MOTET, DANIEL, JEAN-PIERRE DELHOMME and OBERTO SERRA, Schlumberger, Montrouge, France

ABSTRACT: Reservoir Description and Characterization from Well Logs and Electrical Images

Characterization of the reservoir requires its description in terms of volumes and surfaces. The internal organization of volumes is described in order to determine their flow properties. The transmissivity properties of surfaces are deduced from their nature and origin. Imaging techniques play a fundamental role in achieving this characterization. High-resolution images bring numerous details about bed heterogeneities and sedimentary structures. This information can now be quantified through geology-driven image analysis techniques. Linked to the lithological information derived from standard logs, this allows identification of facies, genetic sequences and depositional environments. In turn, this is the key to inferring the lateral extent of permeability barriers or paths and identi ying the major flow units in each well.

Flow baffles and conduits related to tectonic events, such as faults and fractures detected in borehole images, are also integrated into the description of each reservoir unit. Within flow units, directional information can be derived from an automated analysis of sedimentary structures over cross-bedded intervals or of open fractures over fractured intervals.

This reservoir zonation in terms of flow properties and the tectonic information that is obtained in each well, provides data for the reconstruction of interwell reservoir geometry.

The detailed information brought by electrical borehole images is very helpful to develop a geologically-reasoned description of the subsurface in terms of large-scale reservoir units. This description can be refined by reconciling it with well tests and flow data at each reasoning step.

The approach is illustrated by case studies in carbonate and siliciclastic environments.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.