ABSTRACT This paper reports the experiences of SLP Energy as a project developer in planning, procuring and managing the environmental, geophysical and geotechnical site investigations for Sheringham Shoal offshore wind farm. The paper examines the lessons that have been learned by SLP and suggests areas in which the current Society of Underwater Technology (SUT) guidance document, "Site Investigation for Offshore Renewable Energy Projects" 1 , can be developed to improve the guidance available to developers of marine renewable energy projects, especially offshore wind Background Introduction The development of an offshore wind farm is a complex process, bringing together a diverse range of considerations including environmental, economic and technological issues. Understanding the parameters of an offshore wind farm site is fundamental to its development, and therefore the correct choice of survey methods and equipment is a key factor in the success of such projects. The offshore renewables industry is relatively new and brings with it new challenges and perspectives. Unlike other sectors of the energy industry, the economic benefits of offshore wind projects are marginal and carry a high level of uncertainty; this is demonstrated by the fact that only around 20% of planned Round 1 capacity has so far been installed 2 . With the UK government setting the aim of 20% of the UK electricity supply to come from renewables by 2020 3 , there are also significant time pressures placed on projects to drive them forward. Comprehensive guidance is required for the offshore renewables industry to help developers specify surveys that will inform environment impact assessments (EIAs), facilitate front-end engineering design (FEED) studies and yield sufficient levels of information to satisfy marine contractors, investors and stakeholders. This must be done whilst keeping costs proportionate to the maturity of the project at each development stage and meeting project timescales. Guidance is required that will focus surveys on the key uncertainties affecting future development decisions. Background reading This paper has been written as a follow-up to the article entitled ‘The Importance of Careful Site Selection and a Systematic Approach to Site Investigation for Offshore Windfarms’ by Fish in 2003 4 . The article discusses the site investigation experiences from a typical Round 1 offshore windfarm project at Kentish Flats in the Thames Estuary. Environmental surveys To achieve consent to build an offshore wind farm, an EIA must be completed. A range of seabed environmental surveys have to be undertaken to inform the EIA process. The topics of interest normally include, but are not limited to, Biogenic reefs (e.g. Sabellaria spinulosa ) Seabed sediments (with respect to plumes, scour and cable burial methods) Seabed mobility (e.g. sand waves and shoals) Benthic communities Marine archaeology (e.g. wrecks and buried evidence of paleolithic communities) Unexploded explosive ordnance (UXO). Both geophysical and shallow geotechnical surveys are required to provide the relevant data to investigate these topics: Biogenic reefs - swathe bathymetry, side-scan sonar Seabed mobility - swathe bathymetry Seabed sediments - vibrocores and cone penetration testing (CPT) Benthic communities - grab samples Marine archaeology - vibrocores Unexploded ordnance (UXO) -magnetometer.

