Identification of Oil Type Hydrocarbon Using Mud Gas Logging and Petrophysical Logs Evaluation in the Kangan and Dalan Formations

The Kangan and Dalan formations have long been considered as gas reservoirs due to their deep burial history. However, this study investigated the type of hydrocarbon fluid in these reservoirs based on the geochemical interpretation of mud gas logging and petrophysical evaluation in the Persian Gulf. The study was conducted in three stages. Firstly, well logs were evaluated under the assumption that the reservoir is an oil-type reservoir. In the next step, the type of fluid was identified based on the geochemical interpretation of mud gas logging, using the Haworth and Pixler methods. The final fluid type was determined based on the integration of geochemical methods. In the last step, a petrophysical re-evaluation was done in the susceptible oil zone. According to the primary petrophysical interpretation, there are three oil zones including K1, K2 and K4 in the reservoir. Meanwhile, based on the geochemical interpretation of mud gas logging, K1 and K4 zones are gas type and only the K2 zone contains oil-type hydrocarbon. Petrophysical re-evaluation of the K2 zone (identified as oil-type reservoir zone) indicated an effective porosity of 6% and water saturation of 29%. The results of this study suggest that paying attention to mud gas logging interpretation when determining the appropriate interval for perforation and selecting the appropriate zones for reservoir tests can reduce drilling costs and time.