A new log interpretation system called TITEGAS has been developed to analyze the reservoir characteristics and producibility of tight gas sands. The system is based upon equations which define the response of conventional logging tools. A basic log suite of density, neutron, and resistivity are the only logs required by the system, however TITEGAS also allows for utilization of various other logs including photoelectric effect, spectral natural gamma, micro-resistivity, microwave travel time, dielectric constant and acoustic travel time.

The new system includes several innovative analytical procedures:

  • A technique to compute porosity in zones having variable gas saturation and clay content.

  • A new method to quantify gas saturation in the zone investigated by the density and neutron tools.

  • An improved method using the gamma ray to determine clay content in compacted sands composed predominately of illite-type clays.

  • An improved method to determine clay content from the sonic and density log when illite is not the dominant clay type.

  • A new non-geometric mathematical model using neutron and density logs to calculate clay content. This equation makes it possible to refine the clay log response constants.

  • A new technique for the interpretation of formation water resistivity. This procedure is useful in thick sand-shale sequences where water salinity is variable.

  • New methods to refine matrix density of the reservoir. Matrix is dealt with as a foot-by-foot variable rather than as a constant.

  • A new technique to analyze invasion profile and qualitative formation permeability.

  • New methods to detect natural fractures through the the modeling of logs that are generally available.

The TITEGAS system is applied to the DOE/Sandia MWX wells. Comparisons are made between the TITEGAS system results and the high-quality core data and well test data from these wells. The comparisons indicate that the system is a powerful new procedure for the analysis of tight gas sands.

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