Hasil untuk "Petrology"

Hamed Chenari, Yaser Ahmadi, David A. Wood

Abstract The precipitation and deposition of asphaltenes in oil reservoirs severely impair production efficiency by reducing permeability and clogging pore networks. Developing effective, environmentally sustainable inhibition strategies is therefore critical for flow assurance and enhanced oil recovery. This study investigates a novel green nanocomposite (NCs) of ZnO/SiO2/xanthan-gum/walnut-shell composition for controlling asphaltene adsorption using Iranian heavy crude and 99.99% CO2 at 89 °C and pressures up to 33 MPa. An integrated approach combining ultraviolet-visible (UV-Vis) spectrophotometry, high-pressure CO2-crude oil interfacial tension (IFT) measurement, and atomic force microscopy (AFM) surface topography mapping was employed to evaluate the NCs performance under simulated reservoir conditions (89 °C, up to 33 MPa). This study reports the first direct, quantitative correlation between NCs-induced surface smoothening (via AFM) and macroscopic permeability retention in native-state crude systems under reservoir conditions, a linkage not previously quantified. Adsorption behavior was modeled using Langmuir and Freundlich isotherms, and core flooding experiments were used to assess permeability preservation. The NCs demonstrated superior asphaltene inhibition. Adsorption isotherm analysis confirmed a monolayer chemisorption process, best described by the Langmuir model (R2 = 0.9951), suggesting surface-limited monolayer adsorption with a high capacity (Qm = 434.78 mg/g), exceeding conventional adsorbents like silica. IFT measurements revealed that the NCs significantly modified the pressure-dependent interfacial behavior, enhancing the IFT slope in the high-pressure regime (> 30 MPa) by 38.5% compared to the untreated system. AFM topographic analysis quantitatively confirmed a dramatic reduction in surface roughness on sandstone substrates: average roughness (Ra) decreased by ~ 21.66%, root mean square roughness (Rq) by ~ 40.23%, and peak-to-valley height (Rt) by ~ 95.08%. Core flooding tests corroborated these nanoscale findings, showing substantial permeability and porosity preservation in NCs-treated cores. The results conclusively demonstrate that the NCs effectively inhibits asphaltene deposition through three synergistic mechanisms: interfacial thermodynamics modification, high-capacity monolayer adsorption, and nanoscale surface smoothening. The key novelty of this work lies in establishing a direct, quantitative correlation between NCs-mediated surface roughness reduction (AFM) and macroscale permeability preservation, a link not previously documented. This study provides a sustainable, high-performance solution for managing asphaltene-induced formation damage in depleting oil reservoirs.

Å. Fagereng, J. F. A. Diener, C. J. Tulley et al.

Abstract The Malawi Rift is localized within Precambrian amphibolite‐granulite facies metamorphic belts, bounded by up to 150 km long border faults, and generates earthquakes throughout ∼40 km thick crust. Rift‐related faults are inferred to exploit pre‐existing weaknesses that allow rifting of otherwise dry and strong crust. It is unclear what these weaknesses are, and how localization into weak zones can be reconciled with strength required for lower crustal seismicity. We present results of mineral equilibria modeling, which indicate that Proterozoic metamorphism generated dry crust dominated by a quartz‐feldspar assemblage that is metastable at current conditions. For rift propagation to be possible at current cool thermal gradients and in mechanically strong, dry quartzofeldspathic rocks, mid‐ to lower‐crustal strain must be localized into relatively weak, inherited shear zones that deform primarily by aseismic, viscous creep. These shear zones are embedded within high‐strength crust, and interaction between creeping shear zones and enveloped or surrounding rocks may locally increase stress and trigger frictional, seismic slip at mid‐ to lower‐crustal depths. Over time, this interaction may produce a fracture network that allows infiltration of fluids. We therefore suggest that during rifting of previously deformed and metamorphosed crust, major faults are most likely to grow from below, with their location and orientation prescribed by underlying inherited viscous shear zones. In this case, fluids may infiltrate and locally weaken metastable lower crust, including allowing time‐dependent fluid‐driven seismicity and local partial melting, but length‐scales of this weakening is limited by the scale of the permeability network.

Michiel Arts, Carlo Corradini, Monica Pondrelli et al.

