G.1 Drilling fluid resistance test

Drilling fluids are used in almost every oilfield drilling operation. The fluids used in the socalled
drilling fluid systems may come into contact with cables and may affect the functioning
of the cables. The suitability of electric cable sheathing materials (as given in IEC 60092-359)
to exposure to these drilling fluids is heavily dependent on the type of drilling fluid present.

G.2 Drilling fluid to be used

The various drilling fluids can be grouped in three categories and for the water-based and oilbased
mud, specific test drilling fluids are defined here
A material for which drilling fluid resistance is needed in one or more of the categories below
shall also fulfil the normal oil test as given in IEC 60092-359 for SHF2 materials, as well as a
test in IRM 903 oil (in accordance with ISO 1817) following the procedure described in
Annex F for enhanced oil resistance. For this test in IRM 903 oil the following requirements
are applicable:

a) tensile strength: maximum variations from unaged samples of 30 %;
b) elongation at break: maximum variations from unaged samples of 30 %;
c) linear swell: maximum variation from unaged samples of 30 %;
d) change in weight: maximum variation from unaged samples of 30 %.

In order to qualify a material in one or more of the drilling fluid categories, the material shall
be tested separately for each category in the representative test drilling fluid.


1.Water-based mud     : Calcium Bromide Brine
2.Oil-based mud          : Carbo Sea
3.Ester-based mud      : Under consideration

NOTE The specific test drilling fluids and test method for ester-based mud is under consideration.

G.3 Procedure

Five tests pieces shall be prepared in accordance with procedures described in 9.2.2 and
9.2.3 of IEC 60811-1-1.
The test for determination of linear swell is carried out on dumb-bell samples of thickness
(1, 25 ± 0, 25) mm.
The method of the determination of the cross-sectional area of test piece is given in 9.2.4 of
IEC 60811-1-1.

along the axis of the dumb-bell (to one decimal place) shall be measured at room
temperature.
Then, the test pieces shall be immersed in the particular fluid previously heated to (70 ± 2) °C
and shall be maintained at that temperature for 56 days. At the end of the specific duration,
the test pieces shall be removed from the fluid, blotted lightly to remove excess fluid and
suspended in air at ambient temperature for at least for 16 h but not more than 24 h, unless
otherwise specified in the relevant cable standard. At this end of this period, any further
excess fluid shall be removed by lightly blotting the test pieces, and then the linear swell,
weight and mechanical properties of each test piece shall be measured.

G.4 Expression of results

The calculation of tensile strength shall be based on the cross-sectional area of the test piece
measured before immersion.
The difference between the median value obtained of the five test pieces immersed in fluid
and the median value of the values obtained for the unaged test pieces, expressed as a
percentage of the latter, shall not exceed the percentage specified in the requirements given
in G.5-a, and G.5-b.
The change in linear swell and weight are calculated as follows:
– ((linear dimension after immersion/linear dimension before immersion) x 100) - 100%
– ((weight after immersion/weight before immersion) x 100) - 100%

G.5 Requirements

a) Tensile strength: Maximum variation from unaged samples of 25 %
b) Elongation at break: Maximum variation from unaged samples of 25 %
c) Linear swell: Maximum variation from unaged samples of 20 %
d) Change in weight: Maximum variation from unaged samples of 15 %

NOTE Materials meeting this drilling fluid resistance qualification test are not automatically approved for use in a
specific drilling fluid or in particular operating conditions, specific agreement with the cable manufacturer and/or
additional testing in the specific oil and particular conditions being needed. The requirements in due time will be
transferred to IEC 60092-359.