New Approach of Using Wells Static Pressure Measurements in Identifying Dynamic Regions and Sectors in a Giant Carbonate Reservoir

Abstract

Compartmentalization (vertical and lateral) is often a major uncertainty at the field appraisal stage, impacting important investment decisions. Unfortunately the most definitive compartmentalization data (dynamic production data or high resolution 4D seismic) are not usually available so early in field life. Usually geometrically equal sectors are defined to start with to be used as a guide to monitor and manage the reservoir. In mature reservoirs, these data are available. The understanding of the different zones and compartments boundaries is crucial for better re-sectorization and better effective management strategies especially in case of the giant field with gas and water injection schemes. This paper illustrates how indications of compartmentalization and limits of sectors can be achieved by analyzing the sporadic pressure static data dispersed in time and space. The first step of this work is to integrate seismic re-interpretation of the faults with Bottom-Hole Static Pressure (BHSP) analysis to identify acting faulting and barriers. This is achieved by overlapping all isobar maps and then by taking the derivatives of the pressure versus x and y directions. The pressure contrast in space can be highlighted based on a given threshold. If this pressure contrast is overlapped by a seismically identified fault, it can be considered as a barriers or semi-barrier or just absent based on the degree of pressure contrast. The second step is to use the identified boundaries as guidance to limit and confine the different zones and fault blocks that are suspected to act more or less as isolated units. After identifying the boundaries more or less sealing a classification of the static pressure measurements using k-mean value will help to identify the dynamic regions that behave in the same way. A re-sectorization of the field will be based on those units. A forward calculation of voidage replacement ratio and injection production versus pressure can be used as a criterion for identifying the best sectoring scenario.