Carlos Rodriguez, Pablo Gómez, Felipe Martí
et al.
This paper presents a microstructural, mineralogical, and mechanical study of low-carbon autoclaved concrete (AC), achieved by partially or fully replacing ordinary Portland cement (OPC) with ground-granulated blast furnace slag (BFS) and substituting lime with calcium carbide slag (CCS). Fourteen mixes were produced and evaluated in the green state and after autoclaving. Quantitative X-ray diffraction (XRD) using the Rietveld method, density, compressive strength, and life cycle assessment (LCA) were conducted. Results show that mixes containing BFS achieve green strengths equal to or higher than the OPC reference, ensuring integrity during autoclaving. Using BFS with an adequate calcium supply promotes the formation of pre-autoclave portlandite, which in turn favors tobermorite development and yields post-autoclave strengths comparable to the OPC reference. Partial lime replacement with CCS (50%) maintains mineralogy and strength, whereas excessive CCS may reduce available portlandite and lower strength. Life-cycle assessment indicates that raw material supply dominates emissions and that removing OPC cuts total CO<sub>2</sub> by 44% without compromising mechanical performance. These findings demonstrate the feasibility of OPC-lean/OPC-free, lime-optimized autoclaved concretes with substantially lower embodied impacts.
Abstract In recent decades, Enhanced Oil Recovery (EOR) has emerged as a primary method to increase reservoir oil recovery rates. One of these methods involves injecting miscible and immiscible gases. In miscible gas injection, the minimum miscibility pressure (MMP) is crucial, representing the critical pressure at which these gases can mix effectively with the oil phase. However, accurately determining the minimum pressure required for CO2 to miscible combine with the oil phase has always been a significant challenge. Various methods, including slim-tube tests, analytical models, and empirical correlations, are employed to determine MMP. Nevertheless, experimental measurements are time-consuming and costly. At the same time, mathematical models may yield different estimations. This study introduces an innovative approach using machine learning (ML) techniques to determine CO2-MMP during CO2 flooding. These methods produce reliable models, and advanced CO2-MMP techniques have demonstrated improved performance, significantly reducing time and costs. Furthermore, ML algorithms such as Artificial Neural Networks (ANN), Bayesian networks, Random Forest (RF), Support Vector Machine (SVM), LSBoost, and Linear Regression (LR) were employed to estimate MMP. Input data for these algorithms include CO2, H2S, N2, C1, C2, C3, C4, C5, C6, C7+, MWC5+, MWC7+, T, alongside vol/int. Comparative analysis with experimental MMP data revealed that the Glaso method achieves an accuracy of 0.8749, among the most precise methods, while SVM performed best among the mentioned ML algorithms with an accuracy of 0.986 and RMSE of 0.027.
Marjolène Jatteau, Jean Cauzid, Cécile Fabre
et al.
Strategic metals are indispensable for meeting the needs of modern society. It is then necessary to reassess the potential of such metals in Europe. For the exploration of strategic metals, portable XRF (X-Ray Fluorescence) and LIBS (Laser Induced Breakdown Spectroscopy) are powerful techniques allowing their multi-elementary analysis. This paper presents a database providing more than 2000 pXRF data and more than 4000 pLIBS spectra acquired on minerals from the Mineralogy and Petrology Museum of National and Kapodistrian University of Athens (NKUA), selected based on their potential in bearing strategic metals. The combination of these two portable techniques, along with expanding dataset on strategic metal-rich minerals, provides valuable insights into strategic metal affinities and demonstrates the effectiveness of portable tools for exploring strategic raw materials. Indeed, such database allows to strengthen the knowledge on strategic metals by producing statistic and chemometric analyses (e.g., boxplot, PCA, PLS) on their distribution.
