Project Description
The Iraq Ministry of Oil has selected a consortium led by Kuwait Energy Iraq Limited Company (KEIL) for the development of the Siba Natural Gas Field. KEIL is planning to conduct a full field development in the Siba Field.
The Project will further develop into constructing gas processing facilities and three main export pipelines to pre- identified metering stations.
It has been estimated that the Siba gas field holds approximately 2.9 billion cubic meters (m3) of gas.
Siba Gas Field is situated in the southern part of Iraq, in Basrah Governorate, about 30 km southeast of Basrah and extends north east to the Shatt Al Arab River. The field is an anticline NE-SW structure with multiple culminations separated by structural lows. The field is about 21 km long with a width between 6 and 13 km. Its area is about 200 km2.
GTL were appointed during FEED as Geotechnical and Foundation Engineering Consultants and later included Engineering Design for piled foundations.
Topography
The Siba field itself is approximately 21km long and 6-13 km wide. It is located within the Zagros Foreland Basin. This Basin is bounded to the east by the Zagros Mountains, to the west by the Arabian Plate and to the south by the offshore areas of the Arabian Gulf. To the northwest lies the Euphrates Valley. The general gradient of the plainis1mper20km.Themain geomorphological units of the accumulation fluvial origin are terraces, alluvial fans, sheet run-off plains, flood plains, shallow depressions, marshes and lakes, and sabkhas. There are a number of individual marshes and lakes that have developed in shallow depressions in different parts of the Mesopotamian Flood Plain and are distributed in three main areas. The oil field is located in an area known as Central Marshes, which lies to the north of Euphrates
Client Name
Kuwait Energy Iraq Ltd AMEC Foster Wheeler
Project Name
SIBA Gas Field Development Project
Services Provided
Concept & FEED Design
Geotechnical interpretation & Consultancy
Modularisation study Structural Design
Dynamic Design and analysis Foundation Engineering Design of specialist piles
Project Managemen
Location
Basra Governorate, Iraq
Approx. Project Value
USD undisclosed
Completion
2013/15
Senior Management
- Gavin Rixon – Project Director
- Karsten Richter – Lead Geotechnical Engineer
- Samuel Lauber- Design Manager
Geology
The whole Iraqi territory could be classified into seven physiographic provinces. In the middle part, the Mesopotamia Plain is developed which starts from the Arabian Gulf and extends to the northwest for about 730 km, attaining to a height of about 150 m (a.s.l.), near Baiji. It comprises of alluvial sediments of the Tigris and Euphrates Rivers with their distributaries, and Shat Al-Arab, exhibiting different geological hazards, like floods, piping, sabkhas, sea water intrusion and depressions.
The near surface geology in the project area comprises Quaternary deposits underlain by Tertiary Pliocene age sedimentary rocks of Dibdiba and Mahmudia Formations. These references indicate that the base of the Quaternary age deposits in the project area is approximately 100 m below existing ground surface level. The Quaternary deposits comprise Holocene age flood plain deposits (up to about 20 m thick) underlain by Pleistocene age sediments of the Euphrates and Tigris Rivers. In general the Holocene age flood plain sediments comprise silts, clays and sands. The vertical boundaries between different materials may be both gradual and abrupt and the thickness of individual layers may vary from a few centimetres to few meters. The clays often contain carbonate nodules and gypsum (as powder of fine crystals). The sands are usually fine grained, grey and brown and may contain pebbles. Thicker beds of sand may be present in abandoned (buried) river channels.
The Pleistocene sediments comprise inter- bedded pebbly sands, sandy gravels, sands, silts and silty clay. The sands are deposited as thin layers inter-bedded with silts and clay or as thick sequence. The sands may be cemented by gypsum or carbonates forming horizons of sandstone like material.