The type-Silurian Cellon section in the Carnic Alps in Austria underpins much of the current Silurian conodont zonations, forming the basis for the Silurian timescale. However, the Silurian record of the Cellon section lacks radiometric and astrochronological age constraints, making it difficult to gain insights into the processes pacing Silurian (anoxic) events. To attain age constraints and investigate the pacing Silurian (anoxic) events by astronomical cycles, a cyclostratigraphic study was conducted on high-resolution pXRF (CaO, Al2O3, and Fe2O3) and induration records spanning the Ludlow and Pridoli parts of the Cellon section. Astronomical cycles ranging from precession to the 405-kyr eccentricity cycle were first recognised visually in the field and in proxy records. The visual detection of astronomical cycles served as an input for the WaverideR R package, enabling the tracking of the 405-kyr eccentricity period in each proxy’s continous wavelet transform scalograms. These tracked period curves were combined with external age controls through multiple Monte Carlo simulations, generating an (absolute) age model. This age model is used to assign ages and durations and their respective uncertainties to a hiatus in the Ludfordian, conodont zones, lithological units, geochronological units and events, yielding new ages for Silurian stage boundaries (e.g., Gorstian-Ludfordian boundary at 425.92 ± 0.65 Ma, the Ludfordian-Pridoli boundary at 423.03 ± 0.53 Ma, the Silurian-Devonian boundary at 418.86 ± 1.02 Ma), and new durations for the Ludfordian at 2.89 ± 0.35 Myr and Pridoli at 4.24 ± 0.46 Myr. Furthermore, the imprint of astronomical cycles in the Cellon section itself indicates that the Linde, Klev and Silurian-Devonian boundary events all occur after a 2.4-Myr eccentricity node, indicating pacing by astronomical forcing, similar to other Devonian and Cretaceous anoxic events. The Lau event, however, does not appear to coincide with a 2.4-Myr eccentricity node.

Leonid M. Bogomolov, Dmitry V. Kostylev, Natalya V. Kostyleva et al.

The results of experiments on electrical sounding of the near-surface layer of the Earth's crust in the fault zone, which have involved a recording of seismoacoustic and seismic noise in the close zone near the source (the primary dipole source), are represented. The experiments were carried out in 2021–2022 in the southern part of the Central Sakhalin fault with the use of the generator of electric pulses developed at IMGG FEB RAS, output electric power being up to 3 kW. The aim was to reveal seismoacoustic signatures of the medium reaction to the soundings with current pulses of 5–13 A. The generator provided significantly higher current in the dipole than its typical characteristics in the case of soundings for electrical exploration by resistance methods, as well as in the case of conventional seismic and electrical exploration. At the same time, the range of current amplitudes was much smaller in comparison with the case of a deep sounding based on application of geophysical MHD generators or other extra high-power electric pulses units. Up to now, the inverse seismoelectric effect has remained practically unexplored at currents in the “intermediate” range of ~10 A and scale lengths of the order of few hundreds of meters. The presence or absence of the medium reaction to electrical soundings was distinguished by the records of molecular-electronic sensors developed by R-sensors LLC: the CME-6111 broadband seismometer and the hydrophone, installed at a distance of about 50 m from one of the poles of the electric dipole source. An increase in the average level of seismoacoustic noise during electrical soundings was revealed, which is essentially a variety of the inverse seismoelectric effect of the second kind (excitation of elastic waves during an electric current run in a two-phase medium). Previously, no similar signature of medium reaction to the current pulses was noted in the close zone adjacent to one of the dipole electrodes. The noise level increase occurs almost without delay after the start of electrical soundings, and this is in accordance with the previously obtained results on the responses of seismic acoustic emission to powerful current pulses, which were used for a deep sounding in the Northern Tien Shan.

Shanyong Liu, Nai Cao, Yishan Lou et al.

Abstract Multistage fracturing technology is the primary means of reservoir stimulation in shale gas wells. However, the productivity contribution of each stage varies greatly. It is essential to evaluate the fracturing effect in order to make an optimized treatment design. In this study, we adopted an integrated workflow to assess the main control factors of geological and engineering parameters and a novel approach was proposed for post-fracturing evaluation. For this purpose, the H block in Zhaotong shale gas demonstration zone in Sichuan, China, has been taken as an object of study. The production predicting model was built based on the reservoir fracability index (RFI) which took both fluid type and proppant size differences into consideration. The results demonstrated that (1) if the reservoir quality index (RQI) in the target zone is greater than 5.0, then the area has good reservoir quality and development potential. (2) The RFI of H Block is generally at 4.0–6.0, it can be used as the key parameter to screen out the sweet spot. This method not only serves as a set of practical fracturing evaluation methods but also as a set of productivity prediction and fracturing optimization methods, which can provide strong support for the development of shale gas reservoirs.

