Mehdi Saffari, Pooria Kianoush, Behzad Saffari
et al.
Abstract The Sarvak Formation in the Yadavaran oilfield within the Zagros Basin is a significant hydrocarbon reservoir characterized by complex sedimentological and diagenetic features influencing its reservoir quality. This study aims to investigate the sedimentological facies and diagenetic processes within the Sarvak Formation to enhance understanding of its reservoir potential. A comprehensive analysis was conducted using core samples, thin-section petrography, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The primary objectives included identifying distinct facies assemblages and correlating them with diagenetic alterations. The results indicate the presence of three key facies: lagoonal facies, characterized by fine-grained, bioturbated sediments with a high organic content, exhibiting a porosity of approximately 15–20%; open marine facies, consisting of well-sorted, coarse-grained sands with a lower organic content and porosity ranging from 10 to 12%; and transitional facies, which display mixed characteristics of both lagoonal and open marine environments, with porosity values between 12 and 18%. The integration of advanced analytical techniques, including SEM and XRD, provided detailed insights into mineralogical composition and microstructural features, highlighting the impact of diagenetic processes on reservoir quality. This study contributes to a more nuanced understanding of the Sarvak Formation’s reservoir characteristics, offering valuable insights for hydrocarbon exploration and production strategies in the Zagros Basin.
Abstract Understanding the distribution of shear wave velocity (V S ) in hydrocarbon reservoirs is a crucial concern in reservoir geophysics. This geophysical parameter is utilized for reservoir characterization, calculating elastic properties, assessing fractures, and evaluating reservoir quality. Unfortunately, not all wells have available V S data due to the expensive nature of its measurements. Hence, it is crucial to calculate this parameter using other relevant features. Therefore, over the past few decades, numerous techniques have been introduced to calculate the V S data using petrophysical logs in wells with limited information. Unfortunately, the majority of these methods have a drawback they only offer insight into the location of the wells and do not provide any details regarding the distribution of V S in the space between the wells. In this article, we employed three-dimensional post-stack seismic attributes and well-logging data integration to predict the distribution of V S in the Asmari formation in an Iranian oil field. To accomplish this objective, the model-based seismic inversion algorithm was utilized to convert the seismic section into the acoustic impedance (AI) section. Then, AI and seismic data were utilized in the cross-validation method to determine the relevant attributes for predicting the spatial distribution of V S throughout the entire reservoir area, using an artificial neural network. The proposed method was shown to provide 94% correlation and 109 m/s error between the actual and estimated V S . Also, the calculated V S section has a high correlation with the actual logs at the location of the wells.
Abstract To avoid or mitigate the unwanted water and gas content, inflow control devices (ICDs) are designed and installed in the well to disturb the water and gas breakthrough which are trying to overtake the oil inflow, water and gas coning and sand production. Smart wells with permanent downhole valves such as ICDs are used to balance production and injection in wells. A paramount issue regarding using downhole control devices is determining the required cross-sectional area of them for control of the imposed pressure drop across the device to stabilize the fluid flow. Current methods for calculating the opening size of the ICDs are mainly based on sensitivity analysis of the ICD flow area or optimization algorithms coupled with simulation models. Although these approaches are quite effective in oil field cases, they tend to be time-consuming and require demanding system models. This paper presents a fast analytical method to determine the ICD flow area validated by a genetic algorithm (GA). Analytically, a closed-form expression is introduced by manipulating Darcy’s law applicable to multi-layer injection wells with different layer properties to balance the injection profile in the reservoir pay zone, based on equalizing injected front velocity in layers with different permeability. Considering various scenarios of analytical technique, GA optimization, and sensitivity analysis scenarios for ICD cross-sectional area determination, results for oil recovery, water production, water breakthrough time, and net present value (NPV) are discussed and compared. NPV values obtained by both analytical and GA approaches are virtually identical and greater than those of other scenarios. Compared to the base field case, the analytical method improved the oil recovery by almost 1%, reduced water production by almost 91%, and synchronized the water breakthrough time of high- and low-permeability layers (from a ratio of 1.76–1.06). The proposed analytical solution proved to be capable of providing desirable results with only one reservoir simulation run in contrast to GA and sensitivity analysis scenarios which require iterative simulation runs. The proposed analytical solution outperformed the GA as it is less computationally demanding in addition to its success in case of lowering water production for the field data. The findings of this study can help for a better understanding of the situation where water injection into the oil reservoir is problematic as the layers present different permeabilities which can induce problems such as early water breakthrough from the more permeable layer and hinder the success of the water injection process. Using ICDs and a faster and more accurate approach to calculate its cross-sectional area such as the analytical method that was used in this study can greatly increase the success rate of water injection in case of oil recovery and lower the amount of the produced water.
