--> Abstract: Applications of Mud Gas Isotope Logging to the Tahiti Field Development Program, Gulf of Mexico: Early Assessment of Reservoir Complexity and Assisting Drilling Operations, by Stan Teerman, Bo Cribbs, Scott Turner, Narade Suwatcharapanit, John Bretches, and Russ Kaufman; #90078 (2008)

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Applications of Mud Gas Isotope Logging to the Tahiti Field Development Program, Gulf of Mexico: Early Assessment of Reservoir Complexity and Assisting Drilling Operations

Stan Teerman1, Bo Cribbs1, Scott Turner1, Narade Suwatcharapanit1, John Bretches1, and Russ Kaufman2
1Chevron, Houston, TX
2Chevron, San Ramon, CA

While planning the Tahiti Field development, reservoir compartmentalization was identified at an early stage as having the most potential to negatively impact reserves, well count and oil recovery. Compartmentalization risks include: limitations to sub-salt 3D images, mapped as well as unmapped sub-seismic faulting, reservoir complexities near the salt face, mass flow events and pay sand sub-divisions. At the completion of each development well a rapid decision was required to determine if commercial objectives could be met; otherwise, an immediate sidetrack was considered.

Because near real-time definition of reservoir architecture was required, mud gas analyses were completed at a shore-base laboratory to provide compositional and isotopic logs of target zones during or immediately after drilling. Mud gas isotope logging is an extension of standard mud logging that measures the isotopic ratios of hydrocarbon gases collected during drilling. High resolution mud gas profiles were compared with MWD and wireline logs to provide early definition of reservoir connectivity and pay sand sub-divisions. Results helped design MDT pressure and fluid sampling programs to further evaluate reservoir continuity and well objectives. Mud gas fingerprints combined with other fluid data and high-resolution seismic helped: 1) identify specific pay sands in zones of stratigraphic complexity, 2) evaluate fluid communication where wireline results were not obtained due to poor hole conditions, 3) characterize hydrocarbons in non-sampled secondary objectives, and 4) define in-field fluid migration and field filling. Furthermore, mud gas logging assisted drilling decisions and operational planning by identification of the location and origin of gas kicks or fluid influx. Identification of gas sands also helps minimize shallow hazards in updip locations for future in-fill drilling.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas