Комплекс геофизических исследований в открытом стволе скважин с целью оценки нефтеносности разрезов Игольско-Талового месторождения (Томская область)

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Список использованной литературы

1. Вендельштейн Б.Ю. “Исследование разрезов нефтяных и газовых скважин методом собственных потенциалов”. - М.: Недра, 1966.

2. «Вестник недропользователя» журнал №16/2005

3. Геофизические методы исследования / под ред. В.К. Хмелевского. - М.: Недра, 1988

4. Геофизические методы исследования скважин / под ред. В.М. Запорожца. - М.: Недра, 1983.

5. Дахнов В.Н. “Геофоизические методы опреления коллекторских свойств и нефтегазонасыщение горных прод”. - М.: Недра, 1975.

6. Добрынин В.И.и др. петрофизика. - М.: Недра, 1991.

7. Латышева М.Г. “Практическое руководство по интерпретации диаграмм геофизических методов исследования”. - М.: Недра, 1981.

8. Материал предоставленный ООО «ТомскГазпромгеофизика».: г.Стрежевой 2008г.

9. Пирсон С.Д. учение о нефтяном пласте. - М.:Госттоптехиздат, 1961г.

10. Эланский М.М. «Извлечение из скважинных данных информации для решения поисково-разведочных задач нефтегазовой геологии».: М, 2000г.

11. ГОСТ 1.12.005 - 88 ССБТ. Общие санитарно-гигиенические требования к воздуху рабочей зоны (01.01.89).

12. ГОСТ 12.0.003 - 74 ССБТ. Опасные и вредные производственные факторы. Классификация.

13. ГОСТ 12.1.003 - 83 ССБТ. Шум. Общие требования безопасности.

14. ГОСТ 12.1.004 - 91 ССБТ. Пожарная безопасность. Общие требования (01.07.92).

15. ГОСТ 12.1.019 - 79 ССБТ. Электробезопасность. Общие требования и номенклатура видов защиты.

16. ГОСТ 12.1.030 - 81 ССБТ. Защитное заземление, зануление.

17. ГОСТ 12.1.038 - 82 ССБТ. Электробезопасность. Предельно допустимые уровни напряжений прикосновения и токов.

18. ГОСТ 12.2.003 - 91 ССБТ. Оборудование производственное. Общие требования безопасности.

19. . ГОСТ 12.2.062 - 81 ССБТ. Оборудование производственное. Ограждения защитные.

20. ГОСТ 12.4.125 - 83 ССБТ. Средства коллективной защиты работающих от воздействия механических факторов. Классификация.

21. СНиП 2.04.05 - 91. Отопление, вентиляция и кондиционирование.

22. СанПиН 2.2.2/2.4.1340-03. Санитарно-эпидемиологические правила и нормативы «Гигиенические требования к персональным электронно-вычислительным машинам и организации работы».-М.: Госкомсанэпиднадзор, 2003.

23. СанПиН 2.2.4.548-96. Гигиенические требования к микроклимату производственных помещений.

24. СНиП 21-01-97. Пожарная безопасность зданий и сооружений. М.: Госстрой России, 1997.

25. СНиП 23-05-95. Естественное и искусственное освещение.

26. СН 2.2.4/2.1.8.562-96. Шум на рабочих места, в помещениях жилых, общественных зданиях и на территории жилой застройки.- М.: Госкомсанэпиднадзор России, 2003.

27. Основные санитарные правила обеспечения радиационной безопасности(ОСПОРБ - 99).

28. Пожарная безопасность. Взрывобезопасность / Справочник: Баратов А.Н. - М.: Химия, 1987.

29. ППБ 01-03. Правили пожарной безопасности в РФ. - М.: Министерство РФ по делам гражданской обороны, ЧС и ликвидаций последствий стихийных бедствий, 2003.

ПРИЛОЖЕНИЯ

3.2 Oil - General characteristics

Fluids produced from oil and gas wells genrerally constitute mixtures of crude oil, natural gas, and salt water. These mixtures are very difficult to handle, meter, or transport. In addition to the difficulty, it is also unsafe and uneconomical to ship or to transport these mixtures to refineries and gas plants for processing. Further, hydrocarbon shipping tankers, oil refineries, and gas plants require certain specifications for the fluids that each receive. Also, environmental constraints exist for the safe and acceptable handling of hydrocarbon fluids and disposal of produced salt water. It is therеfore necessary to process the produced fluids in the field to yield products that meet the specifications set by the customer and are safe to handle.

CRUDE OIL PROCESSING

Crude oil-gas-water mixtures produced from wells are generally directed, through flow lines and mainfold system, to a central processing and treatment facility normally called the gas-oil separation plant (GOSP). The first step in processing of the produced stream is the separation of the phases (oil, gas, and water) into separte streams. This takes place in mechanical devices known as two-phase gas-oil separators when the produced stream contains no water or three-phase separators when the produced stream contains water. Gas-oil separation carried out in these separators is recognized as the backbone process in a train of field processing units of oil and gas operations. The separators are used to relieve the excess pressure due to the gas associated with the produced crude and, consequently, separating it from the oil. When water exists in the produced stream, separators are also used to separate the free water from the oil. Once separation is done, each stream undergoes the proper processing for further field treatment, as shown in Fig. 3.2.1.

Oil leaving the separator does not generally meet the purchaser's specifications. Oil may still contain between 10% and 15% water that exists mostly as emulsified water.

Figure 3.2.1. An outline of the processing surface field operations.

The presence of this salt water presents serious corrosion and scaling problems in transportation and refinery operations.Water remaining in the oil is known as the basic sediments and water (BS&W). A maximum of 1% BS&W and in some cases less than 0.5% BS&W is acceptable. The limit on the salt content of the remnant water in oils is usually in the range of 10 to 15 PTB (pounds of salt per thousand barrels of oil). If these specifications are not met, then further treatment of the oil leaving the separator will be needed. Such treatment involves emulsion treatment/dehydration and desalting processes. After oil treating, there may be a need to stabilize the crude oil to optimize the oil recovery and reduce its volatility. Some produced crude oils contain hydrogen sulfide and other sulfur products. When it contains more than 400 ppm of H₂S gas, the oil is classified as sour crude.

Sour crude oil present serious safety and corrosion problems. In such cases, another treatment known as the sweetening process is needed to remove hydrogen sulfide or reduce its content to acceptable limits.

A quick comparison between the properties of a typical crude oil produced from a field in the Middle East before and after treatment illustrates the role of field processing the crude oil .

Raw crude oil has the following materials present:

Water: present in two forms: emulsions (10%) and free water (30%)

Salt: 50,000-250,000 mg/L formation water

Gas: dissolved gas (600 scf/bbl crude oil)

H₂S: 1000 ppm

Treated crude oils have the following final specifications:

Water content: 0.3 vol% maximum

Salt content: 10 lbs (as NaCl) per 1000 barrels of oil

H₂S: 70 ppm

Vapor pressure: 10 psig (4-5 psi RVP)

FIELD PROCESSING OF NATURAL GAS

Nature gas associated with oil production (associated gas) or produced from gas fields generally contains undesirable components such as H₂S, CO₂, N₂, and water vapor. Field processing of natural gas implies the removal of such undesirable components before the gas can be sold in the market. Specifically, the gas contents of H₂S, CO₂, and water vapor must be removed or reduced to acceptable concentrations. N₂, on the other hand, may be removed if it is justifiable. Gas compression is usually needed after these treatment processes. In addition, the gas undergoes separation and fractionation for the recovery of some hydro-carbon components that are utilized as a feedstock for the petrochemical industry.

Several schemes can be recommended for field processing and separation of natural gas, but the specific solution is usually a function of the composition of the gas stream, the location of this source, and the markets available for the products obtained. Saudi Arabia's master gas system (MGS), as illustrated in Fig. 3.2.2, is a good example.

Nonassociated gases, including gas condensates, are also a potential source of hydrocarbons for many oil-producing countries. The processing of the gas condensates, however, involves a low-temperature technique to be described later in the text.

Figure 3.2.2 Master gas system (MGS).

Field processing of natural gas, in general, is carried out for two main reasons:

1.The necessity to remove impurities from the gas;

2.The desirability of increasing liquid product recovery above that obtained by conventional gas processing ;

FORMATION AND ACCUMULATION OF OIL AND GAS

Several theories have been proposed to explain the formation and origin of oil and gas (petroleum); these can be classified as the organic theory of petroleum origin and the inorganic theory of origin. The organic theory provides the explanation most accepted by scientists and geologists.

