A region with abundant oil wells for petroleum extraction from the underground is referred to as an oil field. Mostly the oil fields cover a very large area that is, why there are several wells. Full oil exploitation only occurs when there are many wells. Ekofisk oil field is found in the North Sea one hundred and eighty miles away from southwest Norway. It’s precisely at the middle of United Kingdom and Norway. The oil field is characterized by the presence of natural gas and petroleum. This oil field was discovered in the year 1969 though oil production started in the year 1971. The company which played a big part in the oil production at the oil field was Phillips Petroleum Company because it helped in setting up some platforms. The company has aimed at processing oil at the field until the year 2050 (Mello and Katz 61).
Oil Reservoirs. Ekofisk oil field is situated in Ekofisk district. This field comprises of natural gas which was discovered in the year 1968 at Cod and the petroleum field which is located at Tar and it was discovered in the year 1970. Another area where oil production occurs is Albuskjell, this area was discovered in the year 1972. By the year 1980 eighteen offshore platforms with additional fifty well were in operation. This field is gigantic and its discovery changed the whole picture of petroleum exploration in Western Europe. Ekofisk field is the main reason why North Sea is regarded as the best exploration area in the whole world. This region has earned fame to the whole world because of this natural resource. At the moment the oil field produces about 1.5 million oil barrel in a day. And the total oil reserves in the region is about 18 billion oil barrels though the ultimate estimates reserve is about 40 billion oil barrels.
One of the major challenges has been the effects of the tectonic periods which have occurred severally though, the oil field still remains as an intercratonic basin from its discovery. The establishment of the main tectonic fabrics occurred during the orogenies of Hercynian and Caledonian. Today the two remains as the controlling features of sediment distribution and facies. The petrography of the chalk and the surroundings of the main deposition have been revealed by the stratigraphic history. Ekofisk has an average porosity ranging from thirty to forty percent and the reason behind this is the porosity preservation of the area. This is something unique since it’s not attainable under natural circumstances. This has been attained by over pressuring the oil reserve as well as the pressure of pore fluids that are rich in magnesium. Another factor that has greatly contributed to this is the hydrocarbon introduction which was done early than usually. At the moment there are six Ekofisk great fields under construction and all the six were discovered in the year 1960 at the time of the seismic work.
The History of Ekofisk Oil Field. Ekofisk oil comprises of hydrocarbons, natural gas and liquid oil. The oil reserves are located under the North Sea. Extraction of oil for sale on the Northern Sea shores began around 1851. This was started by James Young who was the first person to extract petroleum from torbanite. Gas was discovered by chance in the year 1910 in a well meant for water around Hamburg. Oils meant for commercial purposes were discovered in Carboniferous rocks. The gas being produced in Netherlands was first found in Zechstein carbonates in the year 1948. The exploration well at Groningen was discovered in the year 1952. This well has penetrated the Permian sandstones forming the main gas reservoirs for the Ekofisk fields. In 1969 oil was discovered in chalk at the oil fields. The chalk that contained the oil was of age Danian in the waters of the North Sea. The first productions of oil in the area were done in the Argyll field (Shaw 23).
The Northern weather conditions have been a challenge especially when it comes to drilling of holes. As a result many people have lost their lives during this process. The processes have also turned out to be very expensive due to prevailing hard conditions. It’s proving hard to invent new technologies which can make the work safer as well as efficient because the expenses involved cannot be obtained that easily. The largest oil reserves are held by both United Kingdom and Norway. It’s estimated that the two countries hold about 54% of all of all oil reserves which are in the Northern Sea as well as 455 of all the gas reserves. Research done by the relevant States indicates that more than half of the oil reserves in the whole Northern Sea have already been extracted. The extracted oil reserve covers the area of about 4,601 million cubic meters which corresponds to about twenty nine million barrels (Fleet, Boldy and Burley 1147).
There are frequent earthquake occurrences in the Netherlands which have been induced by the ongoing gas production in the main oil fields. The earthquakes which are estimated to have occurred in the area in the past two years are about 350. The magnitude of these earthquakes has been estimated to go up to 3.5 scales. For these reason the people involved in the production process are required by the law to give future predictions of the seismic activities. The sedimentary rocks of the North Sea in Central Graben have complex regimes of high pressure. The rocks in the place contain an over pressured systems which are deep rooted in the pre-Cretaceous rocks. Another important characteristic of these rocks is the presence of variable regime that is over pressured which is found in the chalk group. The Paleocene sandstones contain interval pressure which is very normal and these characteristics are important for oil production (Gluyas and Hichens 501)
The Ekofisk complex has been able to preserve the overpressure because of the presence of seal on the clay stone which overlay the Paleocene rocks. This overpressure is as a result of compaction disequilibrium. Several pressure cells are the ones that characterize the high pressure being experienced in Graben rocks. Seals form as a result of facial changes. This change occurs in the permeable horizons as well as the faults. The hydrocarbon that is usually generated in the rocks is one of the contributing factors to the existing high pressures. The cretaceous rocks which contain hydrocarbon are the main cause of the over pressure found in the rocks lying below 3,500 m depths. Some of the occurrences at the oil field are the episodic cycles which involve rock fracturing which is a result of the generated hydrocarbon as well as the high pressure in the rock pores. This process is immediately followed by a reversed process of reduced pore pressure which leads to the closing of the created fracture (Law, Ulmishek and Slavin 142).
This process leads to massive loss of rock fluids which is followed by a process of reservoir recharge. This process indicates the existing high pressures and it’s bound to continue for a very long time as long as the rock generating it still exists. The overpressure which has been maintained for a very long time has some important implications. For example it indicates the presence of migration routes for uncommon hydrocarbons as well as preferential evaporation of gas from the existing oils and the reservoirs of gases. This also may indicate the existing of accumulated petroleum deposits beneath the gas chimneys. Due the existing over pressure at the Central Graben the operations for drilling are very hard especially when penetrating the rocks that lay above the over pressured zone. Therefore for safety purpose it’s important for those involved in designing the drilling program to come up with way for encountering the excessive pressure (Law, Ulmishek and Slavin 143).
The main controlling parameters at the oil field are the top seal and the reservoir. Another important aspect is the hydrocarbon migration timing as well as its retention. The challenge is the distribution of the chalk in the sandstones within the deep waters of the sea. The presence of sand below the clay stone reduces the usefulness of the top seal. Porosity is also preserved by the emplacement of hydrocarbons which are enormous. Ekofisk oil field is characterized by intra heterogeneous reservoirs as well as permeability variations which are essential characters of an effective oil field. Also the distribution of the circulating fluids plays an important role as it reflects the existing differences in properties of capillary pressure of the chalk matrix.
At the moment for efficient oil production, mechanisms that are non-structural are being used instead of the structural mechanisms. Example of such methods includes trapping using the seals that are intra chalk. The structural traps in use at Ekofisk mainly involve the use of four way dip closures which was as a result of the mechanism in use. The mechanism mostly employed is salt diapirism (Glennie 497). Ekofisk is among the best existing oil fields in the whole world. In the United Kingdom and Norway it’s rated the best. The reservoirs are enormous thus it is not anywhere near depletion. Some of its important characteristic like the presence of the over pressure is recommendable. Therefore this is a field worth making an investment because resources are still available and in plenty.