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Direct Hydrocarbon Indicator
In reflection seismology, a hydrocarbon indicator (HCI) or direct hydrocarbon indicator (DHI) is an anomalous seismic attribute value or pattern that could be explained by the presence of hydrocarbons in an oil or gas reservoir. DHIs are particularly useful in hydrocarbon exploration for reducing the geological risk of exploration wells. Broadly, geophysicists recognize several types of DHI: * Bright spots: localized amplitudes of greater magnitude than background amplitude values. Equipment prior to the 1970s had the bright spots obscured due to the automatic gain control. * Flat spots: nearly horizontal reflectors that cross existing stratigraphy, possibly indicating a hydrocarbon fluid level within an oil or gas reservoir. * Dim spots: low amplitude anomalies. * Polarity reversals can occur where the capping rock has a slightly lower seismic velocity than the reservoir and the reflection has its sign reversed. Some geoscientists regard amplitude versus offset In geoph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flat Spot In Seismic
Flat or flats may refer to: Architecture * Apartment, known as a flat in the United Kingdom, Ireland, and other Commonwealth countries Arts and entertainment * Flat (music), a symbol () which denotes a lower pitch * Flat (soldier), a two-dimensional toy soldier made of tin or plastic * Flat (theatre), a flat piece of theatrical scenery * Flat, a leading type of wordplay, as identified by the National Puzzlers' League * ''Flat!'' (2010), an Indian film * Flats (band), an English band * Flats (comics), the first stage in the comic coloring process Footwear * Flats, footwear which is not high-heeled * Ballet flats, derived from ballet shoes, for casual wear as well as dancing * Ballet shoes (also known as ballet slippers), often referred to as "flats" or "flat shoes" * Racing flats, lightweight shoes used primarily for running a race Geography Landforms * Flat (landform), a relatively level area within a region of greater relief * Mudflat, intertidal wetland with a substrate of f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection Seismology
Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflection (physics), reflected seismic waves. The method requires a controlled seismic source of energy, such as dynamite or Tovex blast, a specialized Seismic source#Air gun, air gun or a seismic vibrator. Reflection seismology is similar to sonar and acoustic location, echolocation. History Reflections and refractions of seismic waves at geologic Interface (matter), interfaces within the Earth were first observed on recordings of earthquake-generated seismic waves. The basic model of the Earth's deep interior is based on observations of earthquake-generated seismic waves transmitted through the Earth's interior (e.g., Mohorovičić, 1910). The use of human-generated seismic waves to map in detail the geology of the upper few kilometers of the Earth's crust followed shortly thereafter and has deve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seismic Attribute
In reflection seismology, a seismic attribute is a quantity extracted or derived from seismic data that can be analysed in order to enhance information that might be more subtle in a traditional seismic image, leading to a better geological or geophysical interpretation of the data. Examples of seismic attributes can include measured time, amplitude, frequency and attenuation, in addition to combinations of these. Most seismic attributes are post-stack, but those that use CMP gathers, such as amplitude versus offset (AVO), must be analysed pre-stack.Young, R. & LoPiccolo, R. 2005. AVO analysis demystified. E&P. http://www.e-seis.com/white_papers/AVO%20Analysis%20Demystified.pdf They can be measured along a single seismic trace or across multiple traces within a defined window. The first attributes developed were related to the 1D complex seismic trace and included: envelope amplitude, instantaneous phase, instantaneous frequency, and apparent polarity. Acoustic impedance o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrocarbons
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may be similar to that of gasoline or lighter fluid. They occur in a diverse range of molecular structures and phases: they can be gases (such as methane and propane), liquids (such as hexane and benzene), low melting solids (such as paraffin wax and naphthalene) or polymers (such as polyethylene and polystyrene). In the fossil fuel industries, ''hydrocarbon'' refers to naturally occurring petroleum, natural gas and coal, or their hydrocarbon derivatives and purified forms. Combustion of hydrocarbons is the main source of the world's energy. Petroleum is the dominant raw-material source for organic commodity chemicals such as solvents and polymers. Most anthropogenic (human-generated) emissions of greenhouse gases are either carbon dioxide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petroleum Reservoir
A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence of high heat and pressure in the Earth's crust. Reservoirs are broadly classified as ''conventional'' and '' unconventional'' reservoirs. In conventional reservoirs, the naturally occurring hydrocarbons, such as crude oil (petroleum) or natural gas, are trapped by overlying rock formations with lower permeability, while in unconventional reservoirs the rocks have high porosity and low permeability, which keeps the hydrocarbons trapped in place, therefore not requiring a cap rock. Reservoirs are found using hydrocarbon exploration methods. Oil field An oil field is an area of accumulated liquid petroleum underground in multiple (potentially linked) reservoirs, trapped as it rises to impermeable rock formations. In industrial te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrocarbon Exploration