It is believed, and there is evidence, that ancient seas covered much of the present land area millions of years ago. The Arabian Gulf and the Gulf of Mexico, for example, are parts of such ancient seas. Over the years, rivers flowing down to these seas carried large volumes of mud and sedimentary materials into the sea. The mud and sedimentary materials were distributed and deposited layer upon layer over the sea floor. The buildup of thousands of feet of mud and sediment layers caused the sea floors to slowly sink and be squeezed. This eventually became the sedimentary rocks (the sandstones and shales, and the carbonates) where petroleum is found today.

The very large amount of small plant and animal life, which came into the sea with river mud and sedimentary materials, and the much larger amount of small marine life remains already on the sea floors constituted the source of petroleum. These small organisms died and were buried by the depositing silt and, thus, were protected from ordinary decay. Over many years, pressure, temperature, bacteria, and other reactions caused these dead organisms to change into oil and gas.

The gas was formed under the higher-temperature conditions, whereas the oil was ormed under the lower-temperature conditions. The rocks where oil and gas were formed are known as the source rock.

Accumulation of Oil and Gas

The oil, gas, and salt water occupied the pore spaces between the grains of the sandstones, or the pore spaces, cracks, and vugs of the limestones and dolomites. Whenever these rocks were sealed by a layer of impermeable rock, the cap rock, the petroleum accumulating within the pore spaces of the source rock was trapped and formed the petroleum reservoir. However, when such conditions of trapping the petroleum within the source rocks did not exist, oil gas moved (migrated ), under the effects of pressure and gravity, from the source rock until it was trapped in another capped (sealed) rock.

Because of the differences in density, gas, oil, and water segregated within the trap rock. Gas, when existed, occupied the upper part of the trap and water occupied the bottom part of the trap, with the oil between the gas and water. Complete displacement of water by gas, or oil, never occurred. Some salt water stayed with the gas and/or oil within the pore spaces and as a film covering the surfaces of the rock grains; this water is known as the connate water, and it may occupy from 10% up to 50% of the pore volume.

The geologic structure in which petroleum has been trapped and has accumulated, whether it was the source rock or the rock to which petroleum has migrated, is called the petroleum reservoir.

In summary then, the formation of a petroleum reservoir involves first the accumulation of the remains of land and sea life and their burial in the mud and sedimentary materials of ancient seas.

This is followed by the decomposition of these remains under conditions that recombine the hydrogen and carbon to form the petroleum mixtures. Finally, the formed petroleum is either trapped within the porous source rock when a cap rock exists or it migrates from the source rock to another capped (sealed) structure.

TYPES OF PETROLEUM RESERVOIR

Petroleum reservoirs are generally classified according to their geologic structure and their production (drive) mechanism.

Geologic Classification of Petroleum Reservoirs

Petroleum reservoirs exist in many different sizes and shapes of geologic structures. It is usually convenient to classify the reservoirs according to the conditions of their formation as follows:

1.Dome-Shaped and Anticline Reservoirs:

These reservoirs are formed by the folding of the rock layers as shown in Figure 3.2.3.

The dome is circular in outline, and the anticline is long and narrow. Oil and/or gas moved or migrated upward through the porous strata where it was trapped by the sealing cap rock and the shape of the structure.

2.Faulted Reservoirs:

These reservoirs are formed by shearing and offsetting of the strata (faulting), as shown in Figure 3.2.4. The movement of the nonporous rock opposite the porous formation containing the oil/gas creates the sealing. The tilt of the petroleum-bearing rock and the faulting trap the oil/gas in the reservoir.

Figure 3.2.3. A reservoir formed by folding of rock layers

Figure 3.2.4. A cross section of a faulted reservoir.

3.Salt-Dome Reservoirs:

This type of reservoir structure, which takes the shape of a dome, was formed due to the upward

movement of large, impermeable salt dome that deformed and lifted the overlying layers of rock. As shown in Figure 3.2.5, petroleum is trapped between the cap rock and an underlying impermeable rock layer, or between two impermeable layers of rock and the salt dome.

4.Unconformities

This type of reservoir structure, shown in Figure 3.2.6, was formed as a result of an unconformity where the impermeable cap rock was laid down across the cutoff surfaces of the lower beds.

