Producibility Prediction in Gas Sands Through Effective Integration of NMR, Resistivity, and Porosity Log Data

摘要

An interpretation process was implemented that integrates resistivity, NMR, and porosity log data to enhance traditional formation evaluation. The goal was provide a prediction of gas and water production percentages, or water cut, throughout the entire logged interval for the initial production of the well. The integration was done within the framework of a volumetric mineral solver program. It utilized the density-magnetic resonance technique to provide residual gas saturation, gas-corrected total porosity, and gas-corrected NMR permeability. Irreducible water saturation was determined from NMR T_2 data using a fixed T_2 cutoff. Connate water saturation was derived from deep resistivity log data, which may be the result of 2D inversion processes, if necessary. Relative permeability to gas and water were deter-mined using algorithms relating each relative permeability value to the above saturation quantities. Viscosities were derived from reservoir PVT correlations for gas and water and used to calculate relative mobility. Finally fractional flow was derived as a function of these mobilities, providing relative volumes of water and gas. The volumes were displayed as a flow profile that provided a pre-completion open-hole production log. The technique was used in a variety of gas reservoirs in US land environments.