Hydrocarbon Trap and Folding Style of the Pishvar Anticline, Sub-Coastal Fars, Zagros

The Pishvar anticline with Northwest-Southeast trend is located in the Sub-Coastal Fars area. This anticline with 80 Km length and 5 - 7 Km width is located in western part of the Lar area. The Pishvar anticline has two closures that are separated together by smooth down-warp. The oldest units that have outcropped on the surfaces are Asmari and Jahrom Formations. The most faults that observed on the Pishvar anticline are Normal fault. In the study area, the Razak and Hendurabi faults are main faults. These faults are strike slip with sinistral displacement. This anticline has greater dip in Northern flank compared to Southern flank. In this research, the main aim is folding style analysis, based on Description of fold geometry for indicate hydrocarbon trap structure in the Pishvar anticline. Description of fold geometry is important because they allow comparisons within and between folds and pattern-recognition in addition to occurrence and distribution of fold systems. We used Tectonics FP and Global Mapper Software for prepared some data in our study. In addition, we used the common classification of folds for our research. Based on results, the folding pattern of this anticline has indicated the fold style has different type in different parts of the Pishvar anticline. According to fold style variation and deformation analysis from B-B’ to C-C’ parts of the study anticline, it seems that the location of the Razak sinistral strike slip fault has existed in this parts. Fold style change can show this case. In addition, fold style variation and deformation analysis from E-E’ to F-F’ parts of this anticline has been affected of the secondary fault that is related to the Razak sinistral strike slip fault. We introduced this fault for first time. Finally, Based on results in this research, in western part there is little probability for access to hydrocarbon trap in upper horizons, unless the exploratory drilling continues to the deeper horizons.

The geological characteristics of the large-and medium-sized gas fields in the South China Sea

By the end of 2019,more than 220 gas fields had been discovered in the South China Sea.In order to accurately determine the geological characteristics of the large-and medium-sized gas fields in the South China Sea,this study conducted a comprehensive examination of the gas fields.Based on the abundant available geologic and geochemical data,the distribution and key controlling factors of the hydrocarbon accumulation in the South China Sea were analyzed.The geological and geochemical features of the gas fields were as follows:(1)the gas fields were distributed similar to beads in the shape of a"C"along the northern,western,and southern continental margins;(2)the natural gas in the region was determined to be composed of higher amounts of alkane gas and less CO2;(3)the majority of the alkane gas was observed to be coal-type gas;(4)the gas reservoir types included structural reservoirs,lithologic reservoirs,and stratigraphic reservoirs,respectively;(5)the reservoir ages were mainly Oligocene,Miocene,and Pliocene,while the lithology was mainly organic reef,with some sandstone deposits;and(6)the main hydrocarbon accumulation period for the region was determined to be the late Pliocene-Quaternary Period.In addition,the main controlling factors of the gas reservoirs were confirmed to have been the development of coal measures,sufficient thermal evolution,and favorable migration and accumulation conditions.

Mud volcano origin of the Mottled Zone,South Levant

The Mottled Zone（MZ） or Hatrurim Formation,which occurs near the Levantine Transform in the South Levant,has been studied during the last 150 years but its origin remains debatable.Mottled Zone Complex/Complexes（MZC/MZCs） consist of brecciated carbonate and low-temperature calcium-hydro-silicate rocks,which include unusual high- and ultra-high-temperature low-pressure（HT-LP） meta-morphic mineral assemblages.The MZ has been regarded as a product of combustion of bituminous chalks of the Ghareb Fm.of Cretaceous（Maastrichtian） age.In this paper we present detailed geographic, geomorphologic,structural and geological data from the MZCs of the South Levant,which show that the MZCs cannot be stratigraphically correlated with the Ghareb Fm.,because MZC late Oligocene-late Pleistocene deposits occur within or unconformable i.e.,with stratigraphic hiatus,overlap both the late Cretaceous and,in places,Neogene stratigraphic units.We propose an alternative model for the formation of MZCs by tectonically induced mud volcanism during late Oligocene-late Pleistocene time. This model explains（i） the presence of dikes and tube-like bodies,which consist of brecciated exotic clastic material derived from stratigraphically and hypsometrically lower horizons;（ii） mineral assemblages of sanidinite facies metamorphism;（iii） multi-stage character of HT-LP pyrometamorphism;and （iv） multi-stage low-temperature hydrothermal alteration.High temperatures（up to 1500℃） mineral assemblages resulted from combustion of hydrocarbon gases of mud volcanoes.Mud volcanism was spatially and structurally related to neotectonic folds and deformation zones formed in response to opening of the Red Sea rift and propagation of the Levantine Transform Fault.Our model may significantly change the prospects for oil-and-gas deposits in the region.