Oil and Gas Exploration

explorationExploration and production is the common terminology applied to that portion of the petroleum industry which is responsible for exploring for and discovering new crude oil and gas fields, drilling wells and bringing the products to the surface.

An exploration and production (E&P) company is in a specific sector within the oil and gas industry. Companies involved in the high-risk/high-reward area of exploration and production focus on finding, augmenting, producing, and merchandising different types of oil and gas.

Exploration and production is known as the upstream segment of the oil and gas industry. The resource owners and operators of E&Ps work with a variety of contractors such as engineering procurement and construction (EPC) contractors, as well as with joint-venture partners and oil field service companies, and as exploration and production operators produce oil and gas, they also build infrastructure and collect massive amounts of analytical data.

Classifications

Crude oils are complex mixtures containing many different, individual hydrocarbon compounds; they differ in appearance and composition from one oil field to another, and sometimes are even different from wells relatively near one another. Crude oils range in consistency from watery to tar-like solids, and in color from clear to black. An “average” crude oil contains about 84% carbon; 14% hydrogen; 1 to 3% sulphur; and less than 1% of nitrogen, oxygen, metals and salts.

The names of crude oils often identify both the type of crude and areas where they were originally discovered. For example, the first commercial crude oil, Pennsylvania Crude, is named after its place of origin in the United States. Other examples are Saudi Light and Venezuelan Heavy. Two benchmark crudes used to set world crude prices are Texas Light Sweet and North Sea Brent.

Oil and Gas

The search for oil and gas requires a knowledge of geography, geology and geophysics. Crude oil is usually found in certain types of geological structures, such as anticlines, fault traps and salt domes, which lie under various terrains and in a wide range of climates. After selecting an area of interest, many different types of geophysical surveys are conducted and measurements performed in order to obtain a precise evaluation of the subsurface formations, including:

Magnetometric Surveys Magnetometers hung from airplanes measure variations in the earth’s magnetic field in order to locate sedimentary rock formations which generally have low magnetic properties when compared to other rocks.

Aerial Photogrammetric Surveys  Photographs taken with special cameras in airplanes, provide three dimensional views of the earth used to determine land formations with potential oil and gas deposits.

Gravimetric Surveys  Because large masses of dense rock increase the pull of gravity, gravimeters are used to provide information regarding underlying formations by measuring minute differences in gravity.

Seismic Surveys  Seismic studies provide information on the general characteristics of the subsurface structure. Measurements are obtained from shock waves generated by setting off explosive charges in small-diameter holes, from the use of vibrating or percussion devices on both land and in water, and from underwater blasts of compressed air. The elapsed time between the beginning of the shock wave and the return of the echo is used to determine the depth of the reflecting substrata. The recent use of super-computers to generate three-dimensional images greatly improves evaluation of seismic test results.

Platform Types

Drilling Techniques

The drilling platform provides a base for workers to couple and uncouple the sections of drilling pipe which are used to increase the depth of drilling. As the hole deepens, additional lengths of pipe are added and the drilling string is suspended from the derrick. When a drilling bit needs to be changed, the entire drilling string of pipe is pulled out of the hole, and each section is detached and stacked vertically inside the derrick. After the new bit is fitted in place, the process is reversed, and the pipe is returned to the hole to continue drilling.

Care is needed to assure that the drilling string pipe does not split apart and drop into the hole, as it may be difficult and costly to fish out and may even result in the loss of the well. Another potential problem is if drilling tools stick in the hole when drilling stops. For this reason, once drilling begins, it usually continues until the well is completed.

Exploration and production companies locate and extract nonrenewable resources from the Earth. The process of oil and gas exploration and production typically involves four stages.

1. Exploration

At this stage, the search for hydrocarbons beneath the ground entails geophysical prospecting for shale formations that hold deposits of oil and natural gas. One method of exploration involves seismology, a process whereby substantial vibrations, via explosives or machinery, are produced at the Earth’s surface. Seismic waves travel to the Earth’s mantle, and the respondent force is analyzed at the surface to identify layers of rock that trap reservoirs of oil and natural gas. Exxon Mobil Corporation maintains many large exploratory fields in the Gulf of Mexico, extending operations to 339 deepwater blocks.

