70 Petroleum Exam Questions and Answers

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Definitions asked in Petroleum Exams and Interviews:

  1. Porosity: is the percentage of volume of pores to total volume of the rock.
  2. Effective porosity: it is the inter-connected pore voids contribute to the flow of fluids or contribute to permeability in the reservoir.
  3. Primary porosity: porosity preserved from deposition through lithification.
  4. Secondary porosity: occur by alteration due to processes like dolomitization, dissolution, and fracturing.
  5. Permeability: is the ability of rock to transmit fluids.
  6. Absolute permeability: the ability of rock to transmit fluids when 69
  7. Relative permeability: ratio of effective permeability of a particular fluid at a particular saturation, to the absolute permeability of that fluid at total saturation.
  8. Sedimentary rocks: are rocks formed by sedimentation at the earth’s surface or within bodies of water.
  9. Sedimentation: is the process in which * accumulation of minerals &/or organic materials take place, or * precipitation of minerals take place.
  10. Sediment: is the particle that accumulates to form the sedimentary rock.
  • Sediment was formed by weathering and erosion at source area, then being transported to the place of deposition by water, wind, mass movement and glaciers before being deposited.
  1. Formation: is the basic unit of nomenclature in stratigraphy,
  • Is a set of rocks that are common in distinctive features of lithology and are horizontally continuous and is large enough to be mapped.
  • Can be divided into members and grouped together into groups.
  1. Sequence: a group of relatively conformable strata, that are represent a cycle of deposition, and are bounded by unconformities or correlative conformities.
  2. Unconformity: a buried surface of erosion or non-deposition.
  • Angular unconformity: A surface that separates younger strata from eroded, dipping, older strata and represents a gap in the geologic record.
  • Non conformity: sedimentary strata overlaying igneous or metamorphic rocks (in an erosion _non-intrusive _contact).
  • Dis conformity: an irregular surface of erosion between two parallel strata.
  • Para conformity: a planar surface between two parallel strata that represents a period of non-deposition but no erosion.
  1. Structure: It is a geologic feature produced by deformation of the earth’s crust, Such as fold or fault.
  2. Fault: It is a fracture or breaking in the rook in which the rock mass on one side of the fracture moves relative to the rock mass in the other side
  3. Normal fault: it is a type of fault in which the hanging wall moves down relative to the foot wall.
  4. Reverse fault: it is a type of fault in which the hanging wall moves up relative to the foot wall.
  5. Thrust: it a type of reverse fault in which the angle is less than 15 degree.
  6. Growth fault: Is a fault occur in sedimentary rocks, contemporaneously and continuously with deposition, usually the hanging wall thicker than the foot wall.
  7. Clysmic fault: It is a rift like what in the eastern part of the Gulf of Suez*/8
  8. Fold: fold occurs when one or more of originally flat surfaces, such as sedimentary strata, are bent or curved as a result of plastic deformation.
  9. Structure contour map: A type of subsurface maps, its contour lines represents the elevation of particular reservoir, geologic layer, or geologic marker, generally beneath the surface.
  10. Mud circulation: It is a process of pumping the mud down to the bit and back up it to the surface in a drilling or work over operation.
  • In mud circulation process the mud starts at the mud tanks, being pumped to the stand pipe through the pump, then to the rotary hose, swivel. To Kelly or top drive, the bit and takes its way to the surface again through annulus to the mud tanks.
  1. Mud log unite: A system that contains sophisticated computers and sensors used to operate a quick and comprehensive interpretation and evaluation of fluids, gases, and cuttings on well site.
  2. Lag time: It is the time between a chip being cut by the bit, and the time it reaches to the surface where it examined by the geologist or the mud logger.
  3. Attice oil: It is oil above the bore hole in horizontal well.
  4. Migration:
  • Primary migration: the movement of the oil from the source rock to the reservoiru rock.
  • Secondary: from the reservoir to the trap
  • Tertiary: from a trap to another, or along the reservoir.
  1. Archie Equation:

Sw = [ (a / ϒm)*(Rw / Rt) ](1/n)

