The Use of Advanced Materials to Reduce System Cost in Offshore Production Facilities

July 18, 2008

Muhammad Abduh (

The challenge of higher CO2 content in Natuna Alpha-D reservoir recently has seen an economic barrier to the development of this field. But the raise of crude oil price has made the non-prospective drilling like Natuna Alpha-D become prospective as well as the driver from development of exploration and production technology that become more cost-efficient. One of the key issues in development of oil and gas production is the use of advanced materials in deep water drilling and more hostile environment (higher CO2 and H2S content).

The ultimate goal for the use of advanced materials in offshore application is to lower system-cost of oil and gas production facilities. The system-cost should be regarded as life-cycle cost (construction and maintenance) rather than capital expenditure cost (construction). Platform owner conservatively tends to push the capital expenditure as low as possible without comprehensively investigating the potential to reduce system-cost by application of advanced material. Conservative material choice also associated largely due to management of change issue since change of ownership of oil and gas production facilities is quite high.

Pilot project for new material application pioneered by Conoco (now StatoilHydro) for their North Sea production Heidrun TLP. Conoco claimed a significant system cost reduction by applying composites to the several risers. Successful new materials application in this region also supported by certification bodies including Det Norske Veritas by issuing technical guidelines for offshore application of non-steel material. However the expanding use of new materials in other region are still reviewed. Mineral Management Service of United States to be waited by industry for the approval of offshore composite application for producing fields in Gulf of Mexico.

Both technical and economic justifications are needed here. Technical justification for the use of advanced material (stainless steel, nickel alloys, aluminum alloys, composites, concrete, titanium alloys, copper alloys) has been provided adequately. And the economic model to propose the cost-benefit of using alternative materials also already proposed. Model incorporating life-cycle approach and risk factor has
already developed by Craig and Swalm. As seen in Figure 1, by taking risk factor into account we can determine economic choice of material selection for length installed pipelines. Future studies with pipeline failure data representatives will improve the model becomes more accurate and comprehensive.

Figure 1 – Probability Limit Curves for Carbon Steel Failure, clad versus carbon steel for 6-inch pipeline, various pipeline length (Craig)

Steel (low carbon steel) will be ever dominant materials since it has tremendous advantage of a large experience base and strong link between producers, designers, fabricators, and regulators. However there is a challenge in advanced material application due to demands for deep water drilling, oil reservoir rich in CO2 and sulfur, large capacity platforms, and ocean vessels. Choice of materials and the application in offshore structures are listed in Table-1.

Table- 1 Materials and offshore application

A comprehensive world industry leader workshop in New Orleans Louisiana United States in 1997 has drawn several recommendations for the use of breakthrough materials in offshore application as follow:

a. Mooring Systems

– Adequate engineering basis for synthetic ropes and composite strands and updated and unified design standards to accommodate taut mooring system.
– Requirement of updated reliability based safety factors and a coupled hull-mooring dynamic analysis methods.
– Requirements for verification of carbon fiber ropes (lightweight, high axial stiffness, excellent fatigue properties) and more investigation on fatigue strength behavior of steel rope.

b. Riser Systems

– Collaborative efforts are needed for successful use of advanced materials involving end-users, material suppliers, academia, and government.
– System-cost saving must be assessed and emphasized when advanced materials are considered.
– Development NDE/NDT techniques for the changing materials from steel to non steel.
– Development of reelable composite tubulars to minimize costly metallic connectors.

c. Floaters

– For Steel: Materials with higher tensile strength capacity combined with good fracture toughness, more efficient corrosion protection, improvement for weldability, fabrication, quality control, and corrosion resistance.
– For Concrete: more efficient construction method with less manning, more efficient quality control, light weight properties and easy fabrication.
– For Composite: cost efficient fibers, resin, easy fabrication, general qualification of composites as construction material, fire and toxicity safety perspectives.
– For Aluminum and Titanium: alloys with higher structural capacities (ultimate strength, fatigue, crack resistance), and improvement of weldability.

d. Secondary Structures
The use of corrugated or honeycomb construction for secondary structures is recommended because of its lightweight and maintained strength and structural integrity.

e. Hulls
With so many different hull arrangements and purpose hybrid design should be investigated to utilize the best material for certain situation.

f. Pipeline

– Update design code to include limit state design
– Welding Standard for corrosion resistance alloy
– To establish H2S limits for 13% Cr Steel

g. Process Equipment

– Technical barrier for new materials application including design issues, manufacturing and fabrication and costs
– Technical database should be provided to increase the knowledge
– Testing, verification of materials and prototype evaluation should be developed to establish experience base for fabrication and service history of materials.

Several barriers in many cases and regions including in Indonesia that prevent the use of advanced material are:

– Lack of knowledge about materials
– Lack of codes and standards for new materials
– Little experience in the use of many new materials

These barriers become high roadblocks to the potential of system-cost saving of advanced materials. End-users still don’t have enough confidence, fabricators shy away from using some of these new materials because of their ignorance on the weldability and fabricability, and the lack of experience will add a lot to cost. For the successful application of advanced materials there is a requirement to overcome the barriers by providing sufficient knowledge to the stakeholders, organizing technicaland economic justification and more research, development and pilot project to raise the user confidence of new materials application.

1. The Influence of Risk Analysis on The Economics of Carbon Steel and CRA Clad FLowlines, B.D Craig and R.S Thompson, Paper for Nickel Development Institute presented at Offshore Technology Conference Houston Texas US May 1-4 1995.
2. International Workshop on Advanced Materials for Marine Construction, Mineral Management Services DOI US and Colorado School of Mines, New Orleans Louisiana US February 4-7 1997


Introduction to Material Selection Matrix

March 22, 2008

Muhammad Abduh (

Being inspired by Material Requirements for Floaters Paper by Kvaerner on International Workshop on Advanced Materials for Marine Construction in New Orleans 1997, there is an opening to One Rule Material Selection:
– Material Property;
– Design Criticality

Why should there be one rule material selection?
– Wrong material is one of the root cause in engineering failures (OPS DOT, EGIG, HSE UK);
– Existing material selection guidelines (ASME B31 Series, Norsok, DNV, ASTM) are rather qualitative;
– Material decision become bias without quantitative judgment;

One Rule Material Selection Method
Approaches to one rule material selection have been provided:
– Material Properties Chart (Cambridge University and MIT), Figure 1
Chart that combine two properties of materials, e.g : density vs strength, density vs cost
– Material Selection Matrix
A more versatile selection tools that combine series of material properties with series of design requirements;


Figure 1. One of the material property charts (Material Engineering Cambridge University UK)

The ground for One Rule Selection Matrix, Table 1:
– Complete and detail material property database eg. mechanical properties, physical properties, corrosion properties, economic properties;
– Specification of design criticality to be provided by material design


Table 1. Collaboratory Requirements from Material Properties Provider and Design CriticalityProviders

Proposed One Rule Material Selection Matrix Methodology

1. Create Property Matrix (Ref. ASTM, AISI, PPI, In-House Testing)


2. Create Design Criticality, Set Maximum Design Value


3. Calculate Material Design Value

Material Design Value = [Steel Property Matrix] x [Design Criticality]

4. Set Priority Selection


5. Refine Design Criticality


6. Validate Result, refine design criticality, and recalculate material design value


Engineering Integrity in Oil and Gas Industry – Part 1

March 10, 2008

1. Duddy Yan Purnadi (
2. Dr. Ir. Slameto Wiryolukito (
3. Muhammad Abduh (
* Print Version Published in PetroEnergy Magazine Edition Nov-Des 2007

I. Introduction
Engineering integrity is a subsystem of integrity management. As a system of a whole, engineering integrity works together with the overall operations policy, health safety and environment standard, integrity performance standard, and legislative compliance. Engineering integrity becomes the major concern for oil and gas operator as a result of high impact of catastrophic accident in many countries. Both integrity standard API 1160 and ASME B31.8 were originally addressed for industry consensus in United States. These documents also referred as governing documents for pipeline safety regulation US DOT CFR 49 192. This paper will present an overview of engineering integrity, the elements and approaches to build and develop in oil and gas industry. Since integrity management covers multi aspects, there is a need to be more focus and to limit boundaries for engineering integrity, what are the elements, and how can this subsystem affects and interacts with other subsystem.
II. Engineering Integrity as Systematic Approach
Engineering structures, equipments, and components play a vital role in oil and gas industry as such to maintain production target. Any threat to these components will also threaten the performance overall structures. We may understand that engineering integrity is an integrated system, which is every element, affects other element in overall system. Then simply we can understand that integrity of a pressure vessel once depend on the welding quality. Any defect in welding will threaten overall performance of the pressure vessel. These process elements in developing engineering integrity can be described in Figure 1.

Figure 1. Element of Process in Engineering Integrity Approach

Figure 1 – Element of Process in Engineering Integrity Approach

III. Materials Selection
As we know materials properties depend on its microstructure, any treatments that alters microstructure will alter material properties. Phase transformation occur when steels are in process of heat treatment, welding, and other thermal affected treatments. Materials integrity can be sustained if we can maintain as received microstructure against all process subjected to it. A reliability of an equipment or engineering structures (piping, fixed offshore platform, floating structures) started from the process materials selection. Basic control points for material selection should be:

– Mechanical properties (acceptable of mechanical load)
– Corrosion Properties (sweet corrosion or sour corrosion)
– Failure Resistance, crack resistance (pitting, HIC, toughness)

Some of the codes for material selection guideline in oil and gas industry:

– Material Load Design: ASME Boiler and Pressure Vessel Section II, IX, X
– API 5L Specification for Linepipe
– Material Selection: Norsok M-001 Material Selection
– Corrosion Resistance Material/ SSC Resistance Material: NACE MR 0103-2003, MR 0175/ISO 15156, EFC Document No 16
– Plastic or Fiber Reinforced Plastic Material Design Basis: ASME Boiler and Pressure Vessel Section X, PPI TR-3/2004, API 15LR, API RP-15S