Mohammad Hassan Karimpour, Nargess Shirdashtzadeh, Martiya Sadeghi

ntroduction The granitic rocks are divided into magnetite and ilmenite series (Ishihara 1977), coinciding spatially with the I-type (εNdi0; (87Sr/86Sr)i~0.704-0.706) and S-type granites (εNdi<0; (87Sr/86Sr)i~0.708-0.765), respectively (Takahashi et al., 1980). Most porphyry Sn deposits are associated with ilmenite (S-type) granitoids (Ishihara, 1977; Neiva, 2002). The published concepts on the origin and tectonomagmatic setting of Sanandaj-Sirjan Zone (SaSZ) Jurassic granitoids of 178-160 Ma are (1) metaluminous I-type granites formed in a magmatic arc of an Andean subduction system (Khalaji et al., 2007; Tahmasbi et al., 2010; Ahadnejad et al., 2011; Esna-Ashari et al., 2012), (2) subduction-related extensional basin (Shahbazi et al., 2010), (3) continental crust melting by roll-back of Neo-Tethys oceanic crust (Zhang et al., 2018), and (4) subduction-related S-type granites (Bayati et al., 2017). In this research, the origin and tectonomagmatic setting of Jurassic granitoids (from 178 to 160 Ma) in Sanandaj-Sirjan Zone and the tin mineralization potential are investigated based on the available geological, geophysical and isotopic geochemical data. Materials and methods We used an integrated collection of published geochemical data (major, trace and rare earth elements of 102 samples), isotopic (e.g., (87Sr/86Sr)I of 50 samples, ƐNdi of 64 samples), geochronological (U-Pb dating of zircons), and geophysical data (airborne magnetic intensity) for the SaSZ granitoids of 178-160 Ma. Result The SaSz Jurassic granitoids include granite, monzonite, diorite, Syenogranite, tonalite batholiths. The (87Sr/86Sr)I>0.707, N-MORB normalized patterns with enrichment in Low- and High Field Strength Elements (LFSE and HFSE) and depletion in P and Ti contents, chondrite-normalized patterns with flat heavy rare earth elements (HREE) patterns, magnetic susceptibility <10-5x100 (ilmenite series), no alteration, and no Sn, Cu, Pb, and Zn anomalies in whole rock composition of granitoids nor in the associated river sediments, absence of volcanic rocks, and occurrence of metamorphic rocks (slate and schist) during Cimmerian orogeny indicate the SaSZ granitoids are S-type granitoids formed in a continental collision zone. Discussion Geological, geophysical and geochemical characteristics of granitoids in Sanandaj-Sirjan Zone (such as the absence of volcanic arc and volcanic rocks, continental crust thickening (56-52 km) and the formation of large-scale (batholith) granitoids at depths >4 km, regional metamorphism at ​​green schist facies (and amphibolite) following Cimmerian orogeny, low (Eu/Eu)N (reducing conditions), magnetic susceptibility <100x10-5 (ilmenite series), negative εNdi and (87Sr/86Sr)I >0.707) show that, unlike previous studies, these granitoids are S-type granitoids formed by melting the continental crust in a collisional zone. Therefore, tin mineralization might probably occurred in connection with them. However, there is ample evidence of the absence of tin mineralization by the magma that forms these S-type granitoids, that are including the lack of hydrothermal fluids and consequently mineralization potential (due to the absence of alteration minerals in ASTER satellite images), low content of tin, copper, lead and zinc elements in these granitoids Sanandaj-Sirjan Zone and associated river sediments, (Eu/Eu)N value > 0.2, Rb/Sr <3, low Y (10-75 ppm), Ba > 200 ppm, as well as the geological, geophysical and geochemical similarities to barren S-type (ilmenite series) granitoids in Lut block (in Najmabad, Sorkh kuh to Shah kuh areas) which have formed in a continental collision system during the Cimmerian orogeny. References Ahadnejad, V., Valizadeh, M., Deevsalar, R. and Rezaei-kahkhaei, M., 2011. Age and geotectonic position of the Malayer granitoids: Implication for plutonism in the Sanandaj-Sirjan Zone, W Iran. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen, 261(1): 61–75. https://doi.org/10.1127/0077-7749/2011/0149 Bayati, M., Esmaeily, D., Maghdour-mashhour, R., Li, X. and Stern, R.J., 2017. Geochemistry and petrogenesis of Kolah-Ghazi granitoids of Iran: Insights into the Jurassic Sanandaj-Sirjan magmatic arc. Chemie der Erde- Geochemistry, 77(2): 281–302. https://doi.org/10.1016/j.chemer.2017.02.003 Esna-Ashari, A., Tiepolo, M., Valizadeh, M., Hassanzadeh, J. and Sepahi, A., 2012. Geochemistry and zircon U–Pb geochronology of Aligoodarz granitoid complex, Sanandaj-Sirjan Zone, Iran. Journal of Asian Earth Sciences, 43(1): 11–22. https://doi.org/10.1016/j.jseaes.2011.09.001 Ishihara, S., 1977. The Magnetite-series and Ilmenite-series Granitic Rocks. Mining Geology, 27(145): 293–305. https://doi.org/10.11456/shigenchishitsu1951.27.293 Khalaji, A.A., Esmaeily, D. and Valizadeh, M. V., 2007. Petrology and geochemistry of the granitoid complex of Boroujerd, Sanandaj-Sirjan Zone, Western Iran. Journal of Asian Earth Sciences, 29(5-6): 859–877. https://doi.org/10.1016/j.jseaes.2006.06.005 Neiva, A.M.R., 2002. Portuguese granites associated with Sn-W and Au mineralizations. Bulletin of the Geological Society of Finland, 74: 79–101. https://doi.org/10.17741/bgsf/74.1-2.003 Shahbazi, H., Siebel, W., Pourmoafee, M., Ghorbani, M., Sepahi, A.A., Shang, C.K. and Abedini, M.V., 2010. Geochemistry and U – Pb zircon geochronology of the Alvand plutonic complex in Sanandaj – Sirjan Zone (Iran): New evidence for Jurassic magmatism. Journal of Asian Earth Sciences, 39(6): 668–683. https://doi.org/10.1016/j.jseaes.2010.04.014 Takahashi, M., Aramaki, S. and Ishihara, S., 1980. Magnetite-Series/Ilmenite Series vs. I-type/S-type granitoids, Granitic Magmatism and related mineralization. Mining Geology, Special Issue, 8: 13–28. Tahmasbi, Z., Castro, A., Khalili, M., Khalaji, A.A. and De, J., 2010. Petrologic and geochemical constraints on the origin of Astaneh pluton, Zagros. Journal of Asian Earth Sciences, 39(3): 81–96. https://doi.org/10.1016/j.jseaes.2010.03.001 Zheng, W., Mao, J., Zhao, C., Zhang, Z., Xiao, W., Ji, W., Majidifard, M.R., Rezaeian, M., Talebian, M., Xiang, D., Chen, L., Wan, B., Ao, S. and Esmaeili, R., 2018. Geochemistry, zircon U-Pb and Hf isotope for granitoids, NW Sanandaj-Sirjan zone, Iran: Implications for Mesozoic-Cenozoic episodic magmatism during Neo-Tethyan lithospheric subduction. Gondwana Research, 62: 227–245. https://doi.org/10.1016/j.gr.2018.04.002

