Petroleum Geology (Module PPT) Final Examination

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123 Terms

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Reservoir rock
is a place that oil migrates to and id held underground
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Coring
processes used to recover formation samples from petroleum reservoirs
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Reservoir rock samples
are used for reservoir description and definition, reservoir characterization and to enhance both geological petrophysical nature of reservoir.
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Sidewall sampling tool
can be used to obtain small plugs from the formation. The tool is run on a wireline after the hole has been drilled.
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Sidewall cores
are useful for identifying hydrocarbon zones, when viewed under UV light
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Whole core
provides larger samples; better and more consistent representation of formation; better for heterogeneous rocks or for more complex lithology
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Plugs or sidewall cores
smaller samples; less representative of heterogeneous formations; within 1 to 2% of whole cores for medium-to-high porosity formation
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Standard analysis
porosity; horizontal permeability to air; grain density
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Special core analysis
vertical permeability to air; relative permeability; capillary pressure; cementation exponent and saturation exponent
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Porosity and permeability
both are important properties that are related to fluids in sediment and sedimentary rocks
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Porosity
the volume of void space in an sediment and sedimentary rock
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Permeability
related to how easily a fluid will pass through any granular material
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Total or absolute porosity
is the total void space in the rock whether or not in contributes to fluid flow
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Effective porosity
implies the ration of the total volume of interconnected voids Vp to the bulk volume Vb of the rock; percentage of interconnected void space with respect to the bulk volume
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Double porous or fracture-porous media
rock having both fracture and intergranular pores
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Fracture porosity
is a form of secondary porosity generated by tectonic fracturing of the rock
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Micro-porosity
part of the pore space that has a characteristic dimension less than 1 micron
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Vugular porosity
is the pore space consisting of cavities or vugs; can occur in rocks prone dissolution, such as limestone, in which case is secondary porosity
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Secondary porosity
is the porosity created through alteration of rock, commonly by processes such as dolomitization, dissolution and fracturing
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Primary porosity
is the space between grains that were not compacted together completely
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Sorting
is the tendency of sedimentary rocks to have grains that are similarly sized
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Poorly sorted
sediment displays a wide range of grain sizes and hence has decreased porosity
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Well-sorted
indicates a grain size distribution that is fairly uniform
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Packing density
the arrangement of the particles in the deposit
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Grain size
has no influence in porosity
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Compaction
particles are forced into closer packing by the weight of overlying deposits, reducing porosity
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Cementation
precipitation of new minerals from pore waters causes cementation of the grains and acts to fill the pore spaces, reducing porosity
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Clays
may form by the chemical alteration of pre-existing minerals after burial
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Feldspars
are particularly common clay-forming minerals
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Clay minerals
are very fine-grained and may accumulate in the pore spaces, reducing porosity
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Quartz
relatively soluble when pore waters have a low
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Pressure solution
the solubility of mineral grains increases under an applied stress and the process of solution is under stress
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Fracturing
- particularly important in producing porosity in rocks with low primary porosity
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Density logs
uses radioactive source to generate gamma rays
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Neutron log
logging tool emits high energy neutrons into formation
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Acoustic (sonic) log
tool usually consists of one sound transmitter (above) and two receivers (below)
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Openhole logging tools
most common method of determining porosity
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Absolute permeability
the permeability of the porous medium if a single fluid is flowing
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Effective permeability
permeability of a fluid if another fluid is present
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Relative permeability
effective permeability divided by the absolute permeability
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Henry Darcy
hydraulic engineer; the discoverer of Darcy’s law; his law is a foundation stone for several fields of study including ground-water hydrology, soil physics and pet eng.
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Original porosity
constituted when the formation was laid
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Secondary porosity
history of the rock
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Effective porosity
continuous or interconnected porosity
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Non effective porosity
discontinuous or isolated porosity
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Seismic
define the structure of the subsurface to perform maps
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Compressive (P, like primary)
the faster one, the direction of displacement of the particles is parallel to the propagation axis
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Shear (S like secondary)
the displacement is perpendicular to the propagation axis
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Surface waves or Stoneley
slower, their displacement follow the surfaces where the characteristics are changing
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Mud-logging
data acquisition during drilling
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Petrophysic
physical properties of the porous network
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framework, matrix, cement, pores
Four major components of sandstone
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bulk density, sonic (acoustic), compensated form
3 main log types
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seismic, mud-logging, core, logging, tests, monitoring
Main ways to get information
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sandstones; limestone and carbonate rocks
Examples of reservoir rock:
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Reservoirs
are not underground "lakes" of oil; they are made up of porous and permeable rocks that can hold significant amounts of oil and gas within their pore spaces.
