Relationship between average maximum and average arbitrary reflection values of coals vitrinite

For a quantitative assessment of the degree of coalification of coals in different countries, either average arbitrary (R0,r) vitrinite reflectance or average maximum (R0,max) vitrinite reflectance are mainly used. Since these indicators differ markedly in magnitude, in many countries, equations of the relationship between them have been established relatively long time ago in order to compare correctly the technological properties of different coals of the same type by indicators R0,max or R0,r. For Russian coals, the relationship between the vitrinite reflection indices R0,max and R0,r has not yet been established. Based on the studies of 40 samples of coals from Russia (Kuznetsk Basin), equations of the relationship between the average maximum (R0,max) and average arbitrary (R0,r) reflection values of coals vitrinite were obtained, taking into account the degree of their genetic recovery. The accuracy of calculating the indicator R0,max through R0,r at that is higher when taking into account the degree of genetic recovery of coals, which was 0.03%, versus 0.04% without accounting it. To compare technological properties of Russian coals by the same type of indicators R0,max or R0,r with the coals of Australia, USA, Canada, Poland, Germany, the equations of the relationship between the average maximum (R0,max) and the average arbitrary (R0,r) vitrinite reflectance presented for the coals of these countries according to publications in scientific journals.

Fluid inclusions in buried quartz of the Yanchang sandstone in the Jiyuan area, Ordos Basin, China: Implications for basin evolution and petroleum accumulation

A fluid inclusion petrographic and microthermometric study was performed on the sandstones gathered from the Yanchang Formation, Jiyuan area of the Ordos Basin. Four types of fluid inclusions in quartz can be recognized based on the location they entrapped. The petrographic characteristics indicate that fluid inclusions in quartz overgrowth and quartz fissuring-I were trapped earlier than that in quartz fissuring-IIa and fissuring-IIb. The homogenization temperature values of the earlier fluid inclusions aggregate around 80 to 90°C; exclusively, it is slightly higher in Chang 6 member, which approaches 95°C. The later fluid inclusions demonstrate high homogenization temperatures, which range from 100 to 115°C, and the temperatures are slightly higher in Chang 9 member. The calculated salinities show differences between each member, including their regression characteristics with burial depth. Combining with the vitrinite reflection data, the sequence and parameters of fluid inclusions indicate that the thermal history of the Yanchang formation mostly relied on burial. Salinity changes were associated with fluid-rock interaction or fluid interruption. Hydrocarbon contained fluid inclusions imply that hydrocarbon generation and migration occurred in the Early Cretaceous. The occurrence of late fluid inclusions implied that quartz cement is a reservoir porosity-loose factor.

COMPARATIVE ORGANIC GEOCHEMICAL STUDY OF CRETACEOUS RESERVOIRS OF ZUBAIR OIL FIELD, SOUTHERN IRAQ

Three formations were chosen in the present study, these are Yamamma, Zubair and Mishrif formations, which are considered the main reservoirs at Zubair oilfield southern Iraq, especially during the Cretaceous period. The studied reservoirs are distinguished by different rocks, facies and environmental specifications. Thirteen wells were selected for the present study these are: Zb-44, Zb-202, Zb-10, Zb-294, Zb-81, Zb-233, Zb-329, Zb-49, Zb-9, Zb-156, Zb-8, Zb-256 and Zb-187. To studying the geochemical parameters of crude oils. Geochemical analysis of crude oil was applied. The results of the isotope analyses indicate that the source rock of oil is a mature marine rock that contains a high percentage of sulfur. The American Petroleum Institute values are ​​ranging from 35-20 indicate medium to light hydrocarbons. The results show that the Kerogen type is type II which is derived from marine algae organism. The burial history indicates that the subsidence is high at the late Jurassic - early Cretaceous period and also at the Miocene, and the slow subsidence during the late Cretaceous and moderate subsidence at the Paleogene. The results of the Vitrinite Reflection and Production Index show that the thermal maturity is happened at the early to the main stage, which was represented at the Zb-44 and Zb-202 wells. The transformation ratio of Zubair and Yamamma formations indicates that the possibility of kerogen to yield oil and gas is high in the future with temperature increasing.

Clay mineralogy of the Paleozoic-Lower Mesozoic sedimentary sequence from the northern part of the Arabian Platform, Hazro (Diyarbakır, Southeast Anatolia)

Clay mineralogy of the Paleozoic-Lower Mesozoic sedimentary sequence from the northern part of the Arabian Platform, Hazro (Diyarbakır, Southeast Anatolia)The Paleozoic-Lower Mesozoic units in the Diyarbakır-Hazro region consist of sandstone (subarkose, quartz arenite), mudstone, shale, coal, marl, dolomitic marl, limestone (biomicrite, lithobiosparite, biosparite with lithoclast, dololithobiosparite, dolomitic cherty sparite) and dolomite (dolosparite, dolosparite with lithoclast, biodolosparite with glauconite). These units exhibit no slaty cleavage although they are oriented parallel to bedding planes. The sedimentary rocks contain mainly calcite, dolomite, quartz, feldspar, goethite and phyllosilicates (kaolinite, illite-smectite (I-S), illite and glauconite) associated with small amounts of gypsum, jarosite, hematite and gibbsite. The amounts of quartz and feldspar in the Silurian-Devonian units and of dolomite in the Permian-Triassic units increase. Kaolinite is more commonly observed in the Silurian-Devonian and Permian units, whereas illite and I-S are found mostly in the Middle Devonian and Triassic units. Vertical distributions of clay minerals depend on lithological differences rather than diagenetic/metamorphic grade. Authigenetic kaolinites as pseudo-hexagonal bouquets and glauconite and I-S as fine-grained flakes or filaments are more abundantly present in the levels of clastic and carbonate rocks. Illite quantities in R3 and R1 I-S vary between 80 and 95 %. 2M1+1Mdillites/I-S are characterized by moderatebcell values (9.005-9.040, mean 9.020 Å), whereas glauconites have higher values in the range of 9.054-9.072, mean 9.066 Å. KI values of illites (0.72-1.56, mean 1.03 Δ2θ°) show no an important vertical difference. Inorganic (mineral assemblages, KI, polytype) and organic maturation (vitrinite reflection) parameters in the Paleozoic-Triassic units agree with each others in majority that show high-grade diagenesis and catagenesis (light petroleum-wet gas hydrocarbon zone), respectively. The Paleozoic-Triassic sequence in this region was deposited in the environment of a passive continental margin and entirely resembles the Eastern Taurus Para-Autochthon Unit (Geyikdağı Unit) in respect of lithology and diagenetic grade.