Upstream
The upstream sector includes searching for potential underground or underwater crude oil and natural gas fields, drilling exploratory wells, and subsequently operating the wells that recover and bring the crude oil and/or raw natural gas to the surface.
The upstream segment of oil and gas is also known as exploration and production (E&P)
· LICENSING: Obtaining a lease and permission from the owner of the territory
· EXPLORATION: Activities to search for oil and gas deposits on the certain location beneath the earth surface
· APPRAISAL: Activities to define the oil and gas volume and characteristic more precisely after discovery
· DEVELOPMENT: Activities to build the subsurface and surface facilities to produce oil&gas safely and efficiently. Development can take from a few weeks to many years.
· PRODUCTION: Activities to extract hydrocarbons to the surface and process them. Bringing hydrocarbons to the surface. Maximizing the recovery of the hydrocarbons
· ABANDONMENT: To prepare a well to be closed permanently, usually after either logs determine there is insufficient hydrocarbon potential to complete the well, or after production operations have drained the reservoir. Definition from schlumberger oilfield glossary.
Production is the stage which need to be shown more detailed. It will be the next topic, I suppose
In few words about unconventional methods of oil and gas extraction.
Midstream
As its name implies, the midstream oil and gas segment encompasses facilities and processes that sit between the upstream and downstream oil and gas segments.
Activities can include processing, storage and transportation of crude oil and natural gas.
In most cases, oil and gas reserves are not located in the same geographic location as refining assets and major consumption regions
Processing oil and gas liquids into marketable products is the beginning of the midstream segment of the business. These products then continue into the refining processing portion of the downstream segment.
Field processing is the first phase of oil and gas processing starting in the onshore or offshore oil or gas production field.
Here, surface facilities are designed and installed that:
· Measure the production rate of the oil, gas, and water that is produced from the reservoir
· Separate the oil, gas, and water from one another
· Remove impurities to prepare the crude or gas for sale or the next process
· Temporarily store the crude or gas until it is ready to be moved to the next process
Transportation is a big part of midstream activities and can include using pipelines, trucking fleets, tanker ships, and railroads.
Downstream
The downstream sector is the refining of petroleum crude oil and the processing and purifying of raw natural gas, as well as the marketing and distribution of products derived from crude oil and natural gas.
Refining & purifying
· refineries convert crude oil into the variety of products (gasoline, diesel, asphalt, jet fuel, plastics, lubricants and etc.)
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Retail
· provision thousands of products to the end-user customers around the globe
This is the approximate scheme of the interaction of these sectors.
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Exploration of oil and gas.
Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum geologists and geophysicists for deposits of hydrocarbons, particularly petroleum and natural gas.
Hydrocarbons - organic compounds consisting entirely of hydrogen and carbon. OIl and gas are made of a mixture of different hydrocarbons.
Crude oil is oil in its natural state before it has been processed or refined.
Natural gas (also called fossil gas) is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxide, nitrogen, hydrogen sulfide, or helium.
The figure shows examples of compounds in crude oil and natural gas.
The Petroleum System consists of a mature source rock, migration pathway,reservoir rock, trap and seal.
Read more at https://www.geologyin.com/2014/08/petroleum-system.html#XkWWwgvGxfu1Eg0D.99
Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum geologists and geophysicists for deposits of hydrocarbons, particularly petroleum and natural gas.
The main question is “How to find oil and gas”?
Many years ago, geologists interpreted surface features, surface rock and, perhaps, some small core samples obtained by shallow drilling. But modern oil geologists examine surface rocks and terrain, with the additional help of satellite images. These images providing by satellites can measure subtle changes or anomaly in the Earth's gravity and magnetic fields, caused by sub surface variations in rock type and structure.
In order to find oil and gas, geologists and geophysicists work closely together using a variety of methods.
Areas thought to contain hydrocarbons are initially subjected to a gravity or magnetic survey to detect large scale features of the subsurface geology. Features of interest (a.k.a. leads) are subjected to more detailed seismic surveys. Finally, when a prospect has been identified and evaluated and exploration well is drilled in an attempt to conclusively determine the presence or absence of oil and gas. A prospect is a viable target evidenced by geological and geophysical indications that is recommended for drilling an exploration well.
Exploration methods
Goal of exploration is to identify and locate a prospect, to quantify the volume of hydrocarbon which might be contained in the potential reservoirs and to evaluate the risk inherent the project itself.
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Geophysical methods
Geophysical methods allow to study the physical properties of the subsurface rocks and they can be used in different phases of the exploration in order to collect different types of information. The objects of geophysical survay are to locate subsurface geological structures or bodies and where possible to measure their dimensions and relevant physical properties.
A geophysical survey consists of a set of mesurements, usually collected to a systematic pattern over the Earth`s surface by land, sea or air, or vertically in a borehole.
Gravity method
The gravity method is based on the measurements of the variations in the pull of gravity from the rocks in the upper layers of the earth`s surface.
Denser rocks have greater gravitational attraction than less dense rocks. For example,a structural uplift of denser will appear as an anomaly on the gravity map.
Gravity surveys for hydrocarbons are caried out on land, in the air on helicopters, and at sea on ships.
This for example, is a satellite derived gravity anomaly map. The bright red to purple regions reflect sub surface features that in some instances might trap oil or gas.