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Diagenesis
The first stage in the transformation of freshly deposited organic matter into petroleum is called _______. This process begins at the sedimentary interface and extends to varying depths,
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Catagenesis
is the stage of thermaldegradation of kerogen that forms oil and gas.
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Metagenesis
The metagenesis stage is reached at great depths, or in areas of high geothermal gradients at shallower depths. Metagenesis usually begins at depths of approximately 4,000 meters.
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Paraffins
also called alkanes and have the general fomula of CnH2n+2,
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Naphthenes
or cycloparaffins are ring or cyclic saturated hydrocarbons with the general formula of CnH2n.
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Aromatics
are an important series of hydrocarbons found in almost every petroleum mixture from any part of the world. This series of aromatics is called alkylbenzenes and have a general formula of CnH2n
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Primary Migration
expulsion of petroleum from the source rock and also refers to movement of hydrocarbons
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Secondary Migration
movement of oil or gas within reservoir
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Subsurface Mapping
is a valuable tool for locating undereround features that may form trapso outline the boundaries of a possible reservoir.
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Structural Contour Maps
show a series of lines drawn at regular intervals.
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Liquid Petroleum
known as crude oil" to distinguish it from refined oil". It is most important commercially.
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Natural Gas
which is the lighter fraction of hydrocarbons, can be free or dissolved.
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Asphalt, Tar, Pitch
these are solid or semisolid forms of hydrocarbons, the heavy fraction.
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Lopatin's TTI V. Lopatin (1971)
recognized the dependence of thermal maturation from temperature AND time. temperatures are weighted with the residence time. This so
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Vitrinite Reflectance (Ro)
measures the reflectance of vitrinite
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Source rock
refers to the formation in which oil and gas originate
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Gravity and Magnetic Surveys
one of the tools used for mineral-bearing ore bodies or even oil-bearing 
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Geochemistry
ldentify possible source rocks (whole rock): usually black to dark brown in color.
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Geologic Fieldwork
Rock identification and sampling
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Cross-Sections
Structural, stratigraphic, and topographic information can be portrayed on
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Isopach Maps
are similar in appearance to contour maps but show variations in the thickness of the bed.
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Lithofacies Maps
show, changes in lithologic character and how it varies horizontally within the formation. This type of map has contours.
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Level of organic maturation (LOM)
is based on coal ranks.
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Pyrolysis
techniques are performed directly on rock samples and offer the major clues in the systematic analysis of kerogen
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The Rock Eval instrument
provides a fast determination of the type and evolution stage of kerogen
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Optical Techniques: Transmitted Light Optical
techniques are widely used to characterize type and maturation of organic matter.
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Optical Studies: Reflected Light
The method most often used to evaluate the maturation of kerogen and to establish the depth range associated with petroleum generation is vitrinite reflectance.
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STRUCTURAL TRAPS
are primarily the result of folding and faulting or both
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Simple fold traps (anticlinal)
with axial culmination. The simplest type of trap is formed when a sandstone bed that is overlain by tight shale is folded into an anticline.
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Salt domes
Strata around the salt dome curve upvward creating traps against the sealing salt layers.
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Growth domes
Domes or anticlines that form during sedimentation when one area subsides more slowly than the surrounding areas.
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Normal faults
commonly associated with graben (rift) structures.
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Strike-slip faults
these may not be sealed due to incremental movements
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Thrust faults
commonly associated with compressional tectonics
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Growth faults
typically form in sediments that are deposited rapidly.
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Stratigraphic traps
are created by any variation in the stratigraphy that is independent of structural deformation
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Primary stratigraphic traps
result from variations in facies that developed during sedimentation.
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Secondary stratigraphic traps
result from variations that developed after sedimentation, mainly because of diagenesis.
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Hydrodynamic Traps
If porewater flow in a sedimentary basin is strong enough, the oil-water contact may deviate from the horizontal
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A reservoir
is a subsurface volumne of porous and permeable rock that has both storage capacity and the ability to allow fluids to flow through it.
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Sandstone reservoirs
are generally created by the accumulation of large amounts of clastic sediments which is characteristic of depositional environments such as river channels, deltas, beaches, lakes and submarine fans.
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Carbonate reservoirs
are created in marine sedimentary environments with little or no clastic material input and generally ina location between 30° north and south of the equator.
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Depth
The physical characteristics of a reservoir are greatly affected by the depth at which they occur.
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Shallow reservoir
Created by the folding of relatively thick, moderately compacted reservoir rock with accumulation under an anticline or some trap.