Multi-Physical Field Imaging Method and System Based on PET-CT and DAS

Abstract

Embodiments of the present disclosure provide a multi-physical field imaging method based on PET-CT and DAS, comprising: wrapping distributed acoustic sensors on a surface of a non-metallic sample to be tested, and then placing them in a pressure device; loading triaxial pressures; preparing a tracer fluid; pumping the tracer fluid into the non-metallic sample; collecting PET images and CT images of internal structure of the non-metallic sample, meanwhile, monitoring internal acoustic emission events of the non-metallic sample in real time; combining the PET images with the CT images, to obtain PET/CT images; locating the acoustic emission events, and obtaining occurrence time and spatial location of internal structural perturbations; and analyzing a mechanism of fluid-solid coupling effect in the non-metallic sample under loaded stress. The imaging method and system of the present disclosure can accurately and reliably image the fluid-solid coupling process in the material.

Description

Claims

1. A multi-physical field imaging method based on PET-CT and DAS, for studying a dynamic fluid-solid coupling effect in non-metallic material, to study hydraulic fracturing process and earthquake induced by the hydraulic fracturing process, comprising: Step A: wrapping distributed acoustic sensors on a surface of a non-metallic sample to be tested, and then placing the non-metallic sample to be tested and the distributed acoustic sensors in a pressure device; wherein the distributed acoustic sensors are phase-sensitive optical frequency domain reflectometers, made of silicon dioxide, the phase-sensitive optical frequency domain reflectometers are configured to have a spatial resolution of 10 cm, a strain resolution of 1nε/Hz,and a vibration sampling frequency of 300 Hz, so as to obtain internal dynamic vibration signals generated from the fluid-solid coupling effect of the non-metallic samples to be tested; the pressure device is made of a composite material of polyether ether ketone and carbon fiber, and the composite material is made from pure polyether ether ketone material filled with 40% by weight carbon fiber;Step B: utilizing electric metering pumps remotely controlled by a computer to load triaxial pressures on the non-metallic sample to be tested, according to requirement of a research experiment, simulating different mechanical conditions to monitor interaction process between fluid and solid and physical response under different mechanical scenarios; wherein experimenters set pressures of the electric metering pumps remotely through the computer outside a PET/CT equipment room, according to the requirement of the experiment, and record pressure changes in real time;Step C: preparing a tracer fluid, and diluting the tracer fluid;Step D: pumping the diluted tracer fluid into the non-metallic sample to be tested through a metering pump remotely controlled by a computer;Step E: continuously and in-situ collecting PET images and CT images of internal structure of the non-metallic sample to be tested; meanwhile, monitoring internal acoustic emission events of the non-metallic sample to be tested by using distributed acoustic sensors in real time;Step F: combining the continuously-obtained PET images with the continuously-obtained CT images, to obtain PET/CT images;Step G: analyzing data from monitoring of the distributed acoustic sensors, locating the acoustic emission events, and obtaining occurrence time and spatial location of internal structural perturbation of the non-metallic sample to be tested; andStep H: combining continuous in-situ dynamic PET/CT images with locating results of the acoustic emission events, to analyze a mechanism of fluid-solid coupling effect in the non-metallic sample to be tested under loaded stress; projecting spatial location information of the acoustic emission events to three-dimensional PET/CT images, to analyze a fluid-solid coupling process in the non-metallic sample to be tested.

2. The multi-physical field imaging method based on PET-CT and DAS according to claim 1, wherein: in the Step A, the distributed acoustic sensors are equidistantly wrapped on the surface of the non-metallic sample to be tested.

3. The multi-physical field imaging method based on PET-CT and DAS according to claim 2, wherein: the pressure device is a pressure device through which positrons and X-rays are able to penetrate.

4. The multi-physical field imaging method based on PET-CT and DAS according to claim 3, wherein: the tracer fluid is a positron tracer fluid.

5. A multi-physical field imaging system based on PET-CT and DAS, wherein the system is configured to implement the multi-physical field imaging method based on PET-CT and DAS according to claim 1.

6. The multi-physical field imaging system based on PET-CT and DAS according to claim 5, wherein the imaging system comprises: a PET machine, configured to scan electrons released by tracers in the non-metallic sample to be tested to obtain internal images of the non-metallic sample to be tested;a CT machine, configured for obtaining CT images of the non-metallic sample to be tested;a distributed acoustic sensing and monitoring system, connected to the distributed acoustic sensors and configured for analyzing obtained acoustic emission monitoring data, picking up data variation points for acoustic emission locating, obtaining spatiotemporal information of the acoustic emission events, and imaging the internal structure of the non-metallic sample to be tested;the pressure device, configured for accommodating the non-metallic sample to be tested and applying pressure to the non-metallic sample to be tested;an electric metering pump configured for applying confining pressure, an electric metering pump configured for applying axial pressure, and an electric metering pump configured for providing tracer; anda pressure loading control system, connected to the electric metering pump configured for applying confining pressure, the electric metering pump configured for applying axial pressure, and the electric metering pump configured for providing tracer.

7. The multi-physical field imaging system based on PET-CT and DAS according to claim 6, wherein the pressure device (10) comprises: a holder body (11), configured to accommodate the non-metallic sample (12) to be tested;a first end cover (17) and a second end cover (18), respectively arranged on two ends of the holder body (11);a confining pressure injection port (14), arranged in at least one of the first end cover (17) and the second end cover (18);an axial pressure injection port (15), arranged in at least one of the first end cover (17) and the second end cover (18);a tracer injection port (16), arranged in the holder body (11); anda pressure transmission core rod (19), arranged between the first end cover (17) and the second end cover (18) and configured to apply axial pressure to the non-metallic sample to be tested.

8. A multi-physical field imaging system based on PET-CT and DAS, wherein the system is configured to implement the multi-physical field imaging method based on PET-CT and DAS according to claim 2.

9. A multi-physical field imaging system based on PET-CT and DAS, wherein the system is configured to implement the multi-physical field imaging method based on PET-CT and DAS according to claim 3.

10. A multi-physical field imaging system based on PET-CT and DAS, wherein the system is configured to implement the multi-physical field imaging method based on PET-CT and DAS according to claim 4.