Constraints on Simultaneous Growth of Hydraulic Fractures From Multiple Perforation Clusters in Horizontal Wells

Abstract

In spite of the fact that multistage hydraulic fracturing from horizontal wells is the fastest growing and arguably the most economically important application for well stimulation, numerous fundamental questions remain that are relevant to determining how long to make each isolated interval and how many perforation clusters to place within each interval. This paper provides new insights into this problem by predicting how many hydraulic fractures can be expected to grow simultaneously from multiple perforation clusters pressurized by a single injection stage. These predictions are obtained from a coupled mathematical model that includes the contributions of fluid flow, rock breakage, and pressure loss through the perforations to the total power requirements for the growth of arrays of multiple hydraulic fractures. For typical shale-gas stimulations, radial hydraulic fractures are predicted to grow from all perforation clusters, with progressive reduction in the number of hydraulic fractures, thereby maintaining a ratio of the radius to the spacing that is a small amount less than unity. If the hydraulic fractures are contained to a height H, then multiple Perkins-Kern-Nordgren (PKN) -like hydraulic fractures are predicted to continue growing, with the length of each hydraulic fracture increasing throughout the injection and with a spacing that is approximately 1.5 H when perforation losses are strong and approximately 2.5 H when perforation losses are negligible. These geometric predictions are consistent with previously published observations based on microseismicity associated with stimulations in the Barnett shale.

Growth model for large branched three-dimensional hydraulic crack system in gas or oil shale

“…Yet, so far, all the previous studies based on fracture mechanics [4,[19][20][21][22][23][24] have dealt with the propagation of one hydraulic crack or, very recently, a few parallel (i.e. non-intersecting) ones spaced by about 10 m [25][26][27][28][29]. These studies have been important for clarifying the micromechanics of the problem, especially the complicated interaction of crack tip singularity with viscous flow and capillarity near the tip.…”

Model‐Based Evaluation of Methods for Maximizing Efficiency and Effectiveness of Hydraulic Fracture Stimulation of Horizontal Wells

“…The spacings used here are the same as in section . Since the most commonly used fluids are slick water (0.003Pa s), linear gel (0.05 Pa s), and cross‐linked gel (0.5 Pa s), the graphs are zoomed in on the most instructive range of viscosity 0.003–1 Pa s. To account for the limited entry, the pressure loss through perforation tunnels is embedded into the simulator via the global energy balance using the power expression (Bunger et al, ) …”

Controlling the Height of Multiple Hydraulic Fractures in Layered Media

“…These studies are invariably based on the assumption that the fractures are primarily contained within the pay zone and use the Perkins-Kern-Nordgren-type fracture geometries in their calculations (Bunger et al 2013). Several natural conditions may facilitate the formation of such favorable fracture shapes.…”

“…However, it is expected that the fracturing-fluid pressure that ensures height containment would depend on the fracture spacing in the case of multiple transverse fractures. It is well-known from the stress analysis of cracked bodies that the interaction between a stack of closely spaced cracks produces a stress-shielding effect (i.e., a reduction in the stress-intensity factor at the same level of applied load) (Delameter et al 1975;Chang and Kotousov 2014). However, this effect was not considered previously in the context of hydraulic fracturing.…”