Akash Talapatra, Md. Mostafijul Karim

Abstract Moisture adsorption in the coal seams affects the gas adsorption capacity and can alter the coal deformation and permeability criteria of the coal seam. The effect of dynamic loss of moisture content, both on moisture and gas sorption-induced coal swelling/shrinkage strains, during the coalbed methane (CBM) production, is crucial. This study investigates the interactions among coal matrix, absorbed gas, and moisture content, based on the coal swelling/shrinkage strains and gas adsorption decay criteria. Consequently, a mathematical model of the coal deformation is developed for the proper evaluation of the moisture effect. For developing the model, this paper considers the standard gas flow and moisture loss equations to assess the volumetric content, equilibrium pressure, and density of the moisture. Finally, it comprehensively analyzes the sensitive factors and effects of elemental parameters of moisture content on coal deformation and coal permeability. The results show that moisture content at adsorbed state significantly changes the coal swelling/shrinkage strain and that distorted swelling and shrinkage characteristics can promote the permeability alternation in wet coal reservoirs. Moreover, the intermolecular attraction between the coal structure and the moisture content has a significant effect on methane adsorption/desorption-induced deformation in coal structure. This study also designs the coal deformation strains as a function of moisture content by the Langmuir type model and evaluates the hysteresis rate between the swelling and shrinkage characteristics. The findings of this paper can characterize a wet coal reserve for CBM production and anticipate future production under different operating conditions.

Mohamed A. Abd El-Moniem, Ahmed H. El-Banbi

Abstract The importance of gas production has increased as gas represents a clean source of energy. We studied different multiphase flow correlations for gas wells. We collected large database for bottomhole flowing pressure for different flow conditions and well configurations. In total, 32 gas wells were selected and our target was to study the effect of multiphase flow correlations input parameters on the accuracy of the predicted pressure drop. Several important multiphase correlations input parameters were selected for this study. These include condensate to gas ratio (CGR) and water to gas ratio (WGR) which represent the production conditions, API and specific gravity of surface gas (Ɣ g) which represent PVT properties and the tubing roughness (ε) which represents the tubing condition. Our method was based on changing the values of these selected parameters by a percentage from its original value and determining the new predicted bottomhole flowing pressure. Consequently, we determined the new error compared to the actual measured bottomhole pressure. We performed 352 cases, and we could obtain the effect of the different parameters on both pressure drop calculations and the selection of the best correlation. Guidelines were developed to explain which parameters are more important to be measured accurately for different conditions.

Oscar J. Nhabanga, Philip S. Ringrose

In order to develop an improved pore pressure prediction model for the overburden mudstones in the Rovuma Basin, offshore Mozambique, we apply Eaton's method to example well data from three exploration wells, which intersect Quaternary, Tertiary and Cretaceous sediments over depth intervals down to ∼3 km below seafloor. The predictive method only included the effects of mechanical compaction, which is a reasonable assumption for the low-temperature shallow sections. We found that Eaton's method applied to resistivity and acoustic log attributes works well and can be used to identify the mudstones that display over-pressured or normally pressured sections. The predicted pore pressures showed a good match to pore pressures in permeable formations. Using this calibration, we derived an improved pore-pressure prediction method for these wells and for the Rovuma Basin in general. The resulting model should give a good basis for future analysis of compaction processes and pore pressure in this basin.

Mehdi Ghommem, Mustapha Abbad, Gallyam Aidagulov et al.

Abstract Accurate acid placement constitutes a major concern in matrix stimulation because the acid tends to penetrate the zones of least resistance while leaving the low-permeability regions of the formation untreated. Degradable materials (fibers and solid particles) have recently shown a good capability as fluid diversion to overcome the issues related to matrix stimulation. Despite the success achieved in the recent acid stimulation jobs stemming from the use of some products that rely on fiber flocculation as the main diverting mechanism, it was observed that the volume of the base fluid and the loading of the particles are not optimized. The current industry lacks a scientific design guideline because the used methodology is based on experience or empirical studies in a particular area with a particular product. It is important then to understand the fundamentals of how acid diversion works in carbonates with different diverting mechanisms and diverters. Mathematical modeling and computer simulations are effective tools to develop this understanding and are efficiently applied to new product development, new applications of existing products or usage optimization. In this work, we develop a numerical model to study fiber dynamics in fluid flow. We employ a discrete element method in which the fibers are represented by multi-rigid-body systems of interconnected spheres. The discrete fiber model is coupled with a fluid flow solver to account for the inherent simultaneous interactions. The focus of the study is on the tendency for fibers to flocculate and bridge when interacting with suspending fluids and encountering restrictions that can be representative of fractures or wormholes in carbonates. The trends of the dynamic fiber behavior under various operating conditions including fiber loading, flow rate and fluid viscosity obtained from the numerical model show consistency with experimental observations. The present numerical investigation reveals that the bridging capability of the fiber–fluid system can be enhanced by increasing the fiber loading, selecting fibers with higher stiffness, reducing the injection flow rate, reducing the suspending fluid viscosity or increasing the attractive cohesive forces among fibers by using sticky fibers.

Aadi Khanal, Ruud Weijermars

Abstract The drainage areas (and volumes) near hydraulically fractured wells, computed and visualized in our study at high resolution, may be critically affected by the presence of natural fractures. Using a recently developed algorithm based on complex analysis methods (CAMs), the drained rock volume (DRV) is visualized for a range of synthetic constellations of natural fractures near hydraulic fractures. First, flow interference effects near a single hydraulic fracture are systematically investigated for a variety of natural fracture sets. The permeability contrast between the matrix and the natural fractures is increased stepwise in order to better understand the effect on the DRV. Next, a larger-scale model investigates flow interference for a full hydraulically fractured well with a variety of natural fracture sets. The time of flight contours (TOFCs) outlining the DRV are for all cases with natural fractures compared to a base case without any natural fractures. Discrete natural fractures, with different orientations, hydraulic conductivity, and fracture density, may shift the TOFC patterns in the reservoir region drained by the hydraulically fractured well, essentially shifting the location of the well’s drainage area. The CAM-based models provide a computationally efficient method to quantify and visualize the drainage in both naturally and hydraulically fractured reservoirs.

Marzieh Ghadirpour, Jamshid Ahmadian, Shahzad Sherafat et al.

