The Use of Drill Cuttings in Reservoir Evaluation

By

D.B. Schafer (BP Exploration (Alaska) Inc.) and G. Bolger (PetroTech Associates)

The use of drill cuttings has been significantly elevated in its importance relative to reservoir evaluation. In the past, drill cuttings commonly have been used to provide simple and qualitative information about the rock types present and not to make concrete decisions about the economic viability of any reservoir. However, the capability exists to perform more advanced reservoir evaluation from the cuttings as it relates to reservoir properties, performance and predictions. An additional caveat is that the cost of obtaining the rock material (conventional cores, sidewall cores) has been eliminated, hence reducing the cost of any well as much as 10–15%. This translates into approximately $350,000 in cost savings per North Slope well in Alaska.

Based on the type of drill bit used, the quality and quantity of drill cuttings can vary. Once drill cuttings are collected and washed they are then ‘picked’ to separate formation representative aggregates from drilling mud and other contaminants. Advanced rock studies, including Thin Section Petrography, X-ray Diffraction, Scanning Electron Microscopy, and Mercury Injection Capillary Pressure can then be performed on the cuttings, yielding high quality results. Using drill cuttings in formation evaluation has opened up an integral avenue of data collection achieved through significant cost savings. The data obtained from this technique is invaluable for making ‘setting pipe’ decisions, improving completion practices and many other aspects regarding how the reservoir should be developed. Here lies yet another very cost effective tool for oil and gas teams to further their understanding of reservoir potential.

AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.