Water-Based Drilling Fluid Using Nanoparticles Proves Effective in Unconventional Shales

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 19342, “Design and Evaluation of a Water-Based Drilling-Fluid Formulation Using SIO2 and Graphene Oxide Nanoparticles for Unconventional Shales,” by Jose Aramendiz, SPE, Abdulmohsin H. Imqam, SPE, and Sherif M. Fakher, SPE, Missouri University of Science and Technology, prepared for the 2019 International Petroleum Technology Conference, Beijing, 26–28 March. The paper has not been peer reviewed. Copyright 2019 International Petroleum Technology Conference. Reproduced by permission. Traditionally, oil-based drilling fluids are preferable in drilling shale plays because of their negligible chemical interactions, but strict environmental regulations have motived the industry to design water-based muds (WBMs) capable of controlling shale/water interactions. Still, conventional additives in general are too large to plug shale microfractures and nanopores. Thus, nanoparticles, because of their size, shape, and other properties, can provide a solution for WBMs. This study focus on the design and evaluation of a customized water-based mud (NP-WBM) using silica oxide nanoparticles (SiO2-NPs) and graphene oxide nanoplatelets (GNPs). Experimental Description Experimental Materials. Conventional Drilling-Fluid Additives. The micro-size additives used in this work included bentonite to provide primary viscosity and xanthan gum to adjust the final rheological properties of the base fluid. Polyanionic cellulose low- viscosity and pregelled starch were included as conventional filtrate-loss additives. Graphite was used as conventional lost- circulation-material (LCM) additive. Potassium hydroxide was included as an alkalinity-control agent. Nanomaterials. SiO2-NPs were supplied in a white powder form. The SiO2-NPs are near-spherical with an approximate diameter ranging between 15 and 20 nm. The NPs were unmodified (bare surface) and nonporous with a density of 0.1 g/cm3, a specific surface area of 170–200 m2/g, and purity greater than 99.5 wt%. GNPs used in this study had a density of 0.13 g/cm3. The GNPs have a 2D structure with an average particle size ranging from 1.3 to 2.3 µm and a thickness of less than 3 nm. Shale Rock Properties. Woodford shale was used to test the effect of using NPs to enhance the inhibition capabilities of WBM. This rock is described as a late Devonian-Early Mississippian marine shale. In this study, shale samples of 1 in. in diameter and lengths between 0.5 to 2 in. were cored and stored in high-purity mineral oil to avoid property alterations. The rock contains 31.5% clay minerals (22.8% illite, 5.4% chlorite, and 3.3% kaolinite), 67% quartz, and 1.5% pyrite, indicating a high degree of brittleness as well as low water sensitivity. Fig.• 1 shows a sequence of scanning electron microscope (SEM) images in which Image A is equivalent to 7,000x magnification and Image B shows a 30,000x magnification with respect to the original sample size. The SEM images suggested a pore-size distribution between mesopores (2–50•nm) and macropores (greater than 50 nm) with an estimated median pore size of 112.84 nm. Therefore, the nanomaterials in this study have a scale matching that of the Woodford shale and can be used as theoretical bridging agents.