Integrated Geological and Petrophysical Evaluation for Completion Planning in Carbonates: A Methodology from Western Offshore India

Tiwari, R. R.²
 Singh, P. P.²
 Shrivastva, Chandramani¹
 Sikdar, Koushik¹
 Ghosh, Arnab¹

Bassein Limestones from Western Offshore India offer various challenges in the development phase due to the inherent uncertainties with their petrophysical and geological characterization. A good completion planning is imperative to control water cut and gas channeling for optimizing the oil production. The objective of this study was to aid in proper segmentation of drain-holes for swell-packer placement during completion design.

Integration of advanced logging measurements in three wells of the field aided in the evaluation of the petrophysical properties and their careful incorporation in conceptual geological models helped in proper understanding of the depositional sub-environments that lead to heterogeneity in the reservoir. Borehole images captured the fabric of the facies due to their high resolution imaging capabilities and sonic logs were processed for formation slowness and Stoneley fracture and permeability results. The logging-while-drilling conventional data acquired in all the three wells was incorporated in the study along with the elemental capture spectroscopy data to understand the gross lithology distribution.

Detailed analysis provided a measure of connectedness between the vugs. Some solution enhanced features were identified on the image logs which were interpreted as minor fractures subjected to dissolution activities. Five different facies were identified in the horizontal wells with considerable (5-10%) secondary porosity due to vugs and dissolution activities in a few facies. Such facies showed varying degree of connectedness in the vugs and were studied carefully to understand their impact on production profile, particularly in view of their near-vertical orientation which subsequently may pose a threat to gas or water breakthrough. The placement depths for swell-packers to segment the drain hole were decided based on the results of the analysis done in real time. This study, therefore, develops a methodology for aiding in completion design in such carbonate fields to honor the geological uncertainties.