Academic literature on the topic 'Lurestan basin'

ABSTRACT The Middle Jurassic–Lower Cretaceous strata of the NE Arabian Plate contain several prolific source rocks providing the charge to some of the largest world-class petroleum systems. They are located within the Zagros Fold Belt and Mesopotamian Foreland Basins covering the northern, central and southeastern parts of Iraq, Kuwait and western and southwestern Iran, particularly the Lurestan and Khuzestan provinces. These source rocks include the Bajocian–Bathonian Sargelu, the Callovian–Lower Kimmeridgian Naokelekan and the Upper Tithonian–Lower Berriasian Chia Gara formations of Iraq and their chronostratigraphic equivalents in Kuwait and Iran. They have charged the main Cretaceous and Cenozoic (Tertiary) reservoirs throughout Iraq, Kuwait and Iran with more than 250 billion barrels of proven recoverable hydrocarbons. These formations represent the transgressive system tracts of sequences deposited within deep basinal settings and anoxic environments. They are dominated by black shales and bituminous marly limestones, with high total organic carbon (TOC) contents (ranging from 1–18 wt%), and by marine Type IIS kerogen. Their Rock-Eval S2 yields may reach up to 60 mg HC/g Rock, particularly along the depocentre of the Mesopotamian Foreland Basin. The immature hydrogen index (HI) values might have been up to 700 mg HC/g TOC, whereas the present-day observed values vary depending on the location within the basin and the present-day maturity. The Source-Potential Index (SPI; i.e. mass of hydrocarbons in tons, which could be generated from an area of 1 sq m in case of 100% transformation ratio) averages around 2–3, but can even reach up to 14–16 along the basins’ centres. The Sargelu and the overlying Naokelekan-basinal Najmah formations (and their equivalents) could represent the best potential shale-gas/shale-oil plays in Iraq, Kuwait and Iran, due to their organic richness, favourable maturity and the presence of regional upper and lower seals. The estimated oil-in-place for the potential Sargelu shale-oil play in Iraq only is around 1,300–2,500 billion barrel oil-equivalent (BBOE) and in Kuwait is about 7–150 BBOE.

The integration of biostratigraphy, strontium isotope stratigraphy, and magnetostratigraphy allowed for the precise dating of the >3.0-km-thick marine to non-marine foreland sedimentary succession within the Dowlatabad growth syncline along the Frontal Fars arc in the Zagros Fold Belt that extends from eastern Turkey to southern Iran. This area was the missing link to complete the dating of syntectonic deposits in the Fars arc and quantify the migration of sedimentary belts as well as the propagation of folding across the entire Mesopotamian foreland basin. Both are essential for defining the interplay of basin evolution and sequence of folding. Deposition of the foreland marine marls in the Mishan Formation started at ca. 11.5 Ma. The transition to a non-marine basin infill occurred at 4.9 Ma by the progradation of thick fluvial deposits of the Aghajari Formation with a fast accumulation rate of 63 cm/k.y. The beginning of growth strata deposition and thus the onset of folding in the Dowlatabad syncline is dated at 4.65 Ma. The first appearance of carbonate conglomerates sourced from the Guri limestone at 2.8 Ma marked the progressive dismantling of the nearby growing anticlines. The tectonic deformation in the front of the Fars arc was active for at least 2.85 m.y. and ceased at 1.8 Ma before the deposition of the discordant and slightly folded Bakhtyari conglomerates characterized by a clast composition derived from the Zagros hinterland. The compilation of magnetostratigraphic ages reveals that both the migration of the Aghajari-Bakhtyari sedimentary belts and the propagation of the folding front was in-sequence toward the foreland at a rate close to 20 mm/yr in the Fars arc and 15 mm/yr in the Lurestan arc, in the last 20 m.y. These high rates of folding propagation are about one order of magnitude larger than age equivalent shortening rates (∼4 mm/yr in Fars arc and ∼2 mm/yr in Lurestan arc) and thus imply an efficient detachment level at the base of the deformed Arabian sedimentary cover. Numerical experiments on both the cover and basement sequences are designed to test the influence of inherited basement structures on the deformation propagation within the cover sequence, providing clues on the partly coeval in-sequence deformation of the Zagros Simply Folded Belt and the local out-of-sequence Mountain Frontal Fault system as illustrated by regional and local geology.

