ACG Offshore Platforms Temporary Pin-Pile Foundations
- Neil Kitney (BP Exploration Operating Co) | Allan David Penman (BP)
- Document ID
- Offshore Technology Conference
- Offshore Technology Conference, 5-8 May, Houston, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2008. Offshore Technology Conference
- 4.1.5 Processing Equipment, 4.1.2 Separation and Treating, 4.5 Offshore Facilities and Subsea Systems, 4.5.5 Installation Equipment and Techniques, 7.2.1 Risk, Uncertainty and Risk Assessment, 7.3.3 Project Management, 1.6 Drilling Operations
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Seabed uncertainties, limitations of marine construction vessels in the Caspian Sea and the size of the two Phase-3 platforms for the ACG development offshore Azerbaijan, led to temporary foundations being needed to support the jackets on the seabed prior to installing the main foundation piles. Pin-piles were selected, requiring development of a sophisticated and innovative scheme for their extremely accurate seabed positioning. A modular space-frame system was designed to position eight individual pin-piles in a single and continuous subsea operation. The system had to be capable of numerous subsea relocations and accurate attitude adjustment to counter a sloping seabed, potential subsidence and have sufficient structural integrity against damage from pile driving loads. Exceptionally tight pin-pile installation tolerances were essential to ensure tieback of pre-drilled wells, bridge linking of the two platforms and accommodation of the piles within the geometry of the jacket legs.
This paper describes the development of the engineering solution from analysis, laboratory testing, fabrication and field trials through to offshore installation.
The ACG field is located in the Azerbaijan sector of the Caspian Sea approximately 130 km east of Baku, in water depths varying between 118m and 175m.
Each of the three project phases included the installation of two fixed jacket structures. In order to optimize project delivery a standardized design approach was employed; this included the temporary foundations. For Phase 1 and 2, temporary jacket seabed support was provided by glass fibre reinforced mudmats in each corner of the jacket base, each mudmat having an area in the order of 700m2 (see Figure 1). These foundations were to provide OBS in 10-year return period environments prior to the installation of permanent foundation piles.
|File Size||6 MB||Number of Pages||18|