Magnetic method
The magnetic method is the oldest geophysical method, and is based on the measurement of variations in the magnetic field due to changes of structure or magnetic susceptibility of the rocks.
Today magnetic surveys for hydrocarbon exploration are usually carried out from the air or from a ship.
The gravitational fields of geologic bodies do not depend on the earth`s gravitational field, whereas magnetic bodies frequently ower their magnetization to the magnetic field of the earth. For this reason, magnetic anomalies are often subject to change with latitude.
The magnetic anomalies of geologic bodies are dependent on their magnetic "susceptibility" and "remanent magnetism".
Rocks and formations fall into two natural groups:
· Igneous rocks and iron ores which are strongly magnetic
· sedimentary rocks, which are generally weak in magnetization
Sedimentary rocks generally have a smaller susceptibility than ineous or metamorphic rocks, so an interpretation of the recorded anomalies can yield the maximum depth value for a sedimentary basin.
Seismology
Drilling is expensive. So oil companies plan carefully before they start drilling. Geophysicists conduct more detailed mapping over the lead using energy or seismic waves. Most petroleum exploration is done by the reflection seismic method.
This is done in marine settings with a survey ship equipped with energy sources, known as guns, that repeatedly fire pressure waves into the water column. Over land, the mapping is done with trucks specially equipped with energy sources on their undersides in the form of plates that vibrate the ground beneath the trucks. In both cases the energy waves produced by the source travel down into the sub surface reflecting off interfaces where rock type properties change. These reflections are then recorded by rays of pressure sensors or geoforms that extend away from the seismic source.
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Reflection seismology or seismic is used to map the subsurface structure of rock formations. This technology is used by geologists and geophysicists who interpret the data to map structural traps that could potentially contain hydrocarbons.
The images produced by seismic reflection mapping differ from what the rock type actually looks like. The seismic reflection profile of the strata looks like this.
Powered by advanced supercomputer power, rapid data loading, high-speed networking and high-resolution graphics, visualization centers provide the ability to display and manipulate complex volumes of 3D data resulting in better interpretation of more data in less time.
Geological mapping.
While the geologist skilled in interpreting seismic data could already begin to develop a model of where the sands are, their model will be much more accurate if there is an existing well that the seismic profile crosses. I`m talking about well logging which mean that one or more geophysical sensors lower down and then raised back up the drill hole, recording the surrounding rock types. And in some instances there might even be core samples of the actual rock. Note, though, that both the well logs and any core samples are for a small lateral area, while the seismic profile can extend for tens of kilometers.
What the geologist is after is understanding where potential reservoirs for oil and gas might be. Given this collection of information, the geologist can develop a detailed model of the subsurface feature structure and rock composition, and make an educated guess as to the location of potential oil and gas reservoirs.
Geologists task is to find the right conditions for an oil trap – the right source rock, reservoir rock and etc.
Geological mapping is basically a technique which allows a graphical presentation of geological observations and interpretations. Geological prospecting make use of geological disciplines such as petrography, stratigraphy, sedimentology, structural geology, geochemistry
In fact, most promising areas are already mapped, but companies are re-mapping. This work is assigned to geologists, whether employed directly by an large companies or under a contract from a private firms.
Geochemical methods
Geochemical methods used in exploring for oil and natural gas are based on the premise that hydrocarbons migrate upward from subsurface petroleum accumulations and produce anomalous patterns near the surface.
Geochemical method is still in an experimental stage and requires extremely precise analysis technique.
Geochemical exploration techniques are both direct or indirect.
· Direct techniques require analysis of microquantities of hydrocarbons that occur in the free state in the soil interstices or that are adsorbed on the fine-grained portions of the soil.
· Indirect geochemical methods are based on the detection, in near-surface soils or in vegetation, of inorganic alteration products that result from upward migration of hydrocarbons.
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| Questions | Level | Answer |
| Exploration, drilling and production operations for crude oil and natural gas. | L | Upstream |
| Compounds which contain only carbon and hydrogen. Petroleum consists of them. | L | Hydrocarbons |
| Refining and marketing operations for crude oil and natural gas. | L | Downstream |
| What is the name of activity that deals with the search for hydrocarbons deposits? | L | Exploration |
| An object that has been intentionally placed into orbit | L | Satellite |
| A measurement on a globe or map of location north or south of the Equator | L | Latitude |
| What devices are used for the registration of vibrations? | M | Geophones and hydrophones |
| Type of rocks which formed through the cooling and solidification of magma or lava | M | Igneous rocks |
| A complex mixture of hydrocarbons with minor proportions of other chemicals such as compounds of sulphur, nitrogen and oxygen. | M | Crude oil |
| The force by which a planet or other body draws objects toward its center | M | Gravity |
| A change in direction of waves when they bounce off a barrier | M | Reflection |
| A porous and permeable formation containing an individual and separate natural accumulation of producible hydrocarbons | M | Reservoir |
| A record of the formations and any events that are encountered in the drilling process | H | Well logging |
| The energy sources that repeatedly fire pressure waves into the water column | H | guns |
| Name two main characteristics of rocks on which their magnetism depends | H | Magnetic susceptibility and remanent magnetism |
| A cylindrical section of a naturally occurring material | H | Core sample |
| A viable target evidenced by geological and geophysical indications that is recommended for drilling an exploration well | H | prospect |
| Name the stage which includes activities to define the oil and gas volume and characteristic more precisely after discovery | H | Appraisal |