Author Unit/Section:

OSD 2.4

Target Audience:

All OSD Inspectors (Bands 0 – 3)

Purpose

To provide guidance on the provision, siting and use of primary and secondary control panels for the operation of xmas tree valves during well intervention operations.

Action

1 Inspectors should take account of the contents of this SPC when undertaking inspection of well intervention operations and during the assessment of safety cases.

Background

2 During the production phase of a well’s life, there are many occasions when the well will be re-entered by wire-line (including braided wire, electric line etc.) or coiled tubing. These operations are seen as routine and few of such interventions on wells on a fixed installation require notification to HSE.

3  During such activities, the well is frequently isolated from the main emergency shut-down (ESD) system and controlled from a primary control panel local to the worksite. The xmas tree and downhole safety valves are held open by hydraulic pressure controlled from this panel. In the event of an emergency, the well must be shut-in by manually pressing a button at the panel. Where there is a risk of the primary control panel not being accessible in an emergency, a second ‘button’ to shut in the well is often provided in a safe area.

4  The arrangements for the panel(s) vary from well to well and installation to installation. Sometimes the equipment is owned by the installation duty holder and sometimes it is third party equipment supplied by the wireline or coiled tubing company.

5  However in all cases the equipment used to hold open the xmas tree valves falls within the definition of ‘work equipment’ and has to be suitable for the purpose for which it is provided and also be maintained. Such equipment is safety critical and should be covered by the installation verification scheme.

6  To date, no significant problem has been found with the actual equipment, however in some cases risk assessments have failed to ensure that the primary panel is sited in a safe area and failed to consider the need for remote operation from a safe location by a secondary ‘button’.

Regulatory requirements

Offshore Installation and Wells (Design and Construction, etc.) Regulations 1996 [DCR]

7  Regulation 13(1) requires well-operators to ensure that each well “is so designed ………. [and] operated, maintained …….. [so that] so far as is reasonably practicable, there can be no unplanned escape of fluids from the well; and risks to the health and safety of persons from it or anything in it, or in strata to which it is connected, are as low as is reasonable practicable”.

8  Regulation 17 requires the well-operator to “ensure that suitable well control equipment is provided for use ……………. to protect against blowouts”, and the operator of the installation to ensure that equipment specified in Regulation 17(1) is deployed.

9 Paragraph 37 of the guidance specifies that “well control equipment includes equipment where the primary purpose is to prevent, control or divert the flow of fluids from the well”. The control system for the xmas trees and downhole safety valves falls under this category.

Offshore Installations (Prevention of Fires and Explosions, and Emergency Response) Regulations (1995) [PFEER]

10  PFEER Regulation 9(1) requires the installation operator to “take appropriate measures to….prevent the uncontrolled release of flammable or explosive substances”. The assessment required by PFEER Regulation 5 should inform this process. The approved code of practice (ACOP) associated with PFEER goes on to indicate that personnel required to implement procedures should be competent to do so and be provided with adequate training, supervision and information about the hazards. Human factor issues should be identified and taken into account in the design of procedures and systems.

11  PFEER Regulation 12 requires the installation operator to provide for the remote operation of plant where this is appropriate for limiting the extent of an emergency. The objective is that the installation operator has appropriate control measures in place to limit escalation in an emergency.

Offshore installations (safety case) regulations 2005 [scr]

12  SCR Schedule 2, paragraph 8 requires a description of the plant and arrangements for the control of operations on a well. Arrangements include policies and procedures relating to well operations. This can be summarised from the arrangements in place to ensure compliance with DCR Regulation 13 to 17 and 21.

Isolation from esd system

13  It is normal practice to isolate the well in question from the ESD system. This is to prevent the xmas tree valves from closing inadvertently due to spurious alarms. The closing of the xmas tree valves will normally shear any wire across the valves and smaller diameters of coiled tubing. However, this will result in a fishing operation with its inherent risks and may damage the valve face.

14  However, as ESD systems become more reliable, the requirement to isolate the well from the system should be addressed in the risk assessment.

Siting of primary control panel

15  The primary control panel is used to open and close the xmas tree and downhole safety valves during the intervention operation. On some installations the xmas tree control panel is the same panel that controls the wireline or coiled tubing BOPs. It is usually situated in, or adjacent to, the wireline or coiled tubing control cabin. On other installations, the primary control panel may be remote from the wireline or coiled tubing control cabin and so is often adjacent to the xmas tree.

16  As the primary control panel is over-riding the ESD system, it should be sited in a safe area away from any hazards which could prevent its operation. These hazards may come from the well (e.g. H2S) or from an external source.

Use of a secondary control function

17  The risk assessment of the operation may identify circumstances where a secondary control function is required with a view to limiting the extent of an emergency. [This stems from the requirements of PFEER Regulation 12.] The secondary control function may not require the full duplication of control functions; a single button to close in the well may be sufficient.

18  Any secondary control function should be sited remotely from the primary panel. Additional human factor considerations may identify that the ‘button’ should be sited in the general direction of escape.

19  Provision of a secondary control function should be identified by risk assessment. However there are a number of situations where it would be difficult to justify not having a secondary function. These include:

• Bridge linked installations where a button at the bridge (escape route) would prevent personnel being put at risk by re-entering a hazardous area.
• Work on installations where there are high levels of H2S either from an individual well or from the process plant; and
• On new installations where the costs of permanent installation of such a system is minimal.

Human factors

20  It is essential that the well is able to be closed in at all times. The primary control panel should therefore never be left unattended during well intervention operations.

Emergency situations

21  Actions to be taken by the panel operator, in the event of an emergency should be clearly defined. The operator should be competent to carry out these actions.

22  The identified actions should include a statement to instruct the panel operator to close in the well at the xmas tree and shear the wire or coiled tubing if the situation deteriorates such that the operator must leave the panel.

23  In an emergency situation the operator should not be expected to remain at the panel unduly, for example by having to contact the OIM (or his deputy) for permission to close in the well at the xmas tree.

Further information

For further information, please contact Head of Discipline - Well Engineering and Operations OSD 2.4, VPN 525 2581.