Formulation of novel ecofriendly microemulsion-based drilling fluids for improving rheological and filtration characteristics

Abstract

The main objective of this work was to formulate not environmentally harmful drilling fluids obtained from microemulsion systems, using an aqueous phase (water-glycerol solution 1:1), an oil phase (pine vegetable oil), and varying nonionic surfactants (Tween 80, nonylphenol ethoxylates 100 and 150). Two types of clays (filtration control) were used in the formulation of fluids, Brasgel PA and Cloisite 20 A, in the presence of a viscosifier (xanthan gum), a weighting agent (baritine), a sealant (calcite), and dispersant (water). Properties such as mass loss, filtrate volume, and rheological characteristics of the formulated fluids were analyzed since these are considered essential characteristics for a successful drilling operation. Shear stress (τ) versus shear rate (s−1) data of fluids was best fitted to the Herschel-Bulkley rheological model with R2 of 0.99. The fluids formulated with Brasgel PA obtained the lowest consistency index (k), ranging from 0.37 to 0.61, and, therefore, the force required to start the flow (τy). The thermogravimetric analysis verified that the microemulsified drilling fluids obtained can operate at temperatures up to 100 °C, making it possible to apply them in oil wells with these thermal characteristics. The fluids' filtrate loss volume varied from 2.4 mL to 4.0 mL; the maximum filtercake thickness measured 0.80 mm, and low permeability (0.0173 mD). The analyzed drilling fluids showed a significant swelling reduction when formulated with the microemulsion systems and improved lubricity. In general, it was observed that ecofriendly microemulsion-based drilling fluids were efficient in reducing swelling, showing good rheological and reduced API filtrate loss, being viable alternatives for use in drilling operations of oil wells.