THE CHINGUETTI DEEPWATER TURBIDITE FIELD, MAURITANIA: RESERVE ESTIMATION AND FIELD DEVELOPMENT USING UNCERTAINTY MANAGEMENT AND EXPERIMENTAL DESIGNS FOR MULTIPLE SCENARIO 3D MODELS

Abstract

The Chinguetti Field was discovered in 2001 offshore Mauritania in 800 m of water. It comprises deepwater, mid-slope turbidite reservoirs, trapped in a dome over a salt diapir. The hydrocarbons are compartmentalised by concentric radial faults, in a low net:gross sequence, with oil mainly in channel sands. The large number of uncertain variables requires a structured approach and a rigorous assessment of the potential sub-surface scenarios. The field is of moderate size and risks in this deepwater environment need to be managed carefully.

The main sub-surface uncertainties were identified by uncertainty framing and are briefly described in the paper. They include:

structure;

hydrocarbon contacts;

fault seal;

distribution of the channel systems;

frequency and amalgamation of channel sands;

shale drape;

internal channel heterogeneity;

effective pressure support;

rock-fluid interaction;

rock compaction;

fluid composition/properties; and

rock properties.

A statistical experimental design determined 27 scenarios should accurately model the probability distribution of reserves. A 3D model was made for each and run through the dynamic simulator to estimate economic ultimate recovery (EUR). Multivariate statistical analysis produced a response equation for EUR and the probability distribution. This is more rigorous than the standard method which produces mid, high and low case models, for which there is no adequate way to assign their probability of occurrence.