The Tigris and Euphrates rivers carry large quantities of salts, and due to the combined effects of excessive irrigation and flooding, and a high water table with poor surface and subsurface drainage these salts have concentrated at the surface of the soil. Degradation of soil quality has also occurred due to contamination by pesticides, untreated industrial discharge, oilfield operations, construction of large dams, and untreated (or partially treated) sewage originating upstream. These anthropogenic impacts have compounded the high naturally occurring salinity levels.
Despite this widespread degradation, because of the low hydraulic conductivity, low groundwater flow velocities, and seasonal fluctuations in flow direction, it is likely that contamination from point sources (e.g. oilfield discharges) has migrated only limited distances in groundwater (MOEN, 2006).
Helical Pile Design
Helical Pile Design
Over 800 piles were designed at various depths and diameters to accommodate a modular type construction.
The foundation pile design was undertaken as a limit state design, whereby a distinction was made in ultimate limit states (ULS) and serviceability limit states (SLS).
Limit states is related to design situations, which was classified in persistent, transient, accidental and seismic design situations.
In accordance with the superstructure operation states, accidental design situations are mentioned and classified in the foundation pile design.
Value Proposition
This Value Proposition centres round the removal of work-scope from the camp and the reduction in uncertainty in the labour rates and productivity.
In general this was achieved by
- Reduction in the numbers of people to be accommodated at the camp. The number generated at Concept Stage did not allow for Iraqi personnel who would commute from the towns local to the field.
- Reduction in the civil scope, especially the volumes of sand/ soil to be moved
- Use of technology to increase the productivity of construction to remove a significant amount of site work
This Value Proposition is for the reduction in the Cost and the Schedule for the Permanent Accommodation Camp (PAC) by the use of Helical (Screw) Piles. The VP does not cover other civil scopes associated with foundations but the cost reductions will be of the same magnitude.
Independant Concept Report
The key risks, constraints and drivers that are recognised to have an impact on project cost are:
- Civils material quantities – uncertainty related to the material volume required for site
- Preparation due to lack of geotechnical data and to the preliminary level of layout definition.
- Civils construction norms – uncertainty related to site preparation man-hour norms and / or productivity due to lack of local contractor input (e.g. to assess manpower and / or machinery availability).
- Civils site labour rate – uncertainty related to man-hour cost as rates are expected to be
- driven by the level of activity in the region.
- Facilities site labour rate – same as above civils site rates, uncertainty related to rates for labour on processing facilities (i.e. modules installation, hook-up, commissioning).
- Construction security – uncertainty related to overall project security cost depending on potential future unrest in the region which might significantly increase the security levels required as well as the manpower and infrastructure costs.
- Equipment and material cost – uncertainty related to the overall cost of equipment, bulks, line pipe and buildings depending on market, as well as outcome of tendering phase.
- Facilities construction norms – uncertainty related to site installation man-hour norms and / or productivity due to lack of local contractor input (e.g. to assess manpower and / or machinery availability).
The Value
Costs are reduced by approx 85%.
Schedule is reduced. This has not been specifically calculated but a saving in of 50% to 80% on schedule is expected. Example – concrete foundations for fence would be circa 40 working days. HSP foundations for fence would be circa 10 working days.
Uncertainty associated with costs of civil works (materials, labour, equipment) is reduced
HSE and Security exposure is reduced due to the shorter duration
Conclusion
The use of Helical Screw Piles significantly
reduces the costs associated with
- Removing sand and replacing with engineering grade soils (eliminated completely)
- Laying concrete foundations (may be one building only)
- The additional costs associated with the uncertainties around labour and equipment costs
The use of helical screw piles reduces the time taken to install modular units but only if dimensional control is utilised such that the units ‘fit-first-time’.
The significant reduction in site man-hours feeds through a reduction in exposure to HSE and Security incidents. The less time spent on site the less likelihood of incidents occurring. The ‘Cost of Safety’ has not been factored into the cost calculations.
The PAC is a small scope of work but the costs can be projected to cover civil works for the Base, CPF, River Gathering Station, Hubs and Trunklines.
