Practical and Theoretical Aspects of Well Testing in the Ekofisk Area Chalk Fields

Abstract

ABSTRACT This paper describes pressure transient testing and analysis procedures used in the Ekofisk Area chalk fields. These chalks consist of low permeability, thick, naturally fractured formations which are stimulated by pseudo limited entry, massive acid fracturing. Transient tests are interpreted in real time utilizing an on site portable computer. Test interpretation requires the use of spinner and/or separator rates for normalization, superpositioning, and pressure derivative data. The induced fracture systems are complex, having multiple fractures which are partially penetrating with limited perforation height and other non-ideal characteristics. It has not been possible to isolate the character of these nonideal conditions through pressure transient analysis. Instead, an equivalent fracture system which behaves similar to the actual system is identified during the test interpretation. Using the eqivalent fracture system concept, it has been possible to accurately forecast production, monitor well performance, evaluate the need for restimulation, and optimize completion and stimulation designs.