Changes

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{| class = "wikitable"

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! Type

! Type || Description

! Description

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| I

| I || Rocks with pores capable of producing gas without natural or artificial fracturing.

| Rocks with pores capable of producing gas without natural or artificial fracturing.

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| II

| II || Rocks with pores capable of producing gas with natural or artificial fracturing and/or interbedded with type I rocks.

| Rocks with pores capable of producing gas with natural or artificial fracturing and/or interbedded with type I rocks.

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| III

| III || Rocks too tight to produce at commercial rates even with natural or artificial fracturing.

| Rocks too tight to produce at commercial rates even with natural or artificial fracturing.

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{| class = "wikitable"

{| class = "wikitable"

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! rowspan ="2" | Pore type

! rowspan ="2" | Pore type || colspan="3" | Characteristics of dry, freshly broken surfaces at 20× magnification || rowspan ="2" | Permeability

! colspan="3" | Characteristics of dry, freshly broken surfaces at 20× magnification

! rowspan ="2" | Permeability

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! Visible

! Visible || Pinpoint || Consolidation

! Pinpoint

! Consolidation

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| I

| I || Abundant to common; interconnection visible on many pores || Very abundant to common || Needle probe easily dislodges many grains from rock surface || ''Type I Subclasses''<br>IA:>100md<br>IB: 10–100 md<br>IC: 1–10 md<br>ID: ±0.5–1 md

| Abundant to common; interconnection visible on many pores

| Very abundant to common

| Needle probe easily dislodges many grains from rock surface

| ''Type I Subclasses''<br>IA:>100md<br>IB: 10–100 md<br>IC: 1–10 md<br>ID: ±0.5–1 md

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| II

| II || Scattered || Abundant to common || Needle probe can only occasionally dislodge a grain from rock surface || ± 0.5–1.0 md (depending on particle size, sorting, and clay mineral content)

| Scattered

| Abundant to common

| Needle probe can only occasionally dislodge a grain from rock surface

| ± 0.5–1.0 md (depending on particle size, sorting, and clay mineral content)

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| style=white-space:nowrap | III

| style=white-space:nowrap | III || None to very isolated || None to a few pores || Usually very well consolidated and/or pores filled with clays or other pore-filling material || Too tight to produce gas at commercial rates even when fractured or interbedded with type I rocks

| None to very isolated

| None to a few pores

| Usually very well consolidated and/or pores filled with clays or other pore-filling material

| Too tight to produce gas at commercial rates even when fractured or interbedded with type I rocks

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