Summary
The conventional casing-running process is personnel-intensive and requires
considerable human contact with the casing. A new casing-running system
facilitates mechanizing the casing-running process. This technology
eliminates potential safety hazards, provides assurance that the casing can be
run to the intended casing point, offers the ability to ream casing to bottom,
reduces personnel requirements for running casing, and eliminates the need for
a stabber in the derrick.
A portable casing-drive tool is used to pick up joints of casing from the
“V-door,” position the casing over the stump in the rotary table, and grip the
top of the casing without making a threaded connection. The drive tool
supports the full torsional and axial load for running the casing and provides
the ability to circulate the well at any time to wash and ream to bottom as
tight hole or fill is encountered. The top drive provides the rotary
power to make up and rotate the casing.
The new portable casing-running system had been used on more than 430 jobs
for more than 40 operators in nine countries (at the end of 2004) to run more
than 3 million ft of casing of various weights, grades, and connection types,
with sizes ranging from 4½ to 16 in. These jobs encompass wells from
vertical holes to high-angle extended-reach wells and include both onshore and
offshore applications. The system has been completely mechanized on one
casing-drilling rig to allow the driller to routinely pick up casing from the
pipe racks and make connections without human contact with the pipe.
Introduction
Multiple strings of casing are run on every oil and gas well. Some
estimates (Tarr 1999) indicate that as much as 12 to 20% of the total rig time
for a well is spent on casing installation. The casing-running process
has changed little in many years, which provides an opportunity for process
improvements that may impact the overall drilling economics.
A “casing crew” rigs up casing-running tools and runs casing as a
specialized operation on most rigs. Casing elevators are used to pick up
individual joints of casing; casing tongs are used to rotate the top joint of
casing while making up the connection; and then the weight of the casing string
is supported with the casing elevators while the string is lowered into the
wellbore. For most rigs, this process has changed little since slip-type
casing elevators were introduced in 1924 (Brantley 1971) and air- and
hydraulically powered casing tongs were introduced in the 1950s (Brantley
1971). While this process is efficient at screwing joints of casing
together, it provides no capability to rotate the entire string of casing
hanging in the well and only very limited and inefficient procedures for
circulating the casing while it is being run.
This conventional casing-running process offers opportunities for
improvements related to safety, efficiency, and capability. First,
consider safety. The floor becomes crowded on many rigs when the
conventional casing-running equipment is rigged up while drillpipe is racked in
the derrick. The casing tongs are often operated from scaffolding set up
on the floor as a work platform. A workman is positioned in the derrick
to help align the casing joint in the elevators with the one in the slips at
the floor (the stump) to prevent cross-threading as the two joints are screwed
together. The overall result is that there is an increased potential for
falls from elevated work positions and for injuries from being caught between
pieces of equipment as the casing is picked up, made up, and run.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
15 November 2004
- Revised manuscript received:
8 March 2006
- Manuscript approved:
11 March 2006
- Version of record:
20 September 2006
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