Ocean Structures

Construction, Materials, and Operations

Srinivasan Chandrasekaran, Arvind Kumar Jain

• Publisher: CRC Press
• Year: 2017
• ISBN:
  9781315357270
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This book addresses the concepts of material selection and analysis, choice of structural form, construction methods, environmental loads, health monitoring, non-destructive testing, and repair methodologies and rehabilitation of ocean structures. It examines various types of ocean and offshore structures, including drilling platforms, processing platforms and vessels, towers, sea walls and surge barriers, and more. It also explores the use of MEMS in offshore structures, with regard to military and oil exploration applications. Full-color figures as well as numerous solved problems and examples are included to help readers understand the applied concepts.

1	Ocean Structures

Ocean structures are unique in design and geometric form apart from the types of environmental loads they are subjected to. In addition to the complexities that arise from their functions and operational conditions, their structural forms are as interesting as they are highly innovative. Similarly, structures that are built for coastal protection have a variety of functional variations with a high degree of common geometric forms. In this chapter, different types of ocean structures that are built to cater to a variety of functional requirements are discussed from a structural engineering perspective. A brief introduction to various terminologies related to oil and gas exploration is also presented.

1.1 INTRODUCTION

Ocean structures are of multidisciplinary interest, attracting professionals with backgrounds in civil and structural engineering and naval architecture. They are also of interest to graduate students of mechanical, electrical, and chemical engineering, and furthermore to students with chemistry and physics backgrounds. This chapter provides an overview of different types of ocean structures, which are generally deployed for oil and gas exploration at sea. Various structural systems that are deployed for shallow water, medium water, deepwater, and ultra-deepwater vary in their geometric configurations. It is rather fascinating to know that structural systems deployed at different water depths are not similar. Under environmental loads, their structural actions vary widely due to their compliancy.

1.2 OFFSHORE INDUSTRY

To understand the basis for designing ocean structures, it is vital to understand the early era of the offshore industry. For example, see Figure 1.1, which refers to a historic photograph of Huntington Beach, California (Chandrasekaran, 2013a). The photo shows several drilling rigs deployed along the coast; a few towers supporting the drilling rigs are also seen. One can also readily observe that most of the structures are built of either steel or wood. Structural configurations consist of truss elements, which are assumed to be the most primitive type of support systems for offshore drilling operations. Furthermore, drilling rigs are located very close to the coast, ensuring that oil was explored at a shallow depth during early days (Chandrasekaran, 2013b).

A similar thing happened in Summerland, California. Figure 1.2 shows a series of drilling rigs, located along the beach side in Summerland. The basic form of the drilling derrick is a truss type, which supports a group of drilling rigs in series. Figure 1.3 shows a photo of production platforms in Summerland. The structural form appears to be stiff and rigid, conveying a meaning that such an insensitive system is required to support offshore drilling activities (William et al., 1984, 2011).

FIGURE 1.1 Huntington Beach, California.

FIGURE 1.2 Summerland, California.

Figure 1.4 shows a typical drilling platform, commissioned in Venezuela, whereas Figure 1.5 shows drilling platforms deployed in the Caspian Sea. A taller truss system with two deck levels, one for drilling operations and the other for maintenance of service, is shown as the structural configuration. One can also notice a few cantilever members extending out to facilitate the operation circumferentially, and the material for construction is essentially steel. It is evident that as the drilling platforms move away from the coast toward seaside, structural configuration becomes more complex (Adams and Baltrop, 1991). This includes an increase in the height of the drilling derrick, member sizes, and so on. One can infer from the above example that a stiff system is preferred to alleviate the environmental loads encountered. It is also evident (see Figure 1.5) that offshore structures are connected to the coast for transporting the explored hydrocarbons for further processing. As they are deployed very close to the coastline, pipelines and barges were not required to t...