Recent Experience in Velocity Uncertainties during Field Appraisal and Development in a Pre-salt System, Case Study Gabon

Ageneau, Guillaume ¹; Chimienti, Pablo ¹; Baillie, John ¹
(1)ADDAX Petroleum, Geneva, Switzerland.

Discovery, appraisal and development of Pre-salt reservoirs in Gabon have been a tremendous challenge over the decades. At the core of the uncertainty matrix is the understanding of the velocity model, the range of its uncertainty and how “geophysical” velocities relate to the geological one (the velocity field one can derive from log data) given the complexity of the overburden. Even in mature developments, offsetting wells that are drilled only a few hundred of meters from existing control points can have large anomalies in apparently well defined settings.

This paper illustrates examples of the results from drilling wells near control to show the range of uncertainty one must consider while mapping and assessing the resource base.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.