Jack-up drilling rigs are built as drilling platforms with jack-able legs. The platform will float when the legs are retracted and can thus be moved around the world on water. The jack-up rig is one of the most versatile rig designs available. The largest jack-up type rigs can work in water depths up to 150 meter and can also work in very shallow water depths. Among the many advantages of the jack-up rig is the fact that as soon as it is jacked up and into drilling position, it is a very stable platform and does not need motion compensation of any sort as required by a floating rig type.

Most jack-up designs today consist of a triangular hull with one leg in each corner. The hull is several floors high (thick) and contains most of the “indoor” equipment required to make the rig work. Indoor equipment includes generator sets, mud pumps, mud mixing and cleaning systems, bulk stores, mud tanks, water and fuel tanks as well as all the systems required for a hotel with accommodation for at least 100 people.

Attached to the top of the hull is first and foremost the living quarters and offices; on relatively old oil rigs, these can still be located below deck level, but this is not allowed anymore). Also on the topside is the drilling package itself, often contained on a cantilevered skid which enables the drilling package to center itself over different slots or wells. The rig is often used to drill production wells from templates or jackets with many well slots and for this reason is required to be able to crisscross over a grid of well heads.

The drilling package is located between two of the corners and positioned in such a way that the drilling package is stable and has maximum load bearing capability.

The legs on a jack-up rig are special. They not only have to withstand and be able to lift the entire weight of the rig, the legs also have to resist twisting forces and high wind loads as well.

Modern Jack-up legs are often triangular in shape and have something called a spud can mounted on bottom of each leg. The spud can is a large dome shaped tank and is working as the foot of the leg absorbing weight of the rig and due to its large area prevents high leg penetration into the seabed.

Let us spend a couple of minutes on the land-based oil rigs. Yes, most of the materials and information presented herein are related to the offshore units; however, it would make sense to know a bit about how this all started. Just read this short article.

As we know, the very first drilling rigs used were land rigs and were invented and subsequently both in Texas, USA and in Germany just over hundred years ago.

Nowadays, the land-based oil rigs constitute an advanced piece of machinery and when thinking of the amount of engineering and care in manufacturing, racing cars can look a bit sedate.

Land rigs come in all sizes, from small trailer mounted rigs to very large rig systems requiring more than 100 trucks to move. One of the first criteria for design of a land rig is how to move it. If the rig has to move on normal roads, it has to be dismantled to pieces that can be easily be transported by truck and does not exceed axle load restrictions.

In addition to weight limitations, the sizes of equipment that has to be moved will also impose problems and cost. In most countries, there are rules for height and width of goods to be transported on roads. When exceeding these rules, police escort and road and bridge modifications may add significantly to the overall cost of drilling a well.

Rigs dedicated for work in deserts are quite often built without regards for road transport. Some of the EDC, standing for the Egyptian Drilling Company, rigs working in Syria and in Egypt have large wheel assemblies, or moving gears retrofitted so the entire Rig with mast and substructure can move in one piece.

This is quite a reduction in loads to move and makes quite a difference in the time it takes to move the rig. If it takes seven days to move a rig without the moving gear attached it will take approximate sixty hours for the rig move with the moving gear attached.

Land rigs have a distinct advantage over rigs made for working on water, space and weight is not a problem. Contractors build rig sites to suit the rig and the equipment not the other way around. A standard desert foot print for a rig location is 400 ft x 400 ft.

Another advantage is that if a project requires special equipment this can be added to the rig inventory without worrying about deck loads and permissions. Also, note that a rig may require additional mud tanks for a well and this will then be no problem as land locations can be expanded easily enough.

Newer land rigs are also designed for fast rig up and rig down as well as minimizing the impact on the landscape and environment. Drive past a pad of producing wells today and there will hardly be anything to evidence that a big rig and a large rig location has been in use. All that can be seen is a few square meters of concrete where the wellhead is located and safely fenced in.

Although this section of our website is devoted to the offshore exploration and drilling activities, this short article is here to cover the major types of oil rigs in general.

Oilfield drilling is, when it comes down to bare essentials, a question of “drilling a usable hole” in the ground. And, in turn, usable hole is commonly characterized by being a hole in the ground that lives up to the requirements of the well-plan and includes benchmarks for production, cost and lifespan.

The main pieces of equipment required to drill a hole in the ground is collectively known as a drilling rig. Drilling rigs are classified according to what the rig is supposed to be standing on when it drills and how it is moved around. The main media to stand on is land and water.

It is pretty simple, but that is how it is.

