Abstract

In association with field development planning to supply gas to Singapore in 2000, a reservoir characterization study of one dedicated reservoir (Beta-1A Zone) was conducted to better understand the critical uncertainties and identify potential field reservoir heterogeneity, in support of a value driven development plan.

This reservoir had previously been intersected by several wells drilled to deeper field objectives. The data available for this integrated study included various subsurface data including 3D seismic (seismic attributes and coherence), wire-line logs, rock data (core, thin sections, XRD, capillary pressure), fluid properties and pressure data.

The results of this study show that the Beta-1A sandstone reservoirs were deposited in a Lower Delta Plain depositional setting. Reservoir facies consist of Tidal Flat and Tidal Channel Bar, with a general channel direction trend based on the seismic coherency attribute being north to north-east. The reservoirs composed predominantly of quartz, minor feldspar and rock fragments with illite as the predominant clay mineral. The porosity and permeability ranges are from 25% to 38% and 33 mD to 2370 mD respectively. The 3D seismic quality is fair to poor, however, the "bright spot" area highlighted the area of good gas bearing sand development. The reservoir gas water contact derived from RFT data agreed closely with the seismic amplitude extraction distributions. Together they have been used to identify the critical field and reservoir limits.

The results of the study have led to a better understanding of reservoir complexity, better estimates of GIP, and have enabled selection of the best strategy for field development. One successful horizontal well was drilled based on this study in a down-flank position in an area with less well control. It resulted in a gas test rate up to 60 MMCFGPD.