Session: 11-02-03 Well Drilling Fluids & Hydraulics

Paper Number: 127383

127383 - Dual Shear Gun for Efficient Drilling Fluid Mixing and Dispersion: Effect of Design Parameters 

Invert emulsion fluids where water droplets are dispersed in an oil phase are often the preferred choice when drilling through problematic formations such as reactive shales.  However, preparing on the order of 100 m3 of stable emulsion requires both energy (high differential pressures) as well as time and space due to the large volumes of fluid involved.  Current shear guns used offshore do not provide sufficient emulsification to generate a stable fluid.  A common practice is therefore to use the bit nozzles as emulsification device by adding fresh drilling fluid to the circulating fluid.  This has to be done at a slow rate to ensure the stability of the fluid.  This is therefore a time-consuming process.

A compact solution for efficient topside emulsification of the drilling fluid would therefore reduce time and costs of drilling operations.  On-site pump pressure capacity may be limited and on-site energy use should ideally be kept as low as possible. With these restrictions in mind, it is desirable to be able to provide a stable emulsion with as little pressure drop as possible, while high pump rate is also preferable in order to minimize mixing time. Both criteria favour larger nozzle sizes.

We here present results from full-scale laboratory tests with a dual shear gun unit, investigating the effect of different design parameters on the oil-water mixing process and on the stability of the resulting dispersion.  Surfactants (emulsifiers) have not been added, to allow fluids to separate and to be re-used after each test, and separation time is used as an indicator of droplet size and thus of the expected fluid stability in a system with emulsifiers.

In this paper we present experimental methodology. Results of effects of nozzle sizes, nozzle-nozzle distance, pressure drop over nozzles, flow rates (which depend on pressures and nozzle sizes), as well as fluid aging and presence of impurities are discussed.

Presenting Author: Ali Taghipour Sintef Industry

Presenting Author Biography: Senior Researcher in Sintef

Authors:

Ali Taghipour Sintef Industry
Bjørnar Lund Sintef
Jan David Yterhus Sintef
Arild Saasen University of Stavanger
Geir Olav Ånesbug JAGTECH AS
Jan Egil Pallin JAGTECH AS