  • Sw: water saturation
  • ϒ: porosity
  • Rw: formation water resistivity
  • Rt: observed bulk resistivity
  • a: a constant (often taken to be 1)
  • m: cementation factor (varies around 2)
  • n: saturation exponent (generally 2)
  1. miscellaneous reservoirs
  • It is reservoir formed from fragment igneous rocks that found mainly in GOS province in SUCO Company in Zeit Bay Field. ( fractured basement topped by basement wash )
  1. Time rock units: A stratigraphic unit based on geologic age or time of origin. Also known as chronolith; chronolithologic unit; chronostratic unit; chronostratigraphic unit; time-rock unit.
  2. Syrian arc structures in Egypt: A series of WSW-ENE trending extensional basins were inverted, creating isolated uplifted and folded areas known as ‘Syrian arc’ structures
  3. Mud cake: A caked layer of clay adhering to the walls of the borehole, formed where the water in the drilling mud filtered into a porous formation during rotary drilling.
  4. Kerogen: material neither petroleum nor coal but an intermediate bitumen material with some of the properties of both.
  5. Bitumen: Petroleum in semi-solid or solid forms.
  6. moh’s scale: The Mohs scale of mineral hardness is based on the ability of one natural sample of matter to scratch another mineral.
  7. Muting: Removing arrivals that are not primary reflections or make them zero.
  8. Transit time: the time required for a sound pulse to travel a fixed distance between a transmitter and receiver.
  9. Stacking: Stacking velocity is used to correct the arrival times of events in the traces prior to summing.
  10. Common mid-point: It is the point at the surface half way between the source and receiver, shared by numerous source receiver pairs.
  11. Pull up: A phenomenon of relative seismic velocity strata whereby, a shallow feature or layer (such as salt domes, salt layer) of high seismic velocity is surrounded by rock with lower seismic velocity caused what appears to be a structural high beneath it.
  12. Ghost multiple: A short path multiple or spurious reflection that occurs when seismic energy initially reverberates up-ward from a shallow subsurface and then is reflected downward, such as between source and receivers and see surface.
  13. Trap
  • The place where oil or gas is barred from further movement.
  1. Crest culmination
  • It is the highest point in the trap
  1. Spill point
  • It is the lowest point in the trap at which H.C. may be contained, it lies at a horizontal contour on a horizontal plane
  1. Closure
  • The vertical distance from the crest to the spill point.
  1. Bottom water
  • It is the zone immediately beneath the petroleum
  1. Edge zone
  • It is the zone of the reservoir laterally adjacent to the trap.
  1. The pay
  • It is the productive reservoir within the trap
  1. Gross pay
  • It is the vertical distance from the top of the reservoir to the oil water contact.
  1. Net pay
  • It is the cumulative vertical thickness of the reservoir from which H.C. may be produced.
  1. Fossil: a relic, remnant, or representation of an organism that existed in a past geological age, or of the activity of such an organism, occurring in the form of mineralized bones, shells, etc, as casts, impressions, and moulds, and as frozen perfectly preserved organisms.
  1. Trace fossils, also called ichnofossils are geological records of biological activity. Trace fossils may be impressions made on the substrate by an organism: for example, burrows borings footprints and feeding marks, and root cavities.
  2. Indexfossils: They Are fossils that used in defining and identifying time periods or faunal stages. They must be commonly found, widely distributed, and limited in time span.
  3. Argillaceous deposits: Containing, made of, or resembling clay; clayey.
  4. Argillaceous sandstone: sandstone containing much clay.
  5. diagenesis : The physical, chemical or biological alteration of sediments into sedimentary rock at relatively low temperatures and pressures that can result in changes to the rock’s original mineralogy and texture.
  6. Erosion: The process of denudation of rocks, including physical, chemical and biological breakdown and transportation.
  7. Interval velocity:
  8. Reflection coefficient:
  9. Snell’s low: (sin0 1/ sin0 2 ) = ( v1/ v2 )
  10. Normal move out (NMO):
  11. Seismic Survey
  12. Seismic waves
  13. Body waves:
  14. P-Waves = Primary waves, the particle motion in the direction of wave propagation, it’s faster than S-waves and propagate through fluids.
  15. S-Waves = Secondary waves, the particle motion is perpendicular to the direction of wave propagation; it’s slower than P-waves and faster than Surface waves and can’t propagate through fluids.
  16. Surface waves
  17. Seismic noises:
  18. Seismic trace
  19. Seismogram