High-Density Drilling Fluids for Managed Pressure Drilling: Lab Development and Field Trial

Abstract

Managed pressure drilling (MPD) offers a closed loop circulation system in which formation fracture pressure, bottom hole pressure and pore pressure are managed at surface. The right choice of drilling fluid used during MPD operation facilitates correct mud management and treatment. Lab formulation and field trial of a high-density water-based drilling fluid comprising a mixture of barite (BaSO4) and manganese tetroxide (Mn3O4) as weighting agents has been described in the paper. Drilling fluids having a mixture of Mn3O4 and BaSO4 as weighting agents would have lower equivalent circulating density (ECD), better sag, better acid solubility and lower fluid cost as compared to conventional BaSO4 based fluids. This paper describes the formulation of three different water-based drilling fluids viz. 100, 120, and 150pcf drilling fluids having a mixture of Mn3O4 and BaSO4 and hot rolled at temperatures of 270, 250, and 300oF, respectively. Rheological properties, sag resistance and high pressure-high temperature (HPHT) filtration properties of the three fluids have been described in the paper. Data obtained from the field trial of 160pcf high density drilling fluids having a mixture of Mn3O4 and BaSO4 for wells with a 300oF bottom hole static temperature has been described. HPHT operations across naturally fractured formations with 0.5–1.0pcf drilling fluid window have been described in the paper. During the field trial, the fluid having a mixture of Mn3O4 and BaSO4 showed good rheological, filtration and sag properties thereby resulting in successful drilling of the well with no issues. MPD operation became more successful and practical with high density drilling fluids having a mixture of Mn3O4 and BaSO4 as it facilitated better drilling fluid management and treatment in comparison to conventional fluids.