FLUIDE DE FORAGE

DRILLING FLUID

Abrégé anglais

T 6100 CAN
A B S T R A C T
DRILLING LIQUID
Drilling liquid comprising a mixture of powdered sulphur
dispersed in an aqueous liquid, the amount of sulphur being between
0.03 and 0.30 kg per kg of drilling liquid.
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Revendications

- 4 - T 6100 CAN
C L A I M S
1. Drilling liquid comprising a mixture of powdered sulphur
dispersed in an aqueous liquid, the amount of sulphur being between
0.03 and 0.30 kg per kg of drilling liquid.
2. Drilling liquid as claimed in claim 1, wherein the amount of
sulphur is between 0.10 and 0.30 kg per kg of drilling liquid.
3. Drilling liquid as claimed in claim 1 or 2, wherein the sulphur
particles have a dimension of less than 100 µm.
4. Drilling liquid as claimed in any one of the claims 1-3,
wherein the aqueous liquid is selected from the group consisting of
fresh water, sea water and brine.
5. Drilling liquid as claimed in any one of the claims 1-4,
further comprising suspended solids selected from the group
including clay, bentonite, attapulgite, calcium carbonate, barite,
hematite and siderite, the amount of suspended solids being between
0.01 and 0.30 kg per kg of drilling liquid.
6. Drilling liquid as claimed in any one of the claims 1-5,
further comprising pH adjusting agents selected from the group
including caustic soda, sodium carbonate and sodium bicarbonate.
7. Drilling liquid as claimed in any one of the claims 1-5, further
comprising an additive selected from the group of carboxymethyl-
cellulose, hydroxyethylcellulose, polyacrylate, xanthan gum, a
heteropolysaccharide, a succinoglycan and lignosulphonate, the
amount of additive being between 0.01 and 0.03 kg per kg of aqueous
liquid.
8. Drilling liquid substantially as described in the specification
with reference to the examples.
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Description

- 2~0~
T 6100 CAN
Hsb
DRILLI~G LIQUID
The present invention relates to a drilling liquid for use to
drill a deep well to an underground formation, generally deeper
than 3 000 m.
To drill such a well a drilling liquid is required that assist
in maintaining the maximum drilling rate, removes drill cuttings
from the bottom of the hole, supports and protects the wall of the
hole and cools the drill bit.
Such a drilling liquid is suitably an aqueous liquid and to
improve the drilling liquid oil is added to the aqueous system.
It is an object of the present invention to provide a drilling
liquid which is substantially free of hydrocarbon oil.
It is a Eurther ob~ect of the present invention to provide a
drilling liquid which can strengthen a borehole wall, provide
lubrication and stabilize shale at temperatures above about 100 ~C.
To this end the drilling liquid comprising a mixture of pow-
dered suLphur dispersed in an aqueous liquid, the amount of sulphur
being between 0.03 and 0.30 kg per kg of drilling liquid.
In the specification and ln the claims the term "powdered
sulphur" is used to refer to sulphur in the form of discrete
particles havLng a dimension which is less than 1 000 ~m (- lmm).
Reference Ls made to Russian patent publication No. 1 004 ~42
dLsclosLng an aqueous drillLng lLquid which contains a minor
amount, up to 2.5~ by mass of sulphur to the aqueous lLquid Ln
order to ensure the thermal s~abilLty of the drilling liquid.
An advantage of the drLllLng lLquld of the present invencLon Ls
that at surface condLtLons the sulphur partLcles are solLd, and
thus they can easily be handled, whereas at down hole condieLons,
at a temperature above 113 ~C (which is the meltLng point of
sulphur) the sulphur melts and a lLquid sulphur-in-water emulsLon
Ls formed.

2 ~
It was found that this sulphur-in-water emulsion had the sa~e
good rheological and filter properties as a conventional oil - in-
water emulsion.
Suitably the amount of sulphur is between 0.10 and 0.30 kg per
S kg of drilling liquid. A sulphur content in this range is particu-
larly suitable if it is required that wall building, lubrication
and shale stabilization properties of the drilling liquid are to be
improved.
To prevent interception on the shale shaker, suitably the
sulphur particles have a dimension of less than 100 ~m.
The aqueous liquid can suicably be selected from the group
consisting of fresh water, sea water and brine. The brine suitably
consists of an aqueous solution of at least one salt selected fronn
the group including sodium chloride, potassium chloride, calcium
lS chloride, magnesium chloride, the amount of salt being between
0.03 kg per k~ of solution and the amount of salt which saturates
the solution.
The invention will now be described by way of example in Inore
detail. An example drilling liquid according to the present inven-
tion is prepared as follows. To 1 m3 of fresh water were added
under agitation (shear rate up to 300 l/s) 60 kg of bentonite, 3 kg
of carboxymethylcellulose and S kg of lignosulphonate, after one
hour of mixlng at the above shear rate were added 120 kg powdered
sulphur and about 3.5 kg caustic soda. The particle size of sulphur
was as follows: 90~ by mass smaller than 53 ~m (ASTM sieve No. 270)
and 100~ by mass smaller than 6~ ~m (ASTM sieve No. 200~. After a
further hour of mixing at the above shear rata, the drilling lLquld
was tested. Its density was l 095 kg/m3 and its pH was 8Ø Tho API
filterloss was 9 ml (millilltre), the plastlc viscosity was 5 mPa.s
and the yieLd point 15 Pa. The filter loss and the rheological
properties were determined as follows: at 115 C and 200 kPa uslng
a conventional high pressure/high temperature filterloss apparatus
from Baroid and a high pressure/high temperature viscosimeter (Fann
50c) substantially as described in G.R. Gray and H.C.H. Darley,

Composition and properties of oil well drilling fluids, 4th Fd.
1980, pages 96-102.
To obtain a sodium chloride drilling li~uid according to the
invention 100 kg NaCl is added to 1 m3 of fresh water and then were
added under agitation (shear rate up to 300 l/s) 60 kg of attapul-
gite, 3 kg of carboxymethylcellulose and 5 kg of lignosulphonate,
after one hour of mixing at the above shear rate were added 120 kg
powdered sulphur and about 3.5 kg caustic soda. The filter loss and
rheological properties of this drilling liquid did r.ot differ
significantly from the properties of the above fresh water drilling
liquid.
A conventional mineral oil-in-water emulsion drilling liquid
contains about 15% by mass of oil and furthermore it includes
approximately the same amounts of clay, salt, cellulose, ligno-
sulphonate and caustic soda as the above drilling liquids. Such anemulsion drilling liquid has the the same filterloss and rheolo-
gical properties as the above sulphur emulsion drilling liquid.
From thLs comparative example it can be seen that the the
drilling liquid according to the present invention is a suitable
one replacing a mineral oil containing drilling liquid.
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