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The web site itself may have changed. You can check the current page or check for previous versions at the Internet Archive. Yahoo! is not affiliated with the authors of this page or responsible for its content. Training, control ensure success of offshore underbalanced drilling Kristian Johnstone, Santa Fe Techserv THE SANTA FE INTERNATIONAL
jackup drilling unit Britannia has been
used successfully for three years by
Shell UK Exploration & Production in
the southern North Sea to drill a series
of underbalanced wells, the first such
wells from an offshore rig. Standard underbalanced drilling tools
and techniques do not lend themselves
directly to an offshore rig operation and
have required considerable engineering. The overriding need to ensure safety of
personnel in a new and untried operat-
ing environment required additional
hardware, training, and the integration
of new personnel into the offshore team. The vast experience base and commit-
ment of the Britannias drilling crew,
specificall, in the areas of multilateral
extended reach (ERD) wells in the
southern North sea, played a key role in
the success of the project. The type D-221 jackup, built in the UK in
1968, is the only one of its kind. The four
legged jackup design is unique and has
the added advantage of a large usable
deck space area, nearly double that
available on an MLT 116C rig design. At the time of the underbalanced drilling
(UBD) implementation, large deck space
was a significant selection factor, as
much of the equipment was a derivative
from land based operations and not for
an offshore environment. U B D P R E P A R A T I O N A Shell Expro/Santa Fe interface docu-
ment was prepared and included a UBD
supplement outlining planned opera-
tions, showing that safety would not be
compromised with as low as reasonably
practical (ALARP) risk to personnel.
The contents included: The arrangements for carrying out
underbalanced drilling, and a process
definition and summary of the plant
required to implement the UBD process; The new hazards generated on the rig
as a result of the technique; The risks on the rig specifically asso-
ciated with UBD; The controls to be implemented to
adequately manage the hazards in
terms of prevention or achievement of
ALARP principles. R I G S P E C I F I C I S S U E S In preparation for the underbalanced
program, these rig specific issues were
addressed: Structural loading considerations; Rig stability for higher air gap; Access/egress due to additional
equipment; Additional lighting for areas not nor-
mally used; Hazardous area re-classification; Certification of all new plant compo-
nents by rig verification authority; Review fire and gas Detection (FEA); Radiation survey for anticipated flar-
ing operations; Additional noise hazard assessment of noise caused by extra generating
equipment and high flare rates. P E R S O N N E L I S S U E S Specific training of personnel was a key
factor for success in implementing the
UBD program. UBD tuition and crew
understanding was achieved by a Shell
Expro in-house training program. The program incorporated rig site input
into the operation from the conceptual
stage, a three-day formal training pro-
gram, and an offshore induction pro-
gram. Supervisory personnel visited land
based UBD operations and participated
in procedural reviews. The program also provided for stepwise
implementation of fully underbalanced
drilling conditions. And a rig site hands
onno pressure familiarization period
gave the opportunity to test, develop,
and improve communication between
various services. C O M M U N I C A T I O N The drill crew manning levels for the
UBD campaign remained similar to
those required for normal drilling oper-
ations, with the inclusion of an extra
crane operator and safety officer during
the rig-up phase. The maximum person-
nel-on-board (POB) restriction for the
Santa Fe Britannia is 104. Total man-
ning levels consistently exceeded 100
due to the requirement of more than 20
UBD-related contractors during the rig
up phase. Diligent planning coupled with good
onshore to offshore communication
ensured operations were managed with
minimum disruption keeping as much of
the rig up as possible as a non-critical
path operation. UBD operations changed the responsi-
bilities of drilling personnel in the fol-
lowing ways. The regular crew members were
charged with the role of becoming the
rig safety officers, responsible for
ensuring that the housekeeping and
third party working practices complied
with the rig safety management system. The Santa Fe driller was designated
focal point for all UBD communications.
