A novel resin-based nanocomposite-coated sand proppant is introduced to address the issue of proppant flowback in post-fracturing fluid flowback treatments and hydrocarbon production. Self-aggregation in the water environment is the most attractive aspect of these developed proppants. In this work, sand was sieve-coated with 0.1% multiwalled carbon nanotubes (MWCNTs) followed by optimized thin and uniform resin (polyurethane) spray coating in the concentration range of 2 to 10%. Quantitative and qualitative evaluations have been carried out to assess the self-aggregation capabilities of the proposed sand proppants where no flowback was witnessed at 4% polyurethane coating containing 0.1% MWCNTs. This applied resin incorporating MWCNT coating was characterized by field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy depicted the dispersed presence of MWCNTs into polyurethane resin corroborated by the presence of 38% elemental carbon on the sand substrate. Proppant crushing resistance tests were conducted, including proppant pack stress−strain response, compaction, and fines production. It was found that the proposed sand proppant decreased the proppant pack compaction by ∼25% compared to commonly used silica sand with the ability to withstand high closure stress as high as 55 MPa with less than 10 wt % fines production. The surface wettability was determined by the sessile drop method. The application of resin incorporating MWCNT coating layers changed the sand proppant wetting behavior to oil-wet with a contact angle of ∼124°. Thermogravimetric analyses revealed a significant increment in thermal stability, which reached up to 280 °C due to the addition of MWCNTs as reinforcing nanofillers.

Controlling scale deposition in tight formations such as shale is commonly achieved by combining fracturing stimulation with squeeze treatment. The squeeze treatment process's success relies on the targeted formation's ability to adsorb the right amount of scale inhibitor and slowly release it during hydrocarbon production. The inhibition lifetime of a standard squeeze treatment lasts from 3 to 6 months depending on the compatibility between the formation and scale inhibitor−operators desire a prolonged inhibition lifetime. Herein, a novel approach of resin-based nanocomposite coated proppants is developed to act as a propping agent and high active surface platform for scale inhibitors to be adsorbed and subsequently slowly released during oil production. In this study, proppants were coated with a thin layer of polyurethane, followed by a layer of carbon-based nanomaterials (Multi-Wall Carbon Nanotubes (MWCNTs) and Graphene Nanoplatelets (GNPs)), and characterized using Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray Analysis (EDX). Due to the concerns of climate change, polyurethane was selected due to its quick curing at lower temperatures and minimal environmental impacts. The potential of the proposed proppant to enhance the adsorption and slow the desorption of a Diethylenetriamine Penta (DTPMP) scale inhibitor, the necessary strength to withstand closure stress, and its thermal stability were evaluated. FESEM and EDX results revealed that an ultrathin uniformed coating layer was established. The stress resistance data showed that the proposed proppants (MWCNTs-RCP and GNPs-RCP) could withstand closure stress as high as 68.9 MPa with less than 10 wt % fines production. In addition, the thermal stability of MWCNTs-RCP and GNPs-RCP reached 347 °C. Scale inhibitor adsorption experiments showed that MWCNTs-RCP and GNPs-RCP adsorbed 583.5 mg/kg and 832.0 mg/kg of DTPMP, respectively. Desorption results indicated that MWCNTs-RCP and GNPs-RCP extended the inhibition lifetime of DTPMP by 400% PV compared to a conventional proppant. Intraparticle diffusion was found to dominate the desorption of DTPMP from MWCNTs-RCP and GNPs-RCP, which explains the slow desorption rate they exhibited. Therefore, the developed proppants could be a promising multifunctional proppant in the oil and gas industry.

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Shale rocks are one of the world's most important unconventional gas resources today, thanks to technical advancements. Fluid adsorption in tight rocks like shale is critical for designing fracturing and treatment fluids. However, adsorption of fluids in shale is not fully understood, and quantifying it remains difficult. In addition, the complicated pore structure of shale rocks makes characterisation challenging. Wettability can be used to understand the affinity of a solid surface to adhere certain fluid. Shales present several basic problems when employing standard techniques because of their small grain size, low permeability, and reactive components. We assessed and compare the wettability of shale using contact angle and spontaneous imbibition methods in two shale samples. The findings showed no correlation between contact angle and imbibition curves. Such behaviour is due heterogeneity of shale surface. Contact angle produces local wetting characteristics, but shale sample is rather complex and contact angle is therefore not representative. Imbibition results might be more reliable since fluids contacts with the whole sample.

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