Evaluation of Low-Quality Sand for Proppant-Free Channel Fracturing Method

Abstract

As more wells are drilled and completed in deeper reservoirs, various methods are being applied to overcome choking effects in propped fractures and enhance well productivity. Choking effects can result from permeability damage caused by fracturing gel residues, low proppant concentrations, proppant crushing from high closure stresses, or embedment/intrusion of formation materials into the proppant pack. This paper describes the laboratory testing of a new well stimulation method that can use low-quality sand for generating stable, highly conductive channels within a propped fracture to help maximize and maintain production of hydrocarbon from the formation reservoir to the wellbore.Mini-pillars of various particulate materials were formed by coating them with a tackifying agent or a curable resin and placing them in molds to be cured before testing. These mini-pillars were installed in conductivity cells using various layout configurations to determine the effect of closure stresses on pillar height, diameter expansion, conductivity measurements, and choice of particulate materials. Laboratory experiments were performed to evaluate the formation and stability of mini-pillars and proppant-free channels surrounding the pillars.The obtained results in this study indicate that flow capacity of conductive channels prepared from proppant pillars with low-quality sands was comparable to those prepared using high-quality sand or high-strength manufactured proppant. Proppant crushing was not observed to be a concern when applying fine particulates during this fracturing process because flow capacity of proppant-free channels between aggregate masses dominates flow through the propped fracture, making the formation of proppant pillars with high-quality sand or high-strength proppant unnecessary. As long as proppant pillars are held in place without being previously dispersed or broken up to ensure the integrity of proppant-free channels, low-quality sand or particulates can be a practical and economical source of solids material for preparing these proppant aggregates.

DEM-CFD Modeling of Proppant Pillar Deformation and Stability during the Fracturing Fluid Flowback

“…As a result, the conductivities measured in the numerical models could be largely dropped due to the occupancy of particles in the fluid channels. The field tests with channel fracturing shows the increase of oil/gas production [3][4][5] compared with the traditional proppant placement scheme, but the improvement is much less remarkable than the experimental results by Gillard et al [1] and Nguyen et al [31]. Due to the flowback of proppant particles, the proppant particles move into the channels between pillars, which results in the single layer or a few layers of proppant particles between pillars (Figure 21).…”

“…The lab experiments by Gillard et al [1] and Nguyen et al [31] show that the conductivity of proppant pillars can be up to two orders of magnitude higher than the one with the traditional proppant placement scheme. The proppant pillar profile after the conductivity measurement (Figures 22 and 23) shows that the proppant particles keep bonded together during the flow testing process and the 12 Geofluids flowback of proppant particles cannot be clearly identified.…”

Experimental and numerical investigations of proppant pack effect on fracture conductivity of channel fracturing

“…Maintaining a relatively high fracture conductivity is one of the key factors for successful fracturing. Moreover, many factors can contribute as damaging mechanisms to fracture conductivity, such as incomplete removal of gel residue, proppant embedment, and proppant crushing 5 . Several technologies can be used to maintain fracture conductivity, such as improving proppant material properties and optimizing the combination of different proppants within the pumping schedule 6,7 .…”