Double Purpose Drilling Fluid Based on Nanotechnology: Drilling-Induced Formation Damage Reduction and Improvement in Mud Filtrate Quality

Abstract

One of the main damage mechanisms identified in the Ocelote field is the drilling-induced formation damage during drilling operations. The productivity of a well during its production life decreases because of fines migration and changes in the wettability due to organic deposits. In this study, we designed a double purpose nanofluid to reduce the drilling-induced formation damage while the invaded mud filtrate enhances the mobility of the crude oil and migration fines control. The nanoparticles (NPs) used were fumed silica and commercial alumina. The effectiveness of the nanoparticles in improving the rheological and filtration properties of the drilling fluid was assessed by conducting rheological and filtration tests under high pressure–high temperature (HPHT) conditions in terms of the NP concentration after the hot rolling process. The experimental results in terms of the plastic viscosity, yield point, and gel strength showed that as the NP concentration increases, the values of the rheological parameters increase, with the Si NPs exhibiting the best performance. Regarding the filtration properties, the Si and Al NPs reduced the filtration volume by 17%, with the Si nanoparticles presenting the highest reduction in the mudcake thickness of 6%. At NP concentrations above 0.3 wt.%, the filtration reduction effect decreases. Therefore, the mud filtrate obtained from the HPHT filtration test conducted on a drilling fluid with an NP concentration of 0.05 wt.% was used to evaluate the mud filtrate quality to improve the mobility of the crude oil by interfacial tension (IFT) reduction and the capacity to alter the oil-wet to water-wet surface. The retention of the fine particles in impregnated Ottawa sand was tested through a break–rupture curve. The results showed that the mud filtrate with Al NPs could decrease the IFT between the intermediate heavy crude (23°API) and the mud filtrate by more than 24% and could alter the contact angle from approximately 66 to 41 °C. Additionally, the core treated with the mud filtrate with Al NPs imbibed twice the mass in 2 h, more than the core treated with the mud filtrate in the absence of NPs. Hence, the Si NPs did not present significant changes in the IFT and wettability alteration but increased the retention of the fine particles in the treated sand. The Al NPs helped reduce the filtration volume, presented a marked impact on the wettability alteration to preferential water-wet, reduced the IFT, and to some extent aided fines migration control; therefore, the Al NPs were selected for the evaluation in displacement tests on rock samples under dynamic and reservoir conditions. Additionally, the drilling fluid with the Al NPs reduced the dynamic filtration volume by 45% with a subsequent reduction in the formation damage by 20% and increase in the critical flow of migratory clays by 66% in comparison with the drilling fluid without NPs. Finally, the residual water saturation was reduced, and the crossover point between the relative permeability curves shifted to the right. Finally, technical studies for field applications will be carried out, where two twin wells with similar properties will be drilled, allowing for a comparative analysis of the application of NPs to drilling fluids with the same formulation in terms of the invasion diameter, well stabilization time, productivity index, and solid production.