Algorithm-free, data-centric multivariate inversion for pulsed neutron logging
A method and system for identifying one or more petrophysical properties in a formation. The method and system may include disposing a pulsed-neutron logging tool into a borehole that is disposed in a formation, emitting a neutron from a neutron source on the pulsed-neutron logging tool into the formation, and capturing one or more gammas expelled from formation in response to the neutron from the neutron source to form a plurality of pulsed neutron logging (PNL) measurements in a log. The method and system may further include comparing the log to a database with a cost function to form a solution; and identifying a plurality of petrophysical properties based at least in part on the solution.
1. A method comprising:
disposing a pulsed-neutron logging tool into a borehole that is disposed in a formation;
emitting a neutron from a neutron source on the pulsed-neutron logging tool into the formation;
capturing one or more gammas expelled from formation in response to the neutron from the neutron source to form a plurality of pulsed neutron logging (PNL) measurements in a log;
comparing the log to a database with a cost function to form a solution, wherein the database is populated with simulated data, wherein the simulated data comprises one or more simulated PNL measurements; and
identifying a plurality of petrophysical properties based at least in part on the solution.
2. The method of claim 1 , wherein the solution is unique solution, and wherein the unique solution is a single solution that corresponds to one of the plurality of petrophysical properties.
3. The method of claim 1 , wherein the solution is a non-unique solution, and wherein the non-unique solution is a plurality of solutions that correspond to one of the plurality of petrophysical properties.
4. The method of claim 1 , further comprising adding a constraint, a geophysical interpretation, or an elimination to the unique or non-unique solution.
5. The method of claim 1 , further comprising adding a constraint, a geophysical interpretation, or an elimination to the log.
6. The method of claim 1 , wherein the database is populated using a Monte Carlo simulation to identify one or more variable of interest.
7. The method of claim 6 , wherein the one or more variable of interest are a borehole size, a casing size, a tool position and standoff, a borehole fluid content, a casing and cement quality, a formation lithology, a formation porosity, a formation oil saturation, or a holdup.
8. The method of claim 1 , wherein the comparing the log to a database with a cost function to form a unique or non-unique solution is performed in real-time.
9. The method of claim 1 , wherein the petrophysical properties are a borehole size, a casing size, a tool position, a standoff, a borehole fluid content, a casing and cement quality, a formation lithology, a formation porosity, a formation oil saturation, or a holdup.
10. A system comprising:
a pulsed-neutron logging tool comprising:
a neutron source to emit a neutron into a formation; and
a neutron detector to capture one or more gammas expelled from the formation to the neutron from the neutron source; and
an information handling system to:
form a log from a plurality of pulsed neutron logging (PNL) measurements based at least in part on the one or more gammas;
compare the log to a database with a cost function to form a solution, wherein the database is populated with a plurality of simulated data of the plurality of petrophysical properties, wherein the simulated data is simulated PNL measurements; and
identify a plurality of petrophysical properties based at least in part on the solution.
11. The system of claim 10 , wherein the solution is a unique solution, and wherein the unique solution is a single solution that corresponds to one of the plurality of petrophysical properties.
12. The system of claim 10 , wherein the solution is a non-unique solution, and wherein the non-unique solution is a plurality of solutions that correspond to one of the plurality of petrophysical properties.
13. The system of claim 10 , wherein the information handling system further adds a constraint, a geophysical interpretation, or an elimination to the unique or non-unique solution.
14. The system of claim 10 , wherein the information handling system further adds a constraint, a geophysical interpretation, or an elimination to the log.
15. The system of claim 10 , wherein the database is populated with variables of interest utilizing a Monte Carlo simulation.
16. The system of claim 15 , wherein the variables of interest are a borehole size, a casing size, a tool position and standoff, a borehole fluid content, a casing and cement quality, a formation lithology, a formation porosity, a formation oil saturation, or a holdup.
17. The system of claim 10 , wherein the compare the log to a database with a cost function to form a unique or non-unique solution is performed in real-time.
18. The system of claim 10 , wherein the petrophysical properties are a borehole size, a casing size, a tool position, a standoff, a borehole fluid content, a casing and cement quality, a formation lithology, a formation porosity, a formation oil saturation, or a holdup.