Land rigs are made for working on solid ground where no special requirements are necessary except the area to be flat and of a certain size. All other rigs are made for working either over water or floating in the water. There are barges and jack-up type rigs which are made to stand on the seabed on the bottom of the water and/or swampland and marshes, and there are semi submersibles and drill ships that float in the water. Each type will be described separately on the next pages. It is important to notice that in general, the main drilling equipment on all these rigs are the same. The difference is how it moves and where the drilling location is situated.

There are other sub-types of drilling rigs that are not specifically described here. These rig types include:

• Heli-Rigs, or Helicopter transportable land rigs, these are made mostly of aluminum,

• Dedicated coiled tubing rigs,

• Slanted drilling rigs, used for the Slant hole drilling ,

• HDD, utility drilling rigs, normally hydraulic-driven.,

Most of them use the same type of equipment to drill and most of the processes are very similar with the exception of coiled tubing drilling systems.

In this lecture on drilling equipment, the focus will be put on the drilling rig and its related equipment. The method of drilling the hole is subject for a different lesson.

Some types of equipment are used on all types of rigs, basically the drilling equipment, and other equipment is rig type-specific, i.e., to be able to compensate problems inherent in the rig design or use.

When looking at different drilling rig types and different locations around the world, all drilling rigs consist of the same basic equipment with the same functions, all over the world. A giant concrete platform rig in the North Sea area with 800 people onboard is essentially doing the same as a humble land rig in east Texas. The same types of equipment and people perform just about the same jobs. Of course, the food is more readily available on the big platforms and they have galleys, television rooms and many other recreational facilities to keep the crew occupied while waiting to go back to work.

The rig floor is the business end of the drilling machine. It is the place where the drilling operation is controlled and where accidents and disasters can be prevented. The rig floor area is under the command of the Driller, the most important person on a drilling rig, because he is the person with the hands on the controls for the drilling machine and also receives alarms and signals from the well directly on his various control panels. The Driller is in charge of the rig crew. He reports to his supervisors which is the Tourpusher and Toolpusher.

A lot of planning is included when building a new drilling rig. The result is often an improvement over existing rigs. When a rig floor is designed there is often collaboration between Drillers, Rig Owner, Engineers and other people with a vested interest in the success of the project.

The layout must consider a number of criteria, including “must do” and “must not do” as well as “need this” and “got to have that”. It is like designing a dream home, everything has to fit perfectly and compromises are only acceptable in the small claims department.

The main elements on and around the rig floor include:

• Doghouse – The drillers control room, where all the main controls for the rig floor area is located.,

• Drawworks – the power winch that lift or lowers drill string into the well. Part of hoisting system which includes mast or derrick, Drill line, Crown block with sheaves, Travelling block with sheaves and finally the drill line and anchor.,

• Derrick/Mast – Supports all the weight of the drill string and allows lengths of pipe to be lifted or lowered into the well and allows racking of lengths of tubular to be racked (stored) in stands when not in use.,

• Rotary table – Where the drill string enters the hole and where slips and other tools are used to suspend drill string and add or reduce number off tools to be run into the hole.,

• Pipe handling equipment – “Automatic” addition or removal of stands from drill string sometimes including stand building capacity.,

• Iron Roughneck – Machine used for Make-up or break-out of tubular in the drill string. Removes the dangerous use of manual operation with rig tongs.,

• Rig tongs (Manual) – Manual tong used for make-up or break-out of tubular in the drill string.,

• BOP control panel – Where the Driller controls the Blowout Preventer Stack. It allows the Driller to close-in the well.,

There are quite a few instruments for the Driller to observe and control and quite a few of the instruments/gauges and buttons seems to be added to the initial set-up giving the overall impression of the cabin as being cluttered and confusing. This is unfortunately quite often the picture of a Drillers Cabin, or Dog house. All sensors and data required for the driller are available on the two screens.

The concept of operating a drilling rig entirely just by two joy-sticks and two screens can be a challenge to the older generation of drillers. They do not like to rely solely on a computer manufacturer to make all the rig safety devices work. Especially when talking about well control equipment (BOP). But this is the future and it creates even higher demands on rig crew competencies than ever before.

