Improving Techniques: Addressing Reservoir Continuity Issues in Near “Real-Time”

Myrt Cribbs¹, Stan Teerman¹, Jefferson Creek¹, Oliver Mullins², and Soraya Betancourt^2
1Deepwater Exploration and Projects, Chevron North America Upstream, Houston, TX
²Schlumberger, Houston, TX

Dealing with unforeseen reservoir compartmentalization in deep water developments is one of the most vexing issues that can increase project cost and result in well production underperforming initial estimates. The conventional work process combines stratigraphic models with fluid characterization, geochemistry and pressure surveys to develop a picture of the vertical and lateral connectivity in a reservoir. This analysis is typically done post-drill with data analysis and integration requiring weeks if not months. Limited rig availability and high overall well cost constrain the ability of an operator to drill enough wells and collect sufficient data to adequately characterize the reservoir prior to making major investment decisions.

A technique recently applied by Chevron is the rapid turn-around analysis of mud gas isotope samples. 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.

The MDT fluid sampling program included another key technology that is now being used for reservoir characterization. Downhole Fluid Analysis (DFA) can be integrated into the geologic and fluid models to identify compartments and compositional variations while the rig is on location. This presentation includes an example of the application of both of these methods to a Deep Water Gulf of Mexico development and explains how this analysis was applied to drilling and completion decisions in near “real-time” to ensure that well objectives are satisfied.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery