Proppant Backproduction During Hydraulic Fracturing-A New Failure Mechanism for Resin-Coated Proppants

Abstract

Summary Back production of proppant from hydraulically fractured wells, particularly those completed in the northern European Rotliegend formation, is a major operational problem, necessitating costly and manpower-intensive surface-handling procedures. Further, the development of unmanned platform operations offshore, required in today's economic climate, is impossible as long as this problem remains unsolved. The most cost-effective potential solution to this problem is provided by curable resin-coated proppant (RCP), which consolidates in the fracture. Early field trials with RCP's, however, were not completely effective in stopping the back production of proppant. Typically, some 10% of the total volume of RCP placed in the fracture was backproduced. Two types of RCP back production were identified: during well cleanup (Type A) and after a long period of proppant-free production (Type B). Type A is believed to be caused by an insufficient strength buildup of the RCP pack. The influence of factors affecting RCP pack strength buildup-resin type, reservoir (curing) temperature, resin/fracturing-fluid interaction (under shear and temperature), and erosion of the resin from the proppant grains, which can reduce the RCP pack strength-have been studied in the laboratory. Type B proppant back production was suspected to be caused by a previously unobserved phenomenon: damage resulting from stress cycling that the proppant pack undergoes each time the well is shut in and put back on production. Further, the applied stress increases as the drawdown is increased and the formation is depleted. We performed a laboratory study to help clarify the effect of curing temperature, water production rate, proppant size, and stress cycling on the integrity of RCP packs. The experiments confirmed the field experience that stress cycling has a dramatic effect on proppant back production of commercial RCP packs. The number of applied stress cycles (i.e., the number of times the well is shut in) and the initial RCP pack strength appear to be the dominant factors that govern proppant back production. Dedicated experiments are therefore required to evaluate the use of RCP's to eliminate proppant back production for a particular field application. Introduction Sand production is an operational problem that has plagued oil and gas wells producing from clastic formations since the early days of the oil industry. By contrast, proppant back production is found only in wells where hydraulically created fractures have been packed with (large) volumes of proppant. The proppant pack is unrestrained at the fracture mouth; once proppant grains enter the wellbore, they can be brought to surface with the well fluids. Such back production of proppant from hydraulically fractured wells, particularly those completed in the northern European Rotliegend formation, is a major operational problem. It necessitates costly and manpower-intensive surface-handling procedures (viz., the daily dumping of proppant) and on-site control of the chokes when beaning up the wells. Further, erosion of well and surface facilities presents a safety hazard, and proppant remaining in the wellbore can shut off production by covering the productive interval. Consequently, the development of unmanned platform operations offshore, required in today's economic climate, is impossible as long as significant proppant back production occurs. Incidentally, a similar tendency for hydraulically fractured wells to backproduce proppant is observed in Alaskan operations; however, owing to the different conditions (onshore oil production), the approach adopted there is "to live with it."

Application of polymers for coating of proppant in hydraulic fracturing of subterraneous formations: A comprehensive review

“…2). Proppant flow back was experimentally conducted by several researchers (i.e., Parker et al (1999); Nguyen and Weaver (2003); Weaver et al (1999); Vreeberg et al (1994); Rickards et al (1998); Johnson et al (2005). Results indicate that adding polymer to proppant can prevent proppant erosion and increase the particles tolerance to higher stress cycles.…”

Mechanics of light weight proppants: A discrete approach

“…Also remaining proppants in a wellbore can shut off production. Costly and manpower intensive surface handling procedure is necessary to handle proppant flowback [52]. The characterization of proppants involves multiple tests including single particle compression, crush analysis tests, sieve analysis, sphericity and roundness characterization particle settlement and conductivity tests [3,4,6].…”

“…The influence of addition of softer particles to a proppant pack on pack permeability has been studied extensively and a reduction in the flow rate has been observed [49][50][51][52].…”

“…A modification to the conductivity test wherein an arrangement is made to collect loose proppant and measure their flow rate is used to study proppant flowback. Several researches have focused on understanding the factors affecting proppant flowback and finding ways to reduce it [14,15,[49][50][51][52]. Apart from the DEM (discrete element method) simulations by Asgian [14] the rest focus on experimental approach.…”

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

“…The existing literatures mainly focus on the mechanical process of the flowback of fiber-free proppant. Vreeburg et al [10] performed a laboratory study on two types of back-production to help clarify the effect of curing temperature, water production rate, proppant size, and stress cycling on the integrity of resin-coated proppant (RCP) packs. The number of applied stress cycles and the initial RCP pack strength appear to be the dominant factors that govern proppant back-production.…”