He was expected to supervise additional
personnel on the rig floor. There was an 38 D R I L L I N G C O N T R A C T O R July/August 2000 Training, control ensure success
of offshore underbalanced drilling A large usable deck space area was a key
advantage when outfitting the Brittania for
underbalanced drilling in the North sea. increased area of authority and knowl-
edge for supervisory personnel extend-
ing from existing rig systems to pipe and
valve systems routing through various
UBD equipment packages. Personnel were expected to deviate
from standard well control mindset. And
finally, personnel were required to oper-
ate under the guidance of the specific
Shell Expro UBD supervisors. R I G U P A N D E Q U I P M E N T The increased cost of the UBD opera-
tions required emphasis on careful plan-
ning, management, and use of craneage
and deck space. The sequence and delivery of major
equipment packages were planned to
make best use of transportation and
more efficient placement on the rig. Additional operations are typical of
UBD requirements. It is necessary to rig
up the required surface equipment, nip-
ple up the UBD stack and associated
snubbing well control equipment, pick
up and rack back contingency drillstring
components, then pick up drillpipe. Stripping trials and a familiarization
period are necessary to debug any
equipment problems. For the original UBD campaign, addi-
tional equipment totaled 140 tons and
included numerous heavy lifts (UBD
systems, steel pipe, nitrogen membrane
units, and generators). Spotting of the equipment was impor-
tant, as there was not much room for
error. Footprints for every piece of equipment
had been marked out in the planning
phase. Much of this equipment had little opera-
tion time in an offshore environment. To counter this lack of experience and
maximize the potential for UBD suc-
cess, the following processes were
implemented: All equipment was subjected to
HAZOP and intensive design verifica-
tion by the UBD team; A strict regime of component testing
was put into place; All equipment measurements were
double checked and footprints con-
firmed with prior offshore visits; Hazards of heavy loads were high-
lighted during the pre-job formal train-
ing; Pre-job safety meetings were con-
ducted for every major step in the
process and on every shift change; Area of testing was restricted to
essential personnel only; Offshore Safety Officers provided 24- hour supervision to new personnel unfa-
miliar with the offshore environment. W E L L C O N T R O L The surface well control equipment
evolved from a basic jackup rig system
(an annular preventer plus three rams)
to a complex set up required for under-
balanced snubbing and drilling opera-
tions. July/August 2000 D R I L L I N G C O N T R A C T O R 39 The rig BOP presently consists of five
rams and an annular preventer Two of
the five rams are designed for opera-
tional use, leaving the remainder specif-
ically for a well control event. The additional operational rams are
designed to provide cover for the high
pressure riser and to enhance single
barrier protection. Double isolation for
the snubbing system from the wellbore
can be achieved at all times. At no time does the modification of the
drilling system compromise the inde-
pendence of the rigs well control equip-
ment. B O P P R E S S U R E T E S T It is good practice to attempt to time
BOP pressure testing events when full
hydrostatic overbalance convention is in
place. However, this is not always possi-
ble. In the underbalanced mode, conven-
tional practices cannot always be
employed to test the BOP while the well
is flowing. Inflow testing against fixed
bore and variable bore rams can be con-
sidered as a means of testing. B O P P A N E L , A C C U M U L A T O R The rig floor BOP control panel will be
set up such that the rigs well control
rams are controlled by conventional
levers. The two additional rams are con-
trolled from additional levers on the
same panel. S E P A R A T I O N E Q U I P M E N T The surface separation equipment is
continuously manned and protected
from the well by hydraulically operated,
air actuated emergency shut down
(ESD) valves responding to high pres-
sure and fluid levels, or manual activa-
tion. Regulation of returns at surface is con-
trolled by a choke manifold system
(independent of the rig manifold), sited
upstream of the separation package. W E L L C O N T R O L B A S I C S While drilling in underbalanced mode,
only a single well control barrier exists.
This barrier exists within the gas enve-
lope between the riser and the connec-
tion to the lowermost VBR on the rig
BOP. With the well live at all times, special
techniques are required to control flow. To minimize risk, it is important that
operations are scrutinized and the dou-
ble barrier policy implemented whenev-
er possible. For example, when out of
the hole with the drillstring, two blind
rams should be closed. For the underbalanced operation, the
conventional means of primary well con-
trol, an overbalanced hydrostatic barri-
er, is removed and thus procedures have
to be implemented for this change. The definition of well control is re-
defined as flow control, meaning the
maintenance of the inflow in a manage-
able window, defined by the surface con-
trol system operating limits. W E L L C O N T R O L S T R A T E G Y The strategy adopted to respond to a
well control incident while underbal-
anced drilling, is to isolate the wellbore
and return operations to a conventional
well control situation. Well killing will be
absolutely necessary when: Personnel safety or installations
integrity is threatened or jeopardized; A persistent inability to maintain
underbalanced drilling flow control
exists; A leak in the BOP stack which cannot
be isolated using the rig BOP is present. H I G H P R E S S U R E R I S E R The HP riser is defined as the weakest
mechanical component in the BOP
stack. For this reason the stress in the
riser is permanently monitored and
alarmed to flag any unforeseen rig
movements. B H A A N D D R I L L S T R I N G Underbalanced drilling with jointed pipe
poses additional risks, increasing the
number of potential leak paths com-
pared to coiled tubing. Drillpipe must be carefully selected,
managed, and maintained to ensure the
string is fit for purpose.Another vital
component of the BHA for underbal-
anced drilling is the drillstring float.
