Maintaining Well Productivity Through Controlling Fines Migration and Scale Formation

Abstract

Abstract The intrusion of formation fines and formation sand grains into the proppant pack drastically reduces the conductivity of propped fractures, which can negatively impact well production. This paper describes the development and field treatments using a new form of surface modification agent (SMA) that is a low-tackiness surface modification agent (LTSMA) that can be applied during primary hydraulic fracturing or remedial treatments of propped fractures. Studies were conducted to demonstrate the mechanisms by which this LTSMA controls migration and intrusion of formation sand and fines into the proppant pack, while inhibiting scale formation in the treated pack. Molecular modeling data on the LTSMA suggests that both the polymer backbones and the hydrophobic chains on the polymers are responsible for its reduced tackiness to the treatment equipment and significant scale inhibition ability. Once coated on the proppant as part of hydraulic fracturing treatment, or injected into the proppant pack and formation matrix surrounding the fractures, this LTSMA forms a thin film on the particulates, covering and anchoring the particulates in place. This LTSMA coating also forms a hydrophobic film on the particulate surfaces, inhibiting chemical reactions that lead to scale formation in the pack matrix and subsequent productivity losses. Laboratory experiments using packed beds of proppant, formation sand grains, and various fines were performed to simulate proppant pack conditions and formation fines before and after remedial treatments. Experimental results indicate that treatments with this particular LTSMA effectively control the migration of formation fines into proppant packs and successfully prevent the buildup of scale in various sand packs to maintain the fluid flow paths. No pressure buildup was noticed, opposed to the proppant that was not treated with the LTSMA, for which severe scaling had occurred by 24 hours, leading to an exponential increase in pressure drop across the proppant pack. Examination with scanning electron microscopy analysis clearly demonstrated that no scale was formed in the pore spaces between the treated proppant grains compared to a massive buildup of scale on the proppant particles and in their pore spaces when not coated with the LTSMA. In addition to remedial treatments, LTSMA treatment fluid can be applied while treating formations following an acidizing treatment, during treatment of formations before a high-rate water pack or frac-pack treatment, or as part of a pad fluid to treat the fracture faces before placement of proppant into a fracture and/or a screen annulus.