Dynamic Positioning for Engineers

Surender Kumar

• Éditeur: CRC Press
• Année: 2020
• ISBN:
  9781000206432
• Édition: 1
• Sujet: Physical Sciences
• Sous-sujet: Physics

Dynamic Positioning for Engineers enables the reader to acquire the basic knowledge of the concepts and understanding of the dynamic positioning (DP) system from the systems perspective. This book illustrates the system, subsystems and components of the DP system to better tackle maintenance, problems and breakdowns, leading to an increased mean time between failures and effective fault finding on dynamic positioning DP-related equipment. Overall, this text will help professionals reduce downtime and higher repair costs. Aimed at onboard electrical engineers, engine room watch officers, chief engineers, DP professionals onboard, in onshore officers and those taking DP training courses, this book:

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• Explains automation and its application in the DP system

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• Describes environmental sensors and position reference sensors as important inputs to the DP system

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• Includes chapters on power management and thrusters

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• Aids engineers in maintaining a the DP system in good operational condition

1 Introduction to Offshore

The offshore industry, which is also known as the oil and gas industry, is considered one of the most technologically advanced industries in the world. The oil and gas industry has played a vital role in modern civilisation and will probably influence it in the future as well, until practical alternatives are found and proved.

There is good historical evidence which indicates that even in Noah’s time, boats were repaired and coated with tar for stopping leakages. The earliest use of tar in history is mentioned in the ancient Indian civilisation of Mehrgarh for storage of grains somewhere around 4000 BC. As time progressed, mankind found various other uses for this wonderful product which influences our lives greatly. So much so, that if we seriously look at the daily use of products around us, more than 80% of them have an input from hydrocarbons.

The oil and gas industry is popularly also known as the hydrocarbon industry. Hydrocarbons, as defined by Schlumberger (n. [Geology]) is, “A naturally occurring organic compound comprising hydrogen and carbon”. How many atoms of C and H are combined together to form a molecule of hydrocarbon defines the final product. It may be a simple combination like methane (CH4 – it has one atom of carbon and four atoms of hydrogen) and can go on to form a very complex molecule to form a gas, liquid or a solid like coal and tar.

Hydrocarbon exploration, which is also referred to as oil and gas exploration, may be defined as an activity by a team of experts to plan, search and collect the hydrocarbon deposits under the Earth's surface. Hydrocarbons may include oil and natural gas.

Being a resource-extensive activity, hydrocarbon exploration is generally a state-controlled activity or is owned by oil majors in this industry. There is a big difference in the exploration of hydrocarbons onshore and offshore. As we enter offshore fields, every activity becomes much more expensive. Safety also demands higher levels of investment.

Historically, oil was first discovered naturally in China by a nomadic group when they saw smoke emanating from the nearby hills in the winters. No one really knew what the black material oozing out was!! In the beginning of the eighteenth century a well was drilled about 30 m off the coastline near Baku. It was not a successful venture, but it was marked as the beginning of a new era. The efforts finally led to successfully producing oil in the Caspian Sea in 1925. In India, once again, oil was found by chance in the jungles of Assam by a British Indian Army officer and this led to the first oil being struck, in 1867. Thus, India also ranks among the first to have engaged in oil exploration.

Initially, the oil and gas industry was restricted to onshore locations. It was later that attention was drawn to the resource-rich coastal areas. Technically, oil and gas operations offshore are considered more challenging than those which are land-based. There is a big influence on these by the prevalent environment. Safety of operations is and has always been a major challenge. Large offshore production facilities will need large investments; hence, the stakes are very high.

The Americans came to the forefront due to technological advantage and took the lead at this stage. The Californian oil wells slowly moved into the sea. These oil wells were connected by piers made of wooden (bamboo) structures in those days and were slowly replaced by steel structures.

Offshore drilling started in 1869 from a jack-up rig but when drilling in deeper water it was not possible to install jack-up rigs or use anchors any more due to depth restrictions, strength of the material used and, more importantly, the safety issues.

