Utilizing Mud Log Gas Data for Real-Time Evaluation of Reservoir Fluid in the X Oilfield, Southern Iraq

Abstract

Real-time identification of fluid characterization is important to execute and/or modify the proposed well program and provide a better understanding of the application of gas ratio analysis. In this study, reservoir fluids were characterized during drilling by analyzing light gases released as a result of formation rocks being penetrated. Drilling mud is used to carry reservoir gas during this process. The required data included the values of liberated gas molecules from the main reservoir section extracted by gas chromatograph (GC) during drilling, that data was collected from five wells (A, B, C, D, and E) in the X oilfield. The gas measurements included the gases from Methane (C1) to Pentane (C5) measured in real-time by the gas chromatograph in the mudlogging units. The ratios of C1-C5 gases were used to determine the values of wetness ratio (Wh), and hydrocarbon balance (Bh) in the 3rd and 4th pay reservoirs. Results showed good indications of fluid type compared to the actual well test and were capable of distinguishing between heavy and light hydrocarbons in the reservoir section. A joint interpretation of electric logs and mudlogging gas data leads to an enhanced understanding of well results, which in turn can be used to optimize future logging and well testing.