Bibliography. Library science. Information resources
The exploration and development of shale gas in the Wufeng-Longmaxi Formations (WF-LMX FM) of the Southern Sichuan Basin exhibit pronounced spatial heterogeneity with 3-5 fold gas content variations in strata meeting identical static thresholds (TOC > 2.5wt.%, porosity >5%). This exposes a fundamental disconnect in conventional models that dissociate geochemical potential from tectonic preservation dynamics in post-mature shale systems (Ro > 3.0%). This spatiotemporal decoupling is resolved through process-contingent integration of three critical determinants: thermal maturation trajectories, hydrocarbon generation-preservation windows, and multi-phase tectonic stress imprinting, with fracture connectivity enhancement observed at reduced brittleness thresholds (~35%) via pre-existing microfracture networks inherited from multi-phase deformation events. This study establishes a pioneering multivariate evaluation framework integrating well logs, 3D seismic interpretation, and experimental petrology to decode five governing parameters: Total Organic Carbon (TOC), thermal maturity (Ro), porosity, mineral brittleness, and a preservation potential index (SP) that resolves TOC-Ro-gas content decoupling by quantifying fault throw/erosion rate equilibrium calibrated with shale bed thickness anomalies. Systematic analysis reveals that optimal enrichment necessitates threshold recalibration beyond static paradigms-TOC > 4.0wt.% redefines hydrocarbon potential in high-maturity regimes, while the 3.0-4.0% Ro window balances organic porosity evolution against carbon deposition-induced occlusion. Reservoir viability is further constrained by >4.5% porosity for gas storage capacity and >40% brittle minerals for fracture sustainability. The SP index, incorporating erosional magnitude and fault connectivity, identifies two critical risk zones near the Changning anticline and northern Luzhou, where neotectonic fault reactivation disrupts overpressure maintenance. Spatial synthesis of these constraints delineates two strategic exploration targets: the NW-SE trending Jianwu-Weiyuan slope system exhibiting optimal thermal-structural synergy, and the Luzhou northern anticlinal cluster where fault sealing sustains preservation efficacy. This model resolves the "geochemical preservation paradox" through dynamic process coupling, establishing a transformative paradigm for deep shale gas exploration in thrust-fold terrains.
Hawkar Ali Abdulhaq, János Geiger, István Vass
et al.
This study introduces a robust methodology utilizing Multi-Criteria Decision Analysis (MCDA) combined with an Analytic Hierarchy Process (AHP) to repurpose abandoned hydrocarbon fields for energy storage, supporting the transition to renewable energy sources. We use a geostatistical approach integrated with Python scripting to analyze reservoir parameters—including porosity, permeability, thickness, lithology, temperature, heat capacity, and thermal conductivity—from a decommissioned hydrocarbon field in Southeast Hungary. Our workflow leverages stochastic simulation data to identify potential zones for energy storage, categorizing them into high-, moderate-, and low-suitability scenarios. This innovative approach provides rapid and precise analysis, enabling effective decision-making for energy storage implementation in depleted fields. The key finding is the development of a methodology that can quickly and accurately assess the feasibility of repurposing abandoned hydrocarbon reservoirs for underground thermal energy storage, offering a practical solution for sustainable energy transition.