Figure 3.2.5. Section in a salt-dome structure.

Figure 3.2.6. A reservoir formed by unconformity

5.Lense-Type Reservoirs:

In this type of reservoir, the petroleum- bearing porous formation is sealed by the surrounding, nonporous formation. Irregular deposition of sediments and shale at the time the formation was laid down is the probable cause for this abrupt change in formation porosity. An example of this type of reservoirs is shown in Figure 3.2.7.

Figure 3.2.7 An example of a sandstone lense-type reservoir.

6.Combination Reservoirs:

In this case, combinations of folding, faulting, abrupt changes in porosity, or other conditions that create the trap, from this common type of reservoir.

Reservoir Drive Mechanisms

At the time oil was forming and accumulating in the reservoir, the pressure energy of the associated gas and water was also stored. When a well is drilled through the reservoir and the pressure in the well is made to be lower than the pressure in the oil formation, it is that energy of the gas, or the water, or both that would displace the oil from the formation into the well and lift it up to the surface. Therefore, another way of classifying petroleum reservoirs, which is of interest to reservoir and production engineers, is to characterize the reservoir according to the production (drive) mechanism responsible for displacing the oil from the formation into the wellbore and up to the surface.

There are three main drive mechanisms:

I.Solution-Gas-Drive Reservoirs:

Depending on the reservoir pressure and temperature, the oil in the reservoir would have varying amounts of gas dissolved within the oil (solution gas).

Solution gas would evolve out of the oil only if the pressure is lowered below a certain value, known as the bubble point pressure, which is a property of the oil. When a well is drilled through the reservoir and the pressure conditions are controlled to create a pressure that is lower than the bubble point pressure, the liberated gas expands and drives the oil out of the formation and assists in lifting it to the surface. Reservoirs with the energy of the escaping and expanding dissolved gas as the only source of energy are called solution-gas-drive reservoirs.

This drive mechanism is the least effective of all drive mechanisms; it generally yields recoveries between 15% and 25% of the oil in the reservoir.

II.Gas-Cap-Drive Reservoirs:

Many reservoirs have free gas existing as a gas cap above the oil. The formation of this gas cap was due to the presence of a larger amount of gas than could be dissolved in the oil at the pressure and temperature of the reservoir. The excess gas is segregated by gravity to occupy the top portion of the reservoir. In such a reservoirs, the oil is produced by the expansion of the gas in the gas cap, which pushes the oil downward and fills the pore spaces formerly occupied by the produced oil. In most cases, however, solution gas is also contributing to the drive of the oil out of the formation.

Under favorable conditions, some of the solution gas may move upward into the gas cap and, thus, enlarge the gas cap and conserves its energy.

Reservoirs produced by the expansion of the gas cap are known as Gas-cap-drive reservoirs. This drive is more efficient than the solution-gas drive and could yield recoveries between 25% and 50% of the original oil in the reservoir.

III.Water-Drive Reservoirs:

Many other reservoirs exist as huge, continuous, porous formations with the oil/gas occupying only a small portion of the formation. In such cases, the vast formation below the oil/gas is saturated with salt water at very high pressure. When oil/gas is produced, by lowering the pressure in the well opposite the petroleum formation, the salt water expands and moves upward, pushing the oil/gas out of the formation and occupying the pore spaces vacated by the produced oil/gas. The movement of the water to displace the oil/gas retards the decline in oil, or gas pressure, and conserves the expansive energy of the hydrocarbons.

Reservoirs produced by the expansion and movement of the salt water below the oil/gas are known as water-drive reservoirs. This is the most efficient drive mechanism; it could yield recoveries up to 50% of the original oil.

FINDING OIL AND GAS EXPLORATION

As explained in the previous sections, oil and gas exist in reservoirs located thousands of feet below the Earth's surface and ocean floors. These reservoirs would exist only in certain locations depending on the geologic history of the Earth. Therefore, determining the location of petroleum reservoirs is a very difficult task and is, probably, the most challenging aspect of the petroleum industry. Finding, or discovering, a petroleum reservoir involves three major activities: geologic surveying, geophysical surveying, and exploratory drilling activities. The following subsections provide a brief background on each of these activities.

