Abstract: Turbidite Identification and Evaluation for Hydrocarbon Production Using Open Hole Logs and Borehole Images

HANSEN, STEVE
Schlumberger Wireline and Testing, Houston, TX;
TOM FETT
Schlumberger Wireline and Testing, Al-Khobar, Saudi Arabia

Turbidite sands as thin as 1 cm, can be identified and evaluated with modern open hole logs and borehole imaging tools. Generic descriptions of the sands such as "massive, graded, thick, thin, sharp or gradational contacts, slumped, fining or thinning upwards and continuity" etc., can be used with the appropriate model to define the reservoir's depositional environment, geometry and even orientation. Subtle changes in the dip of the beds can delineate depositional flow units.

This information can be used along with the core data (whole or sidewall) and structural information, to better define net sand, pay sand, perm trends, barriers, and production potential. Experience with deep water "turbidite" sands in the Gulf of Mexico has highlighted problems in even detecting these sands, much less getting correct net sand and water saturations in many of the pay zones. Modern high-resolution resistivity and porosity logs, corrected by the images for thin bed effects, allow much improved formation evaluation. In addition to the thin bed problems, textural features such as slumping, bioturbation and secondary cementation, often are the keys to productivity of these reservoirs.

A photo gallery of images mainly from the Gulf of Mexico, illustrates these features and when possible, their relationship to production results.

AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas