dpt well s & a

DPT Well Suspension & AbandonmentIPM

WELL SUSPENSION & ABANDONMENT

IPM DPT


SCOPE

What has to be done (and why) in a well prior to its permanent abandonment or its suspension ?


DEFINITIONS, TERMINOLOGY

• Well abandonment (permanent)

• Well suspension (or temporary abandonment)

• “P & A” = Plug And Abandonment


PERMANENT WELL ABANDONMENT

A well is permanently abandoned when there is no future use envisaged, i.e.:

• It is a dry hole (generally exploratory well)• Discovery of hydrocarbons in non commercial

quantities• Discovery of hydrocarbons, but well not retained as

part of a future development scheme• It is a depleted production well


TEMPORARY SUSPENSION OF A WELL

• Exploratory (or development) well suspended because the objective has not been reached yet (iceberg season coming up, raging civil war requiring interruption of operations,…)

• Well has reached its objective (planned TD or geological marker) and is kept for future use (exploratory well or pre-drilled development well)


OVERALL OBJECTIVE OF AN ABANDONMENT

The abandonment must create permanent barriers within the well bore to prevent fluid movement in order to ensure long term zonal isolation and protection of the environment. It is an attempt to re-establish the original barriers that existed before the well was drilled and that were preserving the natural balance. This applies to entire wells and to hole sections that are permanently abandoned.


OBJECTIVE (Cont’)

How is it achieved ? Basically by applying the two-barrier concept (IPM Standard IPM-ST-WCI-012 : Barriers) & by implementing IPM Standard IPM-ST-WCI-026 : Temporary and Permanent Abandonment).

In practice: by setting (mechanical and/or cement) plugs, by squeezing perforations, and testing the barriers installed.


Suspension vs Permanent Abandonment :the main difference

• Permanent Abandonment : there is no plan to re-enterthe well

• Suspension : the well will be re-entered later, which implies that the temporary abandonment ops do not compromise the ability to re-enter the well (eg. : wellhead is not cut off).


LOCAL REGULATIONS

• Be familiar with the local regulations (their “level” varies from country to country) and assess how stringent they are compared to ours.

• Governmental regulations for well abandonment are generally minimal guidelines (they also vary from country to country), and following these guidelines will not absolve you from future liability.

• Be aware of the reporting and/or approval requirements from the local Authorities


Abandonment/suspension program

• A specific program has to be prepared (to include the downhole mechanical condition of the well, the formation plugging / isolation techniques to be used)

Why is abandonment/suspension so important ? because Operators are kept accountable by Government agencies and are responsible for all future liability should the abandonment fail.Also because of high cost of intervention.


And primarily to avoid this !!


Another view !!


COURSE CONTENTS

• Permanent well abandonment• Wellhead removal• Sidetrack• Particular case of a radioactive source• Temporary well suspension• Re-entry of a suspended well• Particular case of a floating rig


PERMANENT WELL ABANDONMENT METHODOLOGY

The starting point is the identification of all the potential leak paths in the well bore, by making an inventory of: perforated intervals, other hydrocarbon-bearing zones, over-pressured intervals, liner top(s), freshwater zones, non-cemented annuli….


OBJECTIVES OF AN ABANDONMENTA good abandonment/suspension aims at reducing the risk of leakage

(whether internal or to surface) to an ALARP level. Among other things :

protecting the reserves remaining in the reservoir

protecting freshwater sources penetrated by the well bore

Blocking leakage af any wellbore fluids to surface,preventing surface pollution

Isolating all permeable hydrocarbon and water zones from each other (thus eliminating flow path between higher-pressured zones to lower-pressured intervals, i.e. crossflow)

Preventing pressure build-up


PERMANENT WELL ABANDONMENT GENERAL PRINCIPLES

• All hydrocarbon bearing zones shall be isolated from non-hydrocarbon permeable zones

• All zones of different pressure regimes shall be isolated from one another

• Two (pressure) barriers are required for isolation from surface


Permanent Well Abandonmentwith open hole or perforated casing

• Openhole hydrocarbon bearing zones or perforated zones : set a cement plug across the zone (min 100 ft below & 100 ft above).

• Where there is open hole below the deepest casing string : set a cement plug across the shoe (100 ft below shoe and 200 ft above)


Typical cement plug to isolate a permeable zone

Permeable Zone

100 ft

Cement Plug

100 ft


Typical abandonment cement plug across a casing shoe

Cement Plug 200 ft

100ft


Permanent Well AbandonmentTop of liner & casing cuts

• Liner laps and casing stubs must be isolated by setting a cement plug across : min 100 ft into liner / inner casing string

• However a liner lap can be considered a barrier if there is evidence of good cement (as shown by CBL/CET) and if it has been pressure/inflow tested : in this case no cement plug (i.e. isolation) is required.


Cement Plugs (multiple zones)

Permeable Zone Cement Plug

Permeable Zone

Cement Plug

100 ft

100 ft


PERMANENT WELL ABANDONMENTSurface plug

• A surface plug (such as a 300 ft cement plug from surface/seabed down) shall be set, in the absence of more stringent country or client specific requirement


Testing of cement plugs

• The cement plugs (uppermost one in case of multiple plug sequence) shall be weight tested to 20,000 lbs (if a plug is found to be less than 100 ft, the plug shall be repeated). This plug should also be pressure tested above the leakoff test at the last casing shoe.


COURSE CONTENTS



Permanent well abandonment : removal of surface equipment

& site restoration

• Casings / conductors to be cut 12 ft below the seabed (offshore), 5 ft below surface (land well)

• Wellhead to be removed: site and its vicinity to be left clear of debris (and/or protruding above the seabed)

• Land wells: site to be reinstated to its former status• AGAIN: CHECK THE LOCAL REGULATIONS


Permanent well abandonment : land well site restoration

• Location to be leveled into the surrounding area with similar soil to enable vegetation to return

• Site to be cleared of all debris, equipment or material that does not belong to the natural environment


Permanent well abandonment : removal of surface equipment

Mechanical or hydraulic pipe cutters

Internal casing cutters are available in various sizes, but alsomulti-string cutters suitable for one-run cuts (offshore).

The casings are recovered using a spear.

Lastly, ‘single-trip abandonment and recovery systems’ have been proposed, that further save time.


Permanent well abandonment: use of mechanical or hydraulic cutters

The main manufacturers of such equipments are:

Logan Oil Tools: http://www.loganoiltools.com

Sii Smith Services: http://www.siismithservices.com

Weatherford: http://www.weatherford.com

Baker Oil Tools: http://www.bakerhughes.com


Typical hydraulic casing cutter


Well abandonment : casing cutting

LOGAN OIL TOOLS : pipe cutters & spear


Single-trip casing cutter system


Use of explosives for well abandonment

• JRC Jet Research Center: http://www.jetresearch.com• SII Smith Services: http://www.siismithservices.com• Weatherford: http://www.weatherford.com

NOTE : the use of explosives is not always allowed


Record keeping & reporting

• The relevant authorities must be informed that the rig is moving off location

• Records of all plugs and test results shall be kept• Offshore, it is recommended to record a videotape of the

seafloor before and after the removal of the wellhead. Tape to serve as an evidence and to be included in the well file


Well abandonment. Reporting (Ctd)

End-of-well report : a schematic of the well is to be included with all the necessary information (depths of cement plugs, perforations, bridge plugs, casing shoes, cement in the annuli, casing cuts, type of fluid left in casing, etc..). Reference depth must be indicated.


COURSE CONTENTS



Abandonment of part of the hole (‘sidetrack’)

• A sidetrack implies the permanent abandonment of part of the hole

• Can be accidental (fish) or intentional (geological)• Can take place in open hole or cased hole• In all cases, it implies plug-back operations• What is specific to these plug-back operations ?