Introduction Clinopyroxene is one of the most common of the rock forming minerals. Its long formation period (from the earliest crystallization of magma in the core of phenocrysts to the final microcrystalline crystallization in the rock background) can show the history of the host magma crystallization. The composition of clinopyroxene, especially those phenocrysts, in volcanic rocks could well establish the magmatic nature of the host lava. The clinopyroxene composition can point out the magmatic series, the tectonic environment and the source rock (Kushiro, 1960; Nisbet and Pearce, 1977, Leterrier et al., 1982). In addition, it is possible to estimate the temperature and pressure of rock formation by studying the chemistry of clinopyroxenes (Nimis and Taylor, 2000; Putirka, 2008). The study area is located in the middle part of the Urumieh- Dokhtar magmatic belt. It exactly lies in the area between Tarq and Mazdeh, its longitude is 51° 43' to 52° 00' E and its latitude is 33° 15' to 33° 30' N. The Eocene magmatic rocks vary from rather basic to acidic in composition, but they are mainly intermediate and they are rather basic rocks (Ghadirpour, 2017). Previously, various studies on using the chemical composition of the major elements of clinopyroxene were conducted to discover the conditions for the formation of igneous rocks in different parts of Iran (Sayari and Sharifi, 2016; Falahaty et. al., 2016; and Mohammadi et. al., 2017). So far, in all of these studies that have been conducted on volcanic rocks, the mineral chemistry of clinopyroxene has not been used to evaluate the magma's features such as temperature, pressure, and oxygen fugacity. In this article, we are going to study the mentioned features of magma by using chinopyroxene chemistry. Materials and Methods To determine the geotectonic setting and the physicochemical conditions of volcanic rocks, thirty thin sections have been prepared. Their minerals and texture have been studied by using polarizing binocular microscope (Olympus BH-2). After detailed mineralogy and selection of suitable samples, microprobe analysis is done by EPMA (JEOL- JXA) in the Naruto University, Japan. The mineral analysis is performed at 15 nA intensity of current and accelerate voltage of 15 Kev. Discussion The study area is situated in the South of Natanz, between Tarq and Mazdeh villages. The volcanic rocks vary from acidic to rather basic (basaltic andesite to andesite and rarely rhyolite). Microlitic porphyric, glomeroporphyric and vesicular are some textures which are observed in the volcanics. Plagioclase and euhedral clinopyroxene occasionally with simple twinning are characteristic minerals of rocks. According to Wo-En-Fs diagram (Morimoto, 1989), clinopyroxene shows mainly the composition of augite. It is concluded that the magmatic series of rocks is calc-alkaline which is in relation to the subduction of the Neotethys oceanic crust under the central Iranian plate. There are several diagrams that are used for this purpose which are as follows. The Al2O3-Ti2O diagram (Le Bas, 1962): In this diagram, the studied clinopyroxene shows the nature of calc-alkaline. One of the diagrams used to determine the tectonic setting according to clinopyroxene composition is the F1- F2 diagram (Nisbet and Pearce, 1977). Based on this diagram, the Tarq- Mazdeh volcanic rocks belong to the magmatic arc environment. The Clinopyroxene temperatures are calculated by using a variety of methods which indicate that most of clinopyroxene in temperature range of 1150 to 1200°C has been crystallized (Soesoo, 1997). The temperature indicates changes in crystallization of clinopyroxene. Result The calculated temperatures of clinopyroxenes by using various methods show that they are crystalized in the temperature range of 1150 to 1200˚c. It mainly means that there is a change in temperature during clinopyroxene crystallization. By considering the barometric diagram, the pressure of clinopyroxene formation has been determined below 10 kb, in the depth range of 2 to 5 km. References Falahaty, S., Noghreyan, M., Sharifi, M., Torabi, Gh., Safaei, H. and Mackizadeh, M., 2016. Clinopyroxene application in petrogenesis identification of volcanic rocks associated with salt domes from Shurab (Southeast Qom). Journal of Economic Geology, 8(1): 21–38. (in Persian with English abstract) Ghadirpour, M., 2017. Petrology and geochemistry of volcanic rocks in south of Natanz (between Tarq and Mazdeh). M.Sc. Thesis, Payam Noor University, Isfahan, Iran, 110 pp. Kushiro, I., 1960. Si- AI relation in clinopyroxenes from igneous rocks. American Journal of Science, 258(5): 548–554. Le Bas, N.J., 1962. The role of aluminous in igneous clinopyroxenes with relation to their parentage. American Journal of Science, 260(4): 267–88. Leterrier, J., Maury, R.C., Thonon, P., Girard, D. and Marchal, M., 1982. Clinopyroxene composition as method of identification of the magmatic affinities of paleo-volcanic series. Earth and Planetary Science Letters, 59(1): 139–154. Mohammadi, S.S., Bayani, R., Nakhai, M., Chung, S.L. and Zarrinkoub, M.H., 2017. Petrography, mineral chemistry, geochemistry and geotectonic setting of tertiary volcanics of Shushk (East of Sarbisheh), Southern Khorasan. Iranian Journal of Crystallography and Mineralogy, 25(1): 167–186. (in Persian) Morimoto, N., 1989. Nomenclature of pyroxenes. The Canadian Mineralogist, 27(1): 143–156. Nimis, P. and Taylor, W.R., 2000. Single clinopyroxene thermobarometry for garnet peridotite. Part 1. and Calibration testing of a Cr-in-Cpx barometer and an enstatite-in-Cpx thermometer. Contributions to Mineralogy and Petrology, 139(5): 541–554. Nisbet, E.G. and Pearce, J.A., 1977. Clinopyroxene composition of mafic lavas from different tectonic settings. Contributions to Mineralogy and Petrology, 63(2): 161–173. Putirka, K., 2008. Thermometers and Barometers for Volcanic Systems. Reviews in Mineralogy and Geochemistry, 69(1): 61–120. Sayari, M. and Sharifi, M., 2016. Application of clinopyroxene chemistry to interpret the physical conditions of ascending magma, a case study of Eocene volcanic rocks in the Ghohrud area (North of Isfahan). Journal of Economic Geology, 8(1): 61–78. (in Persian with English abstract) Soesoo, A., 1997. A multivariate statistical analysis of clinopyroxene composition: empirical coordinates for the crystallization P-T estimations. GFF, 119(1): 55–60.

