Affiliation:
1. University of Alberta (Corresponding author)
2. ResFracTM Corporation
3. University of Alberta
4. University of Waterloo
5. University of Saskatchewan
Abstract
Summary
Sustained injection of industrial-scale volumes of cold CO2 into warmer subsurface rock will result in extensive cooling which can alter rock mass mechanical behavior and fluid migration characteristics. Advanced simulation tools are available to assess and characterize such phenomena; however, the effective use of these tools requires appropriate injection temperatures and rock thermophysical parameters (in addition to geomechanical and hydraulic properties). The primary objective of this study was to demonstrate the sensitivity of injection-induced tensile fracturing and fault reactivation to injection temperature and reservoir thermophysical properties during CO2 injection operations. This was achieved by (1) compiling and reviewing thermophysical parameter data available for formations in the province of Alberta, Canada, and CO2 injection temperature records for CO2 injection projects in western Canada and (2) using a 3D, physics-based, fully integrated hydraulic fracturing and reservoir simulation numerical model to examine the geomechanical response of several potential CO2 reservoirs in the Alberta Basin as a function of injection temperature, thermal conductivity (TC), and coefficient of linear thermal expansion (CLTE) values. The simulation results indicate that reducing the fluid injection temperature from 15°C (assumed in previous work) to 2°C (conservative value selected based on temperature data reviewed in this work) could trigger extensive vertical (20–130 m high, 100–600 m long) tensile fractures with rapid fracture initiation and full vertical growth within short periods (weeks to months) and continued horizontal length increase. When low values for thermophysical properties are used, the results show that thermally-induced tensile fracturing is unlikely, whereas the use of high values results in extensive tensile fracturing in all simulations. A similar conclusion was reached for the thermally-induced reactivation (unclamping) of proximal, critically-stressed faults. Notably, slip is predicted for all simulations where high thermophysical property values are used. This confirms that accurate determination of minimum fluid injection temperature and thermophysical parameters is important for containment risk assessment for commercial-scale CO2 storage projects. Another significant outcome of this work is the observation that most thermophysical parameters in the available data were measured using experimental conditions and/or temperature paths that are not representative of CO2 injection projects. As such, the development and validation of best practice approaches for accurate assessment of these parameters seem necessary.
Publisher
Society of Petroleum Engineers (SPE)
Reference72 articles.
1. Effect of Temperature and Pressure on the Thermal Conductivity of Sandstone;Abdulagatova;Int J Rock Mech Min Sci,2009
2. Alberta Energy Regulator
. 2021. Directive 056: Energy Development Applications and Schedules. https://static.aer.ca/prd/documents/directives/directive-056.pdf (accessed11 December 2023).
3. ASTM International Standard
. 2004. C177-19: Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus. https://doi.org/10.1520/C0177-19 (accessed23 February 2023).
4. ASTM International Standard
. 2014. D5335-14: Standard Test Method for Linear Coefficient of Thermal Expansion of Rock Using Bonded Electric Resistance Strain Gages. https://doi.org/10.1520/D5335-14.2 (accessed10 January 2023).
5. ASTM International Standard
. 2021. D4535-21: Standard Test Methods for Measurement of Thermal Expansion of Rock Using Dilatometer. https://doi.org/10.1520/D4535-21.2 (accessed22 June 2021).