A New Biopolymer-Free, Low-Solids, High-Density Reservoir Drilling Fluid: Laboratory Development and Field Implementation

Abstract

Summary Low-solids, brine-based reservoir drilling fluids (RDFs) are widely accepted as beneficial to optimizing compatibility with the completion design while minimizing fluid-related formation damage. Traditionally, the maximum density attainable with a low-solids fluid has been limited because of either the prohibitively high cost of the required base brine or the poor performance of viscosifying biopolymers in a dense, divalent cationic environment. An RDF has been developed that exhibits unusually high quality rheological behavior in high-density calcium- and zinc-based brines without the aid of a biopolymer. The new fluid shows a unique shear-thinning rheological profile that features a relatively low high-shear-rate viscosity along with a relatively high low-shear-rate viscosity (LSRV). This behavior is highly unusual in high-density, brine-based RDFs. A result of this behavior is that effective hole cleaning is provided without generating excessive high-shear-rate viscosities that lead to excessive equivalent circulating densities (ECDs). The first field trial of this fluid was on the reservoir section of Well 34/10 I-1-AH in the Gulfaks Satellites Development in the Norwegian sector of the North Sea. Fluid properties during pretesting, mixing, drilling, and completion of this section are detailed in this paper.