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7.4.1

General

Concurrent operations are defined as the simultaneous execution of two or more risk activities which, due to their interaction, result in an increased operational complexity and enhanced level of risk.

Any combination of the risk activities is considered to increase the probability of incurring risk consequences when carried out concurrently. Such activities would include the following:

• production • construction • maintenance • drilling • workover • well testing • well services • diving • heavy lifts • transport operations.

This subject is summarised below but prior to any concurrent operations being undertaken, reference shall be made to the local concurrent operations manual. Where no manual exists, SIEP can assist in one's development, generally by supplying examples from other Opcos.

While this process is ongoing, specific controls shall be agreed by relevant supervisors at co-ordination meetings and approved by department heads.

The advice given in this sub-paragraph is particularly aimed at operations involving an independent rig working alongside a production platform.

Some general observations are:

• all supervisors involved in concurrent operations should meet daily to identify and resolve any potential overlap of operations and responsibilities

• a fundamental rule for concurrent operations is to classify all operations as either hazardous or non- hazardous and only allow one hazardous operation to occur at any one time

• single point responsibility is essential. All supervisors controlling operations shall report and liaise through the single point

• the person in charge of concurrent operations shall be trained/competent to be able to make sound decisions

• management inspections should be carried out jointly by platform and rig based supervisors

• plan directional drilling logically.(high angle wells from outer slots) to minimise collision risks and make well paths uncomplicated

• have a well-defined cone of uncertainty and a resulting well shut-in policy.

7.4.2

Procedures

Clear written instructions and plans are required in order to limit the extra risk associated with concurrent activities.

An operations plan shall be prepared for each location where concurrent operations are to take place stating the conditions to be met and procedures to be followed. This plan shall cover at least the following areas:

• a narrative description of all operations

• individual duties and responsibilities

• arrangement and location of equipment

• integration of alarm and emergency systems between rig and platform

• integration of mustering system between rig and platform

• routing of all pipelines and their service

• integration of hazardous zone delineations

• periodic special testing and drills of safety systems and devices

• conditions for securing and restarting of activities

• communication procedures and reporting lines

• escape routes

• contingency plan

• dissemination of information to all involved parties

• on-site containment, rescue and evacuation training

7.4.3

Supervision

Principle

Concurrent operations necessitate optimum co-ordination of activities and defined lines of responsibility to ensure operational efficiency and the safeguarding of personnel and equipment. To this end, the OIM, or person in charge, shall chair a daily, minuted co-ordination meeting attended by all on-site department heads and others necessary for the effective conduct of the meeting.

The meeting should cover the planned operations for the day, any hazards which may arise out of the individual operations or their concurrency with other operations, and permits or other requirements necessary for their safe management.

Overall supervision

Single point responsibility for management of the location where concurrent operations are being carried out shall be maintained at all times. The responsible person will be the Offshore Installation Manager (OIM) or his equivalent in an onshore facility.

Each individual activity shall be supervised by a competent supervisor, who has the responsibility to verify that the activity is adequately protected by a minimum of two barriers with proven integrity. He is also responsible for reporting status, and change of status, to the single point co-ordinator.

Communication

Regular meetings should take place between the supervisors to discuss HSE issues and the planned work programme. Changes from a previously agreed programme shall be highlighted and adequately discussed with all involved parties.

Permits-to-work

All concurrent activities other than routine production, drilling, maintenance or construction operations shall be rigorously controlled by the use of work permits signed by supervisors of the individual activities and the supervisor/manager responsible for the overall operation.

Control of personnel movement

The movement of personnel between drilling rig and platform shall be strictly controlled. At no time shall there be more people on the rig or the platform than life saving equipment exists for or certification allows for. Procedures for the mustering of, or accounting for, personnel on the two locations shall be in place, well known and practised. Escape routes to and from the rig shall be clearly indicated.

Personnel arriving at the installation shall be provided with any required personal protective equipment for transit from the arrival point to the accommodation and report immediately to the OIM or his nominated deputy.

7.4.4

Specific requirements

Specific requirements shall be detailed in the local concurrent operation manual and should be used in conjunction with any local statutory requirements to produce the written plan for each case.

