Perpustakaan Digital ITB

The AX Field is one of the largest onshore oil fields in Indonesia and contributes significantly to the country’s oil production. After reaching peak production of approximately higher than 220 MBOPD, the field has entered a mature production stage characterized by declining oil rates and increasing water production rapidly. The main producing reservoir is the heterogeneous carbonate buildup of the Kujung Formation that can create preferential flow paths and lead to uneven fluid displacement. This study aims to analyze declining production and rapidly increase of water production in the AX Field through an integrated evaluation of field performance and well-level diagnostics for maintenance field production performance in the future. The study workflow begins with the collection and validation of production and injection data based on production history data from August 2009-May 2025, followed by the development of a historical field production performance plot to evaluate reservoir behavior over time, complemented by the construction of a combined Voidage Replacement Ratio (VRR) and reservoir pressure versus time plot to assess reservoir drive mechanisms and pressure support. Then, production historical evaluation is conducted using Decline Curve Analysis (DCA) to determine decline rate (Di) field and wells. Based on these evaluations, a problematic well is identified for further detailed analysis based on wells production history data. Water production behavior is then examined for every well in the field using DCA method, fractional method, and Watercut/Life time method. Further diagnostic analyses include Chan plot evaluation for production wells, Hall plot interpretation for injection wells, and assessment of well completion data alongside oil–water contact (OWC) conditions. The integration of these analyses provides the basis for proposing appropriate mitigation strategies to optimize production performance and manage excessive water production. The results indicate that injection pressure support successfully stabilized reservoir pressure after the early depletion stage. However, diagnostic analysis shows that channeling is the dominant mechanism causing water breakthrough in several wells, with some wells also exhibiting bottom-water coning. Fractional flow analysis estimates a theoretical breakthrough watercut of approximately 85.7%, and comparison with field data suggests that several wells experienced earlier breakthrough due to preferential flow through high-permeability pathways. The integrated analysis provides insights for identifying problematic wells and supports the implementation of targeted water-management strategies to improve sweep efficiency and sustain oil recovery in the AX Field.