eval module 2 & 3 Flashcards
What does Rt mean
True formation Resistivity.
Name the six basic logs that the triple combo and platform express use
Resistivity Sonic porosity Neutron density porosity Gamma ray Sp Calliper
What is the Archie equation ?
SW=(f*Rw)/Rt)^1/n
What are the API gravity ranges for Light Medium Heavy Extra heavy
Light > 31
Medium 22 - 31
Heavy 10 - 22
Extra heavy < 10
Define water saturation
The percentage of the pore space that is occupied with formation water. Calculated using the Archie equation.
What is the formula for calculating oil reserves
Effective porosity * area * thickness * oil saturation * Bo * Rf
What are porosity and lithology derived from
Sonic log
Compensated neutron formation density log
The core
Rw measurements are made on water samples recovered from ?
DSTs and production tests
Archie equation variables Sw F Rw Rt n
Sw=water saturation F=formation Resistivity factor Rw=formation water Resistivity Rt=true formation Resistivity n=saturation exponent ---- usually 2
Is F gay? If so what is it’s formula?
F=a/porosity^m
What is m in the formation factor equation ??????????!!!!?!!!?!???!!!?!
The cementation exponent
Varies with grain specifics
And tortuosity (complexity of paths between pores)
What is the normal value for tortuosity(a)?….
O
N
E
What is the normal value for the cementation exponent (m)?
T
W
O
The Archie equation must always be corrected to what?
The formation temperature (Tf)
what is Rt
The true Resistivity of the fluid filled formation in the uninvaded zone.
What is absolute permeability?
permeability of a single phase fluid
What is effective permeability?
The ability of a porous medium to transit a fluid in the presence of more than one phase.
What are the factors affecting relative permeability?
Fluid saturation
geometry and size distribution of the pore spaces
Wettability
Fluid saturation history
What is capillary pressure?
The pressure requires to squeeze a hydrocarbon droplet through a pore throat to overcome the interfacial tension between oil and water phases. Capillary pressure is higher for smaller pore spaces.
What is wettability?
measure of the relative preference of the pore surface of rocks to be covered by a certain phase and is affected by the minerals present in the pores.
What is a water wet rock?
a rock with much more affinity for water than oil
What is intermediate wettability?
occurs when some pores are water wet and some are oil wet
Most kind of water do most reservoir sands contain?
Connate waters (present in pores at time of deposition)
How is temperature formation measured?
bottom-hole temperature logs
What is the assumption for temperature formation?
that there is linearity of the geothermal gradient
What are the two main reasons Formation temperature is an important characteristic of subsurface rocks?
Tool measurements that are sensitive to temperature need to be corrected
The temperature may be used as an indicator of source rck maturity.
Define Darcy’s law?
rate of fluid flow through a porous medium is proportional potential energy gradient within that fluid. e.g.. compaction/cementation
What is diagenesis?
post-depositional process in which sediments are exposed to physical, chemical and biological changes.
What factors affect primary porosity?
angularity packing sorting cementing stress vugs/fracture
Secondary porosity generally develops in which 2 rock types?
Sandstones
Shales
What are the 3 most important logs in determining if economically recoverable volumes of hydrocarbon are present in the well?
Resistivity
Porosity
Gamma Ray