Rig crews in the future must be multi-skilled specialists trained to work with and maintain special equipment and tools not seen in any other industry. Additional equipment usually placed on the rig floor or in the immediate vicinity includes:

• Air winches – Winches either air- or Hydraulic driven with a load range approx. 10000 lb. used for lifting pipe to the rig floor from the pipe deck or used for lifting heavy things around on the rig floor or even for lifting and hang off equipment in the Derrick. One type of air winch must also be available on the rig floor and this is a winch which must be used for lifting personnel and only be used for this purpose.,

• Standpipe manifold – A system of valves piping and connections used for routing drilling fluid piped up from pump room to standpipe(s) in the Derrick into the mud hose (Kelly hose) through the swivel and down the drill string.,

• Choke manifold – A system of valves piping and connections used in well control situations where BOP is closed and mud and well bore fluids coming from the well (Annulus) are routed from the BOP up the choke line to the choke manifold and then through the choke and the Mud/gas separator where gas is removed from the mud and then over shale shaker and to the mud process tanks.,

• Pipe rack – Racking area on the pipe deck. On a land rig special racks are built so that pipe can be rolled right onto the catwalk and the hoisted to the rig floor. Horizontal pipe storage area for pipe or casing.,

• Catwalk – Movable walkway where pipe is landed when removed from rig floor to pipe deck storage or vice versa. This walkway is also attached to the V-Door ramp which is the slide coming from rig floor towards pipe deck.,

The rig floor has to accommodate all these tools and equipment and it is even more complicated by the fact that electrical systems may have to be explosion proof. This includes making the equipment electrically safe and spark proof to prevent accidental fires and explosions if gas or oil leaks out of the well. EX proofing is expensive and under stringent requirements and special training is required for electricians working with this type of equipment.

It is an amazing engineering feat to see the complex jumble of high-pressure piping, air lines, mud hoses, hydraulic hoses/piping and electrical wiring fitted underneath the rig floor and terminating up through the rig floor in just the right place.

Ever since man started to dig holes in the ground, searching for salt, fresh water and minerals, there has been a continuous development. In digging technology, the first wells were dug by hand and as one got deeper, the wells were lined with rocks and wood to prevent them from collapsing.

When entering the oil-bearing zones, fumes and gases started to interfere with “digging”. It became necessary to drill rather than dig and this was the start of the oil drilling industry.

All types of drilling, whether it is for water, minerals or oil, have to abide the laws of physics. It is therefore no coincidence that most of the drilling techniques developed in the different areas of the world, are quite similar. Although a mining rig looks very different from and oil drilling rig, they perform the same function, namely “drilling a usable hole”. Drilling for oil and gas successfully is a process that requires a number of skills and a lot of advanced equipment. As the drilling process becomes more complicated, the drilling tools and the way they are used, must also be updated.

The oil industry began over five thousand years ago. In the Middle East, oil seeping up through the ground was used in waterproofing boats and baskets, in paints, lighting and even for medication.

Whale oil has been used in more recent times as a source of light in houses. However, the high premium for whale oil decimated whale populations and as their numbers dropped the prices rose further.

The demand for oil was now far higher than the supply. Many companies and individuals were looking for an alternative and longer lasting source of what would later become known as black gold. Apart from a brief period of coal oil, the answer came with the development of drilling for crude oil. Land oil wells were first and as demand continued to grow exploration companies began to look below the sea bed.

The first oil well structures to be built in open waters were in the Gulf of Mexico. They were in water depths of up to 100m and constructed of a piled jacket formation, in which a framed template has piles driven through it to pin the structure to the sea bed. To this, a support frame was added the working parts of the rig such as the deck and accommodation. These structures were the fore-runners for the massive platforms that now stand in very deep water and in many locations around the world, including the North Sea. How did they know to look for oil beneath the North Sea? In 1959 the massive Groningen land gas field was discovered in the Netherlands. Geologists estimated that the same rock formations might be found beneath the southern North Sea basin in UK waters. They were right and gas was discovered of the English East Coast in the 1960s.

Clues around the coast of Greenland gave Geologists the idea that there may be oil and gas around Scottish waters.

There have been land oil wells in Europe since the 1920s. It wasn't until the 1960s that exploration in the North Sea really begun, without success in the early years. They finally struck oil in 1969 and have been discovering new fields ever since. The subsequent development of the North Sea is one of the greatest investment projects in the world.

The development of the offshore oil industry in hostile waters has been made possible by many achievements comparable with the space industry. Many fields are located far from land and they are getting further away. New fields are being explored in ever deeper and wilder waters, like the Atlantic Ocean west of Scotland.

After the North Sea UK disaster in 1988 when on 6 July, the North Sea Piper Alpha oil platform caught fire and exploded killing 167 of the 228 on board. The industry and the government waited until 1990 for the publication of the Cullen report. Lord Cullen discovered that the main cause of the explosion was the failure in the operation of the permit to work system, for which there are now very strict guidelines. This system is used to over-sea work, preventing potentially dangerous work being carried out. It also prevents dangerously conflicting work being carried out by a combination of workers and it ensures that proper laid down procedures are adhered to. The report brought about many changes and a journey towards much greater safety awareness, procedures and regulations.

