Iranian Journal of Oil and Gas Science and Technology

Abstract Natural gas storage process in aquifer, due to fluid flow behavior of gas and water in the porous medium and because of their contact with each other under reservoir conditions, faces several challenges. Therefore, there should be a clear understanding of the injected gas behavior before and after the injection into the reservoir. This research simulates the natural gas storage in aquifer by using Eclipse 300 software. For this purpose, a core sample was considered as the porous medium for gas injection, and a composition of natural gas was injected into the core in different conditions. Moreover, by using Plackett-Burman method, all of the factors affected in this process were screened, and finally four main significant parameters, including the flow rate of injected gas, permeability, pressure, and irreducible water saturation were selected for designing a design of experiments (DOE) plan. Response surface method (RSM) is one of the best methods of experimental design used for optimizing the process and finding the best combination of parameters to have a high stored gas volume and a high recovered gas volume. The simulation includes 28 runs with four considered parameters, and the output is the recovered gas, which in turn is vital for the process accomplishment. Sensitivity analysis and grid independency test were checked. To this end, three grids with different number of cells in x-direction were generated, and by analyzing the results of gas saturation in the porous medium for each model, a grid with 11250 cells (50 elements in x-direction and 15 elements in y- and z-directions) was then chosen as the main grid. Uncertainty analysis and the validation of numerical simulations were carried out, and good agreement was observed between the numerical results and experimental data. In addition, the numerical results showed that the flow rate of the injected gas had a significant impact on the process in comparison with other parameters. Furthermore, increasing permeability and decreasing pressure and irreducible water saturation raise the amount of trapped gas in aquifers. Therefore, for having the maximum stored gas volume and a high recovered gas volume, the best combination of parameters is a high gas injection flow rate (0.9 cc/min), high permeability (1.54 md), a low pressure (2254 psi), and irreducible water saturation. (0.46). Finally, in a natural gas storage operation in an aquifer, both rock properties and operational parameters play important roles, and they should be optimized in order to have the highest amount of stored gas.

Abstract Hydrochloric acidizing is a routine operation in oil fields to reduce the mechanical skin. In this paper, practical acidizing in a typical carbonate oil reservoir located in the southwest of Iran is practiced, which shows an unexpected improvement after acidizing. To understand the acidizing effect on reservoir rock, the formation rock is analyzed on different scales. An acidizing laboratory test is also carried out on formation core samples to understand the acidizing performance. The results show that the main feature of this reservoir is its dominated secondary porosity and its special pattern of distribution. Practically, this porosity percolation has caused high mechanical skin during drilling and a large productivity improvement after acidizing. The acidizing increased the ultimate recovery of the reservoir with existing wells and prolonged the production plateau.

Abstract Recently, due to the very good market in ethane as a feedstock for petrochemical complexes, there are some plans to make a deep ethane recovery from the gases produced in Iran southern fields. In this work, the feasibility of different technologies for deep ethane recovery from a specified feed gas produced in one of the Iran southern fields is reviewed. Three different processes are selected and simulated for the specified feed gas. These processes are compared from technical and economic viewpoints and the advantages and disadvantages are discussed. The results show that RSV and CRR processes are technically more feasible for high levels of ethane recovery (greater than 95%). The economic evaluations show that the CRR process is the most appropriate one for the feed gas specified in this study.

Abstract Net pay thickness is defined as that portion of a reservoir which contains economically producible hydrocarbons with today’s technology, prices, and costs. This thickness is a key parameter of the volumetric calculation of in-place hydrocarbons, well test interpretation, and reservoir characterization. A reservoir interval is considered as net pay when it contains hydrocarbons that can flow at an economic rate. Therefore, to define net pay, cutoffs of hydrocarbon storage properties besides flow properties of reservoir rock are necessary. Frequently, petrophysical log-derived rock storage properties like porosity and water saturation are linked to core measured properties like permeability to find a relation between them. Then, by use of a fixed limiting value for permeability, log-derived properties cutoffs are determined. The basic problem of these methods is related to permeability cutoff, since in most cases there is no knowledge about it, and the permeability cutoff can differ from field to field or even well to well.
A new methodology has been developed to find a logical permeability cutoff for gas reservoirs which can differ for different wells and/or fields. This technique is based on gas flow through porous media in tight rocks. Accordingly, a relationship between porosity and permeability is derived as a cutoff value at reservoir pressure and temperature, which is considered as a discriminator plot. Then, the core data of the specified reservoir are added to this plot and the data points reflecting net pay zone are identified. This technique has been applied to four real gas reservoirs in Iran and indicated acceptable results confirmed by the drill stem test (DST) and production data. The results show that the proposed procedure is less dependent on experts’ experiences and acts as a straightforward and powerful tool for the refinement of net pays. In addition, the cutoff values calculated from this method contain a scientific base supporting the main procedure.

