SONAT_WUBS-PRS-OPS-015 (Rev0.

0) - Page 1

Tripping

Client Sonatrach Onshore Operation X Gas X

Region Algeria Offshore Operation Oil X
Contract No 03/SH.EP.FOR/2001 Underbalanced Drilling X H2O
Document No SONAT_WUBS-PRS-OPS-015 Production Testing H2S
Rev No & Date Well Services CO2

Purpose This chapter outlines the policies and procedures that ensure safe working practices when
tripping.

Scope These policies and procedures apply to all Company employees.

In this document
Topic See Page
General Guidelines 2
Tripping Procedure 3

General This document defines the procedures for:

Guidelines
• Tripping of drill string

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 SONAT_WUBS-PRS-OPS-015 (Rev0.0) - Page 2

Tripping

General Guidelines
UBD Tripping Prior to reaching the pipe light conditions or the BHA on trips, the well must be
Philosophy transferred from an underbalanced dynamic circulation state to a static balanced
state. Stopping nitrogen injection and allowing reservoir fluids to balance formation
pressure should accomplish this.

The objective of this procedure is, tripping in or out of the hole without exposing the
well to excessive overbalance conditions and, at the same time, allowing
conventional tripping to be performed. This operation provides safety advantages
aligned with the main objective of drilling this well in the shortest amount of time
with minimum HS&E exposure to the rig personnel onsite as follows:
• No pipe light conditions are experienced or induced.
• The use of extra equipment on the rig floor like push and pull down
equipment will not be required, thus the operation will be safer due to
minimizing the hazards of having extra equipment and people on the rig
floor.
• Stripping out the BHA with a 10 ft stroke machine is time consuming.
• Connections are time consuming when stabilizers in the string.
• Logging while drilling tools (like resistivity) may not be suitable for stripping
out due to sensors not being designed for stripping operations.
• Once well is balanced the down hole pressures are easily maintained while
tripping and changing the BHA conventionally. By continuing to pump
nitrogen into the well while tripping, there is a risk of displacing all fluid
from the injection point up, exposing the reservoir to an almost complete
draw down during trips, then when drilling resumes, down hole pressure
will be back at nearer balance conditions. These extreme cycles in the
bottom hole pressure are not recommended even if the RSA (Rock
Strength Analysis) show that the Cambrian is a very competent formation.

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Tripping

Tripping Procedure
Sonatrach The Wellsite Supervisor should co-ordinate tripping procedures and safe working practices
Project Tripping with all personnel. The procedures and guidelines should be followed closely with constant
Procedure communication between all personnel being essential. These procedures apply to tripping
and simultaneously allowing the well to balance itself.
Step Action
The Driller should circulate a minimum of two times bottoms up, or until no drilled
1 solids are observed in the return stream at the sample catchers. Viscous pills or
sweeps, if used, should also be circulated out before beginning tripping operations.
POOH washing each stand until bit is 10 feet out of the 7” liner shoe, this is to
avoid damaging the casing when the bit rotates inside the casing. (Refer to the
connections section). Record PWD pressures and depth at each connection, this
2 gives an idea of how the hole is being cleaned, trends are to be observed as are
pressures at the same points from former trips. Washing and back reaming while
coming out of hole in the open hole section assists in removing solids that are
laying on the low side of the hole in the horizontal section.
After the hole is clean, the Driller will shut down rig and WFT will switch N2 to by-
pass. The well will remain lined up to the separator and the nitrogen will be bled
3 off under controlled conditions. Ensure that responsibilities are well identified and
all personnel (Sonatrach, Weatherford, ENTP) are in their positions. Verify that
communications equipment is working properly.
The driller will pull out of the hole and WFT will bleed off the nitrogen from the
annulus while the rig crew pulls out of the hole. The drill string will be pulled
4 (stripped) through the rotating head and the well will be allowed to come into
balance. Slugging the pipe before pulling out and filling up the hole while pulling
out will not be necessary.
All the pressure should be bled off the annulus before reaching the BHA. When
5 the BHA is reached, utilize the echo meter to determine the fluid height in the
annulus
When the BHA is reached, and all the pressure is off the well, and the well is
6 static, WFT to release RCH bearing assembly and retrieve same on the last stand
of drillpipe.
The Driller is to close the blind rams after pulling the bit above them. The annulus
should remain open and be monitored by WFT personnel while the blind rams are
7 closed to make sure no flow occurs. Before running the BHA back in the hole, the
blind rams will be opened by the Driller only after check with WFT to confirm that
no flow is present.
The BHA is to be changed and run back in the hole along with 10 stands of
8
drillpipe.
The RCH bearing assembly is to be reinstalled in the head and the motor/turbine
9
and MWD function tested.
10 The drill string is to be run back in the hole (stripped) through the RCH.
Once 1000 meters of pipe are in the hole or 4 hours before reaching the end of the
11 casing (whichever is later), begin injecting nitrogen down the concentric string. As
the well begins to unload, control returns through the choke and separator.
When the bit has cleared the bottom of the casing. Pump each stand down with
12 the top drive while continuing to pump nitrogen down the concentric string and re-
establish proper liquid and nitrogen rates.
13 Continue washing to bottom and resume drilling.

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Tripping

To be signed if document SONAT_WUBS-PRS-OPS-015 has been reviewed and accepted by all parties
concerned.

Weatherford Sonatrach ENAFOR

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