유체 주입을 동반한 절리 암반의 수리-역학 특성 평가에 대한 고찰

A Technical Review of Hydromechanical Properties of Jointed Rock Mass accompanied by Fluid Injection

Abstract

최근의 이산화탄소 심지층 처분, 인공지열저류층 형성 및 발전, 원유회수증진 사업 등에는 고압의 유체를 주입하는 과정이 수반되고 이들 사업의 안전하고 성공적인 수행을 위해서는 대상 부지 절리 암반의 투수 특성 및 주입압에 의한 역학적 변형에 기인한 변화를 정확하게 평가하는 것이 중요하다. 본 고에서는 절리 암반 수리-역학 특성 파악을 위한 해석적 및 실험적 평가 방법에 대해 검토하였다. 먼저 유체 주입 전 절리 암반 초기 투과 특성 및 수리-역학 특성 평가에 고려해야 할 기술요소를 분석하고 현장 시추공 실험을 통해 이들 수리-역학 특성을 직접 측정하기 위한 최근의 SIMFIP 실험장치의 특징 및 활용방안에 대해서도 검토하였다.

Permeability and its change due to a fluid injection in jointed rock mass is an important factor to be well identified for a safe and successful implementation of Carbon Capture and Sequestration (CCS), Enhanced Geothermal System (EGS) and Enhanced Oil Recovery (EOR) projects which may accompany injection-induced hydromechanical deformation of the rock mass. In this technical report, we first reviewed important issues in evaluating initial permeability using borehole hydraulic tests and numierical approaches for understanding coupled hydromechanical properties of rock mass. Recent SIMFIP testing device to measure these hydromechanical properties directly through in-situ borehole experiments was also reviewed. The technical significance and usefulness of the device for further applications was discussed as well.

Fig. 1. Transmissivities for selecting a type of hydraulic tests

Fig. 2. The effect of hydromechaical characteristics due to injection on fluid pressure build-up

Fig. 3. Comparison of two different approaches to define a stress-permeability relation in jointed rock mass (Rutqvist, 2015)

Fig. 4. Components and setup of SIMFIP devices (Gugliemli et al., 2014) (a) Schematic installation of the devices (b) Downhole probe

Fig. 5. Deformation measurement unit in the downhole probe(Gugliemli et al., 2014)

Fig. 6. Installation of SIMFIP device at the side wall of underground research cavern(http://sanfordlab.org/experiment/sigma-v)

Fig. 7. Theoretical pressure evolution and joint deformation during SIMFIP test (Gugliemli et al., 2014)

Fig. 8. Graphical interpretation of SIMFIP test results(Gugliemli et al., 2014)

Fig. 9. Field conditions for the SIMFIP test at the Tournemire URL site (Guglielmi et al., 2015)

Fig. 10. The results of SIMFIP test at the Tournemire URL site (top: pressure and flow rate with regard to time, bottom: displacement at hanging wall of the fault, Guglielmi et al., 2015)

Fig. 11. Three dimensional plots of measured displacement of SIMFIP test at the Tournemire URL site (Guglielmi et al., 2015)

Fig. 12. Model geometry and boundary conditions for the numerical simulation of SIMFIP test (Guglielmi et al., 2015)

Fig. 13. Results of both measured and calculated by numerical simulations of SIMFIP test at the Tournemire URL site (Guglielmi et al., 2015)

Fig. 14. The results of numerical simulations of SIMFIP test at the Tournemire URL site (Guglielmi et al., 2015)

Fig. 15. Stereographical representation of incremental joint displacement measured from SIMFIP test

Table 1. The estimated hydromechanical properties of the joint (Modified from Guglielmi et al., 2015)