Enhancing Proppant Pack Conductivity With Consolidation and Agglomeration Performance: A Laboratory Study

Abstract

To control proppant flowback during well production, proppant is often coated with a curable resin to obtain bonding between grains. However, current curable resin systems often have short cure times, allowing the resin coating on proppant to cure prematurely before complete placement into the target fractures, or creating operational issues if removal of the proppant from the wellbore is required. As another option, proppant can be coated with a tackifier polymer to maintain propped fracture conductivity by mitigating migration and intrusion of formation particulates into the proppant pack. The use of only a tackifier polymer does not offer sufficient cohesion to lock the proppant in place under high production flow rates. This paper presents the results of a laboratory study to demonstrate and quantify the performance of a new resin system that provides both tackiness and the option of delayed consolidation to effectively overcome these shortcomings. To achieve both delayed consolidation and agglomeration properties, a study involved coating proppants with a resin mixture comprised of a curable resin, a tackifier polymer, and a catalyst (when needed) before blending the coated proppant grains into a fracturing fluid. After the coated proppant was packed in place, consolidation levels were observed to increase as a function of time and temperature. Mixing ratios between resin and tackifier components of this new resin system are adjustable to achieve the designed coating performance (e.g., high consolidation strength with low tackiness, or vice versa). Catalyst addition controls cure kinetics to obtain consolidation for the proppant pack, when necessary. Combining the delayed consolidation and agglomeration properties into a single proppant coating provides the ability to immobilize the proppant and also mitigate formation sand and fines migration to greatly enhance and sustain proppant pack conductivity. Potential applications for field treatments using this resin system are discussed. In multistage fracturing treatments, the delayed curing resin allows a more flexible schedule so that drilling/milling techniques are not required to retrieve the consolidated proppant left inside the wellbore between fracturing stages. With respect to frac-pack type treatments, delayed consolidation also allows effective removal of excess coated proppant by reversing out after its placement into the fractures and screen-casing annulus packing is complete.

A model of the proppant flowback: setup of the theoretical framework

“…In addition to the above-listed reasons of flowback following from the experimental results presented in literature [Vo et al 2014;Lu et al 2016], the form and coating of the proppant grains affecting the internal friction forces between individual proppant particles have a significant effect on the removal process, which in turn affects the stability of the proppant pack. Furthermore, from experimental data and from results when modeling the proppant removal process by the distinct element method, it follows that the packing becomes unstable, starting with a certain ratio of the average grain diameter to the width of the crack opening.…”

“…where σ r is the closure stress. Many authors note that this stress affects proppant flowback and consider it as one of the main terms to control the proppant flowback [Milton-Tayler et al 1992;Asgian et al 1995;McLennan et al 2015;Andrews and Kjørholt 1998;Canon et al 2003;Aidagulov et al 2007;Vo et al 2014;Lu et al 2016;Barree and Conway 2001;Larsen and Smith 1985;Ely et al 1990]. The value of the closure stress is significant enough to hold the packed proppant in the fracture even when the outgoing force is big enough.…”

A Multiwalled Carbon Nanotube-Based Polyurethane Nanocomposite-Coated Sand/Proppant for Improved Mechanical Strength and Flowback Control in Hydraulic Fracturing Applications

“…In comparison, an RCP’s cured proppant pack provides chemical bonding between grains to prevent proppant flowback. An RCP is typically only partially cured during storage and transportation, resulting in the RCP’s inability to provide adequate consolidation strength to the proppant pack and a weaker proppant flowback control capability . Furthermore, the partially cured coated proppant generally requires the addition of chemical activators and a particular temperature to cure, increasing the cost of the coating process.…”

“…An RCP is typically only partially cured during storage and transportation, resulting in the RCP's inability to provide adequate consolidation strength to the proppant pack and a weaker proppant flowback control capability. 26 Furthermore, the partially cured coated proppant generally requires the addition of chemical activators and a particular temperature to cure, 27 increasing the cost of the coating process. Another efficient approach for controlling proppant flowback is to inject fibers into the fracturing fluid with the proppants.…”

Proppant immobilization facilitated by carbon nanotube mediated microwave treatment of polymer-proppant structures

“…A number of methods have been investigated to improve proppant performance including modifying them with different resins, polymers, and fibers [3][4][5][6][7][8][9][10]. The use of resin coated particles is well documented method to control proppant flowback in a wide variety of oil and gas wells.…”