Technical Category: “Smarter and More Efficient Field Development”

The Culzean field is a high pressure, high temperature (HPHT) gas-condensate field located in block 22/25a in the UK sector of the central North Sea. In order to determine the appropriate well count and facility capacity, it is important to accurately assess the individual well mid and long-term productivity.

This paper presents analytical and numerical Pressure Transient Analysis for the Culzean field and several other Skagerrak formation HPHT fields and proposes a method to predict mid-term reser-voir performance from log data. Skagerrak reservoir productivity is shown to be typically tenfold lower than what is estimated from core permeability. It is also shown that the core permeability is not a good predictor of mid-term well performance: whereas the permeability distribution for vari-ous Skagerrak fields is very similar, their field performance is not. The Pressure Transient Analysis of the various Skagerrak fields also shows similar trends, and hence this cannot serve as a good predictor either.

What is driving mid-term well performance in Skagerrak is the sand-sand connection far away from the wells, which can be estimated from the well test build-up data using a reservoir simulation box model and automatic history matching. It is then shown that the net to gross estimated from the Neutron/density log forms a reasonable predictor of the sand-sand connectivity and hence mid-term well performance.

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