Картография в нефтяной промышленности

to map составлять карту

cross section геологический разрез

lineation линейность

foliation слоистое строение

trend горизонтальное направление пласта

plunge откос

scale масштаб

signs and symbols обозначения и символы

gross thickness общая толщина пласта

net thickness толщина нефтяного или газового пласта

topographic map топографическая карта

geologic map геологическая карта

gentle slope / steep slope небольшой уклон / крутой уклон

strike простирание жилы или пласта

dip наклонение

pay zone промышленная зона

capture field data собирать, фиксировать данные с помощью цифровых технологий

Task 1. Read and translate the text:

Задание 1. Прочитайте и переведите текст:

Maps and cross sections

Maps and cross-sectional diagrams are used by petroleum geologists and geophysicists to illustrate the location of oil and gas reservoirs. Making and interpreting maps and cross sections is an essential part of their work. The easiest way to explain the difference is to say that a map is a view taken from above the Earth’s surface and you are looking down at it, whereas a cross section is a view taken by cutting vertically through the Earth’s surface, as if you are looking at it face-to-face. Does that make sense?

A geologic map or geological map is a special-purpose map made to show geological features. Rock units or geologic strata are shown by colour or symbols to indicate where they are exposed at the surface. Bedding planes and structural features, such as faults, folds, foliations and lineations, are displayed with strike and dip or trend and plunge symbols, which give these features three-dimensional orientations.

A cross section shows a vertical section through a volume, whereas a map projects a view taken of the surface of the geological are – a bird’s eye view. Cross sections are often used to show the different types and orientations of formations found under the surface. Here is an example of a very large cross section taken over a horizontal distance of several hundred miles.

To show a petroleum reservoir correctly, you need to have a number ofdifferent maps and cross sections to distinguish the various layers in the reservoir. The maps will show the structure of the formation, but also other important factors, such as gross and net thickness, porosity, water saturation and so on. A full set of maps and cross sections like this is normally called a reservoir description or a reservoir model.

Nowadays, petroleum geologists are increasingly using information and communications technology to manage and deliver geoscientific information, and this is driving the development of digital methods for geological data visualization, recording and interpretation in both 2D and 3D. An example of this is the British Geological Society’s SIGMA project (System for Integrated Geospatial Mapping), which is updating geological survey methods to harness these rapidly developing innovations.

Task 2. Read information about different types of maps and answer the questions:

Задание 2. Прочитайте информацию о разных видах карт и ответьте на вопросы:

A topographic map shows the elevations of an area where oil and gas may be present. The lines are contour lines showing the land elevation above sea level. This map shows a ridge with a gentle slope on the north-east flank and a steep slope on the south-west flank. You will notice that the greater the contour intervals, the gentler the slope. The scale on this map can be 1 centimetre to 500 metres.

A geologic map shows the orientation of the rock layers by defining strike and dip. Strike is the horizontal orientation of the formation, dip is the downward angle perpendicular to the strike, including the angle of the plane.

A subsurface map called an isopach map shows the thickness of the rock layers. For example, when an oil or gas field has been drilled, an isopach map can be used to describe the pay zone. This could be a gross pay map, which contours the thickness of the whole reservoir, including non-productive water-bearing or tight zones. Or it could be a net pay map, showing only the productive thickness.

What are three different types of maps?

What does each map show?

Task 3. Give Russian equivalents to the following expressions:

Задание 3. Дайте русские эквиваленты следующим выражениям:

topographic map, geologic map, isopach map, contour lines, a steep slope, a gentle slope, the scale of a map, strike, dip, angle of the plane, sea level, pay zone.

Task 4. Complete the questions in the columns below. You can ask direct questions such as 'How is a cross section made?' or indirect questions such as 'Can you explain how a cross section is made?' Then answer these questions from the information from the previous exercise, or from your own knowledge:

Задание 4. Заполните таблицу. Обратите внимание, что вопросы могут быть прямыми, например, 'How is a cross section made?', или косвенными, например, 'Can you explain how a cross section is made?' Затем дайте ответы на эти вопросы, используя информацию из предыдущего упражнения или собственные знания:

Task 5. Speak on petroleum mapping.

Задание 5. Расскажите о картографии в нефтяной промышленности.

Практическое занятие 21

Seismic Surveying

Сейсмические исследования

seismic acquisitionсбор.................. сейсмических данных

sound wave..................................... звуковая волна

sound source................................... источник звука

reflect.............................................. отражать

receiver............................................ приемник

geophone......................................... сейсмограф

velocity........................................... скорость

amplitude........................................ амплитуда

offset............................................... расстояние между источником звука и

........................................................ приемником

random noise............................. .... случайный шум, помехи

coherent signal................................ когерентный сигнал

vibrator truck.................................. ................ вибрационная сейсмическая установка

spread............................................. расстановка сейсмографов

shot point........................................ точка возбуждения

emit................................................. издавать, испускать

sweep.............................................. продолжительный сигнал

thumper truck................................. сейсмический ударный источник

tow.................................................. тянуть

travel time....................................... скорость распространения

impedance....................................... сопротивление, импеданс

reflection coefficient........................ коэффициент отражения

Task 1. Read and translate the text:

Задание 1. Прочитайте и переведите текст:

Bright spots

In a seismic survey, sound waves from a sound source partially reflect off boundaries between different underground strata to form echoes that are detected at the surface by receivers called geophones. Those echoes provide information about the subsurface geology, including the locations of potential oil and gas traps.

