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US 10,247,849 B2Granted
Method for measuring formation water salinity from within a borehole
AssigneesSchlumberger Technology Corporation, Saudi Arabian Oil Company
InventorsHarold Pfutzner, James A. Grau, Ronald E. Plasek, Raghu Ramamoorthy, Shouxiang Ma
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Abstract
Methods and systems are described for using pulsed neutron ?-ray spectroscopy to measure formation water salinity from within a borehole. Through generating a cross-plot of database values of ratios of spectroscopically determined yields of hydrogen (H) and chlorine (Cl) from two detectors, deriving apparent salinities therefrom, formation and borehole water salinities can be determined.
Claims17
A method, comprising
- lowering a pulsed neutron tool into a borehole penetrating a formation;
- irradiating the formation with neutrons;
- measuring neutron induced gamma ray spectra with at least two gamma ray detectors comprising different sensitivities to borehole and formation gamma rays, wherein a first detector of the at least two gamma ray detectors is configured to measure a borehole signal and a second detector of the at least two gamma ray detectors is configured to measure a formation signal, wherein the first detector comprises back-shielding facing the formation and the second detector comprises back-shielding facing the borehole;
- in a computer, generating a cross-plot forming a quadrilateral of at least one of:
- ratios of spectroscopically determined yields of hydrogen (H) and chlorine (Cl) obtained from a database;
- and
- near detector apparent salinity and far detector apparent salinity values determined from the ratios and obtained from the database, wherein said quadrilateral has four endpoints corresponding to:
- (1) low borehole salinity and low formation salinity, (2) low borehole salinity and high formation salinity, (3) high borehole salinity and low formation salinity, and (4) high borehole salinity and high formation salinity;
- in the computer, deriving formation fluid apparent salinities from measurements obtained from the two gamma ray detectors in the pulsed neutron tool and positions of such measurements on the quadrilateral cross plot;
- measuring water saturation of the formation in which the pulsed neutron tool is disposed;
- and
- in the computer, computing formation water salinity from the formation fluid apparent salinity and water saturation.
9 more elements
A method for determining formation water salinity, comprising:
- in a computer, generating a cross-plot forming a quadrilateral of at least one of ratios of spectroscopically determined yields of hydrogen (H) and chlorine (Cl) obtained from a database, and near detector apparent salinity and far detector apparent salinity values determined from the ratios and obtained from the database, wherein said quadrilateral has four endpoints corresponding to:
- (1) low borehole salinity and low formation salinity, (2) low borehole salinity and high formation salinity, (3) high borehole salinity and low formation salinity, and (4) high borehole salinity and high formation salinity;
- lowering a pulsed neutron tool in a borehole penetrating a formation;
- irradiating the formation with neutrons;
- measuring neutron induced gamma ray spectra with at least two gamma ray detectors located in the pulsed neutron tool, wherein a first detector of the at least two gamma ray detectors is configured to measure a borehole signal and a second detector of the at least two gamma ray detectors is configured to measure a formation signal, wherein the first detector comprises back-shielding facing the formation and the second detector comprises back-shielding facing the borehole;
- and
- in the computer, deriving formation water salinities based on position of pulsed neutron measurements within the quadrilateral.
4 more elements
Dependencies are inferred from the claim text.