A combination of high-pressure jetting tool and organic dissolver fluid was proposed as an alternative method to break the congealed oil. The method uses kinetic energy from the jetting tool to shatter the solidified oil by pumping brine. Afterwards, a fluid mixture composed of organic dissolver and additive is pumped to dissolve the remaining congealed oil. Following the treatments, the pilot well showed significant improvements. The treatment successfully revived well production after the well had stopped producing for more than 3 months. The flowback tank was filled with as much as 10-in.-deep broken oil residue. Such a solid removal has not been accomplished with any other technique. The well has been producing for more than 10 months without any pump issues, and production continues to increase. Another three well candidates with low productivity issues were treated with the same technique. All the wells delivered good results. If, in the future, the congealed oil accumulates again, high-pressure jetting and organic dissolver will be the first method used for remediation. All the wells treated with this approach have been producing significantly more than those treated using any other technique, well beyond the target set by the operator. This study discusses the benefits of combining the techniques of high-pressure jetting, organic dissolver, and high-rate injection to overcome severe congealed oil problems that impair well production. Details the approach are provided, and its effectiveness is compared to other former attempts to solve the congealed oil problem. This case also illustrates the importance of maintaining well interventions to improve production while meeting the cost criteria in this challenging time in the oil and gas industry.