Otimização de sistemas de fluidos aquosos altamente inibidos.

Abstract

The inhibited fluids are used in drilling hydratable shales, to prevent found clays to be hydrated and cause stuck tools. The knowledge of the filtration properties of the fluids is important during drilling, since the control of these properties ensures less drilling problems and improves well productivity. This work aimed to study and improve the filtration properties of aqueous fluids inhibited with potassium salt chlorine-free (potassium citrate), for their application in drilling hydratable and dispersive clays and shales. For this purpose, the drilling fluids with and without addition of the inhibitor potassium citrate were studied. It was determined the rheological properties (apparent viscosity (AV), plastic viscosity (PV), yield limit (YL) and gel strength (GS)), filtration (filtrate volume (FV), spurt loss (SL), cake thickness (CT) and permeability (k)) and the inhibition power (dispersibility test and the bentonite inhibition test) of the studied fluids. According to the obtained results it was concluded that the study fluids showed pseudoplastic behavior and addition of potassium citrate to the fluid did not cause changes in the pseudoplastic behavior of fluids. It was concluded that the combined use of additives starch, CMC LV and calcite reduces more effectively the filtration properties of drilling fluids studied and the filtration properties of the fluids inhibited with potassium citrate were optimized since the FV values obtained were lower than the considered base fluid. The formulations which showed efficient filtration and inhibition properties were prepared with high concentrations of potassium citrate. They have presented low values of FV and lower values of SL.