Ali Hassani, Masood Mostofi, Mohammad Reza Kamali

Abstract Formation damage is a great concern in reservoir management and can potentially occur due to exposure of formation to alkaline fluids. Exceeding pH over a critical pH may result in an in situ release of fine particles and therefore can cause pore plugging. In this study, a series of core-flooding experiments was carried out to determine the critical pH of alkaline fluids flooding through core samples of Fahliyan carbonate formation. Alkaline fluids with different pH were injected into the core samples and the alkaline sensitivity of the carbonate formation was measured in both qualitative and quantitative forms. The applied approach provides an accurate determination of the degree of formation damage at a base pH (pH = 7) following successive changes in the fluid alkalinity. In addition, the pH values corresponding to different degrees of formation damage, determined qualitatively in other works, are calculated precisely in this paper. The flooded cores showed different response when exposed to fluids with different alkalinity while the degree of induced formation damage varied from ‘negligible’ to ‘severe’ which were, in some cases, noticeable and often irreversible. A polynomial relationship between the fluid alkalinity and the corresponding degree of formation damage was proposed for core no.3, which is compared with the conventional methods (Renpu method) underestimating the degree of formation damage (D k) compared to the modified approach introduced in this paper.

Олег Александрович Максимов, Oleg Maksimov

New geological and petrological data are presented for the Precambrian eclogites of Gridino area, Belomorian Province. The detailed optical and microprobe studies of eclogites in the Samylino locality allow distinguishing the essential features of eclogitic metamorphism in this area. The early stage of high-pressure metamorphism in this tholeiitic series mafic rocks is recognized by the presence of diopside-plagioclase symplectitic inclusions (symplectites I) in the central parts of large omphacite (jadeite 30–35 %) crystals and in the cores of zoned garnet grains. The eclogitic metamorphism is distinguished by omphacite in the matrix and its inclusions in the garnet (pyrope 27–30 %, almandin 48–52 %, grossular 19–23 %) inner zones. The high-pressure amphibolite facies<br />overprinting is represented by garnet rims (pyrope 22–24 %, almandin 52–56 %, grossular 22 %) and diopside-plagioklase (± hornblende) symplectites II. These data suggest a two-stage character of eclogitic metamorphism in Gridino area.

Mian Umer Shafiq, Hisham Khaled Ben Mahmud, Muhammad Khurram Zahoor et al.

Abstract Properties of rock, such as effective porosity, permeability and pore size distribution (PSD), are generally referred to as petrophysical properties. These properties are among the most significant for reservoir evaluation. Acid stimulation treatments are usually used in sandstones to mitigate the impact of formation damage, with the aim of restoring or enhancing the natural matrix permeability and consequently boosting the well productivity. Hydrochloric acid (HCl) is commonly used in the preflush stage to remove calcium and other metal ions, preventing the development of calcium fluoride (CaF2) and other silicate precipitates that could block the pore throats, while an acid mixture (HF–HCl combination) is usually preferred as the main stimulation fluid for the removal of quartz and remaining metal ions. However, sometimes the application of these acids can lead to other problems, including fast reactions, corrosion of pipes, environmental hazards, precipitation reactions and formation damage due to the incompatibility of HCl with clay minerals, so chelating agents have been proposed as an alternative for matrix stimulation fluids. In this study, three different chelating agents, ethylenediaminetetraacetic acid (EDTA), N-(2-hydroxyethyl) ethylenediamine-N,N′,N′-triacetic acid (HEDTA) and N-acetyl-l-glutamic acid (GLDA), have been used to stimulate Berea sandstone, Colton tight sandstone and Guelph dolomite samples. Core flood experiments were conducted on 1.5 × 3 (in2) core plugs, at a temperature below 180 °F. A slow injection rate of (1–0.5 cc/min) was chosen for the treatment fluid, promoting the dissolution of ions by increasing the contact time between the fluid and the rock. Furthermore, nuclear magnetic resonance, wettability and micro-computed tomography (CT scan) analyses were employed to evaluate the effect of the acid treatment on formation properties such as porosity, PSD, pore topology, wettability and pore structure. After exposing the samples to HEDTA, large wormholes were detected in their pore network, demonstrating that HEDTA has the highest potential to create new pore spaces when compared to GLDA and EDTA when reacted with both types of samples.

