Temperature-strain detection system and method for reservoir rock mass

A temperature-strain detection system for reservoir rock mass, which is applied to temperature-strain detection for reservoir rock mass under true triaxial high temperature loading conditions;

• the temperature-strain detection system for reservoir rock mass comprises:
• a light source, a strain measurement module, a temperature measurement module, a sensing optical fiber, a processing module, a first optical switch and a second optical switch;
• the light source is respectively connected to the strain measurement module and the temperature measurement module;
• the strain measurement module and the temperature measurement module are both connected to the processing module;
• the strain measurement module and the temperature measurement module are both connected to the sensing optical fiber;
• the sensing optical fiber is arranged in reservoir rock mass;
• the sensing optical fiber is engraved with an ultra-weak Fiber Grating (uwFBG) array, and the uwFBG array comprises multiple uwFBGs;
• select a single uwFBG at a beginning/an end of the uwFBG array as a temperature calibration optical grating to determine an initial position deviation and/or a cumulative position deviation;
• the strain measurement module comprises a first optical coupler, a main interference unit, and an auxiliary interference unit;
• the light source is respectively connected to the main interference unit and the auxiliary interference unit after passing through the first optical coupler;
• the main interference unit and the auxiliary interference unit are both connected to the processing module;
• the main interference unit adopts a Mach Zehnder interference structure to obtain a strain signal of the sensing optical fiber;
• and the auxiliary interference unit adopts a Michelson interference structure to sample the strain signal of the sensing optical fiber at frequency points to obtain a strain reference signal;
• the temperature measurement module adopts a coherent detection structure to measure a temperature signal of the sensing optical fiber and a temperature reference signal through a backscattered Rayleigh scattering signal;
• the processing module is configured to obtain both strain data and the temperature data of the reservoir rock mass based on the strain signal of the sensing optical fiber, the strain reference signal, the temperature signal of the sensing optical fiber, and the temperature reference signal;
• the light source is connected to the first optical coupler and the temperature measurement module through the first optical switch;
• the strain measurement module and the temperature measurement module are both connected to the sensing optical fiber through the second optical switch;
• the Mach Zehnder interference structure adopted in the main interference unit comprises:
• a second optical coupler, a polarization controller, a first optical circulator, a third optical coupler, and a first photodetector;
• one end of the second optical coupler is connected to the first optical coupler;
• an other end of the second optical coupler is respectively connected to one end of the polarization controller and a first end of the first optical circulator;
• an other end of the polarization controller is connected to one end of the third optical coupler;
• an other end of the third optical coupler is connected to one end of the first photodetector;
• an other end of the first photodetector is connected to the processing module;
• a third end of the first optical circulator is connected to one end of the third optical coupler;
• and a second end of the first optical circulator is connected to the second optical switch.