이산화탄소 저장을 위한 Acoustic emission 암반 측정

영신컨설턴트 (02) 529 8803 ystcha@naver.com   2021 5

 

2030년 이산화탄소 배출을 감소시켜 온도 2도를 낮추기 위한 파리 기후 협약 후 지하 이산화탄소 지하에 저장합니다. 배출된 이산화탄소를 지하에 저장할 때 암반의 균열상태를 삼축셀 내부에서 암반 코아에 Acoustic emission부착하여 측정합니다.

 

Carbon Capture and Storage (CCS) is considered an essential mitigation strategy in order to reduce anthropogenic CO2 emissions. To meet the 2 ℃ target set in the Paris Agreement, decarbonization of the global power sector by the 2030s and the heavy industry sector beyond that is critical.  

 

 

이산화탄소 배출과 지하저장

 

삼축셀 내부에서 초음파 측정하여 미세균열 상태 측정

구성

a triaxial cell with 12 passive signal recorders (P-wave pin-transducers)

and 4 active signal recorders (both P- and S-wave sources

and receivers in axial and radial directions).

 

The system can control the axial (vertical) stress, the radial (horizontal) confining pressure and the pore pressure of the fluid inside a core sample.

 

The waveforms are recorded at 10 MHz sampling rate at 12-bit resolution.

 

The resonance frequency of the pin-transducers is about 1 MHz and most of the energy in the signal is centred on 0.5 MHz.

 

A nitrile rubber sleeve is used to isolate the sample from the confining oil and fix the positions of the pin-transducers.

 

Ultrasonic compressional (P) and shear (S) wave velocities of the rock are measured along the axial and radial directions using piezo-electric transducers that are mounted inside the top- and bottom pedestals (axial direction) and to the rubber membrane (radial direction).

 

(a) The schematic representation of the triaxial apparatus, (b) AE sleeve and (c) sketch of a sample with a horizontal borehole in the middle and 12 pin-transducers positioned at the surface (black triangles, S01–S12). Transducers for measuring the P- and S- wave velocities are indicated with red triangles (S13–S16) (Aker et al. 2014).   

 

 

Acoustic Emission test of Rurikfjellet shale core. The instantaneous frequency spectra shows different frequency contents for different-stages in the test. As the test stage goes to the end, the low frequency content is increasing (Park et al. 2018).

 

 

 

(a) Test data example for multiple cycles of loading/unloading and Brine-CO2 drainage/imbibition;

(b) multi-direction and point measurement system cell (Soldal et al, 2015).

a) Schematic representation of hydrostatic cell, b) applied confining stresses, CO2 pore pressure, effective stresses, and temperatures and observed velocities at different temperature (T) and pressure (P) conditions for c) Knorringfjellet and d) Red Wildmoor sandstone core plugs (Moghadam et al. 2016).

 

Sensor orientation relative to rock sample bedding (top). P-wave velocity(left, bottom) and electrical resistivity (right, bottom) versus injected CO2 in pore volume (PV), measured simultaneously at different levels/points and directions during CO2 flooding test with Gres Des Vosges (GDV). (Soldal et al. 2015b)

 

 

a) Illustration of naturally-fractured De Geerdalen sandstone, b) fracture plane extracted from CT scanning, and changes in c) acoustic velocity and d) electrical resistivity during drainage of brine by CO2 in the fracturec (Nooraiepour et al. 2018).

 

a) Schematic diagram of the tested samples in the triaxial cell and the transducer arrangement around the samples, b) the loading paths and test progression with elapsed time for a core plug cut vertical to the bedding and c) Thomsen anisotropy parameters versus mean effective stress (Zadeh et al. 2017).

 

 

Evolution of effective vertical stress (blue line), axial P-wave velocity (orange dot), and P-wave first arrival maximum amplitude (black dot) with time. The first cycle is CO2-saturated, the second one brine-saturated and the last phases is CO2-injection into brine-saturated sample.