The traditional methods for fluid contacts determination in deep seated tight gas reservoirs are very difficult. This is a result of the down hole environment toughness and the complex nature of the rock. In addition to that, most of the tight gas reservoirs have either no, or poorly defined water table.

This paper presents a systematic methodology to determine the proper fluid contacts and to define the movable and unmovable fluids in tight gas reservoirs. It is a comprehensive workflow which integrates core measured Mercury Injection capillary pressure (MICP) and log data measurements.

MICP measurements have been used to detect the irreducible water saturation (Swirr), which was then integrated with core porosity to create the Porosity-Swirr relationships. These relationships have been transformed into bound water volume log profile (Bvwirr) using the log porosity measurements. The gas water contact (GWC) has been located by following the irreducible water saturation (Swirr) and the calculated water saturation (Sw) log profile, and the separation between the bound water (Bvwirr) and the total water bulk volume (Bvw). The GWC is also defined using a synthetic resistivity log, R0 and the relative resistivity discriminator curve (RRD) derived from the simple Archie's equation and following the R0 and true formation resistivity log separation.

These techniques have been successfully applied on the “B” reservoir section of a major gas field to detect the true GWC and to prove the presence of movable fluids. The results were successfully calibrated by well test and production logging results.

As demonstrated in the field case discussed in this paper, the findings of this study have important implications for hydrocarbon maturation assessments, field reserves evaluation and consequently the field development strategy.

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