Abstract In this study, direct laboratory measurements of unsteady-state imbibition test are used in a new approach to obtain relative permeability curves with no predetermined functionality assumptions. Four equations of continuity, Darcy’s law, cumulative oil production, and water fractional flow are employed in combination together under certain assumptions to present the new approach which interprets these data. We assumed that capillary pressure was previously measured and used as the input data in the method. The main difference between this work and previous unsteady-state methods is to replace the saturation profile, needed to obtain relative permeability curves, with a new saturation-dependent graph which can be measured from recovery data rather than being recorded directly during experiments. The method is demonstrated by employing recovery data from the literature, and it is then verified by a numerical simulator. The results show that the accuracy of the proposed method is comparable with accurate complex methods. Performing sensitivity analysis indicates that the proposed method can achieve more accurate results when applied to cases with a relatively high capillary number and/or low water-oil mobility ratio and when applied to media having uniformly sized pores.

Abstract Reservoir characterization has a leading role in the reservoir geophysics and reservoir management. Since the interests of the reservoir geophysics and reservoir managements are the elastic properties and reservoir properties of the subsurface rock for their purposes, a robust method is required for converting seismic data into elastic properties. Accordingly, by employing a rock physics model and using the inverted seismic data, one can describe the reservoir for purposes such as improvement in the production of the reservoir. In the present study, we employ one of the methods for converting the seismic data into the elastic properties. This method of inversion is known as simultaneous inversion, which is grouped in amplitude-variation-with-offset (AVO) inversion category. In this method, unlike the other methods of AVO inversion, the pre-stack seismic data are directly inverted into the elastic properties of the rock and an excellent lithology and fluid indicator (V_P/V_S) are provided. Then, this indicator is tested on one of the oilfields of the Persian Gulf. Moreover, by means of this method, one can locate the fluids contact and the lithological interlayers; also, by the inversion results, which are the cubes of the seismic properties of the rock, one can generate sections of the elastic properties of the rock such as Poisson’s ratio and Young modulus which are useful for geomechanical analysis. Therefore, this kind of method is a quick way for the prior analysis of the studied area.

Abstract The conjugation of two or more Artificial Intelligent (AI) models used to design a single model that has increased in popularity over the recent years for exploration of hydrocarbon reservoirs. In this research, we have successfully predicted shear wave velocity (Vs) with higher accuracy through the integration of statistical and AI models using petrophysical data in a mixed carbonate-siliciclastic heterogeneous reservoir. In the designed code for multi-model, first Multivariate Linear Regression (MLR) is used to select the more relevant input variables from petrophysical data using weight coefficients of a suggested function. The most influential petrophysical data (Vp, NPHI, RHOB) are passed to Ant colony optimization (ACOR) for training and establishing initial connection weights and biases of back propagation (BP) algorithm. Afterward, BP training algorithm is applied for final weights and acceptable prediction of shear wave velocity. This novel methodology is illustrated by using a case study from the mixed carbonate-siliciclastic reservoir from one of the Iranian oilfields. Results show that the proposed integrated modeling can sufficiently improve the performance of Vs estimation, and is a method applicable to mixed heterogeneous intervals with complicated diagenetic overprints. Furthermore, predicted Vs from this model is well correlated with lithology, facies and diagenesis variations in the formation. Meanwhile, the developed AI multi-model can serve as an effective approach for estimation of rock elastic properties. More accurate prediction of rock elastic properties in several wells could reduce uncertainty of exploration and save plenty of time and cost for oil industries.

Abstract This study uses the kernel principal component analysis (KPCA) feature extraction method for facies classification to extract new features from the measured well logs. After applying the principal component analysis (PCA) and KPCA feature extraction approaches, the classification was made using three robust classifiers: multilayer perceptron neural network (MLP), support vector machine (SVM), and random forest (RF). Finally, the predicted results for the test data that were not included in the training process were evaluated with the F1 score criterion. The PCA method did not significantly affect the classification performance due to the nonlinear structure of the facies. Our results show that the KPCA improves the performance of facies classification. Compared with the conventional approach based on well-log data, our new approach improves the classification accuracy for each classifier algorithm. In the RF results, the classification accuracy has increased by about 6%, while using the KPCA feature extraction approach raises classification accuracy from 52% to 58% compared to the original well-log data.