Barriers

Each individual activity is protected by barriers (protection mechanisms) which would have to fail before control is lost. Operations may proceed if each individual activity is protected by a minimum of two independent and tested barriers, with the provision that neither of these barriers becomes nullified by virtue of the concurrent activity. Where a barrier fails, immediate action shall be taken, within the constraints of concurrent operations, to restore two barrier integrity.

The following may be considered as barriers:

• drilling fluid in the hole of sufficient density to overbalance formation pressures. The drilling fluid shall be subject to continuous monitoring to qualify

• a tested BOP stack

• cased hole where the casing is unperforated or has not been drilled out, or where a tested cement or bridge plug is in place.

For completion and workover operations the following barriers once tested may also be considered:

• deepset wireline plug (below production packer)

• drilling or completion fluid in the well of sufficient density to overbalance formation pressures. The fluid shall be subject to continuous monitoring to qualify

• Xmas tree

• a two way check valve is installed in the tubing hanger and on the annulus side:

• a tested packer/completion (production) packer

• tested seals on the tubing hanger

The safety of the drilling or workover operation may be threatened by events occurring in other concurrent activities.

Surface Controlled Sub-surface Safety Valves (SCSSV)

A Surface Controlled Sub-surface Safety Valve (SCSSV) shall not be considered as a 'programmed' barrier with regard to well intervention. In cases of emergency, where other barriers cannot be installed and tested, an SCSSV may be regarded as a barrier, provided that it was in place and tested before the emergency arose. (i.e. it has a working track record). Even in this case, management consent shall be gained prior to the start of work and contingency arrangements, in case the barrier fails, shall be in place and tested.

Well interference

Attention should be paid to sub-surface cones of uncertainty of adjacent wells, with travelling cylinder collision plots being produced for critical situations. The criteria for terminating as mentioned in the 'Borehole Surveying Manual' (Ref. 47) should be expanded to include consideration for:

• the situation where well bore paths are converging

When the well being drilled is on a converging course with an existing production well and the criteria mentioned above apply, the production well shall be closed-in and equipped with an inflow tested downhole plug located below the packer.

Conductor driving operations also require special attention which shall include monitoring the conductor path and closing-in wells within the cone of uncertainty.

Rig moving operations

When moving a rig or tender on or off the platform and while positioning same at the platform, it may be necessary to cease and secure all other activities if an unacceptable risk exists to the platform or

personnel.

A pre-move meeting attended by drilling, production and marine staff shall be held to plan the move and assess the risks. An effective well handover procedure shall be in place which details the status of wells and other production facilities on the platform. See 4.4.5 for additional information.

Well testing using temporary facilities

Well testing activities using temporary facilities are not permitted concurrently with any activities except routine production and maintenance. No hot work permits shall be issued for the immediate vicinity while these activities are in progress.

7.4.5

Wireline activities (slickline and electric logging)

The surface integrity for completion and production wireline operation is assured by the following barriers:

• the lubricator/stuffing box/BOP assembly

• the Xmas tree with a remote-controlled upper master valve with wireline cutting capability (or an actuated valve installed on top of the tree).

Normally the wireline retrievable SCSSV will be pulled (or when using a tubing retrievable sub-surface safety valve ( TRSSV) it will be hydraulically maintained open) during wireline operations, so that a downhole barrier will not be available. For this reason wireline work in live wells requires special attention. Wireline work may have to be interrupted and well made safe to allow other critical work to progress.

The appropriate operating procedures and equipment shall be used as mentioned in 'Well Services

Guidance Manual'(Ref. 48). Selected safety precautions from the referenced manual (chapter 8) are given here to emphasise their importance:

• A wireline blowout preventer shall be used for work on all wells capable of flow

• Control of the SCSSV and surface safety valve shall be transferred to a remote panel operated by the wireline crew during wireline operations

• Where possible, when depressuring lubricators, gas should be vented through existing facilities

• Depressurisation of a lubricator shall be confirmed by opening the second 1/2 inch connection in the lower section of the lubricator to check that hydrate blockage of the primary depressurisation needle has not occurred

• After installation on the wellhead, the lubricator shall be pressurised and tested according to procedures.

During concurrent operations the work shall be discussed at the daily co-ordination meeting and appropriate controls put in place to assure its safe conduct.

The same guidelines as listed above are valid for non-rig assisted logging work.