Field Test of a Novel Low Viscosity Fracturing Fluid in the Lost Hills Field, California

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe Monterey formation, Belridge Diatomite is a high porosity (45%) low permeability (0.5 -7 md), low Young's modulus (~100,000 psi) oil reservoir with few stress barriers for fracture containment. Due to the low permeability it is desirable to optimize the fracture length per pound of proppant placed. Conventional cross-linked fluids are not well suited for this purpose as they create excessive width -reducing the effective fracture length generated for a given amount of proppant. Post-treatment production tests often show only 30 -100 ft of effective fracture length even for relatively large treatments designed for longer length. Not only is production limited by these shorter-than-designed half-lengths; excessive fracture width combined with low closure stress often leads to serious sand production problems. Pseudo-3D simulations indicated that longer fractures could be realized by significantly reducing fluid viscosity.A novel low viscosity fracturing fluid, designed to address the serious problems unique to low-modulus formations, was field-tested in the Lost Hills field, California. The lowviscosity fluid developed for this application was composed of a linear gel and a fibrous material. Laboratory studies established that the fiber greatly hinders proppant settling, while maintaining a low slurry viscosity required for fracture length creation. Proppant concentrations up to 12 PPA were pumped with this fluid.Seven new wells were treated with the novel fluid. All wells were fractured in multiple stages; 1,250,000 to 1,500,000 lbm of proppant was used in each well. Real-time pressure data was collected on all stages, and treatments on the first two wells were observed with downhole tiltmeters. Both pressure and tiltmeter data indicated that for similar sized treatments, longer fracture half-lengths were achieved with the new fluid -200-400 ft -versus 30-100 ft for conventional crosslinked gels. Production from the test wells compares favorably to offsets, while using 30% less proppant than conventional treatments.Furthermore, it appears that proppant flowback and sanding problems are significantly reduced.

Applicability Assessment of Viscoelastic Surfactants and Synthetic Polymers as a Base of Hydraulic Fracturing Fluids

“…Systems with such a viscosity can hold the proppant volume in the well and transport it to the resulting fracture, thereby ensuring high efficiency of the whole operation. Rotational viscometry is a widely used method for determining the effective viscosity of fracturing fluids [49][50][51][52][53]. However, this type of measurement does not fully describe the structural and mechanical properties of liquids, which leads to a reduced spread of systems based on VES and synthetic polymers.…”

Effect of fiber on the rheological properties of gelled acid

“…Many studies had reported the rheological properties of fiberassisted fracturing fluid and the effects of fiber on the rheological characterization for fracturing fluids that may not be uniform. Vasudevan et al (2001) first reported that the addition of fiber increased the apparent viscosity of linear guar fracturing fluid and led to a three-time increment. However, it was still much lower than the borate cross-linked fracturing fluid under the same condition.…”

Dynamic bridging of proppant particles in a hydraulic fracture

“…The effects of fibers on bridging have been studied in [22,23] based on the partitioning of energy approach following Bagnold's theory. Flow energy imparted to the moving slurry is partitioned into useful shear work, kinetic energy of particles, and a portion lost in dissipative solid-body interactions.…”

“…More sophisticated criteria take into account experimental observations [15], which demonstrate that the critical width is also dependent upon the concentration of proppant upstream of the bridging point. Although the original criterion of [15] was developed for modeling bridging at perforations, there was a modified version of bridging criterion in a fracture, which demonstrates [18,1] w * = min b, 1 + C p 0.17 The effects of fibers on bridging have been studied in [22,23] based on the partitioning of energy approach following Bagnold's theory. Flow energy imparted to the moving slurry is partitioned into useful shear work, kinetic energy of particles, and a portion lost in dissipative solid-body interactions.…”