Abstract The main objective of this thesis is to unravel burial evolution and thermal-maturation history of the Mesozoic-Cenozoic sedimentary successions of the Lurestan basin in NW Zagros, Iran by integrating petrographic (e.g.vitrinite reflectance) thermal parameters and inorganic (e.g. illite content in mixed layers I-S) thermal parameters derived by the optical analysis of the organic matter dispersed in sediments and by XRD diffraction analysis of clay minerals. The integration of vitrinite reflectance and illite content in I-S may provide important pieces of information on heating rates that cannot be provided by a single indicator. Vitrinite can be used to estimate the degree of maturation of organic matter at low to high temperatures, even to the graphite-grade metamorphic facies. By the1D modeling provided, maximum temperature experienced by the Lurestan sedimentary and the amount of eroded material through time will be determined. Then thermal maturity and quality of source rocks providing insights for hydrocarbon generation and exploration will be determined by Rock-Eval pyrolysis results. The samples collected from eight wells and two sections. Results obtained from organic and inorganic laboratory analysis have been described in the chapter 4 and then integrated for making 1D modeling by Basin Mod1 software and discussed in chapters 5 and 6. Data obtained in this Ph.D. work, in fact, were used to characterize and discriminate the thermal evolution of the Mesozoic and Cenozoic sedimentary succession by focusing more on the Garau Formation as a main source rock in the Lurestan basin. 1D modeling indicate that illite content in I-S is a better paleothermal indicator than vitrinite reflectance in the Lurestan basin. Vitrinite reflectance showed a complex distribution of organic macerals with a wide range of values in most of the wells without a clear trend as a function of depth. In addition, organic thermal indicators often point to higher levels of thermal maturity than those recorded by clay minerals. This could be due to some reasons as following: High vitrinte reflectance values are generally due to dishomogeneity of the organic matter surface, proximity to bright components such as pyrite, size of the particles, orientation of vitrinite fragments due to surface relief/irregularities, mixture of fragments (suppressed/reworked) with the indigenous population of vitrinites, and surfaces with imperfections or "noise" - scratches, (Borrego et al., 2006). Vitrinite macerals can also have different hydrogen contents that may affect thermal alteration. Hydrogen-poor and oxygen-rich vitrinites show higher levels of thermal maturity than those recorded hydrogen rich-vitrinite fragments. Also, vitrinite macerals can be reworked or organic matter can be used as additive during drilling procedure (NIOC personal communication) clouding the thermal signal due to burial. Burial histories calibrated by inorganic thermal parameters revealed a decrease in levels of thermal maturity form the internal to the external part of the Zagros belt. In particular, in the internal part of the belt the Garau Fm experienced maximum sedimentary burials in the order between 3.95 km and 5.45 km and maximum temperatures between 124 and 169°C whereas lower burial conditions occurred in the external part (between 3.65 and 4.9 km) with associated temperatures in the range of 114 - 156°C. These values directly come from the 1D modeling. The onset of hydrocarbon generation for the Garau Fm. occurred before the folding stage of the Zagros belt, from Maastrichtian to early Eocene time. The thickness of eroded rock units decreases toward the external sectors as well from 1.8 - 3km to 1.2 - 2.4 km. Exhumation took place in late Miocene in the internal part of the belt and in early Pliocene time in the external part according to the age of growth strata in the Agha jari and Bakthiari Fms. The base age of the Agha jari Fm is Upper Miocene. The thickness of the Garau Formation in internal part ranges between 577 and 799 m and in external ranges between 200 and 1000 m. The bigger thickness of the Garau Formation is in Kabir Kuh anticline. The Garau Formation by the maximum burial indicate middle mature stage (the Huleylan #1, Mahi Dasht #1, Bankul #1, Samand #1 wells, and Kabir Kuh section), late mature (Baba Ghir #1, Darreh Baneh East #1 wells, and Tang-e Haft section) and overmature stages of hydrocarbon generation and main gas zone (North Shah Abad #1 well). The onset of hydrocarbon generation in the North Shah Abad #1, Baba Ghir #1, Samand #1 wells, and Kabir Kuh and Tang-e Haft sections occurred in the Late Cretaceous time (pre-folding stage), earlier than the other wells, and in the Bankul #1, Mah Dasht #1, Darreh Baneh East wells occurred in the Early Eocene time (pre-folding stage). The onset of hydrocarbon generation in the Huleylan well occurred later than the other wells in the Paleocene time occording the modeling. Vitrinite reflectance data present the late mature and overmature stage of hydrocarbon generation for the wells and sections in internal and external part except Huleylan #1 well that vitrinite reflectance value ranging between 0.61% -0.89% that indicate the peak maturity level for producing of oil. Clay mineralogy data define their paleo-temperatures as they provide a signal throughout the entire sedimentary succession. Respect to Merriman and Frey’ chart ( figure 3.2.1.1), all the samples belong to internal and external part of the Lurestan basin have a potential of producing of hydrocarbon except Darreh Baneh East #1 by random structure Ro and I% in Mixed layers I-S between 46 and 65%. The HI versus Tmax graphs also indicate that the sediments are of type III kerogen and gas prone and they are mature (early - late) and overmature. The TOC contents in all samples of the Garau Formation show a wide range of hydrocarbon potential from poor to excellent. The plot of S1 vs.TOC and show the presence of indigenous hydrocarbon in all samples.