1. Comprehension

Answer the questions:

1. What signs showed early explorers that oil might exist below underground?

2. Why does the author of the article name their search as “hit or miss” process?

3. How does the exploration for oil and gas typically begin?

4. What geologic elements are necessary to form an oil and gas field?

5. What are the physical properties and effects of subsurface rocks and minerals that can be measured at a distance?

6. What kind of information can geophysical data provide petroleum engineers with?

7. What did the pendulum method rely on?

8. What helps geophysicists locate salt domes?

9. What measures gravimeter?

10. What magnetic instruments are used to measure magnetism in rocks?

B. Vocabulary Practice

I. Give English equivalents for:

1) обнажение породы; 2) признаки на поверхности; 3) совпадение геологических компонентов; 4) вызванные движением коры Земли; 5) подземный соляной купол; 6) сбор и объяснение информации; 7) проследить, что лежит под землей; 8) обнаженные породы; 9) ограниченный доступ; 10) важная информация; 11) разработка месторождения; 12) масса породы; 13) боковой слой; 14) миграционный путь; 15) размер водоносного пласта; 16) основные параметры; 17) физическое условие; 18) сила тяготения; 19) колебания маятника; 20) магнитные весы; 21) сила упругости; 22) более точные измерения; 23) проведение магнитной съемки; 24) нефтеносная осадочная порода; 25) все магнитное поле

II. Give Russian equivalents for:

1) through the early 1990s, 2) a matter of luck, 3) oil seeps to the surface, 4) “hit or miss”, 5) geologically likely, 6) in predictable places, 7) subterranean features, 8) a careful blend, 9) structural geology, 10) subsidiary fields, 11) planning of drilling activities, 12) the geometry of the rock bodies, 13) boundary of hydrocarbon-bearing region, 14) reservoir envelope, 15) petroleum kitchen, 16) surrounding rocks, 17) disruptions of the reservoir, 18) orientation of fractures, 19) the reduced benefits, 20) basic control on data quality, 21) electrical resistance, 22) gravitational pull, 23) highly magnetized, 24) slight difference in magnetism, 25) to measure the magnitude

III. Fill in the appropriate word(s) from the list below into the extracts and translate them into Russian:

to map, gravity, exploration, detect, alluvial, channels, delineate, techniques, polarization, in association, structural, indirect, buried, faults, applications, depth, alteration

Geophysical … are routinely used in an … program to help the project geologist … areas favorable for the type of target being pursued. Geophysical techniques can look beneath … cover. They can be used to directly … some minerals, indirectly detect others, and … geological and … features in exploration programs. Direct detection includes using induced … (IP) to find disseminated sulfides, magnetics to delineate magnetite hosting rocks, and … and electrical techniques for massive sulfides.

Examples of … detection of targets include using IP to detect pyrite in association with sphalerite and gold (both non-responders to IP geophysical techniques), and copper and molybdenum in porphyry systems. Magnetics are routinely used to search for hydrothermal alteration … with porphyry systems, and can be used to map … stream … (magnetite sands) that might host placer gold.

Geologic mapping … include using gravity and seismics to map … and thickness of alluvial fill; magnetics and seismics for mapping structure, and possible signatures associated with different rock types; radiometrics for mapping … and geology; and electrical techniques for mapping … to bedrock, structure, and different rock units.

b) extent, gas, sophisticated, hydrocarbons, seismic, well, sound, oil, surface

Visible … features such as oil seeps, natural gas seeps, pockmarks (underwater craters caused by escaping gas) provide basic evidence of hydrocarbon generation (be it shallow or deep in the Earth). However, most exploration depends on highly … technology to detect and determine the … of these deposits using exploration geophysics. Areas thought to contain … are initially subjected to a gravity survey, magnetic survey and regional … reflection surveys to detect large scale features of the subsurface geology. Features of interest (known as leads) are subjected to more detailed seismic surveys which work on the principle of the time it takes for reflected … waves to travel through matter (rock) of varying densities and using the process of depth conversion to create a profile of the substructure. Finally, when a prospect has been identified and evaluated and passes the oil company’s selection criteria, an exploration … is drilled in an attempt to conclusively determine the presence or absence of … or ….

c) trapped, flow, source, overpressure, impermeable, upwards, significant, drill, porous, dense, trap

A prospect is a potential trap which geologists believe may contain hydrocarbons. A … amount of geological, structural and seismic investigation must first be completed to redefine the potential hydrocarbon … location from a lead to a prospect. Five elements have to be present for a prospect to work and if any of them fail neither oil nor gas will be present.

