Datapages, Inc.Print this page

AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

Integrated Formation Evaluation in Horizontal Wells for Completion Optimization: Case Studies from a Complex Carbonate Reservoir in India

Arnab Ghosh1; Sutapa Bhadra1; Theodore Klimentos1; S. Chandrasekaran2; S. Anand2; V. Garg2; S. Bag2

(1) DCS, Schlumberger Asia Services Ltd., Mumbai, India.

(2) ONGC, Mumbai, India.

The carbonate formations of Mumbai High field are the most prolific oil reservoirs in India. These geologically young Miocene carbonates are very complex in nature with extensive lateral heterogeneity. Mumbai High field was put on production in the year 1976. The field has been under water-injection for many years for reservoir pressure maintenance. Presently, some of these layers are producing with high water-cut in drain-hole sections. The main objective of the present study was to enhance productivity and reduce the high-water cut in the newly drilled drain-holes using a workflow of integrated formation evaluation and effective completion strategy.

Carbonate formation evaluation using conventional well-logs to optimize completion has higher uncertainty in high-angle and / or horizontal wells. Integration of advanced well-log data, i.e., dipole shear sonic, formation micro-resistivity imaging, nuclear magnetic resonance and elemental capture spectroscopy helped to reduce this uncertainty and optimize the completion strategy. Formation textural heterogeneity from micro-resistivity image data helped to identify isolated and connected vugular porosities. Moreover, detection of solution enhanced features and fractures were obtained by combining formation micro-resistivity image and Stoneley-wave data. Pore size distribution for free and bound fluid porosity and continuous permeability, determined from NMR, was used to delineate lateral variations in this carbonate reservoir. Accurate lithology characterization in association with heavy minerals, i.e., pyrite was possible from different dry weight elemental concentrations using elemental capture spectroscopy data.

Slotted / cased liner completions have been used in horizontal wells for borehole stability and well integrity purposes. However, these completions may have lower productivity relative to equivalent open hole completions, if the perforated liners are not positioned correctly. The present study has shown that optimizing the performance of the completion can increase well productivity in a cost effective manner. The present case studies established an integrated formation evaluation approach for completion optimization in a timely manner, which resulted in a significant increase of oil production and reduced water-cut. This methodology can be used effectively in Mumbai High horizontal wells, as well as, other carbonate reservoirs.