Influence of Nanoparticle-Based Drilling Fluids on Egyptian Shale Swelling – An Experimental Investigation

Abstract

Abstract Shale swelling is a major challenge in drilling operations and can lead to severe problems. The use of shale swelling inhibitors and plugging additives in drilling mud is a common solution to mitigate these problems. This study aims at investigating the influence of aluminum oxide (Al2O3) and copper oxide (CuO) nanoparticles (NPs) as mud additives on Egyptian shale swelling. Two formations were studied, Duwi and Dakhla shales. X-ray diffraction (XRD) was utilized to reveal their clay mineralogy. Low-solid non-dispersed mud (LSNDM) was tested as the base fluid. LSNDM is a common choice to drill an intermediate section which may contain minor strikes of shaley and problematic formations. Al2O3-NPs (15 nm) and CuO-NPs (40 nm) were added at different concentrations (0.1, 0.3, 0.5, 0.7, and 1.0 wt%) and the rheological and filtration properties were tested using standard viscometer and API filter press. Oedometer tester was used to examine the effect of NPs-based LSNDM on shale swelling. Adding NPs to the LSNDM yielded better rheological behavior. An increase in the yield point (YP) was obtained when using 0.3 and 0.5 wt% of Al2O3-NPs and 0.1, 0.3 and 1.0 wt% of CuO-NPs, which implies less solids sagging, higher cuttings carrying capacity and thus, more efficient hole-cleaning. Furthermore, the gel strength (GS) of the LSNDM showed improvements when adding NPs compared to the base. Also, the Herschel-Bulkley model was found to best fit the rheological behavior of the NPs-based LSNDM. Moreover, using both NPs yielded better filtration properties, especially at 0.3 wt% of Al2O3-NPs and 1 wt% CuO-NPs. The scanning electron microscopy (SEM) images showed better surface morphology and less porous microstructure of the filter cakes containing 0.3 wt% of Al2O3-NPs and CuO-NPs compared to the base fluid. Also, a decrease in the slope of the filtrate volume curve after 30 minutes (up to 90 minutes) was observed compared to the base fluid, which confirms better NPs dispersion. The composition of the clay minerals ranged from 80% montmorillonite to low kaolinite content (19%) for Dakhla shales, and from 48% montmorillonite to low kaolinite content (22%) for Duwi shales as revealed by XRD, which suggests high swelling ability, especially for Dakhla shales. The Oedometer swelling measurements showed a reduction in Duwi shale swelling by 30 and 35% when using 0.3 wt% of Al2O3-NPs and CuO-NPs, respectively, compared to the base. In addition, a significant reduction in the swelling of Dakhla shale was obtained when using 0.3 wt% of Al2O3-NPs and CuO-NPs by 52 and 63%, respectively. This paper discusses a new application concerning the efficient use of NPs in the drilling fluid industry, which may promote using NPs-based mud to drill the Egyptian oil and gas wells.