Based on comprehensive analysis of core,cast thin section,logging and seismic data,the sedimentary and reservoir architectures of the MB 1-2 sub-member of Mishrif Formation in Halfaya Oilfield,Iraq,are studied.The MB ...Based on comprehensive analysis of core,cast thin section,logging and seismic data,the sedimentary and reservoir architectures of the MB 1-2 sub-member of Mishrif Formation in Halfaya Oilfield,Iraq,are studied.The MB 1-2 sub-member of Mishrif Formation has three types of microfacies,lagoon,bioclastic shoal,and tidal channel,and facies architecture controlled by sequence stratigraphy.In the 4th-order sequence,the lagoon facies aggradated vertically,and the bioclastic shoals in lenticular shape embed in the background of lagoon,the end of the sequence is incised by the"meandering river"shape tide channel,which represents the depositional discontinuity.Three types of reservoirs including tidal channel grainstone to packstone reservoirs,bioclastic shoal grainstone to packstone reservoirs and dissolved lagoon wackestone reservoirs are developed.The reservoir architectures within tidal channel and bioclastic shoal are strickly controlled by grainy facies,whereas the dissolved lagoon reservoirs controlled by both facies and dissolution are related to the sequence boundary.The reservoir sections occur mainly in the 4 th sequence highstand systems tract(HST)and are separated by barriers formed in the transgressive systems tract(TST).Complicated facies architecture and dissolution modification resulted in strong heterogeneity within the reservoir,which showed the characteristics of"attic type"architecture.The results of this study can guide the development of similar reservoirs in the Middle East.展开更多
For a better understanding of the strong heterogeneities of the Mishrif Formation in the H Oilfield of southeast Iraq, the characterization of the carbonate architectures has become one of the key research departments...For a better understanding of the strong heterogeneities of the Mishrif Formation in the H Oilfield of southeast Iraq, the characterization of the carbonate architectures has become one of the key research departments of carbonate rocks. This study aims to reveal the architecture and controlling factors of the carbonate tidal channels in the MB1-2B sub-layer of the Mishrif Formation in response to the delineation of the tidal channels that have hydrocarbon potential. Three architectural elements and three architectural boundaries of the tidal channels were identified by interpreting the cores, well-logging, seismic,and analytical data. The results show that:(1) the architecture characteristics of tidal channels are mainly migrating type in the downstream zone, the side of concave bank of the tidal channels is usually filled with relatively coarse-grained grainstone;(2) the architecture characteristics of tidal channels are mainly swinging type in the upstream zone, showing the high porosity and permeability;(3) the architecture characteristics of tidal channels are mainly vertical-accretion type in the mid-regions, indicating the instantaneous current reversals and high geographical position. This analysis demonstrates that the best reservoir quality within the tidal channels is located in the bend of the tidal channel near the inner lagoon and open sea, it provides the geological models for later exploration and development in the Mishrif Formation.展开更多
The Middle Cretaceous Mishrif Formation of the Cenomanian-Turonian age is an important Middle Eastern reservoir.Previous studies have shown that carbonates in the Mishrif Formation are affected by karstification and a...The Middle Cretaceous Mishrif Formation of the Cenomanian-Turonian age is an important Middle Eastern reservoir.Previous studies have shown that carbonates in the Mishrif Formation are affected by karstification and are concentrated at the top of the formation.However,there is a lack of systematic research on the effects of karstification on the formation’s reservoir characteristics.Based on core samples,scanning electron microscopy of thin sections,and geochemical analysis of C,O,and Sr isotopes from wells in the Missan Oil Fields,unconformity was identified at the top of the B21 subzone of the Mishrif Formation.Core and cast-thin-section observations indicate that there is a significant lithological difference above and below the unconformity,and dissolution pores and voids are well-developed beneath it.Vadose silt fills the intragranular pores and geopetal fabric is developed inside some mouldic pores beneath the unconformity surface.The isotopic values of ^(87)Sr/^(86)Sr(0.707270-0.707722)and δ^(18)O(−5.94‰—−2.32‰)suggest that the top of the B21 subzone of the Mishrif Formation has been severely affected by syngenetic karst.Karstification is the key to high-quality reservoir formation and the reservoir’s oil-bearing heterogeneity.This study will inform oil and gas exploration in the Missan Oil Fields and in other areas with similar reservoir characteristics.展开更多
The Mishrif Formation(Cenomanian-E Turonian)is one of the most important geological formations in the Middle East and Iraq because it contains enormous petroleum accumulations.It is considered to be the first reservoi...The Mishrif Formation(Cenomanian-E Turonian)is one of the most important geological formations in the Middle East and Iraq because it contains enormous petroleum accumulations.It is considered to be the first reservoir in the region,and is still being studied because of its economic significance.The carbonate of the Mishrif Formation derives from a variety of depositional settings,including mid-ramp,shoal,lagoon,and intertidal.The five main microfacies discussed in this paper are wackestone,packstone,grainstone,floatstone,and bindstone.The most frequent fossilised components found in the Mishrif Formation are rudists,benthic foraminifera,echinoderms,burrows molluscs,and algae.According to the microfacies and analysed wireline log data,the sequence stratigraphy of the studied formation is composed of two regression cycles.Five parasequences of transgressive-regressive cycles make up the depositional sequence of the Mishrif Formation.The standard depositional environments seem to demonstrate a gradual regression,beginning with a short period of the outer ramp,then a steady period of the mid-ramp,and ending in the intertidal environment.Additionally,the study recorded two regional maximum flooding surfaces:K-135 and K-140.The former is present in the lowermost part of the formation,while the other lies in the middle.This study shows a close relationship between facies(environments)and hydrocarbon accumulation.The increased accumulation focuses on the lower part of the studied formation,and seems to be lower in the upper part of the formation as a result of changes in the environment of deposition.展开更多
基金Supported by the China National Science and Technology Major Project(2016ZX05004-002)
文摘Based on comprehensive analysis of core,cast thin section,logging and seismic data,the sedimentary and reservoir architectures of the MB 1-2 sub-member of Mishrif Formation in Halfaya Oilfield,Iraq,are studied.The MB 1-2 sub-member of Mishrif Formation has three types of microfacies,lagoon,bioclastic shoal,and tidal channel,and facies architecture controlled by sequence stratigraphy.In the 4th-order sequence,the lagoon facies aggradated vertically,and the bioclastic shoals in lenticular shape embed in the background of lagoon,the end of the sequence is incised by the"meandering river"shape tide channel,which represents the depositional discontinuity.Three types of reservoirs including tidal channel grainstone to packstone reservoirs,bioclastic shoal grainstone to packstone reservoirs and dissolved lagoon wackestone reservoirs are developed.The reservoir architectures within tidal channel and bioclastic shoal are strickly controlled by grainy facies,whereas the dissolved lagoon reservoirs controlled by both facies and dissolution are related to the sequence boundary.The reservoir sections occur mainly in the 4 th sequence highstand systems tract(HST)and are separated by barriers formed in the transgressive systems tract(TST).Complicated facies architecture and dissolution modification resulted in strong heterogeneity within the reservoir,which showed the characteristics of"attic type"architecture.The results of this study can guide the development of similar reservoirs in the Middle East.
