ABSTRACT
Generally, drilling fluids may be defined as fluids with a composition that can assist the generation and removal of cuttings from the borehole to the surface. They are classified according to their base as water based mud (WBM), oil based mud (OBM) or gas. Polymers, densifiers, brines, surfactants, among others are the primary components of drilling fluids. Currently the trend is to develop WBMs, which simulate the high performance of OBMs, with benefits such as reduction of environmental impacts and lower costs associated with cuttings and fluids disposal. This challenge introduces high performance materials in the oil industry such as nanomaterials.
The increasing demand of hydrocarbons has led the study and production of unconventional resources in Argentina and worldwide like shale and tight reservoirs. Shales are sedimentary rocks composed of clay size particles and organic matter with laminar structure, low permeability and nanopores. In these types of rocks wellbore stability and shale inhibition are key factors while drilling with WBM, so it is necessary to avoid pore pressure increase and subsequent penetration of drilling fluid into the formation. In this research nanosilica (12nm) was used to minimize shale permeability through physically plugging the nanopores of shales which are of 30 nm as average. This nanomaterial will minimize not only fluid penetration, pore pressure, shale permeability and fluid-rock interaction but will improve wellbore stability.
In this work the rheological behavior of WBM with nanoparticles was analyzed. Fluids were prepared with the same additives and composition as the ones used in argentine fields. Finally, the rheological behavior of WBM was compared with the OBM´s and the best concentration of nanosilica was determined: 0,5 %p/p. Also, filtration and inhibition tests were performed in agreement with API 13B1-2 and API 13I.
Keywords
water based mud; argentine shale; poral pressure