Geologic Survey

Geologic surveying is the oldest and first used tool for determining potential locations where there would be a possibility of finding underground petroleum reservoirs. It involves examination of the surface geology, formation outcrops, and surface rock samples. The collected information is used in conjunction with geologic theories to determine whether petroleum reservoirs could be present underground at the surveyed location. The results of the geologic survey are not conclusive and only offer a possibility of finding petroleum reservoirs. The rate of success of finding petroleum reservoirs using geologic surveys alone has been historically low. Currently, geologic surveys are used together with other geophysical surveys to provide higher rates of success in finding petroleum reservoirs.

Geophysical Surveys

There are mainly four types of geophysical surveys used in the industry: gravity survey, magnetic survey, seismic survey, and remote sensing.

The gravity survey is the least expensive method of locating a possible petroleum reservoir. It involves the use of an instrument, a gravimeter, which picks up a reflection of the density of the subsurface rock. For example, because salt is less dense than rocks, the gravimeter can detect the presence of salt domes, which would indicate the presence of an anticline structure. Such a structure is a candidate for possible accumulation of oil and gas.

The magnetic survey involves measurement of the magnetic pull, which is affected by the type and depth of the subsurface rocks. The magnetic survey can be used to determine the existence and depth of subsurface volcanic formations, or basement rocks, which contain high concentrations of magnetite. Such information is utilized to identify the presence of sedimentary formations above the basement rocks.

The seismic survey involves sending strong pressure (sound) waves through the earth and receiving the reflected waves off the various surfaces of the subsurface rock layers. The sound waves are generated either by using huge land vibrators or using explosives. The very large amount of data collected, which include the waves' travel times and characteristics, are analyzed to provide definitions of the subsurface geological structures and to determine the locations of traps that are suitable for petroleum accumulation.

This type of survey is the most important and most accurate of all of the geophysical surveys. Significant technological developments in the field of seismic surveying have been achieved in recent years. Improvements in the data collection, manipulation, analysis, and interpretation have increased the significance and accuracy of seismic surveying. Further, the development of three-dimensional (3D) seismic surveying technology has made it possible to provide 3D descriptions of the subsurface geologic structures.

Remote sensing is a modern technique that involves using infrared, heat-sensitive, color photography to detect the presence of underground mineral deposits, water, faults, and other structural features. The sensing device, normally on a satellite, feeds the signals into special computers that produces maps of the subsurface structures.

Exploratory Drilling

The data collected from the geologic and geophysical surveys are used to formulate probable definitions and realizations of the geologic structure that may contain oil and/or gas. However, we still have to determine whether petroleum exists in these geologic traps, and if it does exist, would it be available in such a quantity that makes the development of the oil/gas field economical? The only way to provide a definite answers is to drill and test exploratory well(s).

The exploratory well, known as the wildcat well, is drilled in a location determined by the geologists and geophysicists. The well is drilled with insufficient data available about the nature of the various rock layers that will be drilled or the fluids and pressures that may exist in the various formations. Therefore, the well completion and the drilling program are usually overdesigned to assure safety of the operation. This first well, therefore, does not represent the optimum design and would probably cost much more than the rest of the wells that will be drilled in the field.

As this exploratory well is drilled, samples of the rock cuttings are collected and examined for their composition and fluid content. The data are used to identify the type of formation versus depth and to check on the presence of hydrocarbon materials within the rock. Cores of the formations are also obtained, preserved, and sent to specialized laboratories for analysis.

Whenever a petroleum-bearing formation is drilled, the well is tested while placed on controlled production. After the well has been drilled, and sometimes at various intervals during drilling, various logs are taken. There are several logging tools, or techniques, (electric logs, radioactivity logs, and acoustic logs) that are used to gather information about the drilled formations. These tools are lowered into the well on a wireline (electric cable) and, as they are lowered, the measured signals are transmitted to the surface and recorded on computers. The signals collected are interpreted and produced in the form of rock and fluid properties versus depth.

The exploratory well will provide important data on rock and fluid properties, type and saturation of fluids, initial reservoir pressure, reservoir productivity, and so forth. These are essential and important data and information, which are needed for the development of the field. In most situations, however, the data provided by the exploratory well will not be sufficient. Additional wells may need to be drilled to provide a better definition of the size and characteristics of the new reservoir. Of course, not every exploratory well will result in a discovery. Exploratory wells may result in hitting dry holes or they may prove the reservoir to be a uneconomical devel

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