TY - BOOK

T1 - Source Rock Evaluation, Petroleum Systems Modeling, and oil-oil correlation in the southern part of Iran

AU - Fathi Mobarakabad, Afshin

N1 - no embargo

PY - 2012

Y1 - 2012

N2 - The study area is located in the northern part of the Arabian Plate and includes the the Persian Gulf Basin and the Zagros Simply Folded Belt. The latter is subdivided from NW to SE into the Lurestan, Dezful Embayment, Fars and Bandar Abbas provinces. In the Zagros Simply Folded Belt of Iran and in its contiguous offshore, five petroleum systems caused an impressive accumulation of oil and gas fields that represent some 8 % and 15 % of global oil and gas reserves, respectively. The main study aims are to characterize potential source rocks, to establish 1D petroleum systems models, and to perform oil-oil and oil-source rock correlations. Source rocks have been evaluated in the Dezful Embayment, the Persian Gulf Basin and the Bandas Abbas Province. In the Dezful Embayment the main source rocks for oil are the Kazhdumi and Pabdeh formations containing kerogen type II. Both formations are within the oil window. None of the formations which host source rocks in the Zagros Simply Folded Belt shows source rock characteristics in the Persian Gulf Basin. “Hot shales” at the base of the Silurian Sarchahan Formation, the likely source for gas in the area, was not yet drilled in the Persian Gulf Basin. However, outcrops in the Bandar Abbas Province with overmature Sarchahan Formation support its high organic-matter content. 1D models of 17 wells suggest that Neogene heat flow varied laterally from 47 to 85 mW/m². Present-day heat flow varies generally between 46 to 65 mW/m². Only the Aghar well (Fars Province) is characterized by a present-day heat flow of only 40 mW/m². Models from wells in the Dezful Embayment support earlier ideas of minor Neogene erosion. However, erosion of sediments up to 2000 m thick was reconstructed for wells located in the Fars Province. Main hydrocarbon generation typically started during Neogene time, although Paleogene generation is possible in some parts of the study area. Biomarker- and compound-specific carbon isotope analyses were used to compare oil samples recovered from Jurassic and Cretaceous reservoirs at South Pars and nearby fields in the Iranian portion of the Persian Gulf, and condensate samples associated with the giant gas accumulation in Permo-Triassic reservoirs at South Pars. The results indicate that all of the oil samples, including heavy oil from South Pars are genetically related. The most probable source rocks for these oils are Jurassic limestones or marls deposited under anoxic conditions. A source rock maturity of about 0.8% vitrinite refelctance was inferred. The distribution and maturity pattern of the source rocks suggest migration from a depocentre located to the south, with inferred migration distances of up to 250 km. There is no genetic relationship between the heavy oil in Mesozoic reservoirs at South Pars and condensates in Permo-Triassic reservoirs there. Based on biomarker compositions, the condensates (and the associated gas) at South Pars appear to be derived from Silurian source rocks. High thermal maturities equivalent to 1.7% are also consistent with a Silurian source rock.

AB - The study area is located in the northern part of the Arabian Plate and includes the the Persian Gulf Basin and the Zagros Simply Folded Belt. The latter is subdivided from NW to SE into the Lurestan, Dezful Embayment, Fars and Bandar Abbas provinces. In the Zagros Simply Folded Belt of Iran and in its contiguous offshore, five petroleum systems caused an impressive accumulation of oil and gas fields that represent some 8 % and 15 % of global oil and gas reserves, respectively. The main study aims are to characterize potential source rocks, to establish 1D petroleum systems models, and to perform oil-oil and oil-source rock correlations. Source rocks have been evaluated in the Dezful Embayment, the Persian Gulf Basin and the Bandas Abbas Province. In the Dezful Embayment the main source rocks for oil are the Kazhdumi and Pabdeh formations containing kerogen type II. Both formations are within the oil window. None of the formations which host source rocks in the Zagros Simply Folded Belt shows source rock characteristics in the Persian Gulf Basin. “Hot shales” at the base of the Silurian Sarchahan Formation, the likely source for gas in the area, was not yet drilled in the Persian Gulf Basin. However, outcrops in the Bandar Abbas Province with overmature Sarchahan Formation support its high organic-matter content. 1D models of 17 wells suggest that Neogene heat flow varied laterally from 47 to 85 mW/m². Present-day heat flow varies generally between 46 to 65 mW/m². Only the Aghar well (Fars Province) is characterized by a present-day heat flow of only 40 mW/m². Models from wells in the Dezful Embayment support earlier ideas of minor Neogene erosion. However, erosion of sediments up to 2000 m thick was reconstructed for wells located in the Fars Province. Main hydrocarbon generation typically started during Neogene time, although Paleogene generation is possible in some parts of the study area. Biomarker- and compound-specific carbon isotope analyses were used to compare oil samples recovered from Jurassic and Cretaceous reservoirs at South Pars and nearby fields in the Iranian portion of the Persian Gulf, and condensate samples associated with the giant gas accumulation in Permo-Triassic reservoirs at South Pars. The results indicate that all of the oil samples, including heavy oil from South Pars are genetically related. The most probable source rocks for these oils are Jurassic limestones or marls deposited under anoxic conditions. A source rock maturity of about 0.8% vitrinite refelctance was inferred. The distribution and maturity pattern of the source rocks suggest migration from a depocentre located to the south, with inferred migration distances of up to 250 km. There is no genetic relationship between the heavy oil in Mesozoic reservoirs at South Pars and condensates in Permo-Triassic reservoirs there. Based on biomarker compositions, the condensates (and the associated gas) at South Pars appear to be derived from Silurian source rocks. High thermal maturities equivalent to 1.7% are also consistent with a Silurian source rock.

KW - Iran

KW - Arabian Plate

KW - Persian Gulf Basin

KW - Zagros Simply Folded Belt

KW - source rock

KW - petroleum system modeling

KW - oil-oil correlation

KW - Iran

KW - Arabische Platte

KW - Persischer Golf

KW - Zagros Faltengürtel

KW - Muttergestein

KW - Kohlenwasserstoffsystem

KW - Modellierung

KW - Öl-Öl Korrelation

M3 - Doctoral Thesis

ER -