OTC14060 Spoolable Bonded Flexible Pipes for Gas Service
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Copyright 2002, Offshore Technology Conference This paper was prepared for presentation at the 2002 Offshore Technology Conference held in Houston, Texas U.S.A., 6–9 May 2002. This paper was selected for presentation by the OTC Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Offshore Technology Conference or its officers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Offshore Technology Conference is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented.
Abstract
The paper describes the key properties of the bonded flexible
pipes, including the recent development of bonded flexible
pipes; especially for choke and kill systems as well as for
continuous high pressure gas service. The construction and the
qualification procedures acc. to API specifications 16C [1],
17K Draft5 [2] and RP 17B [3] are discussed. An interesting
application example is introduced, which is believed to be the
first integrally floating high pressure line for live crude oil.
The advantages and limits of the bonded flexible pipes
are presented.
Introduction
The oil industry uses large quantities of flexible pipes,
basically for offshore oil drilling and production, but
frequently onshore as well. Their onshore application can be
explained with the possibility of easier assembly and the
unequal subsidence of the equipment due to the production,
but for offshore production in many cases there is no other
solution at all. The connection between the fixed equipment
placed on the seabed and the floating drilling or production
units can only be achieved by flexible pipes. There are two
basic flexible pipes: "unbonded flexible pipe" described in
API (American Petroleum Institute) Standard 17J [4] and
"bonded flexible pipe"; at the date of submission of the
manuscript the relevant API 17K Standard is in Draft5
stage [2].
The unbonded flexible pipe construction consists of separate
unbonded polymeric and metallic layers, which allows relative
movement between layers. In the bonded flexible pipes the
steel reinforcement is integrated and bonded to a vulcanized elastomeric material. Both constructions are spoolable; the
bonded construction is generally used in short lengths up to
30-40 m, but it is available upto 200 m single pieces. Longer
lines can be assembled with intermediate couplings.
The bonded flexible pipe is a very special composite structure,
where the reinforcing material is steel cable or wire laid in
specific angles and the continuous phase is rubber. The
modulus difference between the reinforcement and the
continuous phase is much bigger than in any other composite,
5 orders of magnitude. This results in unique properties of
bonded flexible lines.
The flexible lines are used in numerous applications e. g. as
rotary drilling hoses, choke and kill lines, production flow
lines, gas or water injection, pile driving etc. In the present
paper we focus our attention to those applications, where the
lines are exposed to high pressure gas service. This is the case
with choke and kill lines intermittently, and with production,
gas injection and gas export lines continuously.
The experiments were carried out on particular design of cable
reinforced flexible pipes. More details can be found in
references [5;6;7;8;9]. Since bonded flexible pipe
manufacturers use different components, coupling designs etc.
special care had to be taken in generalization of the
statements, especially if the reinforcing material is solid wire,
not cable.
Description, Application and Testing of Bonded
Choke and Kill Lines
The choke and kill flexible line is a safety equipment in deep
drilling work as an integral part of the blow-out preventer unit
required for drilling well control [Fig.1]. Importance of
product reliability can not be emphasized enough. A brief
summary of the use of the discussed flexible lines:
The lines have the main task, if a kick occurs during drilling.
The kick is an unintended entry of water, gas, oil or other
formation fluid into the wellbore. If the pressure of the
medium entering in the wellbore is higher than expected, a