Yu-Ming Liu, Yue Dong, Zhen-Hua Rui et al.

Abstract CO2 reservoirs are widely distributed within the Yingcheng Formation in the Songliao Basin, but the extreme horizontal heterogeneity of CO2 content causes difficulties in the exploration and exploitation of methane. Former studies have fully covered the lithology, structure, and distribution of the reservoirs high in CO2 content, but few are reported about migration and accumulation of CO2. Using the East Changde Gas Field as an example, we studied the accumulation mechanisms of CO2 gas. Two original types of accumulation model are proposed in this study. The fault-controlled accumulation model refers to gas accumulation in the reservoir body that is cut by a basement fault (the West Xu Fault), allowing the hydrocarbon gas generated in the lower formation to migrate into the reservoir body through the fault, which results in a relatively lower CO2 content. The volcanic conduit-controlled accumulation model refers to a reservoir body that is not cut by the basement fault, which prevents the hydrocarbon gas from being mixed in and leads to higher CO2 contents. This conclusion provides useful theories for prediction of CO2 distribution in similar basins and reservoirs.

Yu-Feng Li, Wei Sun, Xi-Wu Liu et al.

Abstract Shale fractures are an important factor controlling shale gas enrichment and high-productivity zones in the Longmaxi Formation, Jiaoshiba area in eastern Sichuan. Drilling results have, however, shown that the shale fracture density does not have a straightforward correlation with shale gas productivity. Based on logging data, drilling and seismic data, the relationship between shale fracture and shale gas accumulation is investigated by integrating the results of experiments and geophysical methods. The following conclusions have been drawn: (1) Tracer diffusion tests indicate that zones of fracture act as favorable channels for shale gas migration and high-angle fractures promote gas accumulation. (2) Based on the result of azimuthal anisotropy prediction, a fracture system with anisotropy strength values between 1 and 1.15 represents a moderate development of high-angle fractures, which is considered to be favorable for shale gas accumulation and high productivity, while fracture systems with anisotropy strength values larger than 1.15 indicate over-development of shale fracture, which may result in the destruction of the shale reservoir preservation conditions.

Alijan Aftabi, Hengameh Hosseini-Dinani

The Irankuh mining district is located 20 km southwest of Isfahan and is geologically situated in Sanandaj - Sirjan zone and the lower Cretaceous sequence of Isfahan-Malayer ore mineralization area. The ore minerals are emplaced in the faulted contact of Jurassic shale and Cretaceous carbonates and include pyrite, galena, sphalerite, calcite, barite, dolomite, quartz as well as minor marcasite, smithsonite, cerussite, gypsum, malachite, hematite and goethite. The mineralization is mainly occurred as hydrothermal veins and veinlets associated with fractures and faults, suggesting the deposit is likely to be of epigenetic type. A comparison between geothermometric results obtained from calcite twins and fluid inclusions showed a similar temperature range for the mineralization (less than 170ºc). Fluid inclusion studies indicate the temperature, salinity and density ranges of 80-166ºc, 5.39-20.94 wt.% NaCl and 0.95-1.12, respectively. The obtained data share many similarities with those of the MVT deposits

Xiaohong Wang, Jianliang Xu, Mingtao Liu et al.

International deep seabed resource surveys have accumulated a large amount of valuable marine geochemical data. These data, however, derive from a number of autonomous heterogeneous information sources that show the characteristics of big data, i.e., multidisciplinary, multidimensional, multisemantic, and with strong correlations. The traditional database federation method is thus not applicable. To achieve marine geochemical data interoperation, an approach is proposed in this paper. The approach first builds a marine sample ontology (MSO) based on marine geochemical metadata standards. With support of the MSO ontology, which serves as a specification for the semantics and model of multisource heterogeneous data, the data integration and unified query APIs are accomplished across different databases. The experiment is applied with three databases: the ICP-AES database model in the ODP project, the PetDB marine petrology database model compiled at the Lamont-Doherty Earth Observatory, and the GEOROC database model operated by the German Max Planck Institute. The experimental results show that this method not only improves the efficiency of the marine geochemical data integration but also realizes the reuse of data and models under the premise of ensuring the independence, security, and timeliness of the data sources.

O. Bachmann, C. Deering, J. S. Ruprecht et al.