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The Sichuan Basin was a part of the Yangtze Carbonate Platform (YCP) during the Cambrian–Ordovician, and marine carbonates were deposited in the basin during this interval. Although previous studies have evaluated the paleogeography, paleoclimate and paleoecology of this basin, they have primarily focused on the paleoecology and biological evolution in the basin; however, analysis of paleogeography and paleoclimate is lacking. This study integrated outcrop sedimentological and magnetic fabric data to document sedimentary differentiation and anisotropy of magnetic susceptibility (AMS) within the YCP. The aims of this study were to infer paleowind directions during each epoch of the Cambrian–Ordovician and to constrain the paleogeographic location of the YCP. The northwestern, central and southeastern sides of the YCP were characterized by high-energy deposition (e.g. sub-angular to rounded intraclasts), medium-energy deposition (e.g. sub-angular to sub-rounded intraclasts) and low-energy deposition (e.g. angular to sub-angular intraclasts), respectively. The centroid D-Kmax values for the Early, Middle and Late Cambrian were 116° ± 52°, 145° ± 57° and 159° ± 62° from the present north, respectively; corresponding values for the Early, Middle and Late Ordovician were 169° ± 70°, 139° ± 73° and 91° ± 68° from the present north, respectively. Sedimentary differentiation and AMS results indicated that the prevailing wind directions during the Early Cambrian, Middle Cambrian, Late Cambrian, Early Ordovician, Middle Ordovician and Late Ordovician were 296° ± 52°, 325° ± 57°, 339° ± 62°, 349° ± 70°, 319° ± 73° and 271° ± 68° from the present north, respectively. The present study provides evidence for the location of the YCP during the Cambrian–Ordovician via the correspondence between the paleowind directions over the YCP and the trade winds in the Northern and Southern hemispheres. The novelty of this study lies in the following aspects: (1) it integrates microfacies and AMS analyses to establish paleowind patterns; (2) it constrains the paleo-hemispheric location of the YCP during the Cambrian–Ordovician; and (3) it provides a reference for further studies of the paleoclimate and paleogeography of the YCP during the Cambrian–Ordovician.

At present, oilfield A is in the late stage of development with ultra-high water cut. The comprehensive water cut has reached more than 95%, and the remaining oil in the whole area is highly dispersed. The tertiary infill well in block X of oilfield a was drilled and put into production in 2024. The reservoir is mainly deposited in the outer front of the Delta, and sheet sand is widely developed. After well pattern infilling, fine geological dissection was carried out[11]. The channel sand in S1 and S2 layers of s oil formation was well developed, and the remaining oil was still analyzed by logging technology. In this paper, the underwater distributary channel and estuary bar sandbody are finely identified by logging facies pattern, and the plane and longitudinal residual oil analysis is carried out by combining the dynamic and static analysis. The S1 and S2 layers are perforated, and good development results are achieved. Well m has a daily oil production of 5.7 tons and a water cut of 68.0% in the initial stage of production. This method can provide strong technical support for the later development adjustment of the oilfield.

To identify the principal controls on gas-bearing property heterogeneity in tight reservoirs of the Shaximiao Formation in the southwestern Sichuan Basin, this study systematically examines pore structure characteristics and their influence on reservoir quality through an integrated approach incorporating cast thin sections, X-ray diffraction (XRD), high-pressure mercury injection (HPMI), and parameters such as homogeneity and variation coefficients. The research has indicated that the following findings: (1) The reservoir lithology in the study area is predominantly lithic arkose, with pore types dominated by residual intergranular pores and intragranular dissolution pores, and pore-throat radii ranging from 5 nm to 1 μm. (2) The disparity in reservoir quality is attributed to two primary factors. Firstly, diverse sediment provenance directions and varying mineral compositions directly influence the internal pore structure of the reservoirs. Secondly, differences in diagenetic minerals lead to heterogeneity in pore space development. Specifically, early carbonate cementation in the Pingluoba reservoir occluded porosity, resulting in poor physical properties. In the Yanjinggou reservoir, clay mineral cementation and pore-filling activities significantly reduced reservoir quality. In contrast, the presence of chlorite coatings in the Baimamiao and Guanyinsi reservoirs helped preserve primary porosity, contributing to superior reservoir properties. (3) The variation in gas content between different gas reservoirs is primarily attributed to differences in reservoir heterogeneity on a planar scale, whereas the gas content variation within different intervals of the same gas reservoir is controlled by differences in pore structure among various sand units. Furthermore, gas content heterogeneity within the same interval of a single reservoir results from variations in sand body thickness and connectivity.

