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Abstract

G. P. Eberli, J. L. Masaferro, and J. F. ldquoRickrdquo Sarg, 2004, Previous HitSeismicNext Hit imaging of carbonate reservoirs and systems: AAPG Memoir 81, p. 169-183.

Copyright copy2004. The American Association of Petroleum Geologists. All rights reserved.

Quantitative Previous HitSeismicNext Hit Reservoir Characterization of an Oligocenendash Miocene Carbonate Buildup: Malampaya Field, Philippines

Dietmar Neuhaus,1 Jean Borgomano,2 Jean-Claude Jauffred,2 Christophe Mercadier,2 Sam Olotu,3 Juumlrgen Groumltsch4

1Shell Philippines Exploration BV, Alabang, Muntinlupa, Philippines; Present address: Nederlandse Aardolie Maatschappij, Assen, The Netherlands.
2Shell EampP Technology and Previous HitAppliedNext Hit Research, Volmerlaan 8, Rijswijk, The Netherlands
3Shell EampP Technology and Previous HitAppliedNext Hit Research, Rijswijk, The Netherlands; Present address: Shell Petroleum Development Company, Lagos, Nigeria.
4Shell Abu Dhabi BV, Abu Dhabi, United Arabian Emirates

ACKNOWLEDGMENTS

This article is largely based on work performed during the Malampaya gas-development and oil-appraisal drilling campaign in 2000 and 2001 and the contribution of the subsurface team in Shell Philippines Exploration BV (SPEX), namely, G. Davies, J. Esquito, G. Loftus, and O. Tosun is greatly appreciated. Previous HitSeismicNext Hit processing, special Previous HitseismicNext Hit studies, and reservoir modeling were performed at Shell Exploration and Production Technology and Research (SEPTAR) in Rijswijk, The Netherlands. Contributions by A. van den Berg, T. Carlson, J. Leguijt, L. Mieles-de Pina, E. Sims, and T. Tjan are highly appreciated. Comments by the reviewers Bruce Hart and Gregor Eberli helped considerably to improve the manuscript. We are grateful to SPEX, Texaco Philippines Inc., and PNOC-EC for authorizing publication of these Previous HitdataNext Hit.

ABSTRACT

The complex reservoir architecture of the Malampaya carbonate buildup offshore Palawan, Philippines, was initially controlled by a rugged clastic basement morphology, which was overgrown by atoll structures during the Oligocene and early Miocene. Additional factors with major impact on reservoir quality are frequent and high-amplitude relative sea level fluctuations, ocean currents, and prevailing wind directions. Primary depositional reservoir-quality distribution has been overprinted by diagenetic events, primarily as a result of repeated platform-top exposure and submarine cementation. Inherent noise within the previous Previous HitseismicNext Hit Previous HitdataNext Hit introduced by the complex overburden and buildup morphology has resulted in inconsistent Previous HitseismicNext Hit attribute distribution. Therefore, earlier reservoir modeling efforts used Previous HitseismicNext Hit horizon and volume interpretation only, coupled with the sequence- and cyclostratigraphic architecture and the concept of reservoir rock types for field development planning.

Prior to gas-development drilling, another attempt was made to extract direct reservoir-quality information Previous HitfromNext Hit the reprocessed three-dimensional (Previous Hit3-DNext Hit) Previous HitseismicNext Hit Previous HitdataNext Hit to validate the earlier deterministic reservoir models. Improved Previous Hit3-DNext Hit prestack depth migration based on a new velocity model has been the foundation of the quantitative Previous HitseismicNext Hit analysis for reservoir characterization, static modeling, reserves estimation, and optimized gas development and oil appraisal well targeting. High-porosity areas in the upper part of the reservoir were identified using top-reservoir reflection amplitudes. This provided the tool to minimize penetration of low-porosity, fractured zones prone to mud losses in the gas development wells. A series of acoustic-impedance inversions were Previous HitappliedNext Hit to create reservoir porosity cubes Previous HitfromNext Hit Previous HitseismicNext Hit and to target wells in good reservoir areas. Porosity cubes are also essential for a correct time-depth conversion of the static model, using a linear porosity-velocity relationship in clean carbonates, which was derived Previous HitfromNext Hit well Previous HitdataNext Hit. Several static model realizations were created using the porosity cubes Previous HitfromNext Hit Previous HitseismicNext Hit as a backdrop combined with Previous Hit3-DNext Hit Previous HitseismicNext Hit facies analysis and a depositional model based on well Previous HitdataNext Hit and analogs. The results of the five gas-development wells have confirmed the modeled reservoir-quality distribution within the lagoonal part of the northern Malampaya accumulation. Early production performance following first gas in October 2001 is indicative of excellent lateral pressure communication in this area of the buildup, in accordance with earlier dynamic models.

Porosity-height realizations created Previous HitfromNext Hit the different Previous HitseismicNext Hit porosity cubes proved valuable to visualize uncertainty in reservoir-quality distribution within the Malampaya oil rim and formed the basis for targeting a horizontal appraisal well. The MA-10 horizontal oil-rim appraisal well drilled at the end of 2001 confirmed the forecasted facies distribution and reservoir properties as derived Previous HitfromNext Hit the model.

Based on the new quantitative Previous HitseismicNext Hit reservoir characterization, additional areas of potentially good reservoir quality have been identified in the southern Malampaya culmination and on the western flank of the northern culmination. Both areas were previously considered to contain low-porosity reservoir caused by pervasive early marine cementation.

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