Cuttings Transport With Oil- and Water-Based Drilling Fluids1

Abstract

Deviated well sections are common in most modern offshore well construction designs. In the North Sea region, which is a good example of mature areas, practically all producer or injector wells have highly deviated well sections. These wells must be constructed in an optimal manner with respect to functionality, drill time, risk, and all affiliated costs. Throughout the years, most hole-cleaning and hydraulic models have been developed based on experimental results from relatively small-scale laboratory tests with model fluids. Hole-cleaning properties and hydraulic behavior of practical drilling fluids intended for field application differ from those of most model fluids. Furthermore, results from small diameter tests may not always be relevant for or scalable to field applications because of the presence of a huge number of dimensional quantities like velocity, fluid properties, time, length, and other scale differences. Hence, studies using sufficient large-scale experimental facilities in controlled laboratory environments with the application of various field-designed drilling fluids are necessary to improve engineering models and operational practices. The current paper presents results from such laboratory tests where field-applied drilling fluids have been used. In comparison tests, the different drilling fluids have similar density and viscosity functions within the relevant field-applied shear rate range. This shear rate range is also assessed in the tests. One of the drilling fluids is oil-based, and the other one is an inhibitive water-based drilling fluid of the KCl/polymer type.