Solvent Stimulation as a Solution for Heavy Oil Production in B Structure Pertamina

Abstract

The production of heavy oil requires more effort than normal. The low API degree, high viscosity and high pour point make it quite challenging to produce wells with this type of oil. B Structure in PERTAMINA is facing this problem. The oil has 15-200deg API, 10-300 cp viscosity and 115degF pour point. Producing wells in this structure results in either low production rate or water coning. Altering the oil characteristic by pumping a suitable chemical might be a solution to this problem. Laboratory tests were performed to find the right chemical that can alter the oil characteristics in this structure. The thinking was to utilize a hydrocarbon-based chemical, thus a mixture of xylene and diesel as the main ingredient was chosen. Solubility tests with oil from B Structure showed that the mixture could dissolve the asphaltene and paraffin content. A dose of surfactant, mutual solvent, and potassium chloride was added into the mixture to condition the formation. Compatibility tests with brine from B Structure were conducted with neither emulsion nor sediment forming. The laboratory tests of the mixture showed promising results. Stimulation jobs using the solvent mixture were performed on three wells in B Structure: well B-26, B-122, and B-121. The problem in wells B-26 and B-122 was the same, which was a sudden increase in water cut after performing well service. Well B-121 lost production after water shut off activity. Stimulation was performed using the bullhead method with 6 feet of penetration into the formation and a minimum of 60 minutes soaking time. The best result out of these three treatments was from well B-121: the oil production before treatment was 25 bbls per day and it improved post-treatment to 175 bbls/day, with a decreasing trend in water cut. An improvement also happened in well B-122: oil production pretreatment was 21 bbls/day and it improved to 76 bbls/day. As for B-26 well, improvement was less than the others, producing 18 bbls/day oil from 10 bbls/day pretreatment. All wells were produced with artificial lift and still had more than 300 meters of pump submergence, which opened the door for further production optimization. The success from these stimulation jobs provided a solution for heavy oil production in B Structure in PERTAMINA. Stimulation was further conducted in the next 7 wells and a total 8 out of 10 wells have delivered satisfactory results including 2 newly drilled wells. With this new-found success in aromatic solvent stimulation, this solution to the problem has now been selected as the standard treatment in producing heavy oil in B Structure PERTAMINA.