Damavand stratovolcano is in Alborz Magmatic Belt (AMB), in the north of Iran, and the Iranian plateau. This large dormant volcano was constructed with a composite large cone (more than 400 km2). Damavand is known as the highest mountain (elevation ~5671 m) in the Middle East and South Asia. The youngest known eruptions of Damavand volcano (7.3 Ka), which mostly erupted on the western side of the summit, are composed of trachyandesite, and trachyte lavas with pyroclastic while the older eruptions (1.8-0.6 Ma) consisting of alkali olivine basalts, tephrite basanite, and trachyandesite, emplaced at the base of the volcano. The current Damavand cone is located above the old and eroded building and periodically includes trachyandesite- trachyte lavas with small eruptions of mafic lavas and pyroclastic rock. These lavas formed in the youngest geological period (Quaternary) covered Mesozoic deposits (Shemshak and Lar Formations). The intensity of Alborz volcanic activities extended into the Tertiary, but was not uniform, as its maximum occurred in the late Eocene and Oligocene, and after a period, volcanic activities re-intensified in the Pliocene.Regional GeologyDamavand volcano is in the center of Alborz Mountain Belt, in the Iranian plateau. The stratigraphic evidence indicates that the volcanism occurred in the two phases the older (old Damavand) and the younger sequences (younger Damavand)Analytical MethodsAfter initial petrographic studies, suitable samples were analyzed for whole-rock composition determined by XRF and ICP-MS analyses at the Geological Survey of Iran.Mineral composition determined by EPMA (Electron Probe Micro-Analyser) at Iran Mineral Processing Research Center. The analysis was performed at this center by the electronic microprocessor model CAMECA-SX 100 made by the French company Cameca. This device is equipped with a spectrometer with an electron diode receiver and works automatically based on a high accuracy of 1% and the simultaneous operation of several diode detectors and electron beam stability with a carbon coating.Petrography, Minerals, and Whole Rocks ChemistryThe analyzed samples roughly cluster in the two zones, mafic alkaline rocks (tephrite-basanite) and intermediate-felsic rocks (trachyandesite- trachyte). The main purpose of this study is the mineral chemistry of the Ziar-Lasen trachyandesites, with a SiO2 content of 57wt%. The predominant mineral assemblages of these rocks are plagioclases (andesine-Labradorite), k-feldspar (sanidine-anorthoclase), clinopyroxene (augite-diopside), mica (phlogopite, biotite), apatite, and Ti-magnetite and the dominant textures are porphyry and microlithic porphyry textures with main phenocrysts. Feldspars show signs of disequilibrium and sieve textures in their cores and rim and desorption and skeletal. These phenocrysts, which are sometimes as glomerocrysts, show zoning Some mafic enclaves with variable textures and mineralogy are seen in the matrix of the trachyandesitic rocks.Result and Discussion Volcanic activities in the middle part of Central Alborz Mountain initiated about 2 million years ago with the eruption of mafic to intermediate-acidic lavas and pyroclastic rocks. The most common minerals of the trachyandesits from the south of Damavand (Polour to Ziar-Lasem) are felspar, pyroxene, mica, apatite, and opaque minerals., whereas the intermediate lavas are characterized by the presence of plagioclases (An31-58, andesine), alkali feldspars (Or32-65, sanidine to anorthoclase), pyroxene, mostly augite (Wo42-45 En42-47Fs10-13) rare diopside (Wo46-48 En43-46 Fs8-10), mica phlogopite (Fe2+/(Fe2++Mg) <0.3) as well as high Mg # (67-76) and Ti-magnetite.Chemically, the clinopyroxenes are characterized by high Mg # (97-76) and phlogopites by Fe # <0.33, high Ti (70-79), and high Mg # (76-67) and so, the nature of host magma is sub-alkaline.On the base of thermobarometer data, the clinopyroxene and phlogopite phenocrysts from Ziar-Lasem trachyandesites crystallized at a wide range of temperature and pressure.The crystallization temperature for clinopyroxenes, ranges from 1180 to 1250 °C, at 6-10 kbars pressure (equi. to 22-36.5 km depth), and for mica varies from 819 to 843°C, at 0.1-1.14 kbars pressure (equal to 4-0.65 km depth.). Base on clinopyroxenes compositions (Mg#>80) the crystallization of these minerals was re-equilibrated with high Mg# melts (50–54) (Eskandari et al., 2018). The similarity of these values with those of basalts indicate their deep crystallization from more mafic magma (Lanzafame et al., 2013). It is suggested that the clinopyroxenes of the intermediate volcanic products of Ziar-Lasen were crystallized at 22-36.5 km depth, approximately equivalent to lower crust (28–33 km), and evolved by assimilation, fractionation, and contamination when their parent magma erupted from deep depth to the surface or crystallized at shallow chambers within a thick crust.AcknowledgmentThe author is grateful to the Editor-in-Chief and esteemed referees of the Petrological Journal for their useful constructive comments, to the Research Institute for Earth Sciences and to Dr. Karimi.
Sri Mulyaningsih, Sutikno Bronto, Arie Kusniadi
et al.
