Formation water salinity from borehole measurements

Abstract

The present disclosure describes various embodiments related to methods for determining salinity of water in a borehole of a formation and the water in the formation. Various methods may use inelasticand capture gamma-ray spectra obtained from a pulsed neutron logging tool. Various embodiments may use a ratio of chlorine from a capture spectrum to oxygen from an inelastic spectrum for a near anda far detector to calculate apparent salinity ratios for water in a borehole and a formation. From the apparent salinity ratios, a borehole salinity and a formation salinity may be calculated using atool characterization database and without using formation water saturation for the calculation. Other embodiments may be disclosed or claimed.

Description

technical field [0001] Embodiments of the present disclosure generally relate to the field of downhole measurements in wellbores for hydrocarbon production. More particularly, embodiments of the present disclosure relate to methods and systems for determining wellbore and formation water salinity from pulsed neutron gamma-ray (gamma-ray) spectroscopy measurements in the wellbore. Background technique [0002] Hydrocarbons in subterranean formations may be accompanied by water. Such water can often have high concentrations of dissolved salts. After the formation is disturbed by a hydrocarbon production operation, the water in the formation may have variable concentrations of dissolved salts. This variation can vary with time and location within the formation. This variation may result from the mixing of the various aqueous fluids used during production with each other and with the water in the formation. [0003] Knowledge of the salt concentration (often referred to as s...

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Problems solved by technology

For example, without knowledge of salinity, the instrument may not provide accurate estimates of water and hydrocarbon fractions

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