The main principle in the Offshore Safety Act is that safety and health risks for people that work on an offshore installation are to be assessed, minimised, and identified as far as it reasonably practical. Working on an oil rig is the most dangerous and difficult sphere; its working conditions contain a great range of risks and unexpected consequences. Luckily, many companies and the whole offshore industry are greatly concerned about this matter and much attention is paid to the risk assessment and management.
Drilling rig belongs to the large range of equipment for drilling wells. The composition of the rig components and their design are defined by their purpose, terms and method of drilling. By way of drilling oil rigs are subdivided into rotational (the most common), shock, vibration, and others. Oil rigs include drilling rig, drilling rig (mast), actuators, and different equipment for mechanization tripping. Drilling rigs are also distinguished by the type of drive (electric, diesel, hydraulic) and capacity (light, medium and heavy).
Every oil rig is characterized by: the diameter and depth of the wells, capacity, power output, and other features. Oil rig is usually equipped with test equipment that provides continuous monitoring of the drilling mode (axial load on the rock cutting tool and the frequency of rotation, drilling speed, quantity and pressure washing agent fed into the well). The drilling rigs composition for deep drilling include: the basic mechanisms of the drive unit; pump unit; circulation system consisting of blocks of preparation, storage and mud chemicals, processing and cleaning fluid; emergency drive unit basic mechanisms of preparation; pressure manifold block; receiving unit bridges; storage unit of fuels and lubricants. For storage of replacement parts and components of fast wearing parts rigs are equipped with the storeroom. By appointment rigs are divided into several types: for repair and drilling of deep wells, for gas and oil installations, for Geological and structural (structural exploratory) drilling; by design – on stationary large-scale and building block, block-modular, sectional, portable and mobile phones.
Every year more and more people are trying to get their own source of clean drinking water. There are no large competitors in this business, and there is a shortage of drilling rigs; that is why the competition is only for equipment suppliers. It is important to point out that many oil rigs are located offshore, meaning that they are not built on land, but rather on remote locations in the middle of the sea. Given that extraction and processing is performed (offshore) onsite, oil rigs are also equipped with storage facilities so that the oil and/or natural gas can be stored without being damaged (or signifying a threat) until it can be transported onshore.
Likewise, these facilities hold housing units for workers, since offshore work extends for relatively long period of time and onshore/offshore mobility is impossible. In terms of oil rig operations, it is important to mention, first and foremost, that operations comprehend all phases of the production process (for either oil or natural gas). In other words, an oil rig operation comprehends drilling, extraction, processing, storage, and transportation (once the final product is ready to be transported onshore).
Furthermore, it is necessary to note that oil rig operations are also involved with maintenance, which is crucial to avoid any possible system malfunction (which would surely translate into risk). Oil rig operations necessitate great physical ability, skill, knowledge, and experience. Operating an oil rig requires a significant level of labour specialization; this is not the kind of work that can be done by just any person. Generally, they are engineers, and various technical degree holders in areas that are connected with this work: service unit operation, explosive management, earth drilling, and derrick operations (oil and gas).
It is also important to mention that this paper fundamentally aims to analyse all risk factors that may threaten the performance of oilrig systems (offshore drilling). Furthermore, one of the aims of this paper is to analyse any risks that may attempt against the safety of the operators who are stationed on the rigs and are, therefore, exposed to any risk that might develop on it. Third, risk assessment and risk management strategies will be reviewed so as to determine how to proceed (in terms of preventing, and overcoming, risk) in specific systems and for specific types of risk best.
Before going into a detailed explanation about the different types of oil rigs, or rig systems available, it is important to point out that rig systems are large structures built at offshore locations. These rigs have built-in quarters for workers to live in; they also include machinery that is used to extract natural gas and/or oil. In considering rig systems, these rigs may be fully attached to the ocean floor. However, these rigs may also be built as artificial islands; they may also be built as floating structures. Historically, these systems have been built near continental shorelines, but, with the passing time, technological innovation has allowed companies to develop (and build) offshore structures located farther away from the continental shelf. Today, oil rigs can be built in deeper waters, without implying greater risk, either financial or any other.
