Spectroscopic nanosensor logging systems and methods
Logging systems and methods that employ nanosensors to obtain spectral measurements downhole. The nanosensors can be dispersed in borehole fluids (including cement slurries) that circulate, diffuse, or get injected in a borehole. Because the nanosensors have diameters on the order of 10 nm to 1000 nm, they readily penetrate into cracks, pores, and other voids where their carrier fluids can reach. The nanosensors transport light sources and recording media to measure spectra in these otherwise inaccessible regions. The nanosensors are then recovered and analyzed to reconstruct the measured spectra and determine relevant material characteristics. Among other things, spectral measurements can reveal the presence of certain elements and molecules in the formation and fluids, from which information scientists determine composition and phases of formation fluids and the formation itself. Certain triggering criteria may also be employed to enable the nanosensor measurements to be associated with specific locations, paths, and/or events.
1. A method of measuring formation properties, the method comprising:
collecting nanosensors which have been transported from a formation via a fluid flow;
measuring nanosensor states, the nanosensor states representing optical spectroscopy measurements recorded by the nanosensors before said collecting and while the nanosensors were contact with fluid of the formation; and
reporting formation data derived from said spectroscopic measurements.
2. The method of claim 1 , further comprising:
introducing said nanosensors into said formation before said collecting.
3. The method of claim 2 , further comprising:
causing the nanosensors to emit light while in said formation, wherein said light interacts with an environment around said nanosensors and responsively causes a state change in the nanosensor.
4. The method of claim 3 , wherein said causing includes transmitting an electromagnetic signal or an acoustic signal from a tool in a borehole proximate to the formation.
5. The method of claim 3 , wherein said causing includes providing a time-release membrane that allows a photoluminescent reaction to occur after a predetermined delay.
6. The method of claim 3 , wherein the state change occurs in a photosensitive molecule.
7. The method of claim 6 , wherein the photosensitive molecule is provided with a narrowband sensitivity via a chromophore.
8. The method of claim 1 , wherein said measuring includes using a filter or centrifuge to separate the nanosensors from the fluid.
9. The method of claim 8 , wherein said measuring further includes probing photosensitive materials in the nanosensors with electron spin resonance.
10. The method of claim 8 , wherein said measuring further includes optically examining photosensitive materials in the nanosensors.
11. The method of claim 8 , wherein said reporting includes measuring luminescence of the nanosensors and deriving formation spectra based at least on the measured luminescence and the measured nanosensor states.
12. The method of claim 2 , wherein said introducing includes circulating the nanosensors in a borehole fluid.
13. The method of claim 2 , wherein said introducing includes suspending the nanosensors in a flood fluid.
14. The method of claim 2 , wherein said introducing includes injecting the nanosensors into an isolated portion of a borehole wall.
15. The method of claim 4 , wherein said electromagnetic or acoustic signal targets a particular azimuth.
16. The method of claim 4 , wherein said electromagnetic or acoustic signal targets a particular radial distance.
17. A system for measuring formation properties, the system comprising:
a carrier fluid that conveys nanosensors into a borehole to record optical spectroscopy measurements while the nanosensors contact and penetrate a formation,
wherein at least some of the nanosensors include photosensitive materials, and
wherein at least some of the nanosensors include luminescent materials.
18. The system of claim 17 , Wherein the luminescent materials are triggerable by a time delay or an external signal.
19. The system of claim 18 , wherein the luminescent material includes diamond with nitrogen vacancies that fluoresce in response to electromagnetic signal pulses.
20. The system of claim 17 , wherein at least some of the nanosensors are coated to provide a surface affinity for interacting with a target material in the formation.