High Strength Polyacrylamide/nmSiO₂ Composite Hydrogel for Well Killing

Abstract

Killing pills of high strength composite hydrogel were prepared by polyacrylamide, chromium acetate crosslinker and silica nanoparticles reinforcer. The killing performance of composite hydrogel depended on its viscoelasticity and compression strength, which were both influenced by polymer content, ratio of polymer to chromium acetate and nano silica content. In this work, the effect of these altering factors on strength of composite hydrogel were evaluated, results showed that elastic moduli (G′), viscous moduli (G″) and compression strength all increased as polymer content increased, ascribing to close entanglement among polymer chains and increasing crosslinking density. G′ was proportional to the ratio of polymer to chromium acetate, whereas G″ and compression strength experienced initial increase then decrease, indicating an optimal ratio existed to achieve the strength peak of composite hydrogel. Silica nanoparticles contributed significantly to viscoelasticity and compression strength of hydrogel. From SEM images, we can see silica nanoparticles attached onto network branches and filled into the network pores in aggregation, in this dispersion form to strengthen the microstructure further to enhance the strength of composite hydrogel. Moreover, the polymer/nmSiO2 composite system is shear-thinning fluid, which promises its pumpability as killing fluid during killing operation.

Environmental and strength‐enhanced nanosilica‐based composite gel for well temporary plugging in high‐temperature reservoirs

“…Under the same strain of 45%, the composite gel with 8% nanosilica possessed the stress of 44.6 KPa, which is nearly 10 times higher than the general gel without nanosilica with the stress less than 5 KPa, indicating its excellent mechanical and elasticity strength. The stress-strain performance of this new developed composite gel is better than the nanosilica-based PAM crosslinking chromium acetate nanocomposite gel reported by Sun et al 31,32 After the compress load was released, as it is shown in Figure 4, the general gel (without adding nanosilica) cracked, and there are obvious wide fractures on the bottom, whereas the composite gel with 8% nanosilica is still an undamaged whole with no fractures but a very little shape change. That could be explained as there are more empty space in the general gel network structure, when then general gel was compressed, it is brittle and easy to crack.…”

“…Under the same strain of 45%, the composite gel with 8% nanosilica possessed the stress of 44.6 KPa, which is nearly 10 times higher than the general gel without nanosilica with the stress less than 5 KPa, indicating its excellent mechanical and elasticity strength. The stress–strain performance of this new developed composite gel is better than the nanosilica‐based PAM crosslinking chromium acetate nanocomposite gel reported by Sun et al…”

“…Currently, the crosslinker used most is the chromium acetate. For instance, Aalaie and Sun et al respectively prepared a composite hydrogel composed of nanosilica particles, polymer, and crosslinker Chromium acetate III for well killing and water shut‐off. However, the Chromium acetate III is toxic, so that these systems are hazardous to the environment.…”

The Development and Deployment of Degradable Temporary Plugging Material for Ultra-Deepwater Wells

“…The plugging layer is formed by a curing reaction or volume expansion at the loss-circulation zone, which has the advantages of a low density of plugging slurry, adjustable gelling time and strong ability of plugging slurry to control filtration loss [3][4][5][6][7][8]. The commonly used polymer gel plugging system usually has strong viscoelasticity and deformability [9], and it has been successfully applied in some areas, such as the fractured vicious loss ground layer in northeast Sichuan and other places. In 2018, Bai Yang et al [10] put forward gel lost circulation slurry and lost circulation slurry for drilling.…”

“…In addition, the slurry can quickly form a structure at the fracture of the loss-circulation formation. In 2020, Zhang Hongxu et al [11] proposed a semi-interpenetrating network gel The commonly used polymer gel plugging system usually has strong viscoelasticity and deformability [9], and it has been successfully applied in some areas, such as the fractured vicious loss ground layer in northeast Sichuan and other places. In 2018, Bai Yang et al [10] put forward gel lost circulation slurry and lost circulation slurry for drilling.…”