ABSTRACT BP Egypt has set up a UK-based multidisciplinary team, the Geohazard Assessment Team (GAT), to manage the shallow geological and geotechnical risks to its portfolio of deepwater projects in the West Nile Delta (WND) and to develop plans to mitigate these risks. The GAT was established at the start of exploration and has since been working with project teams in Cairo to optimise geophysical surveys and geotechnical investigations and to reduce whole-life project geohazard risks through avoidance and geohazard-resistant engineering. The WND experiences confirm the benefits of using an integrated experienced team to carry out geohazard risk assessments and of starting the work early in project development. The GAT approach is also providing a sustainable team of specialists that could help BP manage geohazards on other projects at a time of industry skills shortages. Introduction The search for offshore oil and gas in remote deepwater regions poses new technical challenges for the design and installation of wells and facilities 1 . The shallow subsurface processes and conditions in these areas are complex and poorly understood, and the geological hazards are often more widespread and much larger than encountered onshore. Such conditions can pose risks and constraints for hydrocarbon exploration and development, and result in significant construction and operational problems if not properly investigated, assessed and managed. The West Nile Delta (WND) in Egypt is one such geohazard-prone area that has been subjected to cycles of rapid sedimentation, erosion and episodic submarine slide activity for over 250 000 years. The present-day seabed is an irregular patchwork of steep scarps, fluid expulsion features, deeply incised submarine canyons with repeated bank collapses and potentially active faults and slides. BP Egypt (BP) and its equity partners RWE Dea and Egyptian Natural Gas Holding Company (EGAS) have embarked on an ambitious programme of subsea natural gas developments in their WND deepwater concessions. The location and geomorphological setting of the area presently under consideration for development is shown in Figure 1. The possible implications of geohazards and variable soil conditions for wells and facilities in this area was recognised at the outset, and plans to investigate and manage the associated risks were developed during early exploration. This paper summarises the present-day geotechnical engineering and geohazard challenges faced by the offshore industry and specifically by BP in the WND, and describes how BP is managing these issues systematically using a dedicated multidisciplinary team of geo-specialists and engineers called the Geohazard Assessment Team (GAT). The paper focuses more on the management process than the technical execution of the work. Specifically, it concentrates on the rationale and strategy being adopted to ensure that the work is fully integrated, peer reviewed and benchmarked; the geotechnical engineering is cost effective and fit-for-purpose; and the geotechnical and geohazard risks are adequately accounted for throughout the project life cycle ? from exploration to field abandonment. Further details of the work being performed by the WND GAT, and the benefits of the approach are given the companion paper in this volume by Moore et al. 2

Abstract It is now well recognised that certain types of construction development are, from a geotechnical viewpoint, potentially more hazardous than others. In particular, structures supported at shallow depth below ground level and with a significant ground-related component (such as highway projects, onshore) are particularly exposed to geotechnical risk. Based upon a summary of typical deepwater construction, this paper recognizes that deepwater oil- and gas-related developments may fall in this category. It presents an industry survey to examine current practice and identify deep offshore geotechnical risks and, following a brief review of risk analysis techniques, develops the preliminary stage of a risk analysis for an example deep offshore project. State-of-the-art techniques suitable for deep-water geotechnical investigation are reviewed in the context of hazard investigation and risk minimization Introduction A recent industry-wide survey (Power 2001) has clearly illustrated that, for many aspects of deepwater developments, geotechnical risk is being underestimated or even ignored, with the result that project delays and cost overruns are incurred. One of the conclusions of the survey was that systematic risk evaluations were not being performed Consequently, potential risks were being overlooked, or, if acknowledged, were not being adequately communicated down the supply chain or addressed at the right level or at the right time. The use of systematic geotechnical risk assessment techniques has gained widespread acceptance in the U K onshore construction industry over the last 5 years (Clayton, 2001a, 2001b), but has yet to take hold offshore. It is the intention of this paper to illustrate the potential benefits of such an approach and to open the debate regarding the value of this methodology. To do this, it first reviews the typical structures and infrastructure used to develop a deepwater hydrocarbon accumulation and the potential impact of seabed soil conditions on their design, installation and operation. It then describes the risk analysis, modelling and management techniques that are in common geotechnical usage and could be applied in an offshore context. The industry survey, that prompted this paper, is described and its findings summarised. An actual deepwater field development, currently under evaluation, is used to illustrate one approach to more systematic and cost-effective geotechnical risk assessment. Since an essential part of risk evaluation is the collection of the necessary site data, the current state-of-the-art in deepwater geotechnical data acquisition is also briefly summarised. Finally some conclusions are drawn, and recommendations made on how a more rigorous approach to geotechnical risk assessment can help reduce: Cost and time overruns Health and Safety concerns Adverse environmental impact Political repercussions Typical deepwater structures and their geotechnical challenges The majority of deepwater hydrocarbon developments are exploited by means of either subsea structures, or by a combination of subsea structures and floating production systems. A typical field layout is illustrated in the schematic Figure 1.