A Comprehensive Ensemble Modelling Study to Evaluate Subsurface Uncertainties Associated With Tangguh CO2 Enhanced Gas Recovery (EGR) Project to Deliver a Robust and Quality-Optimized Development Plan

Abstract

Tangguh Field, in Bintuni Bay, Papua Barat Province, Indonesia, commenced development following a successful exploration program in the 1990s. Tangguh has been on production since 2009 through development of two liquified natural gas (LNG) trains (Kasim, Titus, Roberts, & Bulling, 2000). Full development includes a third LNG train with the expected first gas in 2023 and Enhanced Gas Recovery (EGR) and Carbon Capture Utilization and Storage (CCUS) in 2026. EGR/CCUS fits within the Government of Indonesia’s (GoI) gas production and carbon emissions reduction targets by 2030. The EGR/CCUS project will inject approximately 90% of reservoir CO2 back into the reservoir in the southwest part of Vorwata Field. Reservoir CO2, that is currently vented, will be captured from the Acid Gas Removal Unit, compressed, flowed via a subsea pipeline to an offshore facility, and then to injection wells. The CO2 is injected at supercritical conditions, to increase gas production and recoverable reserves through pressure maintenance and gas displacement mechanisms. Understanding the subsurface uncertainties and their impacts on production and operations are essential for optimizing field development plans and mitigating risks. The key risks to CO2 injection/capture are early CO2 breakthrough and reduced hydrocarbon recovery. bp’s proprietary Top-Down Reservoir Model (TDRMTM) based ensemble modeling workflow successfully assesses subsurface uncertainties, matches historical performance, and quantifies the value associated with the EGR/CCUS development. TDRMTM driven assisted history matching algorithm was matched the model against 12 years of historical production. Match qualities associated with historical rates and pressures were used as screening criteria to obtain a robust ensemble of history-matched models and ensure a healthy and sufficient exploration of uncertainties. The resulting metrics include the range of net hydrocarbon incremental gas recoverable, CO2 breakthrough times at offset producers, and CO2 sequestration volumes. Results from the ensemble-driven study have enabled a robust development plan, particularly associated with the