A … rock (when organic-rich rock such as oil shale or coal is subjected to high pressure and temperature over an extended period of time, hydrocarbons form);

Migration (the hydrocarbons are expelled from source rock by three density-related mechanisms; the newly-matured hydrocarbons are less … than their precursors, which causes…; the hydrocarbons are lighter medium, and so migrate … due to buoyancy, and the fluids expand as further burial causes increased heating; most hydrocarbons migrate to the surface as oil seeps, but some will get …);

Trap (the hydrocarbons are buoyant and have to be trapped within a structural, e.g. anticline, fault block, or stratigraphic …);

Seal or cap rock (the hydrocarbon trap has to be covered by an … rock known as a seal or cap-rock in order to prevent hydrocarbons escaping to the surface);

Reservoir (the hydrocarbons are contained in a reservoir rock, which is a … sandstone or limestone; the oil collects in the pores within the rock; the reservoir must also be permeable so that the hydrocarbons will … to surface during production).

d) commonly, rapid, measurements, applied, magnetic, tremendous, directly, concentrations, deposits, anomalies, isolation, applying, sedimentary

Exploration using magnetic measurements has been done since the mid-1800’s, making it the oldest geophysical technique. Today the … method is still one of the most … used geophysical tools because of its … versatility. Magnetic … can be obtained easily and cheaply, and they can be … to both deep and shallow structures. But the petroleum industry lost interest in gravity and magnetic (or potential field) techniques during the early ‘90's due to the … advances in seismic techniques. Magnetic minerals may … indicate the presence of oil and gas …, therefore magnetic methods are applied to hydrocarbon exploration in oil-bearing … basins. The basic problem in the application of these methods is the … of weak magnetic anomalies caused by low … of the magnetic minerals. These weak … are often masked by much stronger magnetic anomalies caused by underlying magnetic rocks and/or by rocks in the sedimentary basin. The weak anomalies can efficiently isolated by … selective bandpass frequency filters.

IV. Match the following terms with their definitions and give their Russian equivalents:

exploration, aquifer, torsion balance, conductivity, pendulum, oscillation, latitude, elasticity, precursor, seep

1. An examination of an area of land in order to make a map of it.

2. Flow or leak slowly through porous material or small holes.

3. The degree to which a specified material conducts electricity, calculated as the ratio of the current density in the material to the electric field that causes the flow of current.

4. The ability of a material to return to its original shape, size, and condition after it has been stretched.

5. A body of permeable rock that can contain or transmit groundwater.

6. An instrument for measuring very weak forces by their effect on a system of fine twisted wire.

7. A weight hung from a fixed point so that it can swing freely backward and forward.

8. A repeated movement of something from side to side at a steady speed.

9. The angular distance of a place north or south of the earth’s equator.

10. A person or thing that comes before another of the same kind.

V. Explain the following terms using a specialized dictionary and glossary, give their Russian equivalents and make up your own sentences with them:

cuttings, exploratory well, geophone, gravity meter, resolution, migration route, side-burden, reservoir envelope, thermal conductivity

VI. Give English translation for:

Поиски и разведка нефти

1. Задача обнаружения новых месторождений нефти и газа на практике сводится к поискам возможных ловушек углеводородов. До сих пор нет методик, аппаратуры и механизмов, которые могли бы безошибочно обнаружить подземные площади, где имеются нефтяные или газовые месторождения. Поэтому геологи и геофизики ищут места, где имеются либо структурные, либо стратиграфические условия, благоприятные для аккумуляции углеводородов; эти участки затем опробуются на наличие нефти и газа бурением скважин.

