Flow Properties of Fresh Mud (Drilling Fluid) Used in Horizontal Directional Drilling

Abstract

Fresh mud (uncontaminated by soil or rock cuttings) plays important roles during borehole drilling, and its rheology has been studied for years in the oil and gas drilling industry. However, mud properties in those areas of application are different from mud used during horizontal directional drilling (HDD), one of the important trenchless technologies used for pipe installation. Specialists usually follow their experience or recommendations from mud suppliers when preparing mud for HDD because few documents have discussed the rheology of fresh mud and its related properties with different recipes. This paper focuses on the rheology of fresh mud with different bentonite and soda ash contents and the effect of time on those properties. In addition, the properties of filter cake are also examined such as its thickness and hydraulic conductivities as influenced by the mud recipe, fluid pressure, and time. The work quantifies how rheological properties change with different bentonite or soda ash contents and hydration times and how filter cake thicknesses increase with increased testing time. Decreases in the hydraulic conductivity of filter cakes are also quantified for increases in mud pressure. These data could help specialists quantify the rheology of muds with a range of different bentonite and soda ash contents considering the time effect and properties of filter cakes. The information could be valuable for engineers and researchers choosing their own recipes in practice.