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.
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.
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.
Effective and uniform placement of treatment fluid across multiple zones can be challenging. This is particularly true during stimulation or remedial treatments for formation sand control, as well as during water shutoff treatments. Such challenges can be greatly enhanced when a long interval sand formation is largely heterogeneous. Good diversion technology is often what dictates treatment success. Current laboratory methods used to study diversion at downhole conditions can leave a large gap between laboratory and actual operational results. A recent midscale laboratory study involving a new complex multizone formation testing system has helped provide a method for closely simulating downhole conditions. This paper describes a new laboratory testing setup, which allows an effective dynamic study of diversion. The new testing apparatus allows for evaluation of different critical parameters, such as concentration, temperature, and pressure on the diversion mechanism. Results are presented for laboratory case studies of diversion during different scenarios, including formation sand/fines control treatment and water shutoff treatment. The results generated can provide insight to help bridge the gap between a laboratory study and operations encountering multiple zones.
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