Геологические методы включают исследования на поверхности и в глубинах земли. Поверхностные исследования используют только там, где покров почв и четвертичных (quaternary) отложений достаточно тонкий и имеются многочисленные обнажения коренных пород. Геолог измеряет мощности разрезов обнаженных пород, строит карты геологических формаций, определяет структуру залегания путем наблюдения падений и простираний пластов в тех местах, где рельеф имеет значительную амплитуду. В случае относительно ровного залегания и плоского рельефа используется метод инструментальной съемки с помощью мензулы (planetable) и алидады (index bar). Могут быть использованы аэрофотоснимки. Многие нефтяные месторождения были открыты при разбуривании антиклиналей, обнаруженных в результате поверхностной геологической съемки. В случае перекрытия коренных пород мощным чехлом четвертичных почв, аллювия ледниковых отложений и др. проводится структурное бурение.

При поиске нефти на значительных глубинах широко используются геофизические методы – гравиметрический, магнитометрический и сейсмический; последний наиболее важен и результативен. Собранная и обобщенная информация, полученная разными методами, используется для выявления недоступных ранее структурных и стратиграфических ловушек.

Для определения следов углеводородов проводятся геохимические анализы пород и вод. По содержаниям органического вещества и углеводородов могут быть выявлены нефтегазоматеринские отложения.

2. Гравиметры и магнитометры – портативные приборы, относительно недорогие, простые при использовании. Гравиметр применяется для измерения ускорения свободного падения в конкретной точке земной поверхности. Магнитометр предназначен для измерения напряженности магнитного поля Земли в определенной точке поверхности. Оба этих прибора достаточно малы по размерам, и их можно перевозить в кузове пикапа. Магнитометром можно пользоваться для измерения с помощью летательного аппарата (такие исследования называются аэромагнитной съемкой), а также прикрепляя его к корме судна. Гравиметр нельзя применять ни с воздуха, ни в океане в силу возникающих там вибраций.

C. Discussion

Topics:

1. Geophysical data that can provide petroleum engineers with information concerning the planning of drilling activities;

2. Gravity and magnetic methods.

Unit 2. Geophysical Exploration: Seismic, Stratigraphic and Electrical Methods

Active Vocabulary

1.	transmission	прохождение
2.	refraction	преломление
3.	reflection	отражение
4.	compactness	плотность
5.	succession	последовательность
6.	schist	кристаллический сланец
7.	thumper	ударный источник сейсмических волн
8.	correlation	сейсм. корреляция
9.	isopach	изопахита (линия равной мощности какой-либо стратиграфической единицы)
10.	pinch-out	выклинивание
11.	conductivity	удельная проводимость
12.	contour map	контурная карта
13.	cross section	геологический разрез, поперечное сечение
14.	weak sandstones	тощий песчаник
15.	radioactivity log	диаграмма радиоактивного каротажа
16.	key bed	опорный горизонт, маркирующий горизонт, шпоночная канавка
17.	interstitial water	связанная вода
18.	electrical log	диаграмма электрического каротажа
19.	elastic earth waves	акустические сейсмические волны
20.	concussive force	ударная сила
21.	high velocity bed	пласт, характеризуемый высокой скоростью
22.	seismic detector	сейсмоприемник, сейсмограф
23.	shot point	точка возбуждения, пункт взрыва
24.	sample log	данные анализа проб
25.	driller's log	буровой журнал
26.	time log	хронологический журнал
27.	miscellaneous	разные, разнообразные
28.	sequential	последовательный
29.	unconsolidated	рыхлый, неуплотненный
30.	to keep track	отслеживать
31.	to be subordinated to	подчиняться
32.	to travel	зд. перемещаться, мигрировать
33.	to aid	помогать, содействовать

A third method of exploration is the seismic method. The central physical property upon which seismic prospecting is established is the variation in speed of the transmission of elastic earth waves or sound waves through different geological structures measured by time. There are two principle seismic methods: refraction and reflection. Refraction prospecting consists of elastic earth waves, initiated by some concussive force, traveling down to a dense or high velocity bed, then being carried along that bed until they are rerefracted up to seismic detector locations on the surface some distance from the shot point. What is recorded is the time required for the sound wave to reach each detector location from the shot point. The speed of transmission of the waves through different geological structures is proportional to the density or compactness of the formation. Unconsolidated formations such as sands and shales transmit waves with a low velocity, weak sandstones and limestones with higher speeds, and massive crystalline rocks such as limestones, rock salt, schists, and various igneous rocks with very high speeds. The refraction method aided petroleum explorers in locating salt domes that transmitted elastic earth waves at high rates of speed.