2. Well Development

After identifying potentially viable fields, engineers determine the number of wells needed to meet production requirements and the method of extraction of the liquid hydrocarbons. Platform construction costs are estimated with regard to the site, offshore or onshore, and designs are rendered for systems used to facilitate environmental protections. Newer drilling technologies, prominent in the Marcellus and Bennett shale fields in Pennsylvania and Texas, allow companies such as Chesapeake Energy Corporation to extend horizontal legs about 5,000 feet from vertical wells in search of natural gas pockets, producing four times as much gas at only twice the cost of a vertical well.

3. Production

Liquid hydrocarbons extracted from wells are separated from the non-saleable components such as water and solid residuals. Natural gas is often processed onsite while oil is piped to a refinery before being offered for sale.

4. Abandonment

As exploratory sites are deemed unproductive or existing operations exhaust capacity, companies plug wells and attempt to restore the areas to environmental states that existed prior to drilling activities. As natural gas prices descended to historic lows in January 2016, many exploratory wells were shuttered as high production costs rendered extraction unprofitable. In 2014, the state of Ohio ramped up efforts to plug nearly 600 orphan wells that posed hazards to surface water and aquifers.

Steam Injection

Steam injection, or steam flooding, is a thermal recovery method which heats heavy crude oil and lowers its viscosity by injecting super-hot steam into the lowest stratum of relatively shallow reservoir. The steam is injected over a period of 10 to 14 days, and the well is shut for another week or so to allow the steam to thoroughly heat the reservoir. At the same time the increased heat expands reservoir gases, thereby increasing the pressure in the reservoir. The well is then reopened and the heated, less viscous crude flows up into the well. A newer method injects low-heat steam at lower pressure into larger sections of two, three or more zones simultaneously, developing a steam chest which squeezes down the oil in each of the zones. This provides a greater flow of oil to the surface, while using less steam.

Safety

Drilling and production take place in all types of climates and under varying weather conditions, from tropical jungles and deserts to the frozen Arctic, and from dry land to the North Sea. Drilling crews have to work in difficult conditions, subject to noise, vibration, inclement weather, physical hazards and mechanical failures. The platform, rotary table and equipment are usually slippery and vibrate from the engine and drilling operation, requiring workers to make deliberate and careful movements. The hazard exists for slips and falls from heights when climbing the rig and derrick, and there is risk of exposure to crude oil, gas, mud and engine exhaust fumes. The operation of rapidly disconnecting and then reconnecting drill pipe requires training, skill and precision by workers in order to be done safely time after time.

Construction, drilling and production crews working offshore have to contend with the same hazards as crews working on land, and with the additional hazards specific to offshore work. These include the possibility of collapse of the platform at sea and provisions for specialized evacuation procedures and survival equipment in event of an emergency. Another important consideration when working offshore is the requirement for both deep-sea and shallow-water diving to install, maintain and inspect equipment.

Fire and Explosion

There is always a risk of blowout when perforating a well, with a gas or vapour cloud release, followed by explosion and fire. Additional potential for fire and explosion exists in gas process operations.

Offshore platform and drilling rig workers should be carefully evaluated after having a thorough physical examination. The selection of offshore crew members with a history or evidence of pulmonary, cardiovascular or neurological diseases, epilepsy, diabetes, psychological disturbances and drug or alcohol addiction requires careful consideration. Because workers will be expected to use respiratory protection equipment and, in particular, those trained and equipped to fight fires, they must be physically and mentally evaluated for capability of carrying out these tasks. The medical examination should include psychological evaluation reflective of the particular job requirements.

Emergency medical services on offshore drilling rigs and production platforms should include provisions for a small dispensary or clinic, staffed by a qualified medical practitioner on board at all times. The type of medical service provided will be determined by the availability, distance and quality of the available onshore services. Evacuation may be by ship or helicopter, or a physician may travel to the platform or provide medical advice by radio to the onboard practitioner, when needed. A medical ship may be stationed where a number of large platforms operate in a small area, such as the North Sea, to be more readily available and quickly provide service to a sick or injured worker.

Persons not actually working on drilling rigs or platforms should also be given pre-employment and periodic medical examinations, particularly if they are employed to work in abnormal climates or under harsh conditions. These examinations should take into consideration the particular physical and psychological demands of the job.

 


 

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