Changes

  | part    = Predicting the occurrence of oil and gas traps

  | part    = Predicting the occurrence of oil and gas traps

  | chapter = Predicting reservoir system quality and performance

  | chapter = Predicting reservoir system quality and performance

  | frompg  = 9-1

  | frompg  = 9-96

  | topg    = 9-156

  | topg    = 9-98

  | author  = Dan J. Hartmann, Edward A. Beaumont

  | author  = Dan J. Hartmann, Edward A. Beaumont

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm

  | link    = http://archives.datapages.com/data/specpubs/beaumont/ch09/ch09.htm

==Basis==

==Basis==

Sneider and others at Shell Oil Company developed a methodology for estimating permeability from cuttings by calibrating permeability measured from cores with rock-pore parameters described in cuttings. Cores of known permeability were ground up until chips from the core were the size of cuttings. By using comparators made from core chips, they estimated formation permeability from cuttings with surprising accuracy. Although Sneider and King<ref name=ch09r57 />) describe the method for estimating sandstone permeability from cuttings (presented below), procedures could just as easily be developed to predict permeability of carbonates from cuttings.

Sneider and others at Shell Oil Company developed a methodology for estimating permeability from cuttings by calibrating permeability measured from cores with rock-pore parameters described in cuttings. Cores of known permeability were ground up until chips from the core were the size of cuttings. By using comparators made from core chips, they estimated formation permeability from cuttings with surprising accuracy. Although Sneider and King<ref name=ch09r57 /> describe the method for estimating sandstone permeability from cuttings (presented below), procedures could just as easily be developed to predict permeability of carbonates from cuttings.

==Petrophysical description==

==Petrophysical description==

From examination of cuttings, sandstone permeability can be predicted using the following petrophysical descriptions:

From examination of cuttings, sandstone permeability can be predicted using the following petrophysical descriptions:

* Grain size and sorting

* [[Grain size]] and [[Core_description#Maturity|sorting]]

* Degree of rock consolidation

* Degree of rock consolidation

* Volume percent of clays

* Volume percent of clays

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! Type

! Type || Description

! Description

|-

|-

| 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.

|-

|-

| 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.

|-

|-

| 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.

|}

|}

{| class = "wikitable"

{| class = "wikitable"

|-

|-

! 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

|-

|-

! Visible

! Visible || Pinpoint || Consolidation

! Pinpoint

! Consolidation

|-

|-

| 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

|-

|-

| 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)

|-

|-

| style=white-space:nowrap | III

| 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

|}

|}

==Examples of pore type I==

==Examples of pore type I==

[[file:predicting-reservoir-system-quality-and-performance_fig9-64.png|300px|thumb|{{figure number|1}}Examples of rocks with types IA, IB, IC, and ID. From Sneider and King, 1984; courtesy AAPG.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-64.png|300px|thumb|{{figure number|1}}Examples of rocks with types IA, IB, IC, and ID. From Sneider and King;<ref name=ch09r57 /> courtesy AAPG.]]

The [[Scanning electron microscopy (SEM)|SEM]] microphotographs in [[:file:predicting-reservoir-system-quality-and-performance_fig9-64.png|Figure 1]] are examples of rocks with types IA, IB, IC, and ID.

The [[Scanning electron microscopy (SEM)|SEM]] microphotographs in [[:file:predicting-reservoir-system-quality-and-performance_fig9-64.png|Figure 1]] are examples of rocks with types IA, IB, IC, and ID.

==Pore types II and III==

==Pore types II and III==

[[file:predicting-reservoir-system-quality-and-performance_fig9-65.png|300px|thumb|{{figure number|2}}Examples of rocks with types II and III.]]

[[file:predicting-reservoir-system-quality-and-performance_fig9-65.png|300px|thumb|{{figure number|2}}Examples of rocks with types II and III. From Sneider and King;<ref name=ch09r57 /> courtesy AAPG.]]

The SEM microphotographs in [[:file:predicting-reservoir-system-quality-and-performance_fig9-65.png|Figure 2]] are examples of rocks with types II and III. Note the amount and connectivity of pore space of each subclass.

The SEM microphotographs in [[:file:predicting-reservoir-system-quality-and-performance_fig9-65.png|Figure 2]] are examples of rocks with types II and III. Note the amount and connectivity of pore space of each subclass.

The procedure below is for predicting the permeability of sandstones from cuttings using 20× magnification<ref name=ch09r57 />.

The procedure below is for predicting the permeability of sandstones from cuttings using 20× magnification<ref name=ch09r57 />.

# Estimate grain size and sorting using standard size-sorting comparators, thin section and SEM photomicrographs, and rock photographs.

# Estimate volume percentages using Terry-Chillingar charts made for volume estimates.

# Estimate consolidation using the scheme described in the preceding table.

# Describe the visible and pinpoint [[porosity]] and interconnectedness.

# Estimate permeability from rocks on comparators and/or using rock characteristics described in the preceding table. (Comparators can be made or purchased.)

# Predict permeability for the formation in prospective areas where petrophysical characteristics are believed to be similar

| Estimate grain size and sorting using standard size-sorting comparators, thin section and SEM photomicrographs, and rock photographs.

| Estimate volume percentages using Terry-Chillingar charts made for volume estimates.

| Estimate consolidation using the scheme described in the preceding table.

| Describe the visible and pinpoint [[porosity]] and interconnectedness.

| Estimate permeability from rocks on comparators and/or using rock characteristics described in the preceding table. (Comparators can be made or purchased.)

| Predict permeability for the formation in prospective areas where petrophysical characteristics are believed to be similar

==See also==

==See also==

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting reservoir system quality and performance]]

[[Category:Predicting reservoir system quality and performance]]