This one-way valve prevents flow up the
drillpipe. Types with a mechanical lock-
in for the float insert are preferable. D R I L L P I P E W E A R Underbalanced conditions by their
nature promote a wear rate higher than that experienced on conventionally
drilled wells. Contingency planning and
regular dimensional checking are
required to avoid drill pipe failures. Par-
ticular attention should be paid to
torque and drag modeling, and the pre-
mature onset of buckling, to help mini-
mize these problems. C O N C L U S I O N S To date offshore underbalanced technol-
ogy has been used to drill two low-head
and six underbalanced wells safely from
the Santa Fe Britannia. The success of
the operation is due to the following fac-
tors: A stepwise approach to UBD operations
was used, allowing collective learning
without the usual operational pressures
that new technology brings. The first
three wells were used to safely develop
the technology and the subsequent wells
used to mature it. Discrete portions of the operation were
addressed individually until confidence
and competence levels were reached. Team continuity allowed focus from con-
ception to execution and continuous
improvement, learned from good plan-
ning and cooperation between all con-
tractors involved both onshore and off-
shore. Avoidance of conflicts due to good
supervisory management coupled with
the appropriate education of the UBD
process allowed individuals to under-
stand their role and responsibility. Maintaining offshore input throughout
the project aided continued develop-
ment of the UBD process. Close scrutiny and qualification, includ-
ing auditing, of all equipment and
drillpipe components were critical to the
projects success. A C K N O W L E D G E M E N T S The author would like to thank Shell
UK Exploration & Production, in par-
ticular P Peetteerr B Brreetttt and the UBD team, for kindly allowing Santa Fe to write
and co-present this paper. .Acknowledgement is also due to the
crew and subcontractors of the Santa
Fe Britannia for information includ-
ed in this paper and for safely con-
ducting duties under challenging
conditions. I 40 D R I L L I N G C O N T R A C T O R July/August 2000
The web site itself may have changed. You can check the current page or check for previous versions at the Internet Archive. Yahoo! is not affiliated with the authors of this page or responsible for its content. Training, control ensure success of offshore underbalanced drilling Kristian Johnstone, Santa Fe Techserv THE SANTA FE INTERNATIONAL
jackup drilling unit Britannia has been
used successfully for three years by
Shell UK Exploration & Production in
the southern North Sea to drill a series
of underbalanced wells, the first such
wells from an offshore rig. Standard underbalanced drilling tools
and techniques do not lend themselves
directly to an offshore rig operation and
have required considerable engineering. The overriding need to ensure safety of
personnel in a new and untried operat-
ing environment required additional
hardware, training, and the integration
of new personnel into the offshore team. The vast experience base and commit-
ment of the Britannias drilling crew,
specificall, in the areas of multilateral
extended reach (ERD) wells in the
southern North sea, played a key role in
the success of the project. The type D-221 jackup, built in the UK in
1968, is the only one of its kind. The four
legged jackup design is unique and has
the added advantage of a large usable
deck space area, nearly double that
available on an MLT 116C rig design. At the time of the underbalanced drilling
(UBD) implementation, large deck space
was a significant selection factor, as
much of the equipment was a derivative
from land based operations and not for
an offshore environment. U B D P R E P A R A T I O N A Shell Expro/Santa Fe interface docu-
ment was prepared and included a UBD
supplement outlining planned opera-
tions, showing that safety would not be
compromised with as low as reasonably
practical (ALARP) risk to personnel.