Hydrocarbon exploration (or oil and gas exploration) is the search by petroleum geologists and geophysicists for hydrocarbon deposits, particularly petroleum and natural gas, in the Earth's crust using petroleum geology. Exploration methods Visible surface 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 sophisticated technology to detect and determine the extent of these deposits using exploration geophysics. Areas thought to contain hydrocarbons are initially subjected to a gravity survey, magnetic survey, passive seismic or regional seismic reflection surveys to detect large-scale features of the sub-surface 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 sound waves to travel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oil Well
An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may be termed a gas well. Wells are created by drilling down into an oil or gas reserve and if necessary equipped with extraction devices such as pumpjacks. Creating the wells can be an expensive process, costing at least hundreds of thousands of dollars, and costing much more when in difficult-to-access locations, e.g., offshore. The process of modern drilling for wells first started in the 19th century but was made more efficient with advances to oil drilling rigs and technology during the 20th century. Wells are frequently sold or exchanged between different oil and gas companies as an asset – in large part because during falls in the price of oil and gas, a well may be unproductive, but if prices rise, even low-production wells may ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bright Spot
In reflection seismology, a bright spot is a local high amplitude seismic attribute anomaly that can indicate the presence of hydrocarbons and is therefore known as a direct hydrocarbon indicator. It is used by geophysicists in hydrocarbon exploration. History Bright spots were not commonly identified until the early 1970s because of the extensive and industry-wide use of automatic gain control, which obscured the amplitude effects of hydrocarbon accumulations. Theory A bright spot primarily results from the increase in acoustic impedance contrast when a hydrocarbon (with a lower acoustic impedance) replaces the brine-saturated zone (with a higher acoustic impedance) that underlies a shale (with a higher acoustic impedance still), increasing the reflection coefficient. The effect decreases with depth because compaction for sands and shales occurs at different rates and the acoustic impedance relationship stated above will not hold after a certain depth/age. Below this depth, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Automatic Gain Control
Automatic gain control (AGC) is a closed-loop feedback regulating circuit in an amplifier or chain of amplifiers, the purpose of which is to maintain a suitable signal amplitude at its output, despite variation of the signal amplitude at the input. The average or peak output signal level is used to dynamically adjust the gain of the amplifiers, enabling the circuit to work satisfactorily with a greater range of input signal levels. It is used in most radio receivers to equalize the average volume ( loudness) of different radio stations due to differences in received signal strength, as well as variations in a single station's radio signal due to fading. Without AGC the sound emitted from an AM radio receiver would vary to an extreme extent from a weak to a strong signal; the AGC effectively reduces the volume if the signal is strong and raises it when it is weaker. In a typical receiver the AGC feedback control signal is usually taken from the detector stage and applied t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flat Spot (reflection Seismology)
In reflection seismology, a flat spot is a seismic attribute anomaly that appears as a horizontal reflector cutting across the stratigraphy elsewhere present on the seismic image. Its appearance can indicate the presence of hydrocarbons. Therefore, it is known as a direct hydrocarbon indicator and is used by geophysicists in hydrocarbon exploration. Theory A flat spot can result from the increase in acoustic impedance when a gas-filled porous rock (with a lower acoustic impedance) overlies a liquid-filled porous rock (with a higher acoustic impedance). It may stand out on a seismic image because it is flat and will contrast with surrounding dipping reflections. Caution There are a number of other possible reasons for there being a flat spot on a seismic image. It could be representative of a mineralogical change in the subsurface or an unresolved shallower multiple. Additionally, the interpretation of a flat spot should be attempted after depth conversion to confirm that the a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratigraphy
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostratigraphy (lithologic stratigraphy), biostratigraphy (biologic stratigraphy), and chronostratigraphy (stratigraphy by age). Historical development Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. The first practical large-scale application of stratigraphy was by William Smith in the 1790s and early 19th century. Known as the "Father of English geology", Smith recognized the significance of strata or rock layering and the importance of fossil markers for correlating strata; he created the first geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dim Spot
In reflection seismology, a dim spot is a local low-amplitude seismic attribute anomaly that can indicate the presence of hydrocarbons and is therefore known as a direct hydrocarbon indicator. It primarily results from the decrease in acoustic impedance contrast when a hydrocarbon (with a low acoustic impedance) replaces the brine-saturated zone (with a high acoustic impedance) that underlies a shale (with the lowest acoustic impedance of the three), decreasing the reflection coefficient. Occurrence For a dim spot to occur, the shale has to have a lower acoustic impedance than both the water sand and the oil/gas sand, which is the opposite situation required for a bright spot In reflection seismology, a bright spot is a local high amplitude seismic attribute anomaly that can indicate the presence of hydrocarbons and is therefore known as a direct hydrocarbon indicator. It is used by geophysicists in hydrocarbon explor ... to occur. This is possible because compaction causes the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
