9 Risk Assessment and Management
Risk may be defined as an unexpected or an undesired outcome of an action or series of actions. All human endeavours entail risk. In offshore field developments the risks that are of greatest concern are those that can negatively affect the health and safety of individuals, the environment, or the economics of the project.
9.1 Potential Areas of Risk
The following are potential areas of risk in a subsea development project.
9.1.1 Project Management
Poor interface planning and management.
Poor communications.
Unrealistic schedules or budgets.
Poor resource planning. Inadequate resources.
Poorly trained personnel.
Labour disputes.
Failure to identify or anticipate regulatory requirements.
9.1.2 Engineering
Inadequate or erroneous design information.
Calculation errors.
Drawing errors.
Poor document control and engineering QA procedures.
Inadequate risk or hazard assessment.
Failure to anticipate and design for likely off-spec conditions.
9.1.3 Manufacturing
Delay in receipt of materials.
Defective materials.
Manufacturing errors.
Component failures during testing.
Poor fit-up of components.
Inadequate quality assurance procedures or implementation.
9.1.4 Installation
Inadequate equipment.
Poor interface planning.
Installation equipment availability delays.
Installation equipment failure.
Installation errors or delays.
Equipment or system failures during commissioning.
Failure to anticipate and prepare for weather risks.
9.1.5 Operations
Inadequate operator training.
Unanticipated operating conditions.
9.2 Risk Management
Operators and Contractors should implement proactive risk management programs. Risk is a product of consequence and likelihood of an event. With the accumulation of relevant experience in the industry, risk can be mitigated. When entering a new area of development, extending the limits of current technology, or undertaking a new contractual commitment, new risks are introduced. Risk management should be applied early and continue through the project.
Employees, contractor personnel, operators and other participants should be indoctrinated with an awareness of the risks faced by the project within their sphere of involvement, and the mitigation measures available to them. Adequate resources should be committed to the mitigation of risk and responsibilities formally assigned.
9.2.1 Risk Analysis In The Project Phases
9.2.1.1 Phase 1, Feasibility Study
Identify alternative concepts for screening.
Evaluate relative capital cost and operating costs for each concept.
Identify areas where technology development may be necessary.
Conduct a high-level comparative risk assessment of each concept
9.2.1.2 Phase 2, Concept Study
The concept study focuses on the concept (or concepts) resulting from the feasibility study. The engineering is taken to a higher level of definition.
Prepare conceptual drawings and bases of design.
Conduct a high level hazard identification review.
Identify areas of risk for further study.
9.2.1.3 Phase 3 – Preliminary Engineering
The goal of preliminary engineering is to develop the design to the point that a detailed engineering contractor can carry it to completion. In preliminary engineering the basis of design is firmly established, the scope of work is clearly laid out, and specifications for all major systems and components are prepared.
Conduct a formal hazard identification review and identify areas of focus for further engineering to further mitigate risk.
Conduct a formal hazard and operability review using the project basis of design and the preliminary drawings.
Follow up the hazard reviews with a punch list of items to be addressed by further engineering. As these are addressed, revise drawings and other documents accordingly.
Conduct a follow-up hazard review to assure that all punch list items have been addressed and no new issues introduced.
9.2.1.4 Phase 4 Detailed Engineering
Track and document all changes to the preliminary design basis of drawings during detailed engineering.
Near completion of detailed engineering, conduct final hazard and operability reviews with most up to date drawings, addressing all new developments introduced during detailed engineering.
9.2.1.5 Phase 5, Construction
Review contractor’s qualifications and financial stability.
Review contractor quality plans and QA procedures.
Audit contractor performance.
Review contractor personnel qualifications.
Conduct safety evaluation of work procedures and emergency procedures.
9.3 Lessons Learned
The following are some specific issues arising from “lessons learned” during previous subsea projects.
Fluid incompatibility – particularly completion fluids mixed with control fluids or injection chemicals can result in formation of gels or precipitants, causing line blockage.
Pressure differentials due to hydrostatic column heads of differing fluids. Example: riser full of completion brine and umbilical control line at same depth can result in unexpected pressure differences resulting in component failure or undesired fluid migration.
Even light corrosion (rust) in chemical storage tanks can damage high-pressure chemical injection pumps.
Significant corrosion has been experienced on subsea control pods that had been installed but not operated for some months.
Hydraulic compensation system must accommodate ROV override before control system activation; otherwise seawater can be pulled into the SCM during override functions.
Client imposed requirements have demanded that a vendor change standard product lines to use unsuitable grades of stainless steel.
Catastrophic filter failure has contaminated clean control fluid.
Cracks have occurred in the duplex stainless steel materials after deployment subsea.
Overactive cathodic protection levels have caused hydrogen embrittlement in bolting and other steels.
There is a need for better understanding of the factors inducing cracking in duplex stainless steel materials, when cathodically polarized in seawater.
As with duplex stainless steel materials, there is potential for hydrogen embrittlement, when 13% Cr. is subjected to cathodic protection.
Trees have been dropped due to operator error at hydraulic panel.
Umbilical reels have shifted on deck – should be welded down.
Poorly designed reels have injured people – projections on the reel catch body parts while rotating. Control handle should not be near moving parts.
Thermoplastic umbilical hoses have the potential for hose collapse in deepwater, because during blow-down the internal pressure could be zero. A remedy can be control by operational procedures.
Cleanliness with carbon steel umbilical tubes is difficult to maintain.
Storage fluid in carbon steel tubes should be heavily inhibited.
Hydraulic control equipment should be filled with inhibited control fluid.
Hydrogen cracking has been reported in Monel 400 end fittings in the termination assembly.
Dissimilar metals at pressure fittings must be closely evaluated. Example case is corrosion of copper washers in methanol hose connections caused by galvanic reaction with the Monel® 400 fittings.
Titanium electrical connectors may need to be isolated from the cathodic protection system.
Either coupler or both hydraulic couplers shall be allowed to float in the equipment it is mounted in to allow proper seal usage.
Hydraulic coupler poppets and/or small tubing and tube fittings can cause blockage points in high flow and/or high trash lines like methanol and Annulus vent lines.
Salt crystals in the methanol hose and termination due to ingress of seawater.
Stem seals on tree and manifold valves in some cases were not rated for the appropriate external pressures.
