|In a conventional completion the Electrical Submersible
Pumps (ESP's) are run on the bottom of the completion
string and it is therefore not possible to gain access
below the ESP without first pulling the completion.
An ESP By-pass system allows the well bore below the ESP to
be accessed by hanging the ESP from one side of the
Y-Block. It is then possible to run past the ESP to carry
out logging operations, set bridge plugs, perforate, run
wireline and coiled tubing etc. without first pulling the
completion thereby reducing workover costs and increasing
NOV has designed and supplied its ESP By-pass Systems for
use within highly deviated, extended reach wells and also
manufactures a complete range of associated field proven
wireline and coiled tubing running tools to complement the
TYPICAL USES FOR A BY-PASS SYSTEM
NOV have supplied ESP By-pass systems for the following
Casing sizes: 7", 7-5/8", 9-5/8", 11-3/4", 13-3/8". The
standard By-pass system is run in 9-5/8", with 7" a less
common though not unusual size. The sizing information in
the table opposite will therefore concentrate on these two
- Production Logging
- Through tubing Perforating
- Spotting fluids
- Coiled Tubing operations
- Wireline/Electricline operations
- ESP pump Isolation
- Bridge Plug Setting
- Reservoir Monitoring
- Dual ESP completions (Redundancy or dual zones)
When designing an ESP By-Pass System the first thing to
look at is the fit of by-pass tubing and the ESP inside the
casing. This will give us the maximum allowable ESP size
and the maximum allowable by-pass tubing size. The rest of
the system can then be designed around these figures.
Once the maximum permissible ESP diameter is determined
the required ESP can be designed. The required overall
length of by-pass tubing and quantity of clamps can then be
Clamps should be placed on all the flange connections in
the ESP assembly apart from the connection directly below
the intake. This connection should be left clear so as not
to interrupt flow into the intake.
The 6ft is to ensure a minimum stick-out at the bottom
of the ESP string of 6ft of by-pass tubing. By-pass tubing
can be supplied in any length but is generally supplied in
20ft lengths for the 2-7/8", 2-3/4" and 2-3/8" by-pass
tubing and 15ft lengths for the 2-1/8" by-pass tubing.
In order to prevent re-circulation of well fluids during
normal operations a blanking plug is set in the Telescopic
Swivel Nipple. The maximum O.D. of the plug must be smaller
than the minimum restriction in the tubing string above the
Y-Tool. In selecting the nipple size, the maximum tool
string size to pass through the by-pass tubing should also
'BM' BLANKING PLUG
The main function of the Blanking Plug is to provide a seal
to the By-pass tubing by sealing in the Telescopic swivel
nipple located directly below the Y-tool. This prevents
recycling of the well fluids through the aforementioned
tubing, allowing the ESP to pump the fluids to surface as
NOV have designed their Blanking Plug with extended field
usage in mind. It uniquely offers the following three
fundamental features in one design:
NOTE: NOV can supply all appropriate running/pulling tools
to complement the Blanking plug.
- External fishneck profile to prevent sand intrusion.
The fishneck is located directly below the Y-tool flow
path to prevent fishneck erosion, however the turbulence
created will prevent sand build up on the fishneck,
assisting trouble free Plug retrieval.
- Positive Dog-Locking mechanism to eliminate the
possibility of upward movement during pump operation when
set into the nipple profile.
- Full integral equalization feature, this facility is
achieved by upward movement of the retrieval neck,
allowing the plug to be equalized and retrieved (and
therefore run) in a single slickline operation.
The Y-tool is an internally profiled one piece casting. Its
main function is to offset the ESP away from the main
production string, thereby allowing toolstrings free
vertical access past the pump to carry out various
operations as described in the applications section of this
The Y-tool profile has been carefully designed to minimise
flow erosion. As the produced fluid leaves the ESP it flows
through a pump sub and then joins the main production
string through the Y-tool profile.
The Y-tool also clamps and protects the passing Motor Lead
Extension Cable within slots on each side of the Y-tool
TELESCOPIC SWIVEL NIPPLE (TSN)
The TSN is located directly below the Y-tool on the By-pass
(through bore) side.