基金funded by the PetroChina Science and Technology Major Project (No. 2023ZZ19-1)the PetroChina Science and Technology Development Project (No. 2021DQ0407)+1 种基金the Chinese National Natural Science Fund Project (No. 42272124)the National Key R&D Program of China (2023YFF0804302)。
文摘For a better understanding of the strong heterogeneities of the Mishrif Formation in the H Oilfield of southeast Iraq, the characterization of the carbonate architectures has become one of the key research departments of carbonate rocks. This study aims to reveal the architecture and controlling factors of the carbonate tidal channels in the MB1-2B sub-layer of the Mishrif Formation in response to the delineation of the tidal channels that have hydrocarbon potential. Three architectural elements and three architectural boundaries of the tidal channels were identified by interpreting the cores, well-logging, seismic,and analytical data. The results show that:(1) the architecture characteristics of tidal channels are mainly migrating type in the downstream zone, the side of concave bank of the tidal channels is usually filled with relatively coarse-grained grainstone;(2) the architecture characteristics of tidal channels are mainly swinging type in the upstream zone, showing the high porosity and permeability;(3) the architecture characteristics of tidal channels are mainly vertical-accretion type in the mid-regions, indicating the instantaneous current reversals and high geographical position. This analysis demonstrates that the best reservoir quality within the tidal channels is located in the bend of the tidal channel near the inner lagoon and open sea, it provides the geological models for later exploration and development in the Mishrif Formation.
基金We thank anonymous reviewers for detailed and constructive feedback that helped improve the manuscript.This work was supported by the Chinese“13th Five-year Plan”National Science and Technology Major Project(No.2017ZX05032004-001).
文摘The Middle Cretaceous Mishrif Formation of the Cenomanian-Turonian age is an important Middle Eastern reservoir.Previous studies have shown that carbonates in the Mishrif Formation are affected by karstification and are concentrated at the top of the formation.However,there is a lack of systematic research on the effects of karstification on the formation’s reservoir characteristics.Based on core samples,scanning electron microscopy of thin sections,and geochemical analysis of C,O,and Sr isotopes from wells in the Missan Oil Fields,unconformity was identified at the top of the B21 subzone of the Mishrif Formation.Core and cast-thin-section observations indicate that there is a significant lithological difference above and below the unconformity,and dissolution pores and voids are well-developed beneath it.Vadose silt fills the intragranular pores and geopetal fabric is developed inside some mouldic pores beneath the unconformity surface.The isotopic values of ^(87)Sr/^(86)Sr(0.707270-0.707722)and δ^(18)O(−5.94‰—−2.32‰)suggest that the top of the B21 subzone of the Mishrif Formation has been severely affected by syngenetic karst.Karstification is the key to high-quality reservoir formation and the reservoir’s oil-bearing heterogeneity.This study will inform oil and gas exploration in the Missan Oil Fields and in other areas with similar reservoir characteristics.
文摘The Mishrif Formation(Cenomanian-E Turonian)is one of the most important geological formations in the Middle East and Iraq because it contains enormous petroleum accumulations.It is considered to be the first reservoir in the region,and is still being studied because of its economic significance.The carbonate of the Mishrif Formation derives from a variety of depositional settings,including mid-ramp,shoal,lagoon,and intertidal.The five main microfacies discussed in this paper are wackestone,packstone,grainstone,floatstone,and bindstone.The most frequent fossilised components found in the Mishrif Formation are rudists,benthic foraminifera,echinoderms,burrows molluscs,and algae.According to the microfacies and analysed wireline log data,the sequence stratigraphy of the studied formation is composed of two regression cycles.Five parasequences of transgressive-regressive cycles make up the depositional sequence of the Mishrif Formation.The standard depositional environments seem to demonstrate a gradual regression,beginning with a short period of the outer ramp,then a steady period of the mid-ramp,and ending in the intertidal environment.Additionally,the study recorded two regional maximum flooding surfaces:K-135 and K-140.The former is present in the lowermost part of the formation,while the other lies in the middle.This study shows a close relationship between facies(environments)and hydrocarbon accumulation.The increased accumulation focuses on the lower part of the studied formation,and seems to be lower in the upper part of the formation as a result of changes in the environment of deposition.
