Folding Style Analysis of the Tabnak Sweet Gas Field, Zagros, Iran

The Zagros fold-thrust belt in Iran is home to one of the enormous petroleum producing reservoirs in the word. The Tabnak gas field in this belt is one of the enormous sweet gas fields that discovered on the land. This anticlinal structure is located in the Coastal Fars sub-basin and is bounded from North by the Varavi gas field, from South by the Kuh-e Madar anticline, from East by Assaluyeh gas field and from West by Kuh-e Dehnow anticline. Its length is about 80 km and width is about 15 km. This structure is asymmetric anticline and is located with irregular near the Assaluyeh gas field. The Tabnak gas field is deepest structure between anticlines in the Coastal Fars area. This gas field has a special place for accommodating the enormous Hydrocarbon resources and for this reason, it is very important for Iran country. In this structure, the Dashtak, Kangan and upper Dalan Formations have Hydrocarbon. Analysis and description of fold style elements are essential for structural studies. Based on this case, the comparison of the fold styles and folding mechanism is possible. The main aim in this research is the analysis of the fold style elements of the Tabnak anticline for determining the folding pattern and tectonic regime on this structure. This case has very important for Hydrocarbon exploration between gas fields in the Fars area. In this research, we used the Tectonics FP software, Global Mapper software and geological maps and reports of Iranian National Oil Company. In addition, we used common classification of fold for indicating folding mechanism of the Tabnak anticlinal structure. Based on analysis of the fold style elements, the Tabnak anticlinal structure has variation in fold style. This structure has three different fold styles in different parts. The changes of fold axis, axial plane characteristics and fold classification confirmed several fold styles in different parts of the Tabnak anticline. These changes are observed specially in B-B', F-F' and G-G' sections of this anticline. It seems that these parts have been suffered more deformation in the study anticline. In addition, based on interlimb and folding angle, fold type is close type in all of parts. The close type required more accuracy, because the close type may be ensigns of complication regime. In the study area, G-G' and F-F' section of the Tabnak gas field probable show folding style changes have been affected by Gavbandy Paleo-high.

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.

Deformation, Stratigraphy, Structures and Shortening of the Zagros Fold-Thrust Belt in Southwest Iran Analysis by Restoration

A structural cross-section constructed across the Zagros Fold-Thrust Belt covering the Abadan Plain, Dezful Embayment, and Izeh Zone applied 2D and 3D seismic data, well data, surface and subsurface geological maps, satellite images and field reconnaissance. Besides validation and modification of the cross-section, restoration allows better understanding of the geology, structural style and stratigraphy of the Zagros basin. In the area of interest, the Hormuz basal decollement and the Gachsaran detachment play the most significant roles in the structural style and deformation of the Zagros belt. More complexity is associated with interval decollements such as Triassic evaporites, Albian shales and Eocene marls. A variety of lithotectonic units and detachment surfaces confound any estimation of shortening, which generally decreases with increasing depth. Deformation completely differs in the Abadan Plain, Dezful Embayment and Izeh Zone because of different sedimentation histories and tectonic evolution; gentle and young structures can be interpreted as pre-collisional structures of the Dezful Embayment before the Late Cretaceous. After the Late Cretaceous, the Mountain Front Fault is the main control of sedimentation and deformation in the Zagros Basin, and this completely characterizes fold style and geometry within the Dezful Embayment and the Izeh Zone.