Field Application of the All-Oil Drilling-Fluid Concept
- L.J. Fraser (Intl. Drilling Fluids)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling Engineering
- Publication Date
- March 1992
- Document Type
- Journal Paper
- 20 - 24
- 1992. Society of Petroleum Engineers
- 1.10.1 Drill string components and drilling tools (tubulars, jars, subs, stabilisers, reamers, etc), 3 Production and Well Operations, 4.2.4 Risers, 1.11.4 Solids Control, 2 Well Completion, 1.6.1 Drilling Operation Management, 4.2.3 Materials and Corrosion, 1.6.9 Coring, Fishing, 1.6 Drilling Operations, 1.2.3 Rock properties, 1.8 Formation Damage, 1.11 Drilling Fluids and Materials, 2.5.2 Fracturing Materials (Fluids, Proppant)
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Until recently, a lack of suitable technology limited application of the all-oil or water-free drilling-fluid concept to coring operations. Stable rheological and filtration properties have been difficult to achieve. High levels of solid additives have been used, and this has stifled the rheological performance. The design, development, and field application of a unique, low-solids, oil-based fluid, which is prepared without a water or brine phase, is described.
Oil-based drilling fluids have probably been used, in one form or another, since shortly after the introduction of rotary drilling. In 1919, Swan applied for a patent for a method of drilling wells with a mixture of tars, coal-tar distillates, and organic solvents in place of water. The patent was granted in 1923 and embodied place of water. The patent was granted in 1923 and embodied recognition of some of the potential advantages that we now accept with oil-continuous-phase drilling fluids. These included shale stabilization and corrosion control. High costs, flammability problems, and intolerance to water all played a part in the commercial failure of the all-oil fluid concept at that time.
In the late 1930's and early 1940's, some success was achieved with oil muds, but applications were mainly limited to coring, completions, and releasing stuck pipe. In the 1940's, rapid and far-reaching developments in emulsifier technology brought the water-in-oil problems under control.
Moreover, incorporation of emulsified water provided some benefits. The oil mud could be thickened and filtration control was achieved with the inclusion of an emulsified aqueous phase. Also, with high levels of emulsified water present, the fire hazards associated with oil muds decreased.
The focus on oil-continuous-phase fluids moved quite definitely from the all-oil concept to that of emulsion-based derivatives. The term "invert emulsion" differentiated such fluids from the more commonly used oil-in-water "direct emulsions."
Development and Application of Invert-Emulsion Fluids
Both viscosity and filtration control were achieved in invert emulsion fluids by way of the same component -- the emulsified aqueous phase. Inevitably, a degree of independent control of these phase. Inevitably, a degree of independent control of these properties was lost, the emulsion fluids did not show good gel-building properties was lost, the emulsion fluids did not show good gel-building characteristics, and suspension of barite and drilled cuttings was unsatisfactory. An independent element of rheological control was introduced with the development of organophilic bentonites (around 1950). In addition, it was found in the mid-1960's that amine-treated humates and lignites could be used as supplementary filtration-control additives.
Along with advances in "primary" emulsifier technology and the introduction of a variety of nonionic ("secondary") emulsifiers and wetting agents, these developments provided the arsenal necessary to carry invert-emulsion technology into the 1970's as a major force in the drilling-fluids industry.
Understanding the interactions that can occur between the formation and aqueous internal phase of an invert and introducing the high-spurt-loss, "relaxed-filtrate" inverts increased the usefulness of invert-emulsion fluids.
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