ABSTRACT BP has been developing an integrated and systematic approach for the early assessment of deepwater geohazards to support planning and design of several major gas field development in the West Nile Delta (WND). The approach has involved the assembly of a team of experienced geoscientists from the disciplines of geology, geophysics, geomorphology and geotechnics. The paper will demonstrate the value of early engagement of multidisciplinary team approach for the evaluation of 3D exploration-quality seismic data in frontier deepwater areas where the issue of geohazards could be a potential major constraint to the siting of tophole locations and facilities. Early screening of the geohazard challenges to development can be used to guide the appropriate level of investment, resources and data acquisition programme to support subsequent stages of the project. Early acquisition and calibration of field-wide autonomous underwater vehicle (AUV) engineering-quality data is providing opportunities to ensure that development plans are not exposed to unnecessary, avoidable geohazard risks. A key element of the multidisciplinary team approach is the application of integrated geophysical, geotechnical and engineering geomorphological methods that make best use of the high-resolution data these state-of-the-art technologies provide. The integrated approach is providing valuable in guiding BP's offshore development plans towards properly identifying the geohazard risks and accounting for decision-making at all stages of the project programme (see companion paper by Evans et al. 1 ). The product of the geohazard assessment work underpin strategies for the optimization of field architecture (avoidance of geohazards) and the evaluation of cost effective options for geohazard-tolerant equipment design and protection (geohazard-resistant design). West Nile Delta Gas Developments The Nile Delta is one of the world's largest deltas, with a submarine fan of about 100 000km 2 extending northwards into the Mediterranean Sea (Figure 1), and is a major area of hydrocarbon exploration. The delta extends 20–40km offshore to a shelf break where the water depth is about 100m; the maximum water depth beyond the delta slope is about 1500m. BP Egypt, together with partners RWE-Dea and Egyptian Natural Gas Holding Company (EGAS), intend to develop several offshore fields within the West Nile Delta (WND). The modern Nile Valley is thought to have formed during the late Miocene at the same time as a major desiccation of the Mediterranean Basin. The salt deposits formed at this time were progressively covered by deep sea fan sediments discharged from the River Nile throughout the Pliocene and particularly during the Quaternary 2 . The WND has been subject to cycles of rapid sediment deposition, erosion and episodic submarine landslide activity for at least the last 250 000 years 2 . The resulting present-day seafloor is an irregular patchwork of geomorphological forms and geohazard features including incised canyons, plateaux and escarpments, fault scarps, pockmarks and landslide scars (Figure 2). The shallow soils across the WND are predominately soft marine clays of terrigenous origins and hemipelagic clays. The mechanical properties of these soils are strongly influenced by their depositional histories and most significantly by post-sedimentation events and processes such as landslides, debris flows, turbidity currents and fluid expulsion.

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 A deepwater integrated geotechnical and geophysical site investigation took place m the central region of the Gulf of Mexico The purpose of the site investigation was to evaluate soil properties and shallow geohazards for future foundation design of a floating production facility. Acquiring the necessary data for foundation design in deepwater involves challenges not normally encountered in more shallow water depths To meet these challenges a new non-tethered geophysical tool was developed and a geotechnical tool not normally used in the Gulf of Mexico was adapted to obtain cost effective data These tools were used to identify and characterize subsurface conditions at the site. They proved to be effective in delivering key data m a cost effective manner Integrating results from these tools proved successful in providing crucial information for evaluating seafloor and sub-bottom features and soil conditions that influence foundation design. Integration of the geotechnical and geophysical data as it was collected provided the flexibility to modify the Initial program to ensure that conditions were characterized sufficiently for design Some geophysical data were specifically collected at the foundation locations to enhance the geotechnical program. Results from the targeted geophysical data identified three geohazards that could affect the design of the sucbon caisson foundations intended to moor the host facility. Additional geotechnical data were gathered and integrated with the geophysical data to fully assess these geohazards. The integration of the data collected during this site investigation provided the information required for installation and design of the suction caisson foundations We note, however, that the relatively benign surface and subsurface conditions at this site were conducive to the tools and methodologies chosen to characterize this site. At other more complex deepwater sites the tools and methodologies used at this site may have to be modified. Introduction To site a floating facility m deepwater a number of issues best resolved using geophysics and geotechnics must be addressed. These include (1) understanding soil properties to facilitate the design of the foundations, (2) understanding shallow geohazards that may effect installation and service of the foundations for subsea equipment and the host facility By integrating geophysics and geotechnics an enhanced understanding of both soil properties and shallow geohazards is obtained (e.g Jeanjean et al, 1998) Geotechnical and geophysical information is obtained through a specifically designed site investigation program Careful consideration of the capabilities of available geotechnical and geophysical tools should be made to maximize value while providing acceptable information for design. An example of a successful integrated site investigation that meets these criteria is presented in this paper. Deepwater offers several unique challenges beyond those encountered in shallower waters. To meet these challenges cost effectively new tools must be developed and existing tools adapted to perform in these harsh environments. A recent integrated site investigation in southern Green Canyon, Gulf of Mexico was undertaken using new and recently adapted cost effective tools.