Thus, the need for an alternative method was felt and it was Howard Shatto, an enterprising engineer working for Shell, who came up with a basic idea which later took the shape of the modern dynamic positioning (DP) system. This is how DP was born, and the first DP was used in 1961 on board a vessel called Eureka working for a Shell project carrying out drilling at a depth of 300 m. This was followed by another vessel, Calldrill, in 1964, used for drilling in depths of 2000 m. Since then there have been lots of technological advancements and hence the depth and safety of operations have been significantly improved using DP-enabled vessels. Though the initial use of DP was for drilling operations, as time passed more applications and vessels started making use of this technology. Today the use of DP has spread over not only the entire offshore activities, but also to the main fleet and other activities.

Exploration activities for oil and gas are considered expensive and these involve a certain degree of risk. Considering the harsher environment, nature of investment made, offshore exploration activities are considered more expensive and riskier business activities. Generally, offshore exploration activities are undertaken by very large corporations or government agencies. For example, a normal shallow water oil well in the North Sea may cost tens of millions of Euros but the cost of a deep water well may go up to hundreds of millions of Euros, making it a really expensive business.

1.1 Drilling Operations

Well intervention and drilling are considered the biggest and the most critical investment for any oil company. The collection of all the required data and analysis is considered important, so as to bring the learning curve and expense down. Thereafter, the drilling company follows a well-documented and safe programme to complete the drilling activities.

In general, oil well activities may be divided into the following stages:

• Planning stage.
• Drilling stage.
• Completion stage.
• Production stage.
• Abandonment stage.

After the planning as mentioned above, drilling activity is executed. A well is drilled into the earth and the diameter of the hole is generally between 13 and 76 cm using a drill bit from a rig. After drilling a hole, a steel pipe, normally referred to as “casing”, having a diameter slightly smaller than the hole, is inserted in the hole. Using cementing operations, the pipe (casing) is now secured. This provides strength to the drilling hole. A production tube with a diameter a little less than the casing is used as the production pipe.

Once the drilling casing is in place the well is considered to be “completed”. Well completion may be defined as the process by which the well is prepared to produce oil or gas. The casing is then perforated by drilling holes by using explosives in the depths and areas called the “production zone”. The perforation or the holes in the pipe will provide the passage for the oil trapped in the source rock to flow into the production pipe.

The most important stage in this process is the production stage. This is the stage where the real production of oil and gas is achieved. The well may have been installed with a “Christmas tree”, which is a group of valves. These valves are utilised to regulate pressure and flow. They also provide access to the well bore if further completion work is necessary. From here the flow may be controlled for the purposes of distribution.

It is also very common to classify oil wells by...

Table des matières

• Cover
• Half-Title
• Title
• Copyright
• Contents
• Foreword (by Capt. Rajesh Tandon)
• Foreword (by Venkatraman Sheshashayee)
• Preface
• Author
• Chapter 1 Introduction to Offshore
• Chapter 2 Historical Background to Development of Dynamic Positioning
• Chapter 3 The Seven Components of a DP System
• Chapter 4 Six Degrees of Freedom – Basics of Dynamic Positioning
• Chapter 5 Different Types of DP Vessels and Their Applications
• Chapter 6 DP Class/Equipment Class
• Chapter 7 Basics of Electrical Propulsion and Thruster Types
• Chapter 8 Thruster Controls and Automation
• Chapter 9 Power Management System (PMS)
• Chapter 10 Harmonics in Power System
• Chapter 11 Introduction to Environmental Sensors
• Chapter 12 Introduction to Position Reference Sensors
• Chapter 13 Handling of PRS/PME and Various Tests on PRS/PME
• Chapter 14 Architecture of a DP System
• Chapter 15 Basics of Networking in DP
• Chapter 16 Types of Signals Used in DP Automation
• Chapter 17 Consequence Analysis, Capability Plot, Footprints and Motion Prediction
• Chapter 18 DP Trials and Documentation
• Chapter 19 Circuit Tracing and Fault Finding on DP Equipment
• Chapter 20 Roles and Responsibilities
• Glossary and Abbreviations Used in Dynamic Positioning
• Bibliography
• Index