Its main function is to provide a seal bore for the
Blanking/Logging plugs and Isolation sleeve (Described
later). The no-go and profile are carefully positioned to
ensure the fishneck of the plugs are kept slightly below
the production flow path to avoid erosion. This position
also ensures that the turbulence created above keeps the
plugs free from sand ingress.
The TSN also provides full rotation and up to 18 inches of
linear movement in order to assist system make-up. (See
The neck clamps are a high grade investment casting. Their
main function is to securely hold the by-pass tubing to the
ESP assembly, and maintain clearance between the assembly
OD and the ID of the casing. The neck clamps take
significant loads during tripping and are therefore robust
They also perform the vital function of protecting the
Motor Lead Extension Cable from damage. NOV maintain a
large inventory of all cast components, ensuring we can
respond rapidly to customer completion requirements.
|WIRELINE BY-PASS LOGGING PLUG
The Wireline By-Pass Logging Plug is landed in the seal
bore of the telescopic swivel nipple and prevents
circulation around the ESP during logging operations. The
ESP can therefore continue to operate during logging
operations, in static or dynamic conditions. Sealing is
provided by Vee-packings.
The Wireline By-Pass Logging Plug has an external Fishneck
to prevent sand intrusion whilst set in the nipple. It has
a full equalization facility, and if required a lower tool
catcher collet to prevent loss of the Logging string in the
event of the logging cable breaking. The catcher can be
designed to suit any common logging tool rope socket.
The Wireline By-Pass Logging Plug can be supplied to suit
all common logging cable and slickline sizes.
COILED TUBING BY-PASS LOGGING PLUG
The CT By-Pass Logging Plug utilizes the seal bore of the
Telescopic swivel nipple in the same way as the Wireline
version, however can be run on CT.
The CT By-Pass Logging Plug is connected to the CT by means
of a Dimple/Roll-On connector. When the plug reaches the
no-go of the nipple, sit down weight is applied through the
coil, which releases the connector latch profile, allowing
the CT logging string to be run through the by-pass tubing
to the desired logging depth. Sealing around the coil is
provided by profiled brass casscade seals. The plug is
retrieved simply by over-pulling the logging string through
the nipple, allowing the plug collet latch to retract from
the nipple profile.
BY-PASS ISOLATION SLEEVE
NOV can also supply an Isolation Sleeve which seats in
the blanking plug nipple and an additional upper nipple
above the Y-tool. This effectively straddles the ESP,
allowing free flowing of the well. It can also be used to
protect the ESP in situations where the bullheading of
fluids through the by-pass tubing is required.
|MISCELLANEOUS By-PASS COMPONENTS
Handling Sub/X-over - Located directly above the Y-tool,
this component incorporates an upset shoulder for handling
the system during installation, and also acts as a
crossover to the production tubing thread.
Pump Sub - Connects the ESP assembly to the Y-tool.
By-Pass Tubing - located below the Telescopic Swivel
nipple, this tubing allows the passage of toolstrings past
the ESP. The tubing Utilizes a flush joint connection to
prevent coupling/ESP clashing at clamping points. Re-entry
Guide - Located below the By-pass tubing, this component
acts as guide for wireline, Logging or CT tool strings.
Motor Plug - Connected to the bottom of the ESP, this plug
provides an additional clamping position, as well as
protecting the ESP when running the completion.
NOTE: All NOV By-pass completion equipment is NACE MR-01-75
compliant. Material is Low Alloy Steel as standard, however
13% or 9% Chrome grade material equipment can also be
supplied if required.
MISCELLANEOUS HANDLING EQUIPMENT
Stove Pipe - The stove pipe is used to raise the work
platform to a comfortable working height.
Swivel Lift Sub - The Swivel Lift sub allows the by-pass
tubing to be safely picked up when the elevator is in use.
Safety Clamp - The Safety Clamp is used to retain the
by-pass tubing on the top of the Stove Pipe when adding
additional lengths of tubing.|