Abstract
The Brani-Field is located offshore Northwest Java and currently produces hydrocarbons from a sandstone reservoir with an average watercut of 83%. Some high watercut wells are prone to scale problems and need repetitive clean outs to overcome production decline. In 2019, downhole scale inhibitor treatment was evaluated and planned for application in these wells. Scale inhibitors are able to prevent the formation of scale so the well is able to deliver higher average oil production with lower intervention cost.
In Brani wells, scale deposits are formed in perforations, downhole completion equipment, and flowlines depending on the water composition, temperature, and a reduction in dissolved carbon dioxide partial pressure. These scales deposits restrict the fluid flow causing significant production loss. In extreme conditions, the production tubing was blocked completely with the scale deposits and cease the production. Normally, the scale restriction problem in Brani wells were handled by a combination of mechanical and acidizing treatment using Coiled Tubing (CT) for downhole completion and acidizing treatment for flowline restrictions. These treatment were performed periodically every 2-4 months depending on well conditions with scaling becoming more severe in higher watercut wells. From an economic standpoint, current scale treatment methods lead to very high well intervention costs due to expensive liftboat and CT unit daily rates. The economics of these conventional treatments is further deterred by low yearly average oil production.
Evaluation for scale inhibitor treatment started with the candidate selection, fluids compatibility test, core re-gain permeability test, and economic evaluation. BRG-10 well was selected as first candidate due to scale problem severity and low oil production rate. This well normally delivers 140 bopd with 90% watercut, but scale build up in the tubing and flowline prevented the fluids flow and lowered the production to 30 bopd in just two months.
Laboratory test results demonstrated that the core regained permeability with the main pill fluids to a relatively high, 77.96% without any fluids compatibility issues. Deployment of a scale inhibitor squeeze treatment in BRG-10 well was executed in Jan 2020 by bullheading 657 bbl inhibitor fluids into the formation. The well was then shut in for 24 hours of soaking time. The post treatment results showed a very promising result with much more stable oil production after 11 months treatment, welltest on December 2020 showed the well was still producing 130 bopd with 90% watercut.
Following the successful application in BRG-10, the scale inhibitor treatment was applied in other wells, BRK-7 in June 2020 and BRG-5L in August 2020. So far, those two wells show good production performance with 93 bopd with 85% watercut for BRK-7 and 264 bopd with 76% for BRG-5L.