Unlocking Oil Production with Hydraulic Fracturing Through Side-By-Side Tubing in Dual Monobore Completions: What to Expect and How to Assess Potential Risks in the Semberah Field, East Kalimantan

Abstract The Sanga-Sanga field in East Kalimantan, Indonesia, has been producing oil and gas for over 40 years and has reached a mature stage. Efforts to sustain production decline have been made by applying dual monobore completion since the early 2000s. This approach accelerates production from existing pools on one string while simultaneously completing additional bypassed or new pool discoveries on the other string, resulting in a faster return on operating investment and reduced drilling costs. However, this kind of completion limits well intervention activities due to tubing size and predefined pressure ratings. Additionally, layer development focused on bottom-up opening restricts access to reopening the lower completion on longer strings. With the need for high-pressure stimulation to improve and increase oil recovery, preliminary assessments are critical to avoid operational failures that may result in the loss of a well. A unique rigless hydraulic fracturing treatment in dual monobore wells performed in the Semberah field resulted in positive implications for development of the field. Previous hydraulic fracturing operations were limited to the longer string, as treating the string side by side with the other production strings was considered a high well integrity risk. Two pilot wells were identified for the trial of hydraulic fracturing in the dual-string monobore completion. The well candidates were selected based on their proven hydrocarbon reserves, forecasted potential, and objective layer depth of less than 5,000 ft. Several challenges were faced during the design and execution phases. First, the fracturing tortuosity and high near-wellbore friction pressures due to 90° perforation phasing, combined with the dual monobore architecture of the well, presented problems. Second, it was essential to ensure that the fracture geometry remained within the zone of interest and did not extend into the opened intervals of the other string. Several tools were utilized to help better understand the fracture geometry, including a bottomhole pressure gauge and temperature log. The cement quality within strings was evaluated prior to job execution. Lastly, the other strings were intensively monitored for any significant pressure changes during job execution. The zones of interest were reperforated perpendicular to existing perforations to help reduce the friction due to tortuosity and near-wellbore pressure. The post-injection test temperature log profile observed matched with the fracture growth model. Production increased from 30 BOPD to 300 BOPD after stimulation. This method and the lessons learned have been successfully applied as a new standard to stimulate dual monobore completions, thus opening the possibility of applying the method to more than 500 wells completed with dual monobore. The criteria of assessment and recommended practices to overcome potential risks have also increased the chances of job success.