Improvement of Emulsion Stability and Plugging Performance of Nanopores Using Modified Polystyrene Nanoparticles in Invert Emulsion Drilling Fluids

Abstract

Drilling fluid invasion and pressure transmission caused by the development of micropores and fractures in shale oil and gas formations are the major factors contributing to wellbore instability during drilling using oil-based drilling fluids (OBFs). In this study, a modified polystyrene latex (MPL) material was synthesized through emulsion polymerization and was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), particle size analysis, scanning electron microscopy (SEM) observations, and contact angle testing. The influence of the MPL on the stability of a water-in-oil emulsion was analyzed via sedimentation observations and electrical stability tests. The effects of the MPL on the plugging mechanism of white oil and water-in-oil emulsions were evaluated using 0.1–1.0 μm micro-porous filtration films. The experimental results revealed that the MPL has a favorable thermal stability, with an initial thermal decomposition temperature of 363°C, a median particle size (D50) of 233 nm, and a three-phase contact angle of 103.5°. The MPL can enhance the sedimentation stability of an emulsion to a considerable extent and can improve the electrical stability (ES) of the emulsion, which is conducive to the stability of OBFs. Due to the deformability of the MPL, it has a wide range of adaptations for micro-scale pores and fractures. In both the white oil and water-in-oil emulsions, the MPL can reduce the filtration loss through microporous membranes with pore sizes of 0.1–1.0 μm to within 10 ml. This paper details the methodology of the synthesis of nanomaterials that can effectively plug a formation’s nanopores and fractures; thereby, stabilizing OBFs.

Development of Multiple Crosslinked Polymers and Its Application in Synthetic-Based Drilling Fluids

“…That is because the polymer structure contains many hydrogen-bonded crosslinked networks and rigid particles, which improves the capacities of resist oil-water segregation and structural destabilization at elevated temperatures. On the other hand, because the polymer is a deformable flexible particle and nanoparticle doped aggregate, the particle deformation and PSD distribution are wider under differential pressure, compared with the formation of a denser filter cake after deposition, which prevents the further intrusion of solid-phase particles and liquid-phase, which is conducive to the stabilization of the well wall and the control of reservoir damage [25,26].…”

Temperature-Responsive Nano-SiO2 Composite for Improving Shale Stability in Oil-Based Drilling Fluids

“…Inorganic nanomaterials, such as nanosilica (nano-SiO 2 ), nanozinc oxide (nano-ZnO), and nanotitanium dioxide (nano-TiO 2 ) are filled in the near wellbore zone through bridging to form a tight plugging layer, which decreases the permeability of the reservoir and reduces the filtration of drilling fluid. − However, the surface effect of nanomaterials makes them easily agglomerate together, which hardly guarantees the nanometer size. Under the conditions of reservoir temperature and salinity, organic nanomaterials will undergo physical/chemcal reactions, such as cross-linking, expansion, adsorption, and solidification after entering the pores and fractures of the reservoir, thereby plugging pores and fractures. − Nevertheless, high temperature may break polymer chains of organic plugging materials and result in loss of material properties. Organic/inorganic composite materials composed of an inorganic rigid material as the core and an organic deformable material as the shell could be plugged by synergistic actions. ,− Inorganic core materials could bridge and plug shale nanopores, while organic materials fill the pores formed by rigid bridged nanocomposite through their excellent deformation properties.…”