STUDY OF THE NANOPARTICLE / POLYMER / CaCO3 INTERACTIONS TO OPTIMIZE THE STABILITY OF THE COLLOIDAL SUSPENSION AND THE PACKING OF THE SOLIDS
Palabras clave:calcium carbonate, drilling fluids, filtration, silica nanoparticles, polymer, rheology
increased with the objective of reducing the formation damage and increase the wellbore stability improving the properties of the drilling fluids. In this way, this study aims to evaluate the effect SiO2 nanoparticles in a formulated bentonite-free water-based drilling fluid (BFWBM) to minimize its impact in the formation damage based on the stability of the particle suspension (CaCO3) and the enhancement of the polymer viscosity. Two kinds of SiO2 nanoparticles were evaluated: (1) synthesized through the Sol-Gel Method and impregned with acid treatment (SiA), and (2) fumed silica nanoparticles (SiC). The nanoparticles were characterized by Dynamic Light Scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR) and Zeta Potential. The SiO2 nanoparticles-polymer interactions were evaluated through polymer adsorption onto nanoparticles, rheological studies, and evaluation of thermal stability. The CaCO3-nanoparticle system was evaluated through DLS, zeta potential, and the analysis of forces through the Atomic Force Microscope (AFM). Drilling fluids properties CaCO3/polymer/nanoparticle system) in the presence and absence of nanoparticles were evaluated through the analysis of pH, density, solid content, rheology, and static tests of filtration at high pressure and temperature (HPHT) by standard protocol API 13B -1. SiO2 nanoparticles presented the size of 11 and 7.4 nm for the SiA and SiC nanoparticles, respectively. Results of adsorption experiments showed that isotherms followed a Type III behavior and were modeled using Langmuir, Freundlich, and Solid-Liquid Equilibrium (SLE) models. SiC nanoparticles presented the most quantity of polymer adsorbed. The rheological test of polymers and SiO2 nanoparticles showed a pseudoplastic behavior with a high performance of SiC nanoparticles with an increase of 15% of the polymer viscosity. CaCO3-nanoparticles system presented an increase of the zeta potential and a reduction of the aggregate size. Also, the experimental results showed that the addition of SiO2 did not alter the basic properties as pH, density and solid content. But, nanoparticles increased the plastic viscosity (PV), yield point (YP), yield stress (YS), and gel strength of the drilling fluid. SiA nanoparticles in drilling fluid showed the highest reduction of the filtration volume and thickness cake -22 and -65%, respectively, based on the static tests. Also, the filtration volume showed a relationship with the zeta potential of nanoparticles, for the highest zeta potential value, SiA -48.66 mV @ pH 10, the filtration volume is lower. Finally, the SiO2 nanoparticles were evaluated by dynamic test under reservoir conditions. Drilling fluid with the addition of nanoparticles reduced and stopped the filtration volume by 77%, decreasing the formation damage by 51% and hence increased the permeability returns by 74% compared to the drilling fluid without nanoparticles. In addition, the oil recovery (%OOIP) obtained with the best design fluid using the Si11A nanoparticles was 10% higher than baseline (BFWBM). Also, the effluents obtained from displacement test after drilling fluid injection were evaluated at reservoir temperature using a rotational rheometer at shear rates varying between 1 and 100 s−1, obtaining a reduction of the viscosity of the crude oil up to 28% during 9 pore volume injected using the BFWBM with SiA nanoparticles.
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