The Muria-Peninsula is a Quaternary volcano located in the northern Sunda arc. Its activity was controlled under high potassic and very high potassic magma series resulting in leucite-rich trachyte and pyroxene-rich basaltic-andesite. It is a strato-type volcano that is composed of lava, breccia, and tuff layers, and some dikes have some volcanic craters and maars varying in age and composition. The study area is covering the volcanoes of Muria, Genuk, and Patiayam. This paper aims to describe the petrology, mineralogy, and volcano-stratigraphy of the different volcanic materials. The data and materials were sourced from the primary and secondary data. The methods are field mapping, stratigraphy measurements, collecting samples, thin section analyses, and major element geochemistry using X-Ray fluorescence (XRF). The results describe two groups of volcanic rocks consisting of pyroxene-rich andesitic-basaltic volcanic materials and leucite-rich trachytic volcanic materials. Augite presents in the andesitic basalt together with small grains of olivine and a few anorthite and foid minerals. Aegirine (Na-Pyroxene) is present in the leucite-rich trachyte that is often associated with biotite and hornblende. Na-Ca Plagioclase such as labradorite-andesine is often present in the basaltic-trachy-andesite that is usually rarely leucite. The major elements show high-K volcanic rocks with % K2O is 4-5.9% and very high-K volcanic rocks (with % K2O is between 6-8.24%) and low-K volcanic rocks that contain % K2O is 2-3,9%. There are two groups of high-K to very high-K volcanic materials consisting of silicic-rich volcanic materials (~57-64% of SiO2) and low-silicic volcanic materials (~46-50%). The TAS diagram identifies tephrite, phonolite, and trachyte. Stratigraphic data identifies calcareous sediments of the Bulu Formation as the basement rocks of the Muria trachyandesite. Beds of pumice-rich volcanic breccia of the Ujungwatu Formation are the basement rocks of the basanite-tephrite of the Genuk Volcano, and the tuff of the Ujungwatu is also exposed consisting of the basanite-tephritic-phonolite of the Patiayam Volcano. The leucite-like feldspars are very common in the andesite lava and dikes that compose the crater of Muria. Most of the Muria volcanic materials are rarely in leucite, while some maars contain pumice-rich pyroclastic flows and basaltic lava. The results of the major elemental analysis of the Muria materials indicate that the rock tends to be of medium to high K affinity (~2% K2O). The Genuk and older Muria are consisting of leucite-rich tephrite-phonolite. It was two periods of magmatic series developed in the Muria-Peninsula that was resulting in the high-K to very high-K magmatism and the medium K Kalk-alkaline magmatism.
Tatiana V. Kornyushenko, Nadezhda G. Razjigaeva, Larisa A. Ganzey
et al.
We analyzed human impact on landscapes on the example of Steklyanukha-2 Medieval fortress, which is a multi-layered archaeological site, and adjacent territories. Buried soils, rampart matrix, cultural layer and surface soils were sampled within the fortress. Along with the material sampled at the site, two sections of the Upper Holocene deposits of the high floodplain of the Steklyanukha River were studied. The results of studying the sporo-pollen spectra and diatoms are presented. The paleo-landscapes during the formation of various archaeological cultures have been restored and the signs of anthropogenic impact on vegetation have been identified. The buried soil in the section of the high floodplain is a natural archive for the environment history during the appearance of the people of the Yankovskaya Culture on this territory. The soil was formed under conditions of decreasing watering in the valley; the age is estimated at more than 2 ka. Oxbow lake deposits had been accumulated from 1.6 to 0.5 ka, when the valley was actively developed in the Middle Ages. Floodplain deposits at the top of the sections indicate that the valley has been heavily watered during the Little Ice Age. Pollen signs of settlements of the lower part of the valley in the Early Iron Age, Mohe and Late Middle Ages were found. Signals of the development of secondary birch and oak forests are identified. Ambrosia and Xanthium pollen, which are reliable evidence of agricultural activity in the valley, was found in the cultural layer and sediments that formed in the Middle Ages. The pollen of plants common in anthropogenically disturbed territories was also found. The study of diatoms in a depression within the fortress confirmed the archaeologists’ assumption that it was used to store water reserves. The pollen spectra from the surface soils in the fortress and the high floodplain reflect the active agricultural development of the nearby river valleys since the second half of the 19th century. The largest amount of pollen of alien and synanthropic plants and weeds, as well as spores of pathogenic fungi (pathogens of soybeans and rice) and fire indicators were found here.
