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Research Papers: Petroleum Engineering

The Shielding Effect of Drilling Fluids on Measurement While Drilling Tool Downhole Compasses—The Effect of Drilling Fluid Composition, Contaminants, and Rheology

[+] Author and Article Information
Arild Saasen

Det norske oljeselskap ASA,
Oslo NO-0125, Norway;
Department of Petroleum Engineering,
University of Stavanger,
Stavanger NO-4036, Norway
e-mail: arild.saasen@detnor.no

Songxiong Ding

Tel-Tek,
Porsgrunn NO-3918, Norway;
Faculty of Science and Technology,
University of Agder,
Grimstad NO-4879, Norway
e-mail: songxiong.ding@uia.no

Per Amund Amundsen

Department of Mathematics and Natural
Sciences,
University of Stavanger,
Stavanger NO-4036, Norway
e-mail: pa@bsda.ux.uis.no

Kristoffer Tellefsen

Department of Petroleum Engineering and
Applied Geophysics,
Norwegian University of Science
and Technology,
Trondheim NO-7491, Norway
e-mail: kristoffer.tellefsen@icloud.com

Contributed by the Petroleum Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received June 18, 2014; final manuscript received January 14, 2016; published online May 12, 2016. Assoc. Editor: Arash Dahi Taleghani.

J. Energy Resour. Technol 138(5), 052907 (May 12, 2016) (6 pages) Paper No: JERT-14-1189; doi: 10.1115/1.4033304 History: Received June 18, 2014; Revised January 14, 2016

Materials such as added clays, weight materials, drill solids, and metallic wear products in the drilling fluid are known to distort the geomagnetic field at the location of the measurement while drilling (MWD) tool magnetometers that are used to measure the direction of well path. This distortion contributes to substantial errors in determination of azimuth while drilling deviated wells. These errors may result in missing the target of a long deviated 12 ¼ in. section in the range of 1–200 m, representing a significant cost to be mitigated. The error becomes even more pronounced if drilling occurs in arctic regions close to the magnetic north pole (or south pole). The effect on the magnetometer readings is obviously linked to the kinds and amounts of magnetic materials in the drilling fluid. The problem has recently been studied by laboratory experiments and analyses of downhole survey data. A series of experiments has been carried out to understand how some drilling fluid additives relate to the magnetic distortion. Experiments with free iron ions show that presence of iron ions does not contribute to magnetic distortion, while experiments with bentonite-based fluids show a strong effect of bentonite on magnetic shielding. Albeit earlier measurements showing a strong dependency of the content of organophilic clay, clean laboratory prepared oil-based drilling fluids show no increased shielding when adding organophilic hectorite clays. The anticipated difference between these two cases is outlined in the paper. When eroded steel from an offshore drilling site is added into the oil-based drilling fluid, it is found that these swarf and steel fines significantly increase the magnetic shielding of the drilling fluid. The paper outlines how the drilling direction may be distorted by the presence of these additives and contaminants and how this relates to the rheological properties of the drilling fluid.

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References

Figures

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Fig. 1

The dynamic behavior of magnetic shielding

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Fig. 2

Sketch of the Porsgrunn experimental setup, the magnetometer (Mag-01 (H)), and its probe

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Fig. 3

Magnetic field strength as a function of time for the series of water–bentonite based drilling fluids

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Fig. 4

Magnetic field strength as a function of time for the series of oil-based drilling fluids

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Fig. 5

Magnetic field strength as a function of time for an oil-based drilling fluid and for the same fluid with swarf

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Fig. 6

Magnetic field strength as a function of time for the oil-based drilling fluid with added swarf

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