Computerized Texture Analysis of Borehole Electrical Images from Middle East Carbonate Reservoirs: A Contribution to Porosity Characterization

DELHOMME, JEAN-PIERRE, Etudes et Productions Schlumberger, Clamart, France, and ROY NURMI, Schlumberger, Dubai, United Arab Emirates

Porosity heterogeneities have been found to be common in carbonate reservoirs and are a major factor affecting fluid flow and recovery efficiency. A review of Middle East and Indian reservoirs reveals that there are four types of heterogeneous fabrics: layered porosity, interwoven porosity, isolated porosity, and isolated nonporous within reservoir zones. Their presence can adversely affect the interpretation, testing, and completion of a well. Electrical imagery is a key to defining the spatial arrangement and orientation of the porosity distribution, or porosity fabric.

To assist in the interpretation and quantification of heterogeneous porosity, specialized image analysis techniques have been developed. Although mathematical morphology concepts developed for medical imagery are used, geological imagery has necessitated the development of some original approaches. The initial focus of the computer image analysis is of isolated porosity and also thin porosity layers alternating with nonporous carbonate rock.

The computer analysis of carbonate textures and fabrics includes the calculation of the percentage of porous and nonporous rock fractions as well as their size, arrangement, or orientation parameters specific to a given fabric. This porosity characterization includes the size of vugs, or patches of porosity, and the thickness and planarity of porosity layers. These results are plotted in a "porosity typing" summary log that facilitates comparisons and integration with other porosity logs, well test data, and production logging surveys.

The "porosity typing" summary log of the textural analysis of reservoir porosity has a variety of applications, but it is an immediate input for well testing and well completion design. Moreover, as carbonate image fabrics are generally related to depositional and/or diagenetic facies, a fabric summary and zonation is also valuable for well-to-well correlation in either reservoir or exploration studies.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)