<p>We investigated rare earth element (REE) minerals in low- to medium-grade metapelites sampled in two nappes of the Austroalpine Unit (Eastern Alps, Austria). Combining microstructural and chemical characterization of the main and REE minerals with thermodynamic forward modeling, Raman spectroscopy on carbonaceous material (RSCM) thermometry and in situ U–Th–Pb dating reveal a polymetamorphic evolution of all samples. In the hanging wall nappe, allanite and REE epidote formed during Permian metamorphism (275–261 Ma, 475–520 °C, 0.3–0.4 GPa). In one sample, Cretaceous (ca. 109 Ma) REE epidote formed at <span class="inline-formula">∼440</span> °C and 0.4–0.8 GPa at the expense of Permian monazite clusters. In the footwall nappe, large, chemically zoned monazite porphyroblasts record both Permian (283–256 Ma, 560 °C, 0.4 GPa) and Cretaceous (ca. 87 Ma, 550 °C, 1.0–1.1 GPa) metamorphism. Polymetamorphism produced a wide range of complex REE-mineral-phase relationships and microstructures. Despite the complexity, we found that bulk rock Ca, Al and Na contents are the main factor controlling REE mineral stability; variations thereof explain differences in the REE mineral assemblages of samples with identical pressure and temperature (<span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span>) paths. Therefore, REE minerals are also excellent geochronometers to resolve the metamorphic evolution of low- to medium-grade rocks in complex tectonic settings. The recognition that the main metamorphic signature in the hanging wall is Permian implies a marked <span class="inline-formula"><i>P</i></span>–<span class="inline-formula"><i>T</i></span> difference of <span class="inline-formula">∼250</span> °C and at least 0.5 GPa, requiring a major normal fault between the two nappes which accommodated the exhumation of the footwall in the Cretaceous. Due to striking similarities in setting and timing, we put this low-angle detachment in context with other Late Cretaceous low-angle detachments from the Austroalpine domain. Together, they form an extensive crustal structure that we tentatively term the “Austroalpine Detachment System”.</p>
Elishevah van Kooten, Adrian Brearley, Denton Ebel
et al.
Chondritic components such as chondrules and matrix are the key time capsules that can help us understand the evolution and dynamics of the protoplanetary disk from which the Solar System originated. Knowledge of where and how these components formed and to what extent they were transported in the gaseous disk provides major constraints to astrophysical models that investigate planet formation. Here, we explore whether chondrules and matrix are genetically related to each other and formed from single reservoirs per chondrite group or if every chondrite represents a unique proportion of components transported from a small number of formation reservoirs in the disk. These static versus dynamic disk interpretations of cosmochemical data have profound implications for the accretion history of the planets in the Solar System. To fully understand the relationship between chondrules and matrix and their potential complementarity, we dive into the petrological nature and origin of matrix, the chemical and isotopic compositions of chondrules and matrix and evaluate these data considering the effect of secondary alteration observed in chondrites and the potential complexity of chondrule formation. Even though we, the authors, have used different datasets and arrived at differing interpretations of chondrule-matrix relationships in the past, this review provides clarity on the existing data and has given us new directions towards future research that can resolve the complementarity debate.
The lifetime of mm size dust grains, such as chondrules, in the nominal solar nebula model is limited to $\sim 10^{5}$ yr due to an inward drift driven by gas drag. However, isotopic and petrological studies on primitive meteorites indicate a discrepancy of $\gtrsim 10^{6}$ yr between the formation time of chondrules and that of chondritic parent bodies. Therefore chondrules should survive for $\gtrsim 10^{6}$ yr in the solar nebula against the inward drift without subsequent growth (i.e., planetesimal formation). Here we investigate the conditions of the solar nebula that are suitable for the long lifetime of chondrule-sized dust particles. We take the turbulent strength, the radial pressure gradient force, and the disk metallicity of the solar nebula as free parameters. For 1 mm-radius-chondrules to survive and keep their size for $\gtrsim 10^{6}$ yr, the suitable condition is a weak turbulence ($α\sim 10^{-6}$), a flat radial profile ($η\lesssim 10^{-3}$), and a high metallicity ($Z\sim 0.1$). This condition is qualitatively consistent with the characteristics of protoplanetary disks suggested by recent observations. We eventually propose that planetesimal formation may be induced by the disk evolution, e.g., the inside-out dispersal of the gas component due to the disk wind.