The contents included: The arrangements for carrying out
underbalanced drilling, and a process
definition and summary of the plant
required to implement the UBD process; The new hazards generated on the rig
as a result of the technique; The risks on the rig specifically asso-
ciated with UBD; The controls to be implemented to
adequately manage the hazards in
terms of prevention or achievement of
ALARP principles. R I G S P E C I F I C I S S U E S In preparation for the underbalanced
program, these rig specific issues were
addressed: Structural loading considerations; Rig stability for higher air gap; Access/egress due to additional
equipment; Additional lighting for areas not nor-
mally used; Hazardous area re-classification; Certification of all new plant compo-
nents by rig verification authority; Review fire and gas Detection (FEA); Radiation survey for anticipated flar-
ing operations; Additional noise hazard assessment of noise caused by extra generating
equipment and high flare rates. P E R S O N N E L I S S U E S Specific training of personnel was a key
factor for success in implementing the
UBD program. UBD tuition and crew
understanding was achieved by a Shell
Expro in-house training program. The program incorporated rig site input
into the operation from the conceptual
stage, a three-day formal training pro-
gram, and an offshore induction pro-
gram. Supervisory personnel visited land
based UBD operations and participated
in procedural reviews. The program also provided for stepwise
implementation of fully underbalanced
drilling conditions. And a rig site hands
onno pressure familiarization period
gave the opportunity to test, develop,
and improve communication between
various services. C O M M U N I C A T I O N The drill crew manning levels for the
UBD campaign remained similar to
those required for normal drilling oper-
ations, with the inclusion of an extra
crane operator and safety officer during
the rig-up phase. The maximum person-
nel-on-board (POB) restriction for the
Santa Fe Britannia is 104. Total man-
ning levels consistently exceeded 100
due to the requirement of more than 20
UBD-related contractors during the rig
up phase. Diligent planning coupled with good
onshore to offshore communication
ensured operations were managed with
minimum disruption keeping as much of
the rig up as possible as a non-critical
path operation. UBD operations changed the responsi-
bilities of drilling personnel in the fol-
lowing ways. The regular crew members were
charged with the role of becoming the
rig safety officers, responsible for
ensuring that the housekeeping and
third party working practices complied
with the rig safety management system. The Santa Fe driller was designated
focal point for all UBD communications.
He was expected to supervise additional
personnel on the rig floor. There was an 38 D R I L L I N G C O N T R A C T O R July/August 2000 Training, control ensure success
of offshore underbalanced drilling A large usable deck space area was a key
advantage when outfitting the Brittania for
underbalanced drilling in the North sea. increased area of authority and knowl-
edge for supervisory personnel extend-
ing from existing rig systems to pipe and
valve systems routing through various
UBD equipment packages. Personnel were expected to deviate
from standard well control mindset. And
finally, personnel were required to oper-
ate under the guidance of the specific
Shell Expro UBD supervisors. R I G U P A N D E Q U I P M E N T The increased cost of the UBD opera-
tions required emphasis on careful plan-
ning, management, and use of craneage
and deck space. The sequence and delivery of major
equipment packages were planned to
make best use of transportation and
more efficient placement on the rig. Additional operations are typical of
UBD requirements. It is necessary to rig
up the required surface equipment, nip-
ple up the UBD stack and associated
snubbing well control equipment, pick
up and rack back contingency drillstring
components, then pick up drillpipe. Stripping trials and a familiarization
period are necessary to debug any
equipment problems. For the original UBD campaign, addi-
tional equipment totaled 140 tons and
included numerous heavy lifts (UBD
systems, steel pipe, nitrogen membrane
units, and generators). Spotting of the equipment was impor-
tant, as there was not much room for
error. Footprints for every piece of equipment
had been marked out in the planning
phase. Much of this equipment had little opera-
tion time in an offshore environment. To counter this lack of experience and
maximize the potential for UBD suc-
cess, the following processes were
implemented: All equipment was subjected to
HAZOP and intensive design verifica-
tion by the UBD team; A strict regime of component testing
was put into place; All equipment measurements were
double checked and footprints con-
firmed with prior offshore visits; Hazards of heavy loads were high-
lighted during the pre-job formal train-
ing; Pre-job safety meetings were con-
ducted for every major step in the
process and on every shift change; Area of testing was restricted to
essential personnel only; Offshore Safety Officers provided 24- hour supervision to new personnel unfa-
miliar with the offshore environment. W E L L C O N T R O L The surface well control equipment
evolved from a basic jackup rig system
(an annular preventer plus three rams)
to a complex set up required for under-
balanced snubbing and drilling opera-
tions. July/August 2000 D R I L L I N G C O N T R A C T O R 39 The rig BOP presently consists of five
rams and an annular preventer Two of
the five rams are designed for opera-
tional use, leaving the remainder specif-
ically for a well control event. The additional operational rams are
designed to provide cover for the high
pressure riser and to enhance single
barrier protection. Double isolation for
the snubbing system from the wellbore
can be achieved at all times. At no time does the modification of the
drilling system compromise the inde-
pendence of the rigs well control equip-
ment. B O P P R E S S U R E T E S T It is good practice to attempt to time
BOP pressure testing events when full
hydrostatic overbalance convention is in
place. However, this is not always possi-
ble. In the underbalanced mode, conven-
tional practices cannot always be
employed to test the BOP while the well
is flowing. Inflow testing against fixed
bore and variable bore rams can be con-
sidered as a means of testing. B O P P A N E L , A C C U M U L A T O R The rig floor BOP control panel will be
set up such that the rigs well control
rams are controlled by conventional
levers. The two additional rams are con-
trolled from additional levers on the
same panel. S E P A R A T I O N E Q U I P M E N T The surface separation equipment is
continuously manned and protected
from the well by hydraulically operated,
air actuated emergency shut down
(ESD) valves responding to high pres-
sure and fluid levels, or manual activa-
tion. Regulation of returns at surface is con-
trolled by a choke manifold system
(independent of the rig manifold), sited
upstream of the separation package. W E L L C O N T R O L B A S I C S While drilling in underbalanced mode,
only a single well control barrier exists.
