The mixed-salinity environment poses a significant challenge in petrophysics. The industry still lacks a workable solution for accurate formation measurements in the presence of variable or unknown water salinity, especially in reservoir surveillance. A pulsed-neutron (PN) spectroscopy tool was characterized by use of laboratory limestone formations and with data generated through Monte Carlo simulation. Results from a number of measurements obtained were compared with values determined from formation-tester samples, demonstrating that a solution for accurate formation-water-salinity (FSAL) determination has been established.
Introduction
FSAL is a key input parameter for water saturation Sw calculated from formation-evaluation-resistivity logs by use of an Archie type of equation (details are provided in the complete paper).
,
(1)
or from reservoir surveillance pulsed-neutron-capture sigma (Σ) logs, based on the typical mixing rule,
. (2)
In Eq.