The Aghajari (Upper Fars) Formation in the Folded Zagros Zone, Iran: Insights to Identify Facies, Architectural Elements, Fluvial Systems, Petrography and Provenance

The Aghajari Formation, called also the Upper Fars, develops throughout the Folded Zagros Zone and its thickness in the type section in southwest of Iran is 2966 meters. To analyze the sedimentary basin of this Formation, lithofacies, architectural elements and petrofacies of the related deposits in a section in southeast of Sarvestan in Fars Province of Iran with a thickness of 2221.45 meters were examined. Microscopically studying thin sections, the petrography and the occurrence of the deposits were determined. In this section, 16 lithofacies, 10 architectural elements and 2 sandstone petrofacies were identified. The lithofacies were divided into two major and minor groups, in which the major lithofacies consist of coarse-grained （Gh, Gp, Gt and Gm）, medium-grained （Sh, Sp, St, Sl, Sm, Sr and Ss and fine-grained ones （Fm, Fl and Fsm）, and the minor lithofacies were evaporative and mixed silisiclastic-carbonate. The identified architectural elements are CH, SB, GB, LA, DA, CR, CS, LV, LS, CH （FF） and FF. By combining evidences from facies analysis and architectural elements together, the Aghajari Formation was divided into three parts in which the related sedimentation environments, from top to bottom, are gravel, gravel-sand and fine-grained meandering river respectively. There have also been playas and shoreface in the lower part. Based on petrography, the sandstones of this formation were classified into two groups： litharenite and sublitharenite. The origin of these deposits （sandstones） was appointed to the recycled orogeny and the source of quartz is low and medium to high metamorphic rank. Using the field evidences, the paleocurrent direction was achieved indicating the direction of the paleocurrent from northwest to southeast at the time of deposition. It is hoped that these data can be used in the interpretation of the basin and reconstruction of the paleogeography in the local and regional scales.

Interaction between Downslope and Alongslope Processes on the Margins of Daihai Lake,North China:Implication for Deltaic Sedimentation Models of Lacustrine Rift Basin

Daihai Lake, a modern lacustrine rift basin, located in Inner Mongolia, North China, serves as an important modern analog for understanding deltaic depositional processes in an active rift setting. Two of the deltas （Yuanzigou delta and Bulianghe delta） on the margins of Daihai Lake were surveyed to compare and contrast stacking patterns using aerial photographs, field trenching and sediment sampling. Shallow cores and trench data collected from the margins of Daihai Lake indicate that a variety of depositional processes have been active since Daihai Lake formed. Two 3-D sedimentation models which employ chronostratigraphic correlation technique were generated. The chronostratigraphic sedimentation models predict and represent the architectures and sand-body continuity of sediments. Stratigraphical coincidence of the broad sheeted drifts and channel erosion suggests a coupling between downslope and alongslope processes. Distributary mouth bars are prevalent in the front of deltas on steeper slopes due to the dominance of down-slope flows. On the contrary, the along-slope currents favor the development of distal bar deposits with sheeted sandbodies on gentle depositional slopes. This study provides an insight into the architecture of complex sedimentary facies associated with highlighting key differences between downslope flows and alongslope currents. The distribution of sand within these deltas is of particular interests, with applications in understanding the architecture of hydrocarbon reservoirs formed in lacustrine rift basin.

Deep-water depositional architecture and sedimentary evolution in the Rakhine Basin,northeast Bay of Bengal

Since the consecutive discovery of several gas fields from 2004 to present,the Rakhine Basin has been an active area for petroleum exploration in the Bay of Bengal.High-resolution 3D seismic data and well data from blocks AD1,AD6 and AD8 offshore northwest Myanmar are used to study the Miocene–Pleistocene depositional architecture and sedimentary evolution in the Rakhine Basin.Analysis of seismic facies and seismic attributes indicates that deep-water architectural elements include submarine canyons,confined slope channel complex systems,aggradational channel–levee complexes,isolated channels,frontal splays and mass-transport complexes,which have variable characters(shape,dimension,sedimentary architecture)within predominantly background deep-water slope-basin floor facies.Most of the sediments are interpreted to be sourced from the Ganges–Brahmaputra fluvio-deltaic system to the north with only minor lateral input from the IndoMyanmar Ranges to the east.Investigation of the depositional evolution and architectural elements transformation during the filling history of the Rakhine Basin suggests the Rakhine Basin experienced rapid progradation during the Oligocene–Middle/Upper Miocene,gradual retrogradation during the Middle/Upper Miocene–Early Pliocene and gradual progradation during the Early Pliocene–Pleistocene.Published exploration results indicate that the main reservoirs of the discoveries in blocks A1 and A3 are Pliocene frontal splays and channel–levee fills,dominated by fine and very fine-grained sandstones,in structural and structural–stratigraphic traps.Analytic results from seismic characters and several exploration wells indicate that channel complexes and associated overbanks and frontal splays with fine-grained sandstones and siltstones trapped by the four-way closures are primary reservoir targets.

3D modeling of deepwater turbidite lobes:a review of the research status and progress

Deepwater turbidite lobe reservoirs have massive hydrocarbon potential and represent one of the most promising exploration targets for hydrocarbon industry.Key elements of turbidite lobes internal heterogeneity include the architectural hierarchy and complex amalgamations at each hierarchical level leading to the complex distribution of shale drapes.Due to limitation of data,to build models realistically honoring the reservoir architecture provides an effective way to reduce risk and improve hydrocarbon recovery.A variety of modeling techniques on turbidite lobes exist and can be broadly grouped into pixel-based,process-based,process-oriented,surface-based,object-based and a hybrid approach of two or more of these methods.The rationale and working process of methods is reviewed,along with their pros and cons.In terms of geological realism,object-based models can capture the most realistic architectures,including the multiple hierarchy and the amalgamations at different hierarchical levels.In terms of data conditioning,pixel-based and multiple-point statistics methods could honor the input data to the best degree.In practical,dif?ferent methods should be adopted depending on the goal of the project.Such a review could improve the understanding of existing modeling methods on turbidite lobes and could benefit the hydrocarbon exploration activities of such reservoirs in offshore China.