This barrier exists within the gas enve-
lope between the riser and the connec-
tion to the lowermost VBR on the rig
BOP. With the well live at all times, special
techniques are required to control flow. To minimize risk, it is important that
operations are scrutinized and the dou-
ble barrier policy implemented whenev-
er possible. For example, when out of
the hole with the drillstring, two blind
rams should be closed. For the underbalanced operation, the
conventional means of primary well con-
trol, an overbalanced hydrostatic barri-
er, is removed and thus procedures have
to be implemented for this change. The definition of well control is re-
defined as flow control, meaning the
maintenance of the inflow in a manage-
able window, defined by the surface con-
trol system operating limits. W E L L C O N T R O L S T R A T E G Y The strategy adopted to respond to a
well control incident while underbal-
anced drilling, is to isolate the wellbore
and return operations to a conventional
well control situation. Well killing will be
absolutely necessary when: Personnel safety or installations
integrity is threatened or jeopardized; A persistent inability to maintain
underbalanced drilling flow control
exists; A leak in the BOP stack which cannot
be isolated using the rig BOP is present. H I G H P R E S S U R E R I S E R The HP riser is defined as the weakest
mechanical component in the BOP
stack. For this reason the stress in the
riser is permanently monitored and
alarmed to flag any unforeseen rig
movements. B H A A N D D R I L L S T R I N G Underbalanced drilling with jointed pipe
poses additional risks, increasing the
number of potential leak paths com-
pared to coiled tubing. Drillpipe must be carefully selected,
managed, and maintained to ensure the
string is fit for purpose.Another vital
component of the BHA for underbal-
anced drilling is the drillstring float.
This one-way valve prevents flow up the
drillpipe. Types with a mechanical lock-
in for the float insert are preferable. D R I L L P I P E W E A R Underbalanced conditions by their
nature promote a wear rate higher than that experienced on conventionally
drilled wells. Contingency planning and
regular dimensional checking are
required to avoid drill pipe failures. Par-
ticular attention should be paid to
torque and drag modeling, and the pre-
mature onset of buckling, to help mini-
mize these problems. C O N C L U S I O N S To date offshore underbalanced technol-
ogy has been used to drill two low-head
and six underbalanced wells safely from
the Santa Fe Britannia. The success of
the operation is due to the following fac-
tors: A stepwise approach to UBD operations
was used, allowing collective learning
without the usual operational pressures
that new technology brings. The first
three wells were used to safely develop
the technology and the subsequent wells
used to mature it. Discrete portions of the operation were
addressed individually until confidence
and competence levels were reached. Team continuity allowed focus from con-
ception to execution and continuous
improvement, learned from good plan-
ning and cooperation between all con-
tractors involved both onshore and off-
shore. Avoidance of conflicts due to good
supervisory management coupled with
the appropriate education of the UBD
process allowed individuals to under-
stand their role and responsibility. Maintaining offshore input throughout
the project aided continued develop-
ment of the UBD process. Close scrutiny and qualification, includ-
ing auditing, of all equipment and
drillpipe components were critical to the
projects success. A C K N O W L E D G E M E N T S The author would like to thank Shell
UK Exploration & Production, in par-
ticular P Peetteerr B Brreetttt and the UBD team, for kindly allowing Santa Fe to write
and co-present this paper. .Acknowledgement is also due to the
crew and subcontractors of the Santa
Fe Britannia for information includ-
ed in this paper and for safely con-
ducting duties under challenging
conditions. I 40 D R I L L I N G C O N T R A C T O R July/August 2000
download Training, control ensure success of offshore underbalanced drilling