SIDETRACK

• The fundamental rules of well abandonment continue to apply in this case (permeable zone isolation,…)

• The uppermost cement plug (hard cement) is designed to be the mechanical support for the change of well course


COURSE CONTENTS



Particular case of the abandonment of a radioactive source

• Radioactive material is hazardous• Major risk is over-exposure to personnel with ionizing

radiation (possibly sickness or death)• A lot of precautions taken for handling• But what if a radioactive source is lost in a well ??


Loss of a radioactive source in a well

• OFS Radiation Standard OFS-QHSE-S018 and IPM Standard IPM-ST-WCI-024 are the SLB governing documents

• In a given country, many departments may be dealing with radioactive substances: identify them all, be aware of local regulations. Talk to the relevant Contractor. Be PREPARED.

• Before abandonment, obtain clearance from Regulatory Agency as required


Loss of a radioactive source in a well (Ctd)

If a radioactive source has to be abandoned:• A cement plug shall be set, tagged and polished to provide

a minimum of 200 feet of hard cement above the fish containing the source

• Sidetrack to be planned and conducted so that the new wellbore is a minimum of 20 feet from the fish containing the source at any time


COURSE CONTENTS




• An exploratory or development well may be suspended because the objective has not been reached yet(iceberg season coming up, raging civil war requiring interruption of operations,…)

• Well has reached its objective but kept for future use (cannot be produced now)



• Generally, same principles and standards as permanent abandonment apply, while preserving the ability to re-enter the well

• Depending on the duration of the suspension (> or < 6 months), perforations may be left open, however with a mechanical plug on top, capped with cement

• Hole contents to be displaced to inhibited fluid to prevent corrosion

• Pressure containing corrosion/debris cap to be installed on the wellhead


TEMPORARY SUSPENSION OF A WELLThe most typical suspension

Barriers in place are :• Casing cemented at TD (with shoe & float intact, duly

pressure tested)• Treated drilling mud overbalance• Wellhead corrosion cap or lower Xmas tree block


COURSE CONTENTS



RE-ENTRY OF A SUSPENDED WELL

• Prior to removing wellhead cap, check pressure and monitor pressure

• Install BOPs (pressure test)• Drill cement plugs. Use adequate mud weight.

Always be aware that gas may be trapped underneath a plug !!


Case of a Mud-line suspension


COURSE CONTENTS



PARTICULAR CASE OF A FLOATING RIG

Mobile rigs have their BOPs at the seabed and may have to leave temporarily the location (bad weather, icebergs, BOP problems…).

They have to secure the well before leaving. HOW ?


PARTICULAR CASE OF A FLOATING RIG


Floater moving off location (bad weather)

• The drill string is normally pulled back into the shoe, non return valve is installed, then string is hung off in the wellhead/BOP, blind rams are closed and riser is disconnected. In case of emergency, string is hung off on tooljoint resting on pipe rams, and pipe is sheared.

• For reconnection, pressures are checked prior to opening the BOPs


TESTING FROM A FLOATER• Problem: accidental drive off (DP), bad weather while

testing• Solution: quick disconnection with no spill >>>> use of

a subsea test tree (SSTT)


TESTING FROM A FLOATER (Ctd)

The SSTT system enables well testing operations to be conducted from an offshore floating rig.

It is the primary subsea safety device and provides fast acting and reliable means to:

Isolate the landing string from the test string

Prevent discharge of its contents into the riser

Disconnect the landing string from the test string.


SenTree 3 (SSTT): Sequence of operations• Close Ball Valve

• Close Flapper Valve• Small Delay for wire to move up

• Close Retainer Valve

• Open Bleed Off Valve

• Disconnect Subsea Tree

3 - Retainer Valve

4 - Bleed Off Valve

5 - Latch

2 - Flapper Valve

1 - Ball Valve


Repairs on subsea BOPs on a floater

• BOP malfunction is a relatively common occurrence.• If the subsea BOP has to be pulled, plenty of time is

available to suspend the well in a secure manner. Typically as explained earlier in « Well suspension ».

• Never try to save rig time by not properly suspending the well

dpt well s & a

Documents

suspension abandonmentipmand

abandonment permanent

abandonmentthe abandonment

permanent barriers

temporary abandonment

temporary abandonment

future liability

future use exploratory