Cristiano Nicosia, Federico Polisca, Christopher Miller
et al.
High-resolution sediment analysis allowed us to identify two Middle Bronze Age (MBA 1, 1650-1550 cal a BCE) byre-houses at the waterlogged site of Oppeano "4D", south of Verona (Veneto region, NE Italy). The site lies in a low-lying valley incised by the Adige River in its LGM alluvial fan. In this fluvio-palustrine environment burial and taphonomic conditions were such that the archaeological record was extremely well preserved. The wooden elements making up basal parts of nine 'huts' were in fact exposed at Oppeano, and so were their internal accretion deposits. These featured finely laminated dung units deriving from the stalling of small herbivores, possibly ovicaprids, intercalated with repeated accumulations of wood ash. This was produced in large and multi-stratified hearths that were exposed within each hut. Organic petrology provided evidence of the production of wood tar inside one of the studied structures. At Oppeano 4D it was thus demonstrated that these structures were not just byres or stables, but spaces that housed humans together with animals at least during some periods of the year, hence byre-houses. The identification of byre-houses in a Middle Bronze Age settlement is key for the reconstruction of socio-economic aspects of Bronze Age economy and production systems.
Santosh Dhubia, Alok Kumar Routa, Saurabh Datta Gupta
et al.
Abstract The development of an accurate velocity model is the significant target in the Full Waveform Inversion (FWI) process where the data fitting process is carried out based on an ill-posed technique. In the FWI technique optimization process plays a crucial role through which objective function minimizes, which is related to the misfit function between observed and modelled data. However, the influence of external factors such as data fitting errors (local minima) and the presence of noise in data are involved in the success of this processing technique. The artefacts that arise during gradient computation also affect this processing technique. This study presents a strategy to mitigate the influence of these local minima and other artefacts based on the velocity variation coefficient where an angle-dependent gradient conditioning approach has been proposed. It is an auto-controlled process in which the primary mechanism updates the velocity model from a large angle scale to a smaller angle scale when iteration begins. At each iteration, it preserves the previous result whereby it does not scatter or overlap with the previous one. It covers all the angles smoothly which helps in minimizing the data misfit and providing a high-resolution velocity model. The proposed conditioning approach is demonstrated by implementing the Marmousi model, and the result proves that the method provides a much-improved velocity inversion result which is attained with reasonable iterations. This study represents of a suitable procedure for the FWI processing technique where less sensitive artefacts are identified with negligible time consumption. Furthermore, it also helps to reduce the cycle skips and improve convergence in any complex scenario.
Tushar Meshram, Satyanarayana Mahapatro, VV Sesha Sai
et al.
In this study, we investigate phlogopite-rich pyroxenite from a major terrain boundary, i.e., the interface of Nallamalai Fold Belt and Nellore schist belt, in southern India. Petrographic studies reveal that the clinopyroxenite is composed of clinopyroxene and phlogopite with subordinate pyrrhotite in which cumulus texture is conspicuously noticed. Resorbed grain boundaries noticed in the clinopyroxene indicates crystal melt interaction. The relatively high Mg# (61–67) supports the mantle derived nature of the pyroxenite. The negative Ta, Nb and Ti anomalies along with the Ca (a.p.f.u) and Ti (a.p.f.u) content of clinopyroxene, which indicate that the rock is emplaced in a subduction zone tectonic setting. The incompatible trace element ratios (Hf/Sm-Ta/LaN and Zr/Sm), involving high field strength elements, of these clinopyroxenite is also suggests the vital role of the H2O + CO2 rich fluid-related metasomatism. The pyroxenite of the study area is situated along two major tectono-magmatic arc-back arc domains i.e., Palaeoproterozoic (1.85–1.6 Ga) Kondapalli-Kandra Region (KKR) with subduction related island arc basalt-type setting and Mesoproterozoic (1.35–1.2 Ga) alkali basaltic magmas of Prakasam continental Rift-Zone (PRZ). The tectono magmatic signatures of the phlogopite-rich clinopyroxenite from the study area indicate a petrogenetic link between Palaeoproterozoic subduction related island arc magma and the Mesoproterozoic rift-related magmatism established along the margin of Eastern Dharwar Craton (EDC) and Eastern Ghat Belt (EGB) in Southern India.
