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Abstract

Increased volatility of the gas/oil prices coupled with the high cost of finding new reserves have resulted in an urgent need for better managing newly-found reserves. With this incentive and opportunity, we have undertaken an integrated approach of creating the definitive tool-box for better description and characterization of the reservoir cut by PC4-1 located in Block SK310, East Central Luconia, offshore Sarawak, East Malaysia. PC4-1 is a gas discovery with 454 m gas column with varying amounts of movable<br>water in the studied log coverage of 2648-3274 m (626 m). With the help of integration of geological information, conventional openhole logs, NMR, image logs, and fluid sampling and pressure tests, we have derived and modeled static and approximate dynamic<br>properties of the formation. The work scope in its entirety encompasses a thorough analysis of the geological and wireline datasets acquired in PC4-1 in order to quantify the key reservoir features required for distributing petrophysical properties in three-dimensional space using geologic models. The resistivity (STAR) and acoustic (CBIL ) images of the borehole wall, MREX partial porosity distribution, and Stoneley reflectivity were used for a geological analysis for defining image facies. The reef complex comprises four distinct facies and localized vuggy and karstic zones. The CBIL image and Stoneley reflectivity was particularly useful for locating potential karst/vuggy porosity zones. Stoneley reflections are very sparse and the losses of acoustic energy are rare. A stochastic and deterministic method is used for conventional petrophyscial analysis. The results are comparable, which lends confidence in the parameters used and results obtained. Water and hydrocarbon saturation are computed using conventional Archie model bulk shale analysis techniques. A water level is interpreted at 3238m ahbdf. The Acoustic Log Hydrocarbon Indicator (ALHI) technique is used to generate flag curves for each identified fluid type on a zonal basis. Since NMR data was acquired in the 8.5” hole, we can calibrate the ALHI against the actual NMR results and provide fluid typing for the 6” hole which was not covered by the NMR. There are no core data available for calibration of wireline logs; however, the latest technological advances in MREX and RCI tools in conjunction with the conventional petrophysics, and most recent computational techniques, provide the proper foundation for models and correlations generated from the petrophysical trends. Petrophysical properties such as ermeability, porosity, wetting and non-wetting phase saturations are computed, modeled, and the key controls of the productivity have been extrapolated into the 6” hole sections where we have no MREX data. Furthermore, the analogous behaviors of capillary pressure and 1/T2 decay versus saturation data provide a methodology for deriving synthetic capillary pressure information directly from NMR logs. The methodology and theoretical assumptions are explained in various publications. The technique is extended for PC4-1 by using model equations that would transform the “partial porosity versus time” distribution into capillary pressure versus wetting-phase saturation, after correction of partial porosity bins for gas and polarization effects and because there is no “diffusive coupling”. The main reason behind attempting to derive capillary pressures is to obtain a more representative BVI profile than from a fixed-T2cutoff type of profile. The transformation is done for each MREX level-spacing; the resultant curves generated are representative of<br>minor changes in the lithology or formation. This data feeds into a Productivity Analysis.

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/content/papers/10.3997/2214-4609-pdb.256.R15
2006-11-27
2022-01-21
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