Types of Oil Rigs
Oil rig operation is quite a complex process and each element that oil rig comprises has a very important role. As it is known operation of the rigs is done by a drilling contractor, who can also own them. The first step is to oversee tool assembly of the driller and then start the drilling process. After that the process of making mud starts that is caused by the drill pipe. At this step it is very important to check if the drilling fluid is formulated in the right way. According to particular depth goals the speed and pressure of the drilling process is regulated. All the drilling fluid that appeared as a result of this process is pushed up and it is consequently cycled through shakers. During this process oil is extracted and saved in certain storage and the next step is to ship it to refineries.
The principle of operation of drilling rigs is as follows: the first stage is penetration into soil that is done by a chisel, which has its design features when working with soft or solid ground. The rotation of the bit provides a mix of mud and rocks, which is specifically pumped into the drill pipe, and lifts it up on a hollow tube. Drilling speed is dependent upon a great number of factors, including the nature of the soil and the presence of rocks. Soft soils can produce well drilling depth of 100 meters for the day, with dense layers of the soil reducing the rate of 5-10. In this case, slow down, and periodic replacement of the instrument is accompanied by lifting and lowering of drill pipe.
Once the rig is mounted lower, its triangle is covered with earth in order to prevent water from leaking outside of the triangle, then, in the middle of the triangle, a small depression is dug to enter drill, screw-on swivel bit first rod that is turned on the pump to supply water from the pit inside the first drill rod once went to the water supply. Then, the rig is lowered in order to drill the first bar; the drill is turned in reverse and unscrewed from the first boom lift machine frame rig to wind the second post. After the first tube with a filter has reached the top of bottom of the hole with plastic pipe sticking out of the hole evenly is cut leaving about 50cm from ground level to the protruding end of the pipe is put a coil diameter of 50 adapter for flushing with clean water wells, the site is located outside the territory of a machine with a capacity of half a cubic meter clean water, this water will be cleaned well after the well was washed recruit half a bucket of small gravel fractions 3-10 in the pipe itself, around the pipe pour gravel all serve to filter water.
Having introduced oil rigs, it is also pertinent to mention the major elements of offshore production systems. In principle, all offshore production systems are comprised of wells, well rigs (which are also referred to as servicing rigs), feeder subsea pipelines, processing rigs, export pipelines (for both oil and gas), and tankers for the evacuation of the resource being extracted from beneath the ocean floor (be it oil or natural gas). Another point to be made is that these rigs may either be manned or unmanned.
The first type of oilrigs that will be considered are fixed oilrigs, or fixed rigs. Their particularity is that they are built directly on the ocean’s floor, using either concrete and/or steel legs. Generally, these are the rigs that are constructed for long-term drilling purposes (Jahn, Cook & Col 2008). It is important to note that they are overly attractive, or at least feasible, in waters with the depth of 1,700 feet (or lower).
The second type of rig to be considered is the semi-submersible rig. These rigs, instead of being built directly on the ocean floor, are equipped with legs that are sufficiently buoyant to keep the entire rig above water and in an upright position. These rigs are advantageous insomuch as they can be mobilized to different offshore locations. Furthermore, it is possible to modify the ballast of these rigs by simply changing the buoyancy tanks’ flooding. Given that they are not attached to the ocean floor, but floating, these rigs are usually kept in place by using an anchor. Finally, it is worth noting that these rigs are ideal for water depths ranging between 200 and 10,000 feet.
The third type of oilrig, or rig, is the jack-up rig. What is particular about these rigs is that they can be jacked-up meaning that their legs can be extended in order to lift the entire rig above the water. Generally, these are drills used on offshore locations where the water’s depth does not exceed 400 feet. Also, it is worth mentioning that their design implies mobility; the rig can be moved to different locations. Once in position, the rig can deploy its legs in order to anchor itself to the ocean floor.
Compliant towers, as their name indicates, are essential tower structures that possess a piled foundation (on which a conventional drilling deck functions). These rigs are ideal in water depths that range between 1,500 and 3,000 feet. They are also characterized by high levels of lateral deflection and by the ability to sustain significant forces. In other words, these are stronger and more stable rigs, which in turn allow them to be positioned at more remote (and deeper) locations.