Abstract The primary purpose of this paper is to estimate and evaluate the petrophysical properties of the Ghar formation in the Hendijan and Bahregansar oilfields using a combination of seismic and well-log data. This study follows a step-by-step regression approach. First, sonic, density, and porosity well-log data are collected. Second, seismic attributes, including amplitude, phase, frequency, and acoustic impedance, are extracted from the seismic lines intersecting the wellbore locations. Then, using the MFLN and PNN intelligent systems, a relationship between porosity, shale volume, saturation, and seismic attributes is established. Using this relationship, the physical and petrophysical properties of the reservoir in the Ghar formation are estimated and evaluated. We estimated the reservoir porosity to be between 15% and 20%, higher in the Hendijan oilfield than in the Bahregansar oilfield. The water saturation in the Ghar formation varied from 25% to 30%. On the other hand, the clay content and shale volume of the Ghar formation in the Hendijan field were higher than those of the Bahregansar oil field.

Abstract The current work investigates the performance of a single-stage, bench-scale system using a spray dryer to treat produced water. The produced water is generated in three large reservoirs of Ahvaz, Maroon, and Mansouri fields, which have different compositions but the same high total dissolved solids (TDS) and total organic carbon (TOC). The results of this study indicate that the newly developed bench scale rig is able to reduce the amount of TDS in the water produced in Ahvaz, Maroon, and Mansouri reservoirs to 98.78, 98.65, and 98.90, and TOC decreases the three types of the produced water to zero. Investigating the effect of independent parameters on the performance of this system using response surface methodology shows that the most effective parameters affecting the efficiency of the produced water treatment system are the entering carrier gas temperature (TGIT), the flow rate of the produced water (QL), the carrier gas flow rate entering the spray dryer (QG), and the atomizer pore size (d). Additionally, the optimal conditions are obtained as follows: TGIT = 113.7 °C, QL = 20.8 cc/min, QG = 59.9 m³/hr., and d = 0.03 mm.

Abstract An efficient design of in situ combustion depends on accurate kinetic modeling of the crude oil oxidation. The kinetic triplet of the oxidation reactions of a heavy oil sample was investigated. Once the kinetic triplet is known, the kinetic equation would be deconvolved. The crude oil sample was obtained from Kuh-E-Mond reservoir, located in the southwest of Iran. The samples were analyzed using differential scanning calorimetry (DSC) at atmospheric pressure, in a temperature range of 297- 973 K, and at four different heating rates. Three isoconversional kinetic models were used to obtain a variation of Arrhenius parameters during the course of the high temperature oxidation reaction. The activation energy (Eα) and the pre-exponential factor (A) were obtained at different conversions. Having Arrhenius parameters, the conversion function, f(α), was estimated using an advanced master plot method. It was observed that f(α) follows the Avrami–Erofeev (An) model with n=3. Furthermore, the parameters of truncated Sestak–Berggren (SB) reaction model were obtained. SB fits fairly better than A3 to the experimental data. According to the results, a change in the heating rate does not considerably vary the reaction model.

Abstract Cap rocks are dams which can prevent the upward movement of hydrocarbons. They have disparities and weaknesses including discontinuities, crushed areas, and faults. Gas injection is an effective mechanism for oil recovery and pore pressure. With increasing pore pressure, normal stress is reduced, and the integrity of impermeable boundaries (cap rock, fault, etc.) becomes instable. A successful strategy for reservoir development is the inevitable necessity of conducting geomechanical studies and modeling the reservoir. The construction of a comprehensive geomechanical model, including the stress state is a function of depth (direction and amount), physical properties of the reservoir rock and its formations (rock resistance and elastic moduli), pore pressure estimation, and description and distribution of fractures and faults. In this work, analytical and numerical methods have been used in geomechanical modeling, and the data used for modeling and petrophysical information are downhole tests. The geomechanical modeling of gas injection into the reservoir and, simultaneously, the operation of Asmari reservoir and Marun oilfield cap rock in the southwest of Iran were carried out. The threshold of reactivating faults and the critical pressure of induced fracture were calculated, and the results were presented as analytical and numerical models. Moreover, in addition to analyzing the stress field at depths, the resistance parameters of the formations were determined. The results showed that the most changes and instabilities were around the wellheads, fractures, and the edges of the field.

