Experimental Study of Fracture Propagation: The Application in Energy Mining

Abstract

Hydraulic fracturing has been widely used in recent years as a key technology to improve energy mining efficiency in petroleum and geothermal industries. Laboratory hydraulic fracturing experiments recently were completed in six large-scale 300 × 300 × 300 mm rock specimens to better understand this complex process of hydraulic fracturing. When injection flow rate increases from 5 to 30 mL/min. The fracture initiation pressures and breakdown pressures increase, the propagation times and post-fracturing pressures decrease. The fracture geometries are observed and analyzed, mean injection power is proposed and results show that it could be used to roughly estimate the fracture total lengths. Moreover, the fracture permeabilities based on the pressure data are calculated and linearly ascend with the increase of injection flow rates. These results can provide some reasonable advice for implementing hydraulic fracturing reservoir simulations and improving energy production efficiency on application to field-scale operation.Hydraulic fracturing usually relates complicated solid-fluid coupling processes. Due to the compactness and the low permeability of the granite, an intact large-size granite sample requires a high fracturing pressure to trigger the fracture. To better understand the characteristics of hydraulic fracturing process and fracture network after hydraulic fracturing. In this work, we carried out laboratorial hydraulic fracturing experiments with a true triaxial fracturing apparatus designed by Jilin University. Its cubic specimen fracturing capsule size is 300 × 300 × 300 mm. The granite samples were collected from the Songliao Basin petroleum reservoir field in the northeastern part of China. In order to investigate the injection flow rate on hydraulic fracturing chrematistics, we conducted hydraulic fracturing tests at different injection flow rates for six rocks. The initiation pressure, breakdown pressure, post-fracturing pressure, and propagation time were analyzed based on the fracturing pressure curves. The rock specimens were cut in half after test and the fracture geometry was observed. Based on recorded pressure data and curves, the fracture permeabilities of all specimens were calculated. Results in this study could provide some reasonable advice for implementing hydraulic fracturing reservoir simulations and improving energy production efficiency on application to field-scale operation. Laboratorial Tests BackgroundThe granite samples used in this study are taken from a place nearby YS-2 well (Figure 1) in the Songliao Basin [39]. The YS-2 well (127.25 • E, 52.36 • N) is in the Daqing Oilfield about 78 km from Daqing City, The YS-2 well is a geothermal energy exploration well, and exploration data shows that the geothermal resources here are abundant. As large size intact rock samples cannot be gotten from a wellbore. We use the outcrop rock samples as substitutes (Figure 2a). Three independent triaxial principal stresses are applied on cube-shaped samples to simulate the real field in-situ st...

Machine Learning-Based Accelerated Approaches to Infer Breakdown Pressure of Several Unconventional Rock Types

“…The results are aligned with the experimental results published by Kumari et al in 2018. 5 Figure 17d shows the sensitivity results of the BP of the rock upon changing the injection flow rate of fracturing fluids with increasing 64 The comparison was performed for the cases when there was no confining pressure. The properties of other rocks utilized are given in Table 1.…”

“…The properties of other rock types are obtained from the literature. 64 The comparison was performed for the cases when there was no confining pressure. The properties of other rocks utilized are given in Table 1 .…”

Experimental Investigation of Hydraulic Fracturing and Stress Sensitivity of Fracture Permeability Under Changing Polyaxial Stress Conditions

“…Pressurisation rate or injection rate has been shown to impact breakdown pressures, with higher rates leading to higher breakdown pressures e.g. (Cheng & Zhang, 2020;Haimson & Zhao, 1991;Zhuang et al, 2018). In an attempt to reduce seismicity during hydraulic fracturing and improve efficiency, fatigue hydraulic fracturing through cyclic injection schemes has been proposed.…”

“…Fracture propagation can be inferred from CT scanning (Zhuang et al, 2020), thin section and image analysis (Patel et al, 2017), as well as post experimental destructive analysis using dyed fluid e.g. (Cheng & Zhang, 2020). However, these are all post-experimental analyses that do not capture the propagating fracture front.…”

“…Ishida et al (2004), Stanchits et al (2015), and Zoback et al (1977) all show that high viscosity fluid is more likely to lead to stable fracture propagation based on the conceptual model that high viscosity fluids are unable to penetrate tight fractures to apply the fluid pressure at the fracture tip (Zoback et al, 1977). Pressurization rate or injection rate has been shown to impact breakdown pressures, with higher rates leading to higher breakdown pressures (e.g., Cheng & Zhang, 2020; Haimson & Zhao, 1991; Lockner & Byerlee, 1977; Zhuang et al, 2018). In an attempt to reduce seismicity during hydraulic fracturing and improve efficiency, fatigue hydraulic fracturing through cyclic injection schemes has been proposed.…”