An experimental study on the mechanism of degradable fiber-assisted diverting fracturing and its influencing factors

Abstract

Fiber-laden fluid systems have been successfully applied for reorientation fracturing in tight gas and shale gas reservoirs around the world. Although many successful cases have been reported in the literature, there is a lack of a deep understanding of the mechanical mechanism of fiber-assisted diverting fracturing. Hence, this paper presents a systematic study of the fracture diversion mechanisms of the fiber-diverting fracturing technique. A series of laboratory experiments is conducted with a real tri-axial stress simulation system. Degradable fibers are applied to large-size natural outcrop samples (300 mm × 300 mm × 300 mm) under true triaxial stress conditions. The dynamic filtration experiment to test the temporary plugging ability showed that the fractures were effectively plugged by fiber fluids. A variety of factors related to the fracture reorientation are tested and compared, including injection rate, fracture width and horizontal principal stress difference. The additional pressure drop caused by the fiber filtration cake is calculated and used to quantitatively analyze the effects on fracture reorientation. The net pressure increase is the driving force of the fracture diversion and formation of the fracture network. The conclusions were used to guide carbonate reservoir stimulations in the Tarim oil field, in northwest China. The phenomenon of fracture diversion was evident as the pumping pressure increased considerably after injecting the degradable fiber. The hydraulic fracturing treatment and production results showed substantial pressure responses and excellent hydrocarbon production.

Experimental study on plugging behavior of degradable fibers and particulates within acid-etched fracture

“…On the one hand, there are more fibers and particulates flowing into the fracture model at the same time under the condition of high injection rate, which is conducive to the formation of bridging and plugging. On the other hand, the fibers are more prone to twine around each other at high injection rate, thus capturing the particulates to form tight plugging zones (Wang et al, 2015a(Wang et al, , 2015b. Therefore, it is recommended to use high injection rate for construction on the premise of on-site conditions.…”

Numerical Simulation on Deflecting Hydraulic Fracture with Refracturing Using Extended Finite Element Method

“…The fracturing fluid was injected at a value of 10 mL/min. Parameters presented by Wang et al [40] were used as a reference. Figure 6 shows that the numerical result was similar to that of the experiment in which the diverting fracture nearly propagated perpendicularly to the initial fracture with a stress difference of 2.5 MPa.…”

“…Comparison result between numerical model and experiment: (a) numerical result based on extended finite element method (XFEM); and (b) true tri-axial experiment result[40].…”

Experimental study of acidizing diversion effect on different permeability of heterogeneity sandstone reservoirs

“…However, mechanical technology in the construction process is relatively complex and cost too much; therefore, to simplify the construction process matrix stimulations, chemical placement technique which was called diverters was usually applied in a pre-flush and temporarily plugs the zone or zones of highest permeability, allowing the main flush to react with other less permeable or more damaged zones. Chemical diversion methods (Kelland 2014), including solid particles (Williams et al 2016), polymer gels (Coste et al 2000;Bai et al 2008), foams (Kapetas et al 2015;Kam et al 2007), viscoelastic surfactants (VESs) (Santvoort and Golombok 2015; Fink 2015), fiber (Wang et al 2015), and so on, have been widely used in the industry.…”