Djerfisherite is an important carrier of potassium in highly reduced enstatite chondrites, where it occurs in sub-round metal-sulfide nodules. These nodules were once free-floating objects in the protoplanetary nebula. Here, we analyze existing and new data to derive an equation of state (EOS) for djerfisherites of K_{6}(Cu,Fe,Ni)^{B} (Fe,Ni,Cu)^{C}_{24} S_{26}Cl structural formula. We use this EOS to calculate the thermal stability of djerfisherite coexisting in equilibrium with a cooling vapor of solar composition enriched in a dust analogous to anhydrous, chondritic interplanetary dust (C-IDP). We find that condensed mineral assemblages closely match those found in enstatite chondrites, with djerfisherite condensing above 1000 K in C-IDP dust enriched systems. Results may have implications for the volatile budgets of terrestrial planets, and the incorporation of K into early-formed, highly reduced, planetary cores. Previous work links enstatite chondrites to the planet Mercury, where the surface has a terrestrial K/Th ratio, high S/Si ratio, and very low FeO content. Mercury's accretion history may yield insights into Earth's.
The Karavansalija Mineralized Center (KMC) with its Au–Cu skarn mineralization associated with the Rogozna Mountains magmatic suite in southwestern Serbia belongs to the Oligocene Serbo-Macedonian magmatic and metallogenic belt (SMM-MB). Samples from intrusive and volcanic rocks at the KMC show typical arc signatures of subduction-derived magmas through enrichment in large-ion lithophile elements (LILE) and depletion of high–field strength elements (HFSE). The magmas developed a high-K (calc-alkaline) fractionation trend and evolved toward shoshonitic compositions. Whole-rock trace element data suggest plagioclase-absent, high-pressure amphibole ± garnet fractionation that generates adakite-like hydrous magmas during evolution in lower crustal magma chambers. Zircon LA–ICP–MS and high-precision CA–ID–TIMS dating together with zircon trace elements and Hf isotope measurements were carried out in order to couple the geochronologic and geochemical evolution of the KMC. The results suggest that magmatism starts around 29.34 Ma with granitic to rhyodacitic subvolcanic intrusions followed by a more evolved magmatic intrusion that was emplaced into Cretaceous limestone, generating a widespread skarn alteration at ca. 28.96 Ma. After a period of quiescence of about 1.2 My, either another magma body evolved or the same upper crustal magma chamber was recharged and also likely partly reactivated older plutonic rocks as indicated by xenocrysts. The REE ratios shift from apatite, titanite ± amphibole-dominated fractionation of the older magmatic event to crystallization of allanite, efficiently depleting the LREE and Th/U in the younger upper crustal magma. After a lamproite-like melt was injected, the increased heat and fluid pressure led to the expulsion of a quartz-monzonite porphyritic stock at ca. 27.72 Ma, strongly interacting with the skarns and established a fertile hydrothermal system. Soon after a non-mineralized second pulse of some porphyry dykes cut the previous phenocryst-rich “crowded” porphyries and skarns at ca. 27.60 Ma, thus bracketing the maximum timespan of ore mineralization to about 112 ± 45 Ka. Increased contribution of a lamproite-like melt is inferred from the presence of phlogopite micro-phenocrysts, phlogopitization of biotite, and diopside clusters in the latest porphyry dykes. There is a trend of increased crustal assimilation from the oldest volcanic phase to the emplacement of the youngest porphyry dykes recorded by ɛ-Hf of the zircons. Oligocene occurrences of significant base metal mineralization within Serbia, northern Macedonia, and Greece, e.g., Crnac, Rudnik, Veliki Majdan, Stratoniu, or the Cu–Au porphyry at Buchim (northern Macedonia), are all associated with trachy-andesitic (quartz latitic) porphyry dykes, which originated through post-collisional tectonic settings or upper plate extension involving reworking of crustal arc-derived rocks and partial melting of the mantle wedge. This study demonstrates that on the basis of field relationships and the application of high-precision CA-ID-TIMS zircon age data, pulses of porphyry dykes of a 10ka age range can be distinguished, and the timing of mineralization can be parenthized.
Giulia Perotti, Henning O. Sørensen, Henning Haack
et al.
Protoplanetary disks are dust- and gas-rich structures surrounding protostars. Depending on the distance from the protostar, this dust is thermally processed to different degrees and accreted to form bodies of varying chemical compositions. The primordial accretion processes occurring in the early protoplanetary disk such as chondrule formation and metal segregation are not well understood. One way to constrain them is to study the morphology and composition of forsteritic grains from the matrix of carbonaceous chondrites. Here, we present high-resolution ptychographic X-ray nanotomography and multimodal chemical micro-tomography (X-ray diffraction and X-ray fluorescence) to reveal the early history of forsteritic grains extracted from the matrix of the Murchison CM2.5 chondrite. The 3D electron density maps revealed, at unprecedented resolution (64~nm), spherical inclusions containing Fe-Ni, very little silica-rich glass and void caps (i.e., volumes where the electron density is consistent with conditions close to vacuum) trapped in forsterite. The presence of the voids along with the overall composition, petrological textures, and shrinkage calculations is consistent with the grains experiencing one or more heating events with peak temperatures close to the melting point of forsterite ($\sim$2100~K) and subsequently cooled and contracted, in agreement with chondrule-forming conditions.