Micromechanical analysis of hydraulic fracturing in the toughness-dominated regime: implications to supercritical carbon
- PDF / 2,614,151 Bytes
- 17 Pages / 595.276 x 790.866 pts Page_size
- 9 Downloads / 187 Views
ORIGINAL PAPER
Micromechanical analysis of hydraulic fracturing in the toughness-dominated regime: implications to supercritical carbon dioxide fracturing Mengli Li 1,2 & Fengshou Zhang 2
&
Li Zhuang 3 & Xi Zhang 4 & Pathegama Ranjith 5
Received: 29 June 2019 / Accepted: 21 November 2019 # Springer Nature Switzerland AG 2019
Abstract Supercritical carbon dioxide (SC-CO2) is considered as an ideal non-aqueous fracturing fluid due to its superior properties of liquid-like density, gas-like viscosity, high compressibility, and diffusivity. This study aims to investigate the micromechanical behavior of SC-CO2 fracturing in both intact and fractured rock samples by using a coupled fluid-solid discrete element method (DEM) model. A new numerical algorithm for hydraulic fracturing in the toughness-dominated regime is developed by assuming that the pressure in the whole fracture is uniform. This new numerical algorithm could achieve a much higher computational efficiency compared with the conventional hydromechanical scheme in DEM. Hydraulic fracturing cases using high-viscosity fracturing fluid are also performed for comparison. The results indicate that the fracture propagation induced by SC-CO2 tends to be less smooth and continuous, more asymmetric, and tortuous compared to that induced by viscous fluid. Besides, the lowviscosity fluid like SC-CO2 can lead to a lower breakdown pressure, and the fluid leak-off into the rock matrix can result in a lower breakdown pressure and higher fracture propagation pressure. The simulations also illustrate that SC-CO2 fracturing tends to create a more complex and productive fracture network if the pre-existing natural fractures are involved. As a result, we can conclude that SC-CO2 could be an alternative fracturing fluid to induce a more effective fracture network for hydrocarbon production. Keywords Hydraulic fracturing . Supercritical carbon dioxide . DEM . Toughness-dominated . Tortuosity . Breakdown pressure
1 Introduction Hydraulic fracturing has become a widespread reservoir stimulation technique for hydrocarbon production from low-
* Fengshou Zhang [email protected] 1
State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 100083, China
2
Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China
3
Extreme Engineering Research Center, Korea Institute of Civil Engineering and Building Technology, Goyang, Gyeonggi 10223, Republic of Korea
4
CSIRO Energy, Melbourne, Australia
5
Department of Civil Engineering, Monash University, Clayton, Victoria 3800, Australia
permeability formations. However, conventional hydraulic fracturing with water-based fracturing fluid has some disadvantages, including environmental impacts caused by the flow-back water and the high cost of water usage. Furthermore, since gas productivity is greatly dependent on the water sensitivity of shale gas formations, water-based fracturing is not suitable for the water-sensitive clay-abundant formations [1–4]. There i
Data Loading...