It is of great significance for further exploration in deep-burial carbonates to clarify the distribution of sedimentary microfacies within the high-precision sequence framework and to analyze how the sequence stratigraphy and lithologic types control the karst carbonate reservoirs in the Tarim Basin. For the study area, research on the identification and distribution of fourth-order sequence boundaries is somewhat inadequate. Moreover, methods for identifying sedimentary microfacies using logging data still need to be explored and advanced. Based on field outcrop, drilling cores, thin sections, full-bore microscan imaging (FMI), and conventional logging data, the high-precision sequence stratigraphy and sedimentary facies of the Yijianfang Formation in the Tahe Oilfield have been studied to clarify how they control the formation and distribution of carbonate intra-platform shoals. One third-order sequence and three fourth-order sequences were identified, and the high-precision sequence stratigraphic framework was established. The thicknesses of intra-platform shoal are large in the south and middle parts of this study area, and they are thin in the west and north parts. In addition, eight lithofacies types were identified (oolitic grainstone, intraclastic grainstone, bioclastic grainstone, bioclastic packstone, intraclastic packstone, intraclastic wackestone, bioclastic wackestone, and mudstone) and four subsequent facies associations (inter-shoal sea, low-energy shoal, medium-energy shoal, and high-energy shoal) were then defined within the sequence framework according to different hydrodynamic conditions. Based on the response difference of microfacies types between FMI and conventional logging, four response models were recognized (blocky, linear, porphyritic, and compound). Favorable reservoirs are jointly controlled by sequences and sedimentary facies. Shoals developed in high-energy shoal facies, as the dominant lithofacies, provide the material basis for favorable reservoirs. High-precision sequence boundaries control the development of dissolution, and favorable reservoirs are developed near sequence boundaries and HST; therefore, this work provides a basis for reservoir prediction in the later stage.

Some rock samples (39) have been obtained from Wadi Saal, East Central Sinai, Egypt, for studying electrical, petrographical, and petrophysical parameters. The petrographical analysis shows two major facies. Carbonate (limestone) facies with low porosity (11%) and permeability (69 mD), and sandstone facies with high porosity (28%) and permeability (5901 mD) indicate good reservoir characteristics. Porosity values are related to the bulk density, whereas permeability is controlled by rock porosity and irreducible water saturation. Alternating current (AC) electrical properties were measured with frequency (42 Hz–5 MHz) for samples. Electrical characteristic differences are affected with texture changes, mineralogy, porosity, tortuosity, pore-water salinity, mineral concentrations, permeability, and fluid content. Conductivity and impedance decrease whenever an insulator is existed. The dielectric constant increases with conductor composition (below the percolation) and falls with frequency beyond it. The conductivity expands with the number of conductor pathways connecting the electrodes. The primary objective of this work is to use laboratory AC electrical measurements to shed some light on the relationship between the texture, petrography, petrophysics, and geochemical composition of materials (sandstone and limestone). The goal is to study electrical properties of these mixtures at varying clay concentrations and saturation levels. These analyses could enhance oil and gas recovery by shedding light on reservoir rock electrical characteristics.

We provide a reassessment of the hypothesis of ammonite survival across the Cretaceous–Paleogene (Maastrichtian–Danian) boundary, based on new data from the lower Danian Cerithium Limestone Member at Stevns Klint, eastern Denmark. The occurrence of this unit in disjunct basins between eroded crests of uppermost Maastrichtian bryozoan mounds prompts a reconsideration of ammonite redeposition as an alternative to the survival hypothesis. We describe new ammonite specimens from the Cerithium Limestone, representing the genera Hoploscaphites , Baculites and Fresvillia . In order to elucidate the nature of these fossils, we study their local depositional settings, based on detailed, chiefly taphonomic and sedimentological (microfacies) observations. Results for the main part of the Cerithium Limestone point to the autochthonous nature of the enclosed ammonites, which implies that they are Danian survivors. Only a single individual from the lowermost part of the Cerithium Limestone is considered a reworked Maastrichtian fossil. In summary, our results confirm ammonite survival into the Danian for the bulk of the Cerithium Limestone fauna, stimulating questions for further research of what actually killed the last ammonites that lived on Earth.