Oil and gas occupying rock pores in an oilfield reservoir affect the physical properties of the rock in a way that could alter those sound echoes and thus provide direct evidence of subsurface oil and gas pools. For example, a quite modest amount of natural gas inside a rock will significantly reduce the velocity of sound passing through the rock. That velocity reduction can increase the acoustic contrast between the gas-bearing rock and the adjacent rock formations. And the increased contrast can, in turn, cause an abnormally high amplitude seismic reflection, giving rise to what geophysicists refer to as a ‘bright spot’ in a seismic section.

However, there can be more than one possible explanation for a seismic phenomenon such as a bright spot, and so this type of indicator suggests, but does not prove, the existence of subsurface hydrocarbons. And this is especially true when trying to use seismic data to detect oil. Oil has a much lower acoustic contrast with rock than gas. And, to make things even more tricky, there’s quite a low acoustic contrast between oil and water, thus making these two liquids difficult to distinguish.

Task 2. Answer the questions to the text:

Задание 2. Ответьте на вопросы к тексту:

1. How is natural gas detected in a seismic survey?

2. Why is it more difficult to detect oil?

Task 3. Read the extracts and answer the questions:

Задание 3. Прочитайте и ответьте на вопросы:

1. How does AVO improve the performance of a survey?

2. What is the difference between 3D and 4D seismic?

Developments in seismic technology

Developments in seismic technology have enabled geophysicists to further reduce drilling risk. Here are two examples:

The first technique is known as amplitude variation with offset. AVO is a bi-product of the way in which a seismic survey involves recording underground sound reflections using sound sources and geophone sound detectors in a series of increasing offsets from a single survey point (an offset is the distance between the seismic source and the receiver). The seismic crew record the data from different offsets so that they can add the data together. This addition tends to remove random noise while enhancing coherent signals from underground sound reflections. AVO analysis is more successful in young, poorly consolidated rocks, such as those in the Gulf of Mexico, than in older, well-cemented sediments, such as those from the mid-continent region of the USA.

Another technique is known as 4D seismic. This technique involves shooting several 3D seismic surveys over the same area over a time period of perhaps several years (a 3D survey is a type of survey that results in a three-dimensional image of the subsurface geology). Changes in seismic signals from one survey to the next can provide insights into the movement of fluids, such as oil and gas within the field reservoir.

Task 4. In seismic acquisition, a source of sound energy and a receiver are required. Read the description of the use of a vibrator truck in seismic surveying and decide whether each sentence refers to the source (S) or the receiver (R):

Задание 4. Для сбора сейсмических данных необходим источник звука и приемник. Прочитайте описание работы вибрационной сейсмической установке и определите, относится ли высказывание к источнику (S) или приемнику (R):

Using a vibrator truck

- A vibrator truck acts as the source of sound energy for a land-based seismic survey.

- A group of detectors called geophones is placed in a line or other pattern.

- Several groups of receivers are often used to form a spread.

- A cable is laid between the geophones and a recording truck where the data is recorded.

- The vibrator truck is driven to the shot point, where the sound impulses will be emitted.

- The correct position for the truck is where the angle of incidence equals the angle of reflection).

- A pad or base-plate is lowered from the truck to the surface of the ground until it carries the weight of the truck.

- The hydraulic motors are then activated to enable the weight of the truck to shake the ground.

- This continues for a period of between ten and twenty seconds, and is known as a sweep.

- Both unwanted noise, such as from traffic or wind, and the wanted signal, are picked up by the geophone. The two must be distinguished in the recording truck.

- Explosives, or a thumper truck, can also be used as a seismic source on land.

- At sea, obviously, a vibrator truck cannot be used. The most common alternative is an array of air guns towed behind a seismic ship.

- The signals are received by hydrophones connected to a cable, the streamer.

Task 5. Read and translate the following passage:

Задание 5. Прочитайте и переведите следующий отрывок:

Principles of seismology

Seismology is based on the mathematical principles of acoustics. A sound wave is emitted through a rock formation.

When it reaches a particular boundary in the formation, it is reflected, and the total time it takes to reach the receiver is measured. This is called its travel time. The amplitude of the seismic echo off the top of a surface depends primarily on the contrast in acoustic impedance (sound velocity multiplied by density) between the upper and lower rock layers that form the surface. The greater the contrast, the larger the reflection. The percentage of seismic energy reflected is called the reflection coefficient. Typical sedimentary layers have a reflection coefficient of between 2 and 4%. Gas has a very slow velocity and, if the layer is overlain by a seal, the acoustic impedance contrast will produce an echo of about 16% of the seismic energy, called a bright spot. This is often an indicator of the presence of hydrocarbons. Another type of direct hydrocarbon indicator is a flat spot, which is a level, flat seismic reflector in a petroleum trap produced by rock layers that are not flat, such as an anticline.

Task 6. The following sentences contain a number of factual mistakes. Amend or rewrite the sentences in the spaces provided so that they make sense:

Задание 6. Следующие предложения содержат смысловые ошибки. Исправьте и перепишите предложения так, чтобы они имели смысл:

1) The greater the impedance of the formation, the shorter the travel time of the sound wave.

2) Acoustic impedance is calculated by dividing sound velocity by density.

3) The smaller the contrast in acoustic impedance, the greater the reflection.

4) Typical sedimentary layers normally have a very high reflection coefficient.

5) Gas increases the velocity of sound passing through it.

6) It is easier to tell the difference between oil and rock than between gas and rock.

7) A bright spot is where the contrast in impedance is very low.

8) A flat spot shows a petroleum trap in a flat layer of rock.

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