Changes

==Applications==

==Applications==

[[file:rate-of-penetration_fig2.png|thumb|{{figure number|2}}Example of correlating ROP with gamma ray curves.]]

[[file:rate-of-penetration_fig2.png|300px|thumb|{{figure number|2}}Example of correlating ROP with gamma ray curves.]]

Rate of penetration logs serve as historical records of drilling performance and can aid in optimizing drilling operation and formation evaluation.

Rate of penetration logs serve as historical records of drilling performance and can aid in optimizing drilling operation and formation evaluation.

Shales generally drill slower than sandstones or carbonates, and as a result, ROP logs tend to reflect indirectly the lithology of the formation.

Shales generally drill slower than sandstones or carbonates, and as a result, ROP logs tend to reflect indirectly the lithology of the formation.

===Relative [[porosity]]===

===Relative porosity===

[[Porosity]] in sandstone is qualitatively inferred by observing the ROP in shale and comparing that to the ROP in a known sandstone interval. Porosity in carbonates is inferred by comparing the relatively slow ROP in rocks having low matrix porosity to rocks having higher porosity and faster ROP. This comparison requires that the prevailing drilling conditions (mud weight, bit condition, WOB, and rotary speed) are consistent.

[[Porosity]] in sandstone is qualitatively inferred by observing the ROP in shale and comparing that to the ROP in a known sandstone interval. Porosity in carbonates is inferred by comparing the relatively slow ROP in rocks having low matrix porosity to rocks having higher porosity and faster ROP. This comparison requires that the prevailing drilling conditions (mud weight, bit condition, WOB, and rotary speed) are consistent.