Changes

Particle [[Grain sizes|size]] can be determined from [[Basic open hole tools#Gamma ray|gamma ray]], [[Basic open hole tools#Porosity|porosity]], and [[Basic open hole tools#Resistivity|resistivity]] logs. [[Gran-supported carbonates|Grain-supported]] rocks commonly have lower gamma ray activity then do [[Mud-supported carbonates|mud-supported]] rocks. Other fine-grained rocks, such as shaley and [[organic-rich carbonates]], commonly have the highest gamma ray activity. However, the level of gamma ray activity in some carbonates ([[dolostones]] in particular) is not related to particle size because of the presence of anomalous concentrations of [[uranium]]. [[Calculating Sw from the Archie equation|Water saturation]] is a function of particle size and [[interparticle porosity]], and [[crossplots]] of [[porosity]], water saturation, and reservoir height can be used to determine particle size.

Particle [[Grain sizes|size]] can be determined from [[Basic open hole tools#Gamma ray|gamma ray]], [[Basic open hole tools#Porosity|porosity]], and [[Basic open hole tools#Resistivity|resistivity]] logs. [[Gran-supported carbonates|Grain-supported]] rocks commonly have lower gamma ray activity then do [[Mud-supported carbonates|mud-supported]] rocks. Other fine-grained rocks, such as shaley and [[organic-rich carbonates]], commonly have the highest gamma ray activity. However, the level of gamma ray activity in some carbonates ([[dolostones]] in particular) is not related to particle size because of the presence of anomalous concentrations of [[uranium]]. [[Calculating Sw from the Archie equation|Water saturation]] is a function of particle size and [[interparticle porosity]], and [[crossplots]] of [[porosity]], water saturation, and reservoir height can be used to determine particle size.

Interparticle porosity can be determined by subtracting separate vug porosity from [[total porosity]]. Total porosity can be calculated from porosity logs, while separate vug porosity can be estimated from crossplots of acoustic transit time versus crossplot porosity. Touching vug pore systems can be identified using borehole televiewer and resistivity scanner logs. (For more details, see [[Borehole imaging devices]].)

Interparticle porosity can be determined by subtracting separate vug porosity from [[total porosity]]. Total porosity can be calculated from porosity logs, while separate vug porosity can be estimated from crossplots of [[Interval transit time|acoustic transit time]] versus crossplot porosity. Touching vug pore systems can be identified using borehole televiewer and resistivity scanner logs. (For more details, see [[Borehole imaging devices]].)

Lithology can have a major effect on porosity logs. [[Gypsum]] is of particular concern in carbonate reservoirs because it contains large quantities of [[bound water]]. The bound water is seen by [[Basic open hole tools#Compensated neutron|neutron]] logs as porosity, resulting in erroneously high porosity indications.

Lithology can have a major effect on porosity logs. [[Gypsum]] is of particular concern in carbonate reservoirs because it contains large quantities of [[bound water]]. The bound water is seen by [[Basic open hole tools#Compensated neutron|neutron]] logs as porosity, resulting in erroneously high porosity indications.