Abstract Fractured carbonate reservoirs account for 25% of world’s total oil resources and for 90% of Iranian oil reserves. Since calcite and dolomite minerals are oil wet, gas oil gravity drainage (GOGD) is known as the most influencing production mechanism. The most important issue within gas injection into fractured media is the channeling problem which makes the efficiency of gas injection process extremely low. As a solution, foam is used to change the mobility ratio, to increase volumetric sweep efficiency, and to overcome the fingering problem. In this work, we inspected three main influencing mechanisms that affect oil extraction from matrix, namely foam/oil gravity drainage, viscous pressure drop  due to foam flow in fractures, and foaming agent diffusion from fractures into the matrixes. Foam injection simulations were performed using CMG STARS 2015, on a single matrix unit model and on some vertical cross section models. A number of sensitivity analyses were performed on foam strength, injection rate, fracture and matrix properties, matrix heights, and the initial oil saturation within matrixes. The results show that the roles of the mass transfer of the foaming agent and viscous pressure drop  are significant, especially when matrix average heights are small. Moreover, the mechanism for viscous pressure drop  remains unchanged, which continues to aid oil extraction from matrixes while the other two mechanisms weaken with time.

Abstract The oilfield water in the Upper Sandstone Member of the Zubair reservoir (Barriemian-Hauterivian) at Rumaila North Oil Field was investigated for the interpretation of salinity and geochemical evolution of brine compositions. The interaction of the oilfield water with reservoir rock resulted in a brine water derived from the marine water origin of partial mixing with meteoric water similar to the compositional ranges of formation water from Gulf of Mexico offshore/onshore Mesozoic reservoirs. The high TDS (207350- 230100; average 215625 mg/L) is consistent with the electrical conductivity (340362-372762; average 351024μs), and predominantly represented by Cl (123679 mg/L) as anions and (29200 and 14674 mg/L) for Na and Ca as cations respectively. The contribution of cation (epm%) are as Na (70.2), Ca (18.9), Mg (8.1) and K (1.7); and anion as Cl (99.7), SO4 (0.25), HCO3 (0.07) and CO3 (0.005). sodium (57550-60500mg/L) is greater than of seawater six times, calcium and magnesium three times greater, and chloride 6.5 times greater, but Sulfate is depleted to six times less due to a sulfur release from sulphates and link with different hydrocarbon species, precipices as native sulphur and link with hydrogen forming H2S. The Zubair oilfield water is characterised by acidic pH (pH=5.2- 5.77) enhanced petrophysical properties, high specific gravity (1.228) predicts a high fluid pressure (4866 psi), hydrocarbon saturation (0.43%), water saturation (0.57%) and porosity (12.7). The Mineral saturation model indicates that the Zubair oilfield water is an unsaturated water with respect to all suggested minerals at 5.45, but at simulated pH, brucite being an equilibrium at pH 9.12, but brucite and portlandite being supersaturated at pH 11.9. The mineral solubility responses to the changes in temperature, pressure, pH, Eh, and ionic strength, thereby formation damage is proportionally developed.

Abstract Reservoir characterization plays an important role in different parts of an industrial project. The results from a reservoir characterization study give insight into rock and fluid properties which can optimize the choice of drilling locations and reduce risk and uncertainty. Delineating hydrocarbon bearing zones within a reservoir is the main objective of any seismic reservoir characterization study. In the current study, using limited well control and seismic data, an attempt was made to predict the productive zones of a reservoir using elastic impedance inversion. Elastic impedance logs at near and far angles of incidence have been crossplotted to find the desired productive parts of the formation. Two partial angle stack seismic data have been inverted using a model-based post-stack seismic inversion. The crossplot of the two inverted volumes is interpreted based on the results from the well location. Finally, the hydrocarbon bearing zones of the reservoir was delineated according to the seismic crossplot analysis.

Abstract The gas-assisted gravity drainage (GAGD) process is designed and practiced based on gravity drainage idea and uses the advantage of density difference between injected CO2 and reservoir oil. In this work, one of Iran western oilfields was selected as a case study and a sector model was simulated based on its rock and fluid properties. The pressure of CO2 gas injection was close to the MMP of the oil, which was measured 1740 psia. Both homogeneous and heterogeneous types of fractures were simulated by creating maps of permeability and porosity. The results showed that homogeneous fractures had the highest value of efficiency, namely 40%; however, in heterogeneous fractures, the efficiency depended on the value of fracture density and the maximum efficiency was around 37%. Also, the effect of injection rate on two different intensities of fracture was studied and the results demonstrated that the model having higher fracture intensity had less limitation in increasing the CO2 injection rate; furthermore, its BHP did not increase intensively at higher injection rates either. In addition, three different types of water influxes were inspected on GAGD performance to simulate active, partial, and weak aquifer. The results showed that strong aquifer had a reverse effect on the influence of GAGD and almost completely disabled the gravity drainage mechanism. Finally, we inventively used a method to weaken the aquifer strength, and thus the gravity drainage revived and efficiency started to increase as if there was no aquifer.