Abstract The Terang-Sirasun development is reservoired in the Pacuan limestones of the Plio-Pleistocene. Development of the 1 TCF GIIP is complicated by a range of seismically driven overburden and surface processes that constitute a substantial geohazard risk to planned well bore and gas gathering installations. Terang is characterised by significant shallow gas in the overburden and faults, some of which have seabed expression. Sirasun is characterised by fewer faults and little shallow gas but by the location of the present day shelf-slope break This exhibits extreme erosion and potential mass flow features. The challenge for the business unit is to create a development scenario that, where possible, avoids all geohazards for the lowest CAPEX. This involves identification of the risks from conventional geohazard survey datasets totalling some 2 terabytes of data. Manipulation and integration of the data and the associated interpretahon, has involved a multi-discipline team ranging across 3 different companies using a number of software packages such as Fledermaus, Landmark's Earthcube and 3D Drillview KM to define this development scenario. This paper attempts to detail the methods used to deliver the data sets into visualisation packages, identify and analyse the geohazards, the geohazards themselves and the development scenario through visualisation in bp's visualisation centre based on a novel risk assessment approach of the geohazards themselves. INTRODUCTION The Terang - Sirasun-Batur (T-S-B) fields exist within an area of extremely active geological hazards (geohazards). Indeed the area was ranked second m the world in terms of geohazard seventy as effecting bp developments, second only to Azerbaijan. Eight primary contractors were assembled within a BP management environment and tasked with the key objectives of qualifying the HSE and financial performance risks and, where necessary, revising the development layout based on a programme of geohazard identification and risk quantification. The primary contractors comprised: JP Kenny - Pipeline & Subsea Engineering K & M Technology - Drilling Engineering Hydrosearch - Data Quality & Control Thales (Racal) - Offshore Data Acquisition and Mapping GMI - Subsurface Geotechnical Engineering Landmark Graphics - 30 Visualization Software IVS (Interactive Visualization Systems) - 30 Visualization Software URS - Earthquake Engineering and Geohazards Interpretation BP Indonesia - Project Management

Abstract A geohazard investigation in deep water presents a challenge to all existing investigative techniques This paper reports on the work performed over the last 4 years in developing wireline logging systems which add significantly to the quality and applicability of sample and seismic data gathered during such investigations The systems provide the enhanced geological and engineering detail required for such investigations, and are of great value in putting intermittent sampling into a full borehole context. They are capable of deployment m any deepwater drilling situation A number of innovative techniques and designs are required to cover both the practicality of deployment and the technical requirements for the systems to maximize the effectiveness of the wireline data. This paper shows how good vertical resolution can be achieved with geotechnical wireline logs and how significant this could be in assessing geohazards in deep water by providing geological information, input into seismic models and engineering data. INTRODUCTION The assessment of the Geohazard risks in the deep-water environment presents a number of problems The lack of knowledge of the deep-water depositional environment - Deep water deposits are rarely exposed at the earth's surface for geological inspection and, if they are, they have often gone through considerable alteration. The deep-water environment is thus very much a new frontier both to geological and engineering understandings. Cost of assessment-Given our lack of knowledge and experience, the simple answer would be to gather as much data as possible before exploiting any reserve potential. Deep water is, of course, an expensive place to research and a considerable technical challenge. We must be Innovative and prepared to learn from other fields of geoscience to obtain cost effective investigations of a high enough standard. Potential geohazards may be represented by just a single thin anomalous horizon-To add to the first two problems we may be searching for a needle in a haystack-the likely hazards such as slope failures and shallow flows may be the result of single thin anomalous horizons. They will occur at relatively shallow depths below mud-line in deposits well away from any potential reservoir evaluation, in deposits least like a potential reservoir and in the sector of any exploration or proving well least investigated. The area of geotechnical concern, in effect has to be ‘shut out’ from investigation to prevent any risk to the deeper well. As we will normally have no useable wireline data to assist seismic evaluation the potential hazards also occur in the zones with least control from the seismic evaluation. So what Informahon do we need? We need detailed geological information to understand the depositional environment and determine whether conditions are susceptible to any of our deep water geohazards We need good wireline log data to offer control to our shallow seismic data to fully model and evaluate structure and specify the limits of the potential geohazard by getting the best from that seismic data. We need detailed engineering measurements to confirm that the geohazard is present and most importantly the limiting factors of that risk.

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.