Predicting Deep Reservoir Quality, Offshore Norway

Joann E. Welton

Reducing risk by predicting deep reservoir potential has long been the goal of the explorationist. To successfully evaluate deep reservoir potential requires the integration of information on depositional setting, mineralogy, texture (i.e. grain size and sorting), burial history, temperature, porosity, and permeability.

In 1991, prior to the 14th Round, exploration potential on the Halten Terrace (Offshore Norway) was limited by reservoir predictions (based on generalized mineralogy trends) which suggested economic basement was 4000m. However, an integrated reservoir study conducted between 1991-1993 concluded that in certain Jurassic facies, significant deep reservoir potential existed. The study predicted that coarser-grained, quartz-rich braided stream, delta front, and offshore shelf sandbodies would have good porosity and permeability below 4000m, particularly where early chlorite grain coatings were present to inhibit silica cement.

In the spring of 1995, the discovery of significant hydrocarbon reserves below 4000m on Block 6406/2 confirmed these predictions and proved that integrated reservoir characterization can lead to accurate deep reservoir quality predictions. The integrated methodology used will be discussed.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California