SOCIETY OF PETROLEUM ENGINEERS OF AIME
6200 North Central Expressway
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PAPER
NUMBER 3744
THIS IS
A PREPRINT - SUBJECT TO CORRECTION
Mud programs and drilling problems pertaining to
the tertiary Clays and Shales, Norwegian Northsea
by
I. Siem, Amoco Norway Oil Company,
Oslo, Norway
©
Copyright 1972
American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
This paper was prepared for the SPE-European Spring Meeting 1972 of the Society of Petroleum
Engineers of AIME, held in Amsterdam, The Netherlands, May 16-18, 1972. Permission to copy is
restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract
should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication
elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF
PETROLEUM ENGINEERS JOURNAL is usually granted upo:n request to the Editor of the appropriate
'journal provided agreement to give proper credit is made.
Discussion of this paper is invited. Three copies of any discussion should be sent to the
Society of Petroleum Engineers, P.O.Box 228, The Hague, The Netherlands. Such discussion may be
presented at the above meeting and, with the paper, may be considered for publication in one of the
two SPE magazines.
ABSTRACT
and has
a
high montmorillonite content.
Problems encountered in drilling
A
salt solution base mud is dis•
Tertiary clays and shales in the
southern part of the Norwegian
Continental Shelf and the mud system
cussed as an alternative to the commonly
used lignosulfonate system. Hydration
tests of formation samples in various
most frequently used in this area, are salt solutions indicate that low density
reviewed in this paper.
solid content in the drilling fluid
might be controlled more economically
Severe viscosity problems frequently
arise while drilling the top 10,000 feet
of hole, which predominantly consists
of clays and shales, and are the direct
cause of several problems like swabbing
formation; blocking of flowlines and
shaker screens by very soft sticky clay;
sticking of drill pipe; and bit and
collar balling.
by the use of a salt water base mud and
centrifuges and fine screen shakers.
To date mud properties have
been controlled in the unsatisfactory
manner of discarding old mud and making
up new mud.
It is concluded that
25% on the cost of barite alone seems
possible with salt solution base mud.
a saving of
a
The viscosity problems are the
result of lack of solids removal
equipment, the dispersing type drilling
fluid used which makes the solid
More important however, are the
potentials for reducing rig time and
consequently cost.
separation more difficult, and
facts INTRODUCTION
that the lower 5,000 feet of formation
is overpressured, behaves plastically,
This study presents mud programs
and drilling problems pertaining to the
Tertiary clays and shales in the
southern part of the-Norwegian
References and illustrations at end
of paper.
Continental Shelf (see Fig. I).