A Preliminary Reservoir Engineering Assessment Of Miscible Gas Injection In A Cooper Basin Oil Field
Engineering Honours Degree, 2012
University of Adelaide
This project develops a reservoir engineering assessment of the Field A Oil reservoir. This body of work is the first step to determine the opportunity for Enhanced Oil Recovery (EOR) in Field A. The major objectives of the project are to outline the current state of the reservoir, investigate reservoir fluid properties and the interaction of these hydrocarbons with alternate types of injection gas and assess the potential for EOR by gas injection.
Neighbouring fields with similar reservoir characteristics have commenced miscible gas enhanced oil recovery (EOR) schemes to retain pressure and increase oil recovery, which has typically been low. Santos Ltd has proposed an expansion of EOR in this area commencing with this reservoir engineering assessment of Field A. Recommendations from the project will begin an investigation into EOR by miscible gas in the field.
This has been achieved by a full compilation of reservoir data resulting in evidence of connectivity and reservoir partitioning, pressures, production, and in situ oil and gas volumes. A Material Balance model has given updated original hydrocarbon in place volumes higher than those originally estimated. And using pressure-volume-temperature (PVT) data six types of injection gas were investigated using equation of state (EOS) calculations of miscibility from slim tube test data.
Results found that the original hydrocarbon volume in place determined by regression of the Material Balance model was over twice that of the most recent volumetric estimate, which could lead to reserves booking with further research. From pressure data analysis multiple tanks with no transmissibility have been found in Field A, implying discontinuity in the reservoir. The minimum miscibility pressure (MMP) of each type of injection gas was determined with only Carbon dioxide meeting the minimum pressure required for miscibility at current reservoir conditions. Recovery factors at current reservoir pressure were calculated from the slim tube test for MMP for each gas. Ultimately the injection of carbon dioxide is technically the most beneficial for oil recovery in the field however a full economic analysis of the best injection gases needs to follow this report.