Changes

[[file:migration-of-petroleum_fig7-13.png|thumb|300px|{{figure number|1}}Efficiencies of the expulsion, migration, and entrapment processes. After Magara.<ref name=ch07r5>Magara, K., 1980, [http://archives.datapages.com/data/bulletns/1980-81/data/pg/0064/0012/2100/2108.htm Evidences of primary migration]: AAPG Bulletin, vol. 64, p. 2108–2117.</ref>]]

[[file:migration-of-petroleum_fig7-13.png|thumb|300px|{{figure number|1}}Efficiencies of the expulsion, migration, and entrapment processes. After Magara.<ref name=ch07r5>Magara, K., 1980, [http://archives.datapages.com/data/bulletns/1980-81/data/pg/0064/0012/2100/2108.htm Evidences of primary migration]: AAPG Bulletin, vol. 64, p. 2108–2117.</ref>]]

Typical oil expulsion efficiencies are estimated to be in the 5-10% range, with values in the 15% range uncommon and 30% rarely demonstrated. This efficiency is low because most of the source rock section contains too low a concentration of organic material to participate in the expulsion process. Efficiencies of gas expulsion are estimated to be 50-90%, with values of 75% common. Unfortunately, much of this is gas lost due to solution and does not participate in reservoir charging. For both oil and gas, expulsion efficiencies tend to increase with increasing [[Total organic carbon (TOC)|total organic carbon (TOC)]]. Expulsion efficiencies for oil and gas can be as high as 70-80% for very rich, effective [[source rocks]] near preferential [[migration pathways]].

Typical oil expulsion efficiencies are estimated to be in the 5-10% range, with values in the 15% range uncommon and 30% rarely demonstrated. This efficiency is low because most of the source rock section contains too low a concentration of organic material to participate in the expulsion process. Efficiencies of gas expulsion are estimated to be 50-90%, with values of 75% common. Unfortunately, much of this is gas lost due to solution and does not participate in reservoir charging. For both oil and gas, expulsion efficiencies tend to increase with increasing [[total organic carbon (TOC)]]. Expulsion efficiencies for oil and gas can be as high as 70-80% for very rich, effective [[source rocks]] near preferential [[migration pathways]].

==Procedure==

==Procedure==

[[file:migration-of-petroleum_fig7-14.png|300px|thumb|{{figure number|2}}Procedure for estimating expulsion efficiency. Copyright: McDowell;<ref name=McDowell1975>McDowell, A. N., 1975, What are the problems in estimating the oil potential of a basin? Oil & Gas Journal, June 9, p. 85–90.</ref> courtesy Oil & Gas Journal.]]

[[file:migration-of-petroleum_fig7-14.png|300px|thumb|{{figure number|2}}Procedure for estimating expulsion efficiency. Copyright: McDowell;<ref name=McDowell1975>McDowell, A. N., 1975, What are the problems in estimating the oil potential of a basin? Oil & Gas Journal, June 9, p. 85–90.</ref> courtesy Oil & Gas Journal.]]

In migration volumetrics, it is important to estimate the original petroleum potential of the [[source rock]]—not just its present measured potential (with increasing [[maturation]], a portion of the original potential will have been realized and is therefore unmeasurable). Estimates of expelled hydrocarbons may be derived by measuring the amount remaining in a source and subtracting that value from the amount that should have been generated from the original assumed kerogen content.

In [[migration]] volumetrics, it is important to estimate the original petroleum potential of the [[source rock]]—not just its present measured potential (with increasing [[maturation]], a portion of the original potential will have been realized and is therefore unmeasurable). Estimates of expelled hydrocarbons may be derived by measuring the amount remaining in a source and subtracting that value from the amount that should have been generated from the original assumed kerogen content.

Below is a procedure for estimating expulsion efficiency.

Below is a procedure for estimating expulsion efficiency.

# Estimate the original kerogen content of the rock using TOC values measured from source rock samples.

# Estimate the original [http://www.thefreedictionary.com/kerogen kerogen] content of the rock using [[total organic carbon (TOC)|TOC]] values measured from source rock samples.

# Model the original [[Petroleum generation|hydrocarbon generation]] potential of the source rock using the estimated original kerogen content.

# Model the original [[Petroleum generation|hydrocarbon generation]] potential of the source rock using the estimated original kerogen content.

# Measure the volume of hydrocarbons expelled during pyrolosis (S2).

# Measure the volume of hydrocarbons expelled during [[Rock-Eval pyrolysis|pyrolosis]] (S2).

# Estimate the actual expelled hydrocarbon volume by subtracting the S2 value from the original hydrocarbon generation potential of the source rock.

# Estimate the actual expelled hydrocarbon volume by subtracting the S2 value from the original hydrocarbon generation potential of the source rock.

# Calculate efficiency by dividing the expected volume of expelled hydrocarbons from the actual volume of hydrocarbons generated.

# Calculate efficiency by dividing the expected volume of expelled hydrocarbons from the actual volume of hydrocarbons generated.