Abstract
Coiled tubing (CT) equipped with fiber optics and real-time downhole telemetry and a fit-for-purpose CT tower were used in underbalanced perforating operations in six wells in Indonesia; each operation involved 800 ft of perforating guns, and each was completed in a single trip. The reservoir is thick, with high permeability and characterized by high content of CO2 and H2S. The underbalanced perforating technique was deemed fundamental to minimize formation damage in the near-wellbore area, and the campaign was part of a national strategic project to develop a block's main reserve to supply gas to drive the national economy.
Each well had to be completed with minimum of an 800-ft perforation interval to deliver an average of 60 MMscf/D gas production for 16 years plateau with up to 34% CO2 content and 10,000-ppm H2S. The traditional method of e-line overbalanced perforating in such harsh environment became inefficient because of the number of runs required, which can be as high as 40 runs per well. CT-conveyed perforating guns and a completion insertion retrieval of equipment under pressure (CIRP) system were chosen to execute the task. The fiber-optic CT real-time telemetry system was selected to improve downhole depth accuracy, confirm the underbalance condition, and provide real-time confirmation when the 800 ft of guns detonated downhole. To execute the six-well campaign safely, a customized 100-ft CT tower was brought into the country.
Because this was the first in-country application for fiber-optic-enabled CT in single-trip with an 800-ft underbalanced perforation interval, thorough planning and preparation were critical for a successful campaign. Considering the high gas rate, high CO2, and H2S content, a downhole lubricator valve was added as additional barrier during undeployment, and an H2S and CO2 inhibitor was used to protect CT string integrity. Another risk mitigation plan was to utilize real-time CT inspection to monitor the CT integrity and condition throughout the job. Slickline deployment was used in first two wells to deploy multiple guns into the well, but this was deemed inefficient. The CT deployment method was used to complete the campaign. The project comprised a total of 2,200 operating hours, 29 CT runs, and 4,969 ft of guns in six trips with 917 ft as the longest interval. All six wells were completed with no HSE events, no automotive incidents, 98% operational efficiency, and 21% faster than planned duration.
This successful six-well campaign represents a first in-country application, which contributed to developing this main gas reserve. The campaign provides lessons for job planning and preparation, technology implementation, execution, and continuous improvement, which can be implemented in similar projects in Indonesia and around the region.