Validating of the Reservoir Connectivity and Compartmentalization with the CO2 Compositional Gradient and Mass Transportation Simulation Concepts

摘要

More than 40% of the world's conventional gas reserves are in reservoirs that contain significant amounts of H2S and CO2. The presence of these gases results in a number of challenges for the Field Development Plan (FDP). For a field with multiple fault blocks with unknown fault transmissivity, a key challenge is to understand the field connectivity and compartmentalization which impacts the ability to drain their reserves. This paper presents a comprehensive study to understand reservoir connectivity in a gas and oil fields located in South East Asia. This particular field has variation of the CO2 even in the same zone ranging from less than 10% to more than 80%wt. A key for production strategy and facility design is to be able to accurately quantify CO2 in each reservoir is. Initially, the CO2 study aimed to quantify the CO2 content for each reservoir using an advanced Downhole Fluid Analyzer (DFA), and then to use the DFA measurement as well as the available PVT data from nearby wells to understand reservoir connectivity through the use of a compositional gradient concept. Reservoir fluids that deviated from the compositional gradient were considered to not be in equilibrium. In addition, the use of a PVT thermodynamic calculation with a non-isothermal solution resulted in a possible identification of the CO2 charging location. Although the geochemistry study was conducted to understand the source of CO2 and hydrocarbon isotopes, it did not provide a conclusive result of the reservoir connectivity. As expected the hydrocarbon had a different charge source compared to the non hydrocarbon gases. Since the geochemistry study was inconclusive, a mass transportation simulation was performed to understand the reservoir connectivity and this information has had a great impact on understanding the production mechanism of this field. This paper provides a systematic process to understand the reservoir connectivity by using the integrated reservoir data such as pressure, DFA, PVT fluid properties, geochemistry, as well as the geological and geophysical interpretations of the reservoir. This paper offers an efficient way for reservoir characterization for proper field management for an important hydrocarbon discovery in South East Asia.