Changes

:<math>\mbox{Porosity}  = 18.60 + (4.73 \times \mbox{in quartz}) + (17.37/\mbox{sorting}) </math>

:<math>\mbox{Porosity}  = 18.60 + (4.73 \times \mbox{in quartz}) + (17.37/\mbox{sorting}) </math>

:<math>\quad \ {-}\, (3.8 \times \mbox{depth} \times 10^{-3}) - (4.65 \times \mbox{in age}) </math>

::<math>\quad \ {-}\, (3.8 \times \mbox{depth} \times 10^{-3}) - (4.65 \times \mbox{in age}) </math>

where:

where:

The equation can be used with a high degree of confidence in uncemented to partly cemented sandstones. But if the reduction of porosity by cement exceeds 2.1% bulk volume, then corrections need to be made based on local sandstone quality characteristics. Numbers for percent solid volume quartz and sorting may be difficult to obtain. Use 75% for percent solid volume quartz and 1.5 for sorting when these values are not known.

The equation can be used with a high degree of confidence in uncemented to partly cemented sandstones. But if the reduction of porosity by cement exceeds 2.1% bulk volume, then corrections need to be made based on local sandstone quality characteristics. Numbers for percent solid volume quartz and sorting may be difficult to obtain. Use 75% for percent solid volume quartz and 1.5 for sorting when these values are not known.

The table below shows numbers that Scherer<ref name=ch09r53 />) developed by his analysis of reservoir sandstones.

The table below shows numbers that Scherer<ref name=ch09r53 /> developed by his analysis of reservoir sandstones.

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! Parameter

! Parameter || Unit || Range || Mean || Standard deviation

! Unit

! Range

! Mean

! Standard deviation

|-

|-

| Porosity

| Porosity || Percent bulk volume || 3.9–36.6 || 20 || 7.9

| Percent bulk volume

| 3.9–36.6

| 20

| 7.9

|-

|-

| Age

| Age || Millions of years || 1–460 || 59 || 40.0

| Millions of years

| 1–460

| 59

| 40.0

|-

|-

| Depth

| Depth || Meters || 0–5,960 || 2,230 || 1,150.0

| Meters

| 0–5,960

| 2,230

| 1,150.0

|-

|-

| Quartz

| Quartz || Percent solid rock volume || 12–97 || 75 || 23.0

| Percent solid rock volume

| 12–97

| 75

| 23.0

|-

|-

| Sorting

| Sorting || Trask coefficient || 1.1–4.2 || 1.5 || 0.6

| Trask coefficient

| 1.1–4.2

| 1.5

| 0.6

|}

|}