Abstract Porosity is one of the fundamental petrophysical properties that should be evaluated for hydrocarbon bearing reservoirs. It is a vital factor in precise understanding of reservoir quality in a hydrocarbon field. Log data are exceedingly crucial information in petroleum industries, for many of hydrocarbon parameters are obtained by virtue of petrophysical data. There are three main petrophysical logging tools for the determination of porosity, namely neutron, density, and sonic well logs. Porosity can be determined by the use of each of these tools; however, a precise analysis requires a complete set of these tools. Log sets are commonly either incomplete or unreliable for many reasons (i.e. incomplete logging, measurement errors, and loss of data owing to unsuitable data storage). To overcome this drawback, in this study several intelligent systems such as fuzzy logic (FL), neural network (NN), and support vector machine are used to predict synthesized petrophysical logs including neutron, density, and sonic. To accomplish this, the petrophysical well logs data were collected from a real reservoir in one of Iran southwest oil fields. The corresponding correlation was obtained through the comparison of synthesized log values with real log values. The results showed that all intelligent systems were capable of synthesizing petrophysical well logs, but SVM had better accuracy and could be used as the most reliable method compared to the other techniques.

Abstract Fracture reservoirs contain most of the oil reserves of the Middle East. Such reservoirs are poorly understood and recovery from fractured reservoirs is typically lower than those from conventional reservoirs. Many efforts have been made to enhance the recovery and production potential of these reservoirs. Fractured reservoirs with high matrix porosity and low matrix permeability need a secondary or EOR technique to achieve the maximum production. One of the effective EOR approaches is surfactant flooding, which reduces interfacial tension and alters wettability. Due to the complexity and uncertainty associated with such reservoirs, implementing a simulation and numerical analysis is primarily necessary to evaluate the effect of key engineering parameters on ultimate reservoir performance. This study assesses and provides a good insight into surfactant injection into fractured reservoirs using ECLIPSE software as a numerical simulator. The influences of fracture-matrix permeability ratio, initial water saturation, and the number of grids on reservoir performance were assessed and a sensitivity analysis was carried out. This study takes surfactant-related phenomena such as adsorption, surface tension reduction, and wettability alteration into account. The simulation results demonstrate that fracture-matrix permeability ratio is an important screening quantity for the selection of surfactant flooding as an EOR agent and that uncertainty in the initial water saturation of matrix has a great influence on the simulation outputs.

Abstract The removal of sulfur compounds from petroleum is extremely necessary for industrial and environmental reasons. Sulfur in transportation fuels is a major air pollution source. In this work, the efficiency of nanostructured Ni-clinoptilolite adsorbent was investigated in the removal of sulfur from gas oil. For this purpose, the design of experiments was performed by selecting effective factors in desulfurization process. Response surface methodology was selected to model the desulfurization process. Ni-containing nanoadsorbents were prepared by a wet-impregnation method. Gas oil model containing 300 ppmW [M. N.1]  sulfur was prepared by dissolving a calculated amount of dibenzothiophene (DBT) in n-decane. The concentration of DBT in n-decane was determined by UV-Visible spectrophotometer. The results revealed that sulfur removal extremely depended on the amount of metal and the nature of both metal and support. 5% Ni/support adsorbent resulted in higher sulfur removal efficiency. The optimum ratio of H₂O₂ to gas oil in the studied conditions was in the range of 5% (v/v) and 240 minutes for the best desulfurization performance during the process.



 

Abstract In this study, a chemical additive made by a combination of polymer, alkaline, and silica nano
particles is used to control the oil recovery and relative permeability curves. Various parameters
including the type and concentration of polymer, alkaline, and nanosilica particles have been studied.
To evaluate the efficiency of these additives, we performed unsteady state displacement experiments
under the JBN method and determined the pressure gradient across the core samples. The
experimental observations emphasized that by using the appropriate chemical additives the relative
permeability of the phases is changed towards higher oil relative permeability values, which results in
the oil recovery. The results of this study can improve the chemical flooding for heavy oil recovery.