A. Alhadhrami, C.S. Vishalakshi, B.M. Prasanna
et al.
The energy/heat and diffusion/mass flux occurred due to chemical potential and temperature gradient, respectively have worth in the areas of electrical power generation, solar power technology, chemical engineering, petrology, nuclear waste disposal, hydrology, high temperature processes and geoscience. In connection to this, Soret and Dufour effects on steady, incompressible, laminar flow of non-Newtonian Casson liquid over a stretching sheet in a porous medium under local thermal non-equilibrium (LTNE) conditions have been theoretically investigated in the presence of Stefan blowing and magnetic effects. The energy equations are formulated by using the LTNE, which establishes the separate temperature profiles for both fluid and solid phases. The governing equations for the flow arguments are reduced by selecting suitable similarity transformations, which are then numerically solved using the traditional Runge-Kutta- 4 (RK-4) with shooting method. The flow features in reply to the impact of the emerging parameters are inspected in detail graphically. The significant outcomes of the current study are that, the rise in values of magnetic and porosity parameters decays the velocity but improves the heat transfer. An upsurge in Dufour number decreases the heat transfer rate of both solid and liquid phases. The upsurge in Soret number diminutions the mass transfer rate.
The Garmichay area in the north of Mianeh, NW Iran, features schists, amphibolites, calc-silicates, marbles and granitoids. Granitoids are of S- and A-type nature. Partial melting is the main generation mechanism, the progenitor is a pelite enriched in muscovite and the major melting reaction is muscovite dehydration. The ASI for the S-type granite varies between 1.12-1.5 indicating peraluminous character and crustal origin. Both granitic types are enriched in LREE in relation to HREE with negative Eu anomalies. Lan/Ybn ranges are 1.49-3.09 and 1.34-1.99 for the S-type and the A-type granites, respectively. Moreover, Lan/Gdn varies between 2.45 and 5 for the S-type granite and 1.53 and 1.75 for the A-type granite. The S-type granite has been generated in a collisional zone during Assyntic Orogeny.The A-type granite, however, is formed in a within-plate environment.The A-type granite belongs to A1 subtype formed in a continental rifting setting. The crystallization temperatures for the S-type and the A-type granites vary from 650 to 750 ºC and 800 to 850 ºC،respectively.
J. C. Onyemachi, S. I. Onwukwe, Ugochukwu Ilozurike Duru
et al.
Abstract Application of nanofluids flooding in the oil and gas industry is recently emerging as enhanced oil recovery methods. Nanoparticles have the ability to alter the rock formation in order to recover oil trapped in the pores of the rock to improve oil recovery. In this study, core plug samples were formulated in the laboratory to investigate the effect of nanoparticles on oil recovery. The formulated core samples were saturated in low salinity brine. However, low salinity brine was used because it has the ability to alter rock wettability. After core flooding with brine for secondary recovery process, extracted oil from Irvingia gabonensis was introduced into the formation to investigate the effect of Irvingia gabonensis on oil recovery. The result of the study showed that magnesium oxide, silicon oxide, aluminum oxide and zinc oxide had oil recovery of 38.1%, 45.6%, 47.7% and 35.1%, respectively. However, when the nanofluids with Irvingia gabonensis were injected into the formation as a displacing agent, the oil recovery greatly improved to 50.3%, 52.0%, 53.2% and 52.4% for (MgO, SiO2, Al2O3 and ZnO). The result of the study showed that nanofluid flooding is a promising potential to improve oil recovery in the Niger Delta.