Trend of corrosion resistance alloy (CRA) steel in Oil and Gas
A story of CRA Steel was setback in 1970 era when clad steel and duplex stainless steel were first applied by Dutch operator company NAM1. The story of duplex stainless steel in oil and gas flowlines begins with its greater range of application in term of corrosion resistance. By the end of 2002 duplex stainless steel still the dominant material for flowlines. When facing more corrosive or more sour condition, the choice turned to clad steel. Clad steel with clad material AISI 316L or alloy 825 clad then become the material of choice in H2S environment. It was in Indonesia, for the first time martensitic stainless steel applied by Exxon for Arun Field. Since martensitic stainless steel is less expensive in less corrosion environment and the development of low carbon weldable 13Cr MSS, a research predicted that MSS will dominate the choice for CRA flowlines in the future, Figure 2.


Figure 2. CRA Trend in Flowlines

New Materials Conversion
Facing corrosion problem, oil and gas industry get alternative material choice. The use of fiber reinforced plastic pipe is more economically attractive. Some advantages of this material type compared to conventional steel materials:

– Corrosion resistance;
– More flexibility because FRP is coilable and the installation can be faster;
– Low maintenance cost

The advance material conversion to plastic and plastic reinforced pipe somewhat should consider some limitations as:
– Limited range of pressure application;
– Pipeline integrity program for available methods are for steel materials. There should be further development for developing plastic pipe integrity since the tools and equipment of inline inspection, NDT inspection, and defect assessment is designed for steel material;
– Creep failure of these materials reported. BP Amoco experiencing creep in higher temperature and cyclic loading condition;
– Reactivity of resin with H2S reported by Saudi Aramco for their shallow casing liners;
– Compatibility for connection with other component;
– Brittle like crack in plastic pipe;

IV. Fabrication and Construction
Fabrication and construction become crucial issue when as many studies reported that failure associated with welding and handling. Typical fabrication defect of stainless steel shown in Figure 3. To ensure processes in fabrication and construction maintain materials property there is knowledge demand in phase transformation and material thermodynamic. Unwanted phase transformation can occur during welding. The most stable protective passive film over stainless steel is introduced by passivation. During welding metal is reheated to its melting temperature and variably differ along heat affected zone. Free air exposed to this metal region will produce unstable porous and dense passive film. Unexpected oxidizing during welding can be prevented by application of shielding gas.

Pitting during transport, storage, hydrostatic testing and prior to service
The presence of iron contaminants in contact with stainless steel in aerated water environment tends to break passive film. Effect of pitting becomes worst in stagnant water. Longer periods of stagnant water exposure will create severe pitting attack over stainless steel. A case in relation with pipe handling was experienced by VICO Indonesia in Badak-Bontang pipeline project in 1999. The debris formed during pipe transport to storage in open sandy tropical climate lead to the formation of iron oxide (Fe2O3, Fe3O4) and iron sulfide (FeS). A fingerprint inspection had detected significant 40.000 defect features that can be related with the existence of debris. There were 10 sections replaced against ASME B31.G acceptance limit.


Figure 3 . Typical Welding Related Defect

Deadly Failed Coating
TWI UK said this case as “Deadly Corrosion Failure” as the explosion and fire led to death of several personnel. The pipeline was designed according to ASME B31.4. The breakdown of external coating made cathodic protection overload which cause pitting. Pit coalescence causing a large area to cause failure of rupture exposing and ignite methane gas to open air.
Welding Defect Disaster
Another TWI classic case was the rupture of amine absorber column (designed according to ASME Section VIII Section I, ASTM A516) in 1984, Figure 4. A report said that 17 people dead and economic loss over $ 100 million. Investigation report said that root cause of failure was the formation of hard HAZ in welded part of column shell.


Figure 4. Explosion of Amine Absorber Column (TWI Case, 1984)

Poor Workmanship
Writer’s Company recently had an opportunity to asses a gas plant facility in seashore environment. Investigation has found that some critical components (elbows, etc) experiencing residual stress by the evidence of magnetic properties change. Possible causes of this residual stress are the weld spatter and impact contact with hammer or bolt with the pipe segment.
Lesson learnt from above case is that there is a demand of multidisciplinary peer review for the integrity of fabrication and construction structures, involving stress analyst, inspection engineer, and material engineer. Since all of these structures were already fulfill their design code, multidiscipline validation process is important to reduce potential failure. Every engineer involved in fabrication and construction has responsibilities to give more attention to the small issues big impact as follows:
– Material handling: keep stainless steel clean from iron dust, stagnant water, sand, clay that tend to form debris, pitting, and crevice corrosion, avoid contact with steel component with different composition which make cathodic potential for corrosion.
– More attention to condition of stainless steel pipe in outdoor material storage, in a time between post-commissioning prior to service.
– Welding for critical components should assure acceptance welded joint for design life;
– Be careful with critical components, any impact contact with other tools or weld spatter can make localized cold deformation phase transformation which leads to residual stress. This could be harmful in case of erosion-corrosion phenomenon.