Today the industry is very safety conscious. It has to be for its very survival. For example, the safety record of an exploration rig can make a big difference to whether or not an oil company will want to hire it. Oil companies cannot afford to have their name associated with accidents.

When you first arrive, you are given a tour of the installation, detailing all safety aspects including fire extinguishers, emergency muster stations, lifeboat stations and procedures. You will be introduced to the rig safety programme.

Everyone attends weekly safety meetings and daily pre "tour" meetings. The weekly meeting is an in-depth look at industry wide safety news and other safety related issues on the rig. Companies share safety information with other companies throughout the industry. This helps to avoid repeated incidents. A fire and boat drill are often held on the same day which involves a mock fire and a mock abandon the rig exercise. The pre-tour meeting is usually a description of the work carried out when you are off shift, the work you will be doing, the work others are currently doing that may affect you and any other relevant issues of the day.

Accidents do happen as in every industry. However, statistics show that with the massive improvements in offshore safety procedures, you now have a higher chance of having an accident if you work on a building site than you do on an oil rig.

Petroleum or crude oil is an oily, flammable liquid that occurs naturally in deposits, most often found beneath the surface of the earth. Over millions of years, plant and animal remains fall to the floor of shallow seas. As the seas recede, the plant material is covered by sediment layers, such as silt, sand, clay, and other plant material. Buried deep beneath layers of rock, the organic material partially decomposes, under an absence of oxygen, into petroleum that eventually seeps into the spaces between rock layers. As the earth's tectonic plates move, the rock is bent or warped into folds or it "breaks" along fault lines, allowing the petroleum to collect in pools. Man was not unfamiliar with crude oil. In the Middle East, seepages and escaping petroleum gases burned continuously, giving rise to fire worship. It was also used for building mortar, roads, in a limited way for lighting, but was primarily used for healing everything from headaches to deafness. It was also used in war, for obvious reasons.

In discussing the components of the earth's crust, it is important to distinguish between rocks and minerals. A mineral is a naturally occurring crystalline substance of a definite range of chemical composition. A rock is a mixture of minerals, usually in the form of grains that may be easily visible or microscopic. The most common rock minerals are silicates-crystalline compounds composed largely of silicon in chemical combination with aluminium, magnesium, oxygen, and other common elements.

Igneous rocks are those that cool and solidify from a molten state. They are classified by chemical composition and grain size. These characteristics, in turn, depend on the elements present in the magma and on how long they cool-the longer the cooling time, the larger the crystals.

Rocks that are exposed at the surface of the earth are subject to weathering by climatic agents, especially water. Water breaks down solid rock by changing it chemically, by dissolving some of its minerals, by supporting the growth of plants and animals that grow on and around rock, and by freezing and expanding to wedge the rock apart. Running water then carries fragments of rock and soil to sedimentary basins-low places where sediments can accumulate, sometimes to a depth of several miles. The weight of the accumulating sediments compresses and bonds the deeper beds into layers of sedimentary rock.

Any type of rock that is buried deeply enough or otherwise subjected to great pressure, stress, or heat can become transformed both chemically and physically into another kind of rock: metamorphic rock. For instance, shale, a crumbly sedimentary rock made of clay, can be changed by heat and pressure into hard metamorphic slate. Slate, or any other rock, can in turn be heated until it melts and then cooled into fresh igneous rock, or it can be broken down by weathering so that it contributes to the formation of new sedimentary rock. The principles involved in the transformation of one type of rock into another are illustrated by the rock cycle.

Two of the most important characteristics of sedimentary rocks, attributes that are rarely found in igneous and metamorphic rock, are their porosity and permeability.

Porosity is the amount of empty space present within the rock; it is usually expressed as a percentage of total rock volume.

Permeability is a measure of the ease with which a fluid flows through the connecting pore spaces of a rock; the more connections between pores, the higher the permeability.

Porosity and permeability are of supreme importance to the geologist in determining whether a body of rock can contain petroleum and whether that petroleum can be extracted and brought to the surface.

The young earth's molten surface was in constant motion, like the lava in an active volcano today. As a solid crust began to form, it was carried about on the surface by the moving magma beneath. Although this crust has grown thicker and stronger over time, it is still in motion atop the moving mantle.

