New Approach for Formation Evaluation Using Advanced Mud Gas Analysis of Conventional and Unconventional Reservoirs: A Case Study from Onshore UAE

Abstract

Abstract The formation evaluation of any wildcat, exploratory and/or appraisal well is challenging due to scarcity of information with respect to reservoir presence, its characterization and the expected pressure. It is expected that hydrocarbon bearing reservoirs, especially those located in low resistivity zones and without core for calibration of physical properties, might possibly be overlooked as these are difficult to interpret from petrophysical logs for the presence or absence of hydrocarbons. An advanced surface mud gas acquisition and analysis system, based on membrane technology, was utilized for the first time in the United Arab Emirates. Advanced mud gas analysis and interpretation of conventional and unconventional carbonate reservoirs sections identified interesting hydrocarbon bearing zones which were subsequently confirmed by integration of core, electric log and well-test data. An exploratory well was drilled to explore the hydrocarbon potential of unconventional reservoirs and appraise the conventional carbonate reservoir. Reliable results were achieved in a highly challenging environment including petrophysical uncertainty and a variety of reservoir fluids present. The results from the advanced mud gas analysis were confirmed by down hole sample testing results. The approach developed can be modified or customized to explore/appraise a prospect to capture any hydrocarbon zones, including by-passed zones, and subsequently optimize logging and testing programs resulting in a reliable data set and cost savings.