Graphene Nanoplatelets Extend Life of Scale-Inhibitor Squeeze Treatment

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 215228, “Graphene Nanoplatelets for Extended Lifetime of Scale-Inhibitor Squeeze Treatment in a High-Temperature Reservoir,” by Suzalina Zainal, SPE, Norzafirah Razali, and Mohamad A. Rodzali, Petronas, et al. The paper has not been peer reviewed. _ Scale-inhibitor squeeze (SISQ) treatment is an established method for offshore fields that allows an extended effectiveness of scale inhibitors in preventing deposition over time. One of the primary issues in SISQ campaigns is the short squeeze lifetime of less than 1 year. The study detailed in the complete paper proposed graphene nanoplatelets (GNP) as a preflush system to extend the lifetime of a conventional SISQ treatment. This carbon-based nanomaterial allowed enhanced adsorption of the phosphonate-based scale inhibitor. GNP as a Preflush System A high-surface-area GNP preflush system was chosen to condition the rock surface to overcome the apparent lack of suitable surfaces available for scale-inhibitor adsorption during SISQ treatment. The GNP was injected to coat the rock surface. GNPs consist of a few graphite layers with thicknesses varying from 0.7 to 100 nm. The carbon-based nanomaterial forms a honeycomb structure, regarded as a good alternative to its predecessor, graphene, because of its lower cost and potential for large-scale production. GNP particle size ranges between 100 and 200 nm. This 2D carbon nanomaterial offers several advantages, such as high surface area, a high aspect ratio with a planar shape, and good mechanical properties with excellent thermal and electrical conductivities. It is also inert toward common reservoir fluid. Experimental Procedure Materials. Injection and formation water (brine samples) were prepared based on compositions listed in Table 1 of the complete paper. Berea core plugs were used for static-adsorption and injectivity experiments. In these two experiments, the core samples were used to provide similar rock properties when comparing performances of the baseline preflush (seawater) vs. nano-preflush systems. The average rock permeability for the candidate oil field is between 200 and 400 md. Dispersion Evaluation in High Divalent Brine. Gum arabic (GA) stabilized the GNP in high divalent brine. The polymer-grafted GNP (P-GNP) samples were evaluated in terms of exfoliated sites as compared with GNP alone. Zeta-potential and particle-size analysis also were performed at different P-GNP concentrations. Static-Adsorption Evaluation. A static-adsorption method was designed to replicate preflush injection of P-GNP before introduction of scale inhibitor. Experiments compared the adsorption of the scale inhibitor onto crushed Berea rock, precoated with P-GNP, with another without pre-coating that used seawater preflush only. Coreflood Evaluation. Because of the scarcity of the native core samples, only Berea core samples were used for the injectivity study, while native core samples were used for the SISQ adsorption/desorption coreflood evaluation. In both types of experiments, a P-GNP preflush system was compared with the baseline (seawater preflush).