Research on Application of a Novel Nanophase Material in Water Base Drilling Fluids for Shale Drilling

A layered Nanophase material LDP of 30 nm in particle sizes has been developed to satisfy the needs of shale drilling such as cuttings carrying, plugging nanometer-sized fractures and inhibiting the dispersion of shale formations. Laboratory experiments showed that a 2%LDP suspension, after aging at 120℃, had higher elastic modulus, yield stress and better shear thinning ability than a 6% sodium bentonite suspension. In 0.5%PAC-LV solution, 1%LDP shows better ability in increasing the viscosity and gel strengths of the solution than 4% Na-bentonite. Periodic oscillatory strain scanning demonstrated that LDP suspension showed better ability to restore and break down its gel structure at the switch of high strain and low strain. Particle size measurement and transmission electron microscopy indicated that, compared with Na-bentonite, it is much easier for the LDP to form network structure both in water and in PAC-LV solution. To evaluate the plugging performance of LDP, shale samples rinsed in different solutions were measured for their pore sizes using N₂ adsorption method. The measurement showed that LDP has better plugging capacity than nano SiO₂ and Nabentonite. SEM scanning showed that LDP can plug the long and narrow nano-sized holes in shale. In clay swelling test, the percent core swelling caused by 2%LDP solution was 45% of the percent core swelling caused by fresh water, better than 7%KCl solution. The percent shale cuttings recovery of LDP in hot rolling test at 100℃ was 59.6%, equivalent to 7%KCl solution. Clay clod rinsed in 2% LDP solution for 96 h still kept its integrity. In general, LDP nanophase material is beneficial to viscosity and gel strength enhancement, plugging of nanometer-sized pores and inhibiting shale formations, and is thus prospective in formulating high performance water base drilling fluids for shale drilling.