The crust is divided by a world-wide system of faults, trenches, and mid ocean ridges into six major plates and many minor plates that fit together like the pieces of a jigsaw puzzle, as you can see on the image.

These plates, however, move and change shape. In some places, they slide past one another; in others, they collide or move apart. The theory that explains how these processes work to shape the crust is called plate tectonics.

The earth's surface consists of two kinds of crust. Oceanic crust is thin (about 5 to 7 miles) and dense. The rock that makes up the continents, however, is thick (10 to 30 miles) and relatively light. A continent rises high above the surrounding oceanic crust and extends deeper into the mantle-like an iceberg in a frozen-over sea.

Sometimes a plate splits and begins moving apart. This is the way ocean basins are formed. The picture on the left shows a rift forming in the middle of a continent. As the two parts of the continent pull away from each other, magma rises from the mantle and solidifies in the gap, forming a mid ocean ridge. New crust being thinner but denser than the continents spreads outward between the two "daughter" continents. The Atlantic Ocean was born in just this way about 200 million years ago when North and South America split away from Europe and Africa.

Where plates meet head on, several things can happen. If oceanic crust meets oceanic crust, one plate is subducted that is, it slips beneath the edge of the other plate and descends into the mantle, forming a trench in the ocean floor. The descending plate is melted by the hot mantle in the subduction zone. Some of its minerals melt at lower temperatures than others and rise through the crust as magma, which may either cool and solidify within the crust, forming igneous rock such as granite, or reach the surface as volcanic lava.

If one of the converging plates is made up of continental crust, it overrides the heavier oceanic plate, which bends downward in a trench along the continental margin. When this happens, magma from the descending plate may erupt in continental volcanoes like Mount St. Helens. If both of the plates are continental, the collision buckles and folds the rocks including the sedimentary rocks at the edges of the continents-into great mountain ranges like the Himalayas.

Geologists now obtain close estimates of the age of rocks by measuring their radioactivity. Naturally occurring radioactive elements, such as uranium, change at a measurable rate into other elements, such as lead. By measuring the proportions of different forms of lead, scientists can tell about how much time has passed since a rock was formed. Using such methods, geologists have radically changed our ideas about the age of the planet.

Even the ten million years that it took to carve the Grand Canyon is but the most recent moment of geologic history. The earth was formed about 4.6 billion years ago when frozen particles and gases circling a new yellow star were brought together by mutual gravitational attraction. Heated by compression and radioactivity, this material formed a molten sphere.

The heaviest components, mostly iron and nickel, sank to the center and became the earth's core. Lighter minerals formed a thick, molten mantle, while minerals rich in aluminum, silicon, magnesium, and other light elements cooled and solidified into a thin, rocky crust./span>

The surface of the young planet was an inhospitable place. Molten rock (magma) erupted everywhere through fissures and volcanoes, expelling the gases and water vapor that formed the early, oxygen less atmosphere. As the surface cooled, rain condensed and fell in torrents, and the first oceans began to form.

The earth was devoid of life for perhaps its first billion years. Eventually, out of a mixture of complex carbon-chain chemicals, the first self-replicating molecules appeared in the ocean, perhaps in the muck of some shallow lagoon. Over millions of years these primitive organisms grew more complex and varied, first as single-celled bacteria like forms, later as microscopic protozoa and algae. Some grew in the form of colonies, which over further millions of years evolved into more complex organisms. As photosynthetic single-celled plants, which used carbon dioxide and gave off oxygen, became more abundant, their waste oxygen became a major constituent of the atmosphere.

Few traces of this early life survive, however. Although plant remains and impressions of primitive organisms can be found, it was about 4 billion years before animal life became abundant enough (and developed body parts durable enough) to leave significant numbers of fossils. This early, fossil-poor period, comprising most of the time since the earth formed, is commonly known as the Precambrian era.

The last 600 million years of earth's history comprise the time of abundant life. The first fish appeared about 500 million years ago in the early Palaeozoic era, followed by the first land plants, amphibians, and reptiles. The Mesozoic (220 to 65 million years ago) was the era of the dinosaurs, early mammals, and primitive birds. And the Cenozoic era embraces the time from the extinction of dinosaurs through the recent ice ages to the present.

Here on the right you can see a cross section of Earth illustrating the core; mantle and crust. The enlarged position shows the relationship between the lithosphere, composed of the continental crust, oceanic crust and upper mantle and the underlying asthenosphere and lower mantle.

And on the left, have a look at the cross section of Earth showing the various layers and their average density. The crust is divided into a continental and oceanic portion. Continental crust is 20 to 70 km thick, oceanic crust is 5 to 10 km thick.