Petroleum engineering is an engineering discipline concerned with the subsurface activities related to the production of hydrocarbons, which can be either crude oil or natural gas. These activities are deemed to fall within the upstream sector of the oil and gas industry, which are the activities of finding and producing hydrocarbons. (Refining and distribution to a market are referred to as the downstream sector.) Exploration, by earth scientists, and petroleum engineering are the oil and gas industry's two main subsurface disciplines, which focus on maximizing economic recovery of hydrocarbons from subsurface reservoirs. Petroleum geology and geophysics focus on provision of a static description of the hydrocarbon reservoir rock, while petroleum engineering focuses on estimation of the recoverable volume of this resource using a detailed understanding of the physical behavior of oil, water and gas within porous rock at very high pressure.
The combined efforts of explorationists and petroleum engineers throughout the life of a hydrocarbon accumulation determine the way in which a reservoir is developed and depleted, and usually they have the highest impact on field economics. Petroleum engineering requires a good knowledge of many other related disciplines, such as geophysics, petroleum geology, formation evaluation (well logging), drilling, economics, reservoir simulation, well engineering, artificial lift systems, and oil & gas facilities engineering.
Phase angle
In the context of vectors and phasors, the term phase angle refers to the angular component of the polar coordinate representation. The notation for a vector with magnitude (or amplitude) A and phase angle ?, is called angle notation.
Physical compression
Physical compression is the result of the subjection of a material to compressive stress, resulting in reduction of volume. The opposite of compression is rarefraction tension.
PIN diode
A PiN diode is a diode with a wide, lightly doped 'near' intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor regions. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts.
The wide intrinsic region is in contrast to an ordinary PN diode. The wide intrinsic region makes the PIN diode an inferior rectifier (the normal function of a diode), but it makes the PIN diode suitable for attenuators, fast switches, photodetectors, and high voltage power electronics applications.
Plasticity (physics)
In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of metal or plastic being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. By contrast, a permanent crease in a sheet of paper or a re-shaping of wet clay is due to a rearrangement of separate fibers or particles. In engineering, the transition from elastic behavior to plastic behavior is called yield
Poisson's ratio
Poisson's ratio (?), named after Siméon Poisson, is the ratio, when the sample is stretched, of the contraction or transverse strain (normal to the applied load), to the extension or axial strain (in the direction of the applied load).
When a sample cube of a material is stretched in one direction, it tends to contract (or occasionally, expand) in the other two directions perpendicular to the direction of stretch. Conversely, when a sample of material is compressed in one direction, it tends to expand (or rarely, contract) in the other two directions. This phenomenon is called the Poisson effect. Poisson's ratio ? (nu) is a measure of the Poisson effect.
Positive feedback
Positive feedback, sometimes referred to as "cumulative causation", is a feedback loop system in which the system responds to perturbation in the same direction as the perturbation. In contrast, a system that responds to the perturbation in the opposite direction is called a negative feedback system. These concepts were first recognized as broadly applicable by Norbert Wiener in his 1948 work on cybernetics
Potential difference
In the physics of electrical circuits, the term potential difference or p.d. is sometimes used as an old-fashioned synonym for the modern quantity known as "the voltage (difference) between two positions in an electrical circuit". Following the discovery of the electron by J.J. Thomson in 1897, and later discoveries about electron behaviour and the role of electrons in the conduction of electricity in metals, it is now known that a "voltage difference" (as measured with a voltmeter) is not the same scientific quantity as the pre-atomic-era physical quantity "electric potential difference" (discussed, for example, by Maxwell in the 1891 edition of textbook. A treatise on electricity and magnetism (Vol. 1). Oxford: Clarendon. first printed 1891, reprinted 1998. ISBN 0-19-850373-3. In the context of electrical circuits, use of the term "potential difference" as a synonym for voltage (difference) is dropping out of use. This may be partly because science has no name (other than voltage) for the potential concerned, partly because of the possibility of confusion between the terms "potential difference" and "electric potential difference", which nowadays refer to different physical things. Use of the term "potential difference" as a synonym for voltage (difference) should be regarded as obsolescent/obsolete, and it is recommended that it should not be employed.
For further information on the science involved, see the articles on Voltage and Electric potential.
It is quite common for physics undergraduates either to be taught (incorrectly) that "electric potential difference" and "voltage difference" mean the same thing, or for the issue of "what voltage really is" to be avoided (presumably, on the grounds that this is too complicated for them to understand). Some older textbooks are also incorrect or ambiguous, or do not discuss the issue. However, some advanced solid-state textbooks (e.g., Ashcroft and Merrin Solid State Physics. New York: Holt, Reinhart and Winston. 1976. - see section on Thermoelectric Power) do clearly acknowledge that in principle voltmeters do not measure electric potential difference.
Part of the problem with electricity is that real electric currents involve the flow of electrons in the opposite direction to conventional current; another part of the problem is that electrons are subject to "chemical" effects as well as "electrostatic" effects. This kind of difficulty does not arise in many other areas of physics (e.g., the theory of gravitation): in these areas, there is a unique definition of a related potential, and "potential difference" can be defined without ambiguity as the difference in the related potential.
No comments:
Post a Comment