Term

Definition
the measure of void space in a rock
Φ=pore volume/bulk volume = V_{p}/V_{b }= (V_{b}V_{g})/V_{b}
where Vg= grain volume 


Term

Definition
ρ=m/v
bulk density, ρ_{b}
grain density, ρ_{g} 


Term
relationship between porosity and density 

Definition


Term

Definition
grams/cm^3
quarts=2.65
calcite=2.71
clay (avg)=2.57 


Term
how to measure total porosity 

Definition
 measure the bulk volume (V_{b})
 crush the sample to measure the grain volume
 use formulate V_{p}=V_{b}V_{g} to estimate pore volume
 divide pore volume by bulk volume



Term

Definition
the connectivity of porosity in a rock 


Term
how to measure effective porosity 

Definition
 inject a gas or liquid into the rock after measuring bulk volume
 the gas or liquid only goes where teh porosity is connected
 dreain the gas or liquid, then measure the volume of it, and that equals pore volume



Term

Definition
the largest inscribed circle within a pore space
free porosity<porosity 


Term
factors controlling porosity 

Definition
grain size
grain shape
grain packing and distribution
cementation
compaction



Term

Definition
pore size is smaller than grain size by a factor of 510 


Term
direct methods for measuring porosity 

Definition
 measurement of bulk and grain volume
 optical method: use of petrographic thin section analysis
 imbibition method: imbibing fluid into the pore space
 mercury injection method: forcing non wetting liquid into porespace
 gas expansion method: (He or N_{2})
 density method
 NMR (proton density)



Term
log based methods for measuring porosity 

Definition
 formation factor
 micro resistivity logs
 neutron logs
 gammagamme logs
 acoustic logs
 NMR logs



Term

Definition


Term
average surgace temperature
(land and bottom of ocean) 

Definition
surface temp: 68ºF
ocean bottom: 32ºF 


Term

Definition
lithostatic=overburden=confining
fluid=reservoir=pore=formation 


Term

Definition
the fraction of pore volume occupied by a fluid or gas 


Term
irreducible water saturation (S_{wir}) 

Definition
fraction of the water in the pore space which cannot be produced
'bound water' 


Term

Definition
the capacity of a rock to transmit a fluid
all factors that control effective porosity also control permeability
is affected by the type of clay present 


Term

Definition
 single fluid
 no rock fluid interaction
 incompressible fluid
 laminar flow



Term

Definition
a porous materal has k=1 if a pressure difference of 1 atm will produce a flow rate of 1cm^3/sec of a fluid with 1 cP viscosity through a cube having sides 1cm in length
k = permeability (darcy) 


Term

Definition
calculated in darcy's equation
when the rock is 100% saturated with a single phase (water, oil, or gas) 


Term
effective permeability (K_{eff}) 

Definition
when two or more fluids coexist in a rock
the sum of the effective permeabilittes of all the phases will always be <= the absolute permeability 

