Details of Petroleum Industry E & P sector activities
Petroleum exploration Methods, Geologic and Geo-chemical methods, Geophysical and seismic methods
Mapping
Drilling techniques.
Types of drilling.
Testing for oil.
Types of well tests.Well logging.
Other well surveys.
Well Completion.
Types of well completion.Well Casing and Tubings.
Well heads and Christmas Trees.
Well Production.
A. Petroleum exploration Methods are:
A. Petroleum exploration Methods are:
- Remote sensing and air-photo interpretation
- Geological Mapping (regional and large-scale)
- Geochemical
- Geophysical methods (Gravity, magnetic and seismic)
Applications of remote sensing in oil exploration:- In petroleum exploration Remote Sensing studies used to demarcate basin boundaries.
- To identify large, small and medium sized surface structural features such as folds and faults.
- To understand physiography (drainage pattern, altitude) of the area.
- To know the lithology, weathering and erosional characteristics (whether the rock is resistant or recessive),
- To locate the lineaments of the area.
- To reduce the cost/ risk
Geological exploration methods
The methods and procedures followed in geologic surveying depend upon whether the survey is reconnaissance or detailed (geological, topography and structure mapping).
Reconnaissance surveying: is for the purpose of determining the oil prospects of a relatively large area in a limited space and time. A preliminary survey, usually executed rapidly and at relatively low cost, prior to mapping in detail and with greater accuracy.
Detailed geological survey: Based on these available maps, the geologist must make his own map contains all the geologic and economic data that were obtained. In the search for stratigraphic traps, the geologist must identify the environment of deposition, possible reservoir rocks, but of possible source and seal rocks as well. He also determines the source of clastic sediment and the direction of transport. The field party should also collect stratigraphic data, as well as the geologic and structural maps.
Topographic maps: Topographic maps are maps which show the topography, or shape, of the surface within an area, usually by means of contour lines.
The methods and procedures followed in geologic surveying depend upon whether the survey is reconnaissance or detailed (geological, topography and structure mapping).
Reconnaissance surveying: is for the purpose of determining the oil prospects of a relatively large area in a limited space and time. A preliminary survey, usually executed rapidly and at relatively low cost, prior to mapping in detail and with greater accuracy.
Detailed geological survey: Based on these available maps, the geologist must make his own map contains all the geologic and economic data that were obtained. In the search for stratigraphic traps, the geologist must identify the environment of deposition, possible reservoir rocks, but of possible source and seal rocks as well. He also determines the source of clastic sediment and the direction of transport. The field party should also collect stratigraphic data, as well as the geologic and structural maps.
Topographic maps: Topographic maps are maps which show the topography, or shape, of the surface within an area, usually by means of contour lines.
- A contour line is a line of equal elevation.
- The vertical distance between contour lines is called the contour interval.
- Steep areas will have contour lines close together, and gentle sloped areas will have contour lines far apart.
- Where contour line crosses over a stream or gully on a topographic map, it forms a “V-shape”.
- The V shape will always point upstream.
- A contour line which forms a circle indicates the presence of a peak.
- In addition to their value as base maps for geological study, topographic maps may also yield structural information of great value. Based on topographic maps, anticlines can be easily recognized.
Structural contour map:- Structure contours are lines of equal elevation, just like topographic contours
- These maps are used to show the elevation of the top of a subsurface sedimentary rock layers (surface of a geologic structure like a dome, a fault, anticline).
- The contours are usually in m/ft below sea level, as most rocks located below sea level.
- An important structural map would one contoured on the top of a potential reservoir rock.
Geochemical exploration method.
Third type of method for exploration is the Geochemical surveys. These surveys though have limited indirect application but companies are engaging crews to carry out surveys.
Geochemical methods of prospecting are classified as direct or indirect.
The indirect methods are based on the detection of any chemical, physical, or microbiological changes in the soils, waters, or rocks associated with the oil and gas deposits.The outstanding direct indication of the presence of oil or gas is a seep at the surface.
Oil Seep.
A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the earth's atmosphere and surface, normally under low pressure or flow.
Seeps generally occur above either terrestrial or offshore petroleum accumulation structures.
Gas seeps may be detected by:
Third type of method for exploration is the Geochemical surveys. These surveys though have limited indirect application but companies are engaging crews to carry out surveys.
Geochemical methods of prospecting are classified as direct or indirect.
The indirect methods are based on the detection of any chemical, physical, or microbiological changes in the soils, waters, or rocks associated with the oil and gas deposits.The outstanding direct indication of the presence of oil or gas is a seep at the surface.
Oil Seep.
A petroleum seep is a place where natural liquid or gaseous hydrocarbons escape to the earth's atmosphere and surface, normally under low pressure or flow.
Seeps generally occur above either terrestrial or offshore petroleum accumulation structures.
Gas seeps may be detected by:
- Odor, due to the presence of sulfur compounds;
- Yellow colors in the rock surrounding the opening, caused by sublimation;
- A whistling noise when the gas emerges under pressure opening;
- “Eternal fire” when the gas has become ignited by natural or artificial;
Geophysical exploration Methods
- Gravity and Magnetic surveys to know the basement rocks and also to know the thickness of the sedimentary cover rocks.
- Seismic surveying: The most common geophysical technique for obtaining the detailed geologic structural information needed to pick well locations is, however, the seismic survey.
B. Well Drilling.
After identification of a promising geological structure by sophisticated geological and geophysical mapping that has been done and acquired the petroleum rights in exploration stage, it is time to go ahead and drill to find out if there is any oil or gas present underground.
Definition:
Definition:
Drilling is a cutting process that uses a drill bit to cut or enlarge a hole in solid materials.
The drill bit is a multipoint, end cutting tool. It cuts by applying pressure and rotation to the workpiece, which forms chips at the cutting edge.
The drilling process is fairly similar whether the well is an exploration well or development well. The main difference is that the oil and gas company will usually take more measurements and try to drill more zones in an exploration well than in a development well.
Drilling rig
Wells are drilled using a drilling rig. Drilling rigs tend to be mobile units that are owned by separate contractor and can be used in a variety of environments:
The drill bit is a multipoint, end cutting tool. It cuts by applying pressure and rotation to the workpiece, which forms chips at the cutting edge.
The drilling process is fairly similar whether the well is an exploration well or development well. The main difference is that the oil and gas company will usually take more measurements and try to drill more zones in an exploration well than in a development well.
Drilling rig
Wells are drilled using a drilling rig. Drilling rigs tend to be mobile units that are owned by separate contractor and can be used in a variety of environments:
- Land (Rig)
- Transition zones (barges/submersible rigs),
- Shallow water depths up to 150 meter (jackup rigs) and
- Deep water (semi-submersible rigs and drill ships).
In many wells a single method is not employed throughout the entire work, and in some wells modifications of several methods are successively used. The terminology employed by well drillers throughout the country is fairly uniform. One of the major terms that may be mentioned is the word " rig."
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