Abstract Mudstone reservoirs demand accurate information about subsurface lithofacies for field development and production. Normally, quantitative lithofacies modeling is performed using well logs data to identify subsurface lithofacies. Well logs data, recorded from these unconventional mudstone formations, are complex in nature. Therefore, identification of lithofacies, using conventional interpretation techniques, is a challenging task. Several data-driven machine learning models have been proposed in the literature to recognize mudstone lithofacies. Recently, heterogeneous ensemble methods (HEMs) have emerged as robust, more reliable and accurate intelligent techniques for solving pattern recognition problems. In this paper, two HEMs, namely voting and stacking, ensembles have been applied for the quantitative modeling of mudstone lithofacies using Kansas oil-field data. The prediction performance of HEMs is also compared with four state-of-the-art classifiers, namely support vector machine, multilayer perceptron, gradient boosting, and random forest. Moreover, the contribution of each well logs on the prediction performance of classifiers has been analyzed using the Relief algorithm. Further, validation curve and grid search techniques have also been applied to obtain valid search ranges and optimum values for HEM parameters. The comparison of the test results confirms the superiority of stacking ensemble over all the above-mentioned paradigms applied in the paper for lithofacies modeling. This research work is specially designed to evaluate worst- to best-case scenarios in lithofacies modeling. Prediction accuracy of individual facies has also been determined, and maximum overall prediction accuracy is obtained using stacking ensemble.
Abstract Multi-fractured horizontal wells (MFHWs) are effective for developing unconventional reservoirs. A complex fracture network around the well and hydraulic fractures form during fracturing. Hydraulic fractures and fracture network are sensitive to the effective stress. However, most existing models do not consider the effects of stress sensitivity. In this study, a new analytical model was established for an MFHW in tight gas reservoirs based on the trilinear flow model. Fractal porosity and permeability were employed to describe the heterogeneous distribution of the complex fracture network. The stress sensitivity of fractures was also considered in the model. Pedrosa substitution and perturbation method were applied to eliminate the nonlinearity of the model. Analytical solutions in the Laplace domain were obtained using Laplace transformation. The model was then validated and applied. Finally, sensitivity analyses of pressure and rate were discussed. The presented model provides a new approach to estimate the effect of fracturing. It can also be utilized to recognize formation properties and forecast the dynamics of pressure and the production of tight gas reservoirs.
Through a range of petrological techniques, the petrology, diagenesis, pore characteristics, and controlling factors on the regional variations of reservoir quality of the Chang 7 sandstones were studied. These sandstones, mainly arkoses, lithic arkoses, and feldspathic litharenites, were deposited in a delta front and turbidites in semi-deep to deep lacustrine. The detrital constituents were controlled by the provenance and sedimentary condition, which resulted in a spatially variable composition; e.g., high biotite and feldspar contents in the northeast (NE) of the study area, and high contents of rock fragments, especially dolomite, matrix, and quartz in the southwest (SW). Diagenesis includes intense mechanical compaction, cementation, and dissolution of unstable minerals. Diagenetic minerals which were derived internally include quartz, ankerite, ferrous calcite, albite, illite, kaolinite, and chlorite. Thus the original sandstone composition hadfirm control over the development and distribution of cement. Mechanical compaction and late-stage cementations contribute to the porosity loss of sandstones of Chang7 member. The dissolution porosity in major sandstone, slightly higher than primary porosity is principally dependent on the accessibility of acid fluid. The high content of plastic component facilitated the reduction of primary porosity and limited the mineral dissolution. The best reservoir sandstones are found in W, and partly from NE, M districts, with porosity are primary. The relatively high textural maturity of these sandstones reduces the impact of compaction on primary pores, and commonly existed chlorite rims limited the precipitation of pore filling quartz and carbonate cementation in late stage.