The reflection method of seismic exploration is based on the echo of sound waves off layers of varying density rock, which are reflected at a high angle back to the surface. The Geophysical Research Corporation began experimenting with the seismic reflection method in 1926 and by 1929 had seismic crews employing the method commercially throughout West Texas and the Gulf Coast. In 1931 Petty Geophysical Engineering Company of San Antonio invented and implemented the reverse profile method of reflection shooting that became the standard method of shooting throughout the industry. Now most seismologists, instead of using dynamite to make shock waves, use a machine called a thumper to produce elatic shock waves.

A final method of exploration is the study of stratigraphy. Stratigraphic exploration consists of establishing correlations between wells, matching fossils, strata, rock hardness or softness, and electrical and radioactivity data to determine the origin, composition, distribution, and succession of rock strata. Sample logs, driller's logs, time logs, electrical logs, radioactivity logs, and acoustic logs help geoloists predict where oil bearing strata occur.

Sample logs, compiled from well cuttings and cores, are used to identify key beds and lithologic sequences. A core is a narrow column of rock that is taken from the top to the bottom of a well and shows rock in sequential order as it appears in the ground. Core samples also provide information on porosity, permeability, and saturation of rock in the well. Cuttings are not a continuous record like core samples, but provide a means for identifying sections within larger thick layers through fossil and mineral deposits.

The driller's log provides basic information to the stratigrapher concerning depth, type of rock, density, fluids, and other miscellaneous data. The driller's log keeps track of the time required to drill through various strata and the recognition of key beds he drills through. This data is correlated with other information to enhane te chance of finding oil.

Early electrical methods of exploration in the 1920s tested electrical resistivity and electro-magnetic potential but proved to be more successful at locating metallic ores than oil and gas. Oil and gas have conductivity properties that differ from water, which conducts electricity more readily. Occurrences of oil a nd gas can be located by this difference in resistance. The most useful application of electric testing has been in the development and impact of well logging. Schlumberger electric well logging is now standard in the industry. These logs record the conductivity of interstitial water in rock, the movement of drilling mud into porous strata, and the movement of formation water into the well bore.

Fig 1. Geosoft GMSYS-3D model of a salt body embedded in a 3D density volume

R adioactivity logs, which record both gamma-ray and neutron values, have been in use productively since 1941. Because radioactivity can be measured with precision it can be used to identify different layers within beds. Radioactivity logs give an indication of the type of rocks and fluids contained in those rocks. Acoustic or sonic logs are used to measure the porosity of a formation. This tool measures the speed at which an acoustic or sonic impulse is carried through a specified length of rock. The speed of sound through the rock gives an indication of the porosity and can be helpful in locating reservoirs. Maps, including contour, isopach, cross sections, and three dimensional computer images, also aid the petroleum explorer in locating oil and gas. Contour maps give details of subsurface structural features enabling geologists to visualize three dimensional structures. Contour maps include information about porosity, permeability, and structural arrangements such as faults, pinch-outs, salt domes, and old shorelines. Isopach maps show variations in thickness of a given subsurface formation and are used in calculating the size of reservoirs and secondary recovery operations. A cross section map is a diagram of an imaginary vertical cut along a straight line that reveals subterranean features of a given area much like looking at a road cut. Three dimensional computer maps construct images of subterranean strata as deep as thirty miles. The best way to gain a full understanding of subsurface geology and the potential for natural gas deposits to exist in a given area is to drill an exploratory well.

Geologists also examine the drill cuttings and fluids to gain a better understanding of the geologic features of the area.

Fig 2. Geosoft GMSYS 3D model. The three flat maps along the left side of the workspace show Observed Gravity, Calculated Gravity, and the Difference. The black line marks the location of the seismic section shown in the 3D visualization on the right. The "+" symbol in the flat maps tracks the location of the 3D cursor in the 3D visualization (the long vertical line at the end of the seismic section). The other vertical plane in the 3D visualization is the sub-surface gravity response