Examining Hydraulic Fracture - Natural Fracture Interaction in Hydrostone Block Experiments

Abstract

Field experience in shale gas and some tight gas sandstones suggests significant interaction between hydraulic fractures and natural fractures. Experimental analysis of this problem has mostly focused on frictional interfaces with regard to the natural fractures. We have performed tests to examine the effect of cemented natural fractures on hydraulic fracture propagation. The motivation for this type of work is that core observations from the Barnett and some other shale gas plays suggest that natural fractures are largely cemented (or healed) and trend obliquely or orthogonally to the present day hydraulic fracture direction. We embedded planar glass discontinuities into a cast hydrostone block as proxies for cemented natural fractures. Consistent with theoretical predictions, our results show that oblique embedded fractures are more likely to divert a fluid-driven hydraulic fracture than those occurring orthogonal to the induced fracture path. Hydraulic fracture – natural fracture interaction took three forms – 1) the hydraulic fracture bypassing the natural fracture by propagating around it (via height growth, not curving), 2) the hydraulic fracture arresting into the natural fracture and then diverting along it and sometimes kinking off the end of it, and 3) a combination of bypass and diversion. We also saw some leakage of fracture fluid along the interfaces of multi-layer blocks, even though such interfaces were perpendicular to the maximum compressive stress, suggesting an analogue for laminated and shaly sedimentary sequences.

Investigation of Fracturing Network Propagation in Random Naturally Fractured and Laminated Block Experiments

“…To reflect the physical and mechanical properties of reservoir rock and to take advantage of their readyavailability to prepare the model blocks, artificial cement blocks were generally selected to perform the hydraulic fracturing experiments [26,27]. According to outcrop observation and core measurements of the typical continental shale in the Ordos Basin, shale and silty laminae are alternatively deposited layer by layer, as shown in Figure 1.…”

“…Energies 2016, 9,588 perform the hydraulic fracturing experiments [26,27]. According to outcrop observation and core measurements of the typical continental shale in the Ordos Basin, shale and silty laminae are alternatively deposited layer by layer, as shown in Figure 1.…”

An Experimental Investigation of Hydraulic Fracturing in Shale Considering Anisotropy and Using Freshwater and Supercritical CO2

“…Various studies [23][24][25][26][27][28][29] investigated important factors (such as rock structure, in situ stress, viscosity, and the injection rate of a fracturing fluid) that affect the hydraulic fracturing process. Most of the aforementioned studies focused on the interactions between hydraulic fractures and pre-existing fractures, or the influence of boundary conditions on the subsequent fracture network.…”

A Laboratory Study of the Effects of Interbeds on Hydraulic Fracture Propagation in Shale Formation

“…Therefore, hydraulic fracturing stimulation is one of the key technologies to produce oil and gas in an economical way [1]. Many scholars have undertaken much research on hydraulic fractures through physical experiments, numerical simulations and analytic criteria [2][3][4][5][6][7]. Particularly, conducting physical experiments is not only valuable for validating numerical simulations, but also an efficient way to understand the effects of various factors on fracture propagation.…”

“…The scholars from Delft University of Technology used tri-axial University of Technology used tri-axial test system and acoustic monitoring to study fracture initiation and hydraulic fracture propagation in natural fractures [13,14]. Moreover, the situations of interaction between hydraulic and natural fractures were noted by Beugelsdijk et al [3], Olson and Bahorich [4,5] and Warpinski [9]: crossing, arresting, offsetting, bypass and diversion. Van Eekelen et al [15] studied the hydraulic fracture propagation in layered formation and analyzed the fracture arresting effects.…”