Abstract A synthesis of well logs was carried out and drilling mud weight data were analyzed to figure out anomalous high fluid pressure within the Triassic evaporitic cap rock (the Dashtak formation) and study its impact on the geometry of anticlinal traps in the gas rich Gavbandi province located in the southeast part of the Zagros Mountains. The results indicated that the location of anticlinal traps at the depth in which the Permian Dehram Group reservoir unit exists is horizontally displaced with respect to surficial crest of many anticlines within the Gavbandi area. This crestal shift may be induced by abnormally high fluid pressure in the “A evaporate” member of the Dashtak formation, detected in many exploration wells across the area. When fluid pressure increases due to compaction during shortening, the higher shaliness could probably cap more fluids and consequently increase the fluid pressure within the Dashtak formation. Anomalous high fluid pressure decreases internal friction and shear strength of rock units and facilitates fracturing and faulting within the Dashtak formation, which consequently causes crestal shift of anticlinal traps. This should be taken into account when planning a new exploration well in Gavbandi area in order to prevent trap drilling.

Abstract In this study, the corrosion resistance of a bituminous coating reinforced with different ratios of nanoclay pigment was studied. To make nanocomposite coatings, 2, 3, and 4 wt.% of clay (Cloisite Na+) were incorporated into water emulsified bitumen. The coatings were applied to steel 37. Optical microscopy and X-ray diffraction (XRD) were used to characterize the nanocomposite structure. In order to investigate the anticorrosion behavior of the coatings, electrochemical impedance spectroscopy (EIS) and direct current polarization techniques were used. The results show that the coatings containing nanoclay have better performance compared to the neat bitumen. Moreover, it was revealed that the corrosion resistance of the nanocomposite increased as the clay loading increased up to 4 wt.%.

Abstract Fluid invasion from water-based drilling mud (WBDM) into the shale formations causes swelling, high pressure zone near the wellbore wall, and eventually wellbore instability problems during drilling operations. For the stability of the wellbore, physical plugging of nanoscale pore throats could be considered as a logical approach toward avoiding the fluid invasion into the shale formation. This paper reports the effect of silica nanoparticles (NPs) as a physical sealing agent on the water invasion into Kazhdumi shale. To this end, pressure penetration apparatus was implemented. Typical WBDM in contact with Kazhdumi shale at different concentrations of NPs with different sizes was studied. The results indicated that the addition of NPs to the WBDM decreased water invasion into Kazhdumi shale. WBDM having 10 wt.% of 25 nm NPs reduced fluid invasion up to 72.76%.

Abstract Time-of-flight diffraction method (ToFD) is an amplitude-independent sizing method which is based on the measurement of time-of-flight of defect tip diffracted waves. Although ToFD can measure through-wall length of defect accurately, this method is not capable of measuring horizontal defect size. In this paper, a new ToFD method for evaluating horizontal planar defects is presented. The finite element method (FEM), using the ABAQUS software package, is employed to simulate the ultrasonic wave behavior in the test blocks and its interaction with the embedded planar defects. The phased array technology is also used to model the ultrasonic inspection system parameters. FEM simulation of the new ToFD method for different crack sizes shows that, compared to the conventional ToFD method, the accuracy of results is within acceptable range to use the novel technique for measuring the horizontal planar defects.

Abstract In an attempt to reconstruct the paleoenvironments of deposition for the Middle Jurassic Baghamshah formation, samples collected from six outcrop sections along the Shotori swell were subjected to detailed geochemical analyses. Bulk geochemical and biological marker data indicate a logical trend of the variation of organic input, salinity, and oxicity within Baghamshah paleoenvironments across the studied area. An increase in terrestrial character from southern end towards the central parts of the Shotori swell parallels with a uniform increase in the oxicity and a decrease in the salinity. The northernmost sections are characterized by less terrestrial impact, reduced oxicity, and elevated salinity compared to the central and southern sections. These variations are interpreted in the framework of past geometric configuration and a hypothetical paleogeomorphologic model is tentatively proposed for the Middle Jurassic of the area. According to these results, the depositional setting of the studied formation decreased in depth from Section-1 towards Section-4, suggesting that the proximity of the latter section to the Yazd Block may have had a strong control over the observed geochemical variations. The terrestrial organic input and the oxicity of the environment are conspicuously low for northern sections and their salinity shows a sharp increase compared to other sections. We hypothesize that a fault plan exists across the northern and southern Shotori Mountains that had played an active role in creating the current geochemical variations.