Gas hydrate estimation error associated with uncertainties of measurements and parameters

Downhole log measurements such as acoustic or electrical
resistivity logs are often used to estimate in situ gas
hydrate concentrations in sediment pore space. Estimation
errors owing to uncertainties associated with downhole measurements
and the parameters for estimation equations (weight
in the acoustic method and Archie?s parameters in the resistivity
method) are analyzed in order to assess the accuracy of
estimation of gas hydrate concentration. Accurate downhole
measurements are essential for accurate estimation of the gas
hydrate concentrations in sediments, particularly at low gas
hydrate concentrations and when using acoustic data. Estimation
errors owing to measurement errors, except the slowness
error, decrease as the gas hydrate concentration increases and
as porosity increases. Estimation errors owing to uncertainty
in the input parameters are small in the acoustic method and
may be signifi cant in the resistivity method at low gas hydrate
concentrations.