Detailed well-log interpretations, including gamma-ray, density, neutron, and resistivity, alongside petrographic analysis of 100 samples over 170 m of drill cores, have revealed factors influencing reservoir heterogeneity in the Yamama Formation, Ah’Dimah Oilfield, southern Iraq. The formation comprises four reservoir units (YA-YD) separated by four non-reservoir units (BA-BD). The reservoir units are subdivided into subunits. YB2, YB3, and YC demonstrate the best reservoir quality, while YD2 is water-bearing. Seven microfacies were identified within both reservoir and non-reservoir units, deposited in a shallow carbonate ramp. These include bioclastic wackestone, Lithocodium-Bacinella float/boundstone, peloidal cortoid intraclast grainstone, reefal bioclastic rudstone, bioclastic foraminiferal wacke/packstone, miliolidal pack/grainstone, and spiculitic foraminiferal wackestone. Despite the deep burial depth of the formation (> 4000 m), it maintained good porosity values in most intervals, reaching up to 20%. Early isopachous cement protected porosity and dissolution enhanced porosity, while cementation, compaction, and pyritization reduced it. The reservoir units correlate with depositional environments, being deposited in the shoal area, while non-reservoir units were deposited in lagoon, middle, and outer-ramp settings. The Lithocodium-Bacinella float/boundstone and reefal bioclastic rudstone facies, forming reefal patches and build-ups within the shoal, dominated in YB2 and YC. Targeting these patches northeast of Ah’Dimah Oilfield is promising for field development.

An integrated study, incorporating field observations and petrographic analysis, has been conducted on the Lower-Middle Eocene carbonates of the Umm Russies area, North Eastern Desert, Egypt. These carbonate sequence represented, from base to top, by Minia, Gebel Hof, and Observatory formations, primarily consisting of marl, dolomite, and limestone. The microfacies analysis allowed the identification of seven distinct microfacies types: bioclastic floatstone, ferruginous dolomite, bioclastic packstone, ferruginous peloidal grainstone, sandy rudstone, foraminiferal wackestone, and bioclastic packstone. These microfacies types reflect a deposition in a wide range of environments from high-energy inner ramp to low-energy middle ramp settings. The performed petrographic analysis indicates that the investigated carbonate rocks underwent significant modification through a range of diagenetic processes, such as micritization, glauconitization, and dolomitization, representing marine-phreatic, meteoric-phreatic, burial, and meteoric-vadose environments. These environments are part of three successive diagenetic stages; eogenesis, mesogenesis, and telogenesis. The relationship between diagenetic episodes and depositional settings highlights that high-energy inner ramp environments facilitated early cementation and micritization, while middle ramp conditions promoted dissolution and neomorphism. Restricted platform margin environments favored dolomitization and glauconitization. Integrating microfacies analysis with these diagenetic interpretations facilitates reconstructing paleoenvironmental conditions and provides a framework for understanding carbonate rock formation in various geological settings.

This paper presents an interpretation of sedimentologic, paleomagnetic, and geochemical data collected in the Upper Kimmeridgian–Valanginian carbonates of the Giewont series (Giewont and Mały Giewont sections, High-Tatric succession, Western Tatra Mountains, Poland). The studied succession provides insight into the sedimentary conditions prevailing in the South Tatric Ridge (Tatricum), a submarine elevation located between the Zliechov Basin (Fatricum) and the Vahic (=South Penninic) Ocean. The sedimentary sequence includes micrites, pseudonodular limestones, cyanoid packstones, lithoclastic packstone, and encrinites. The results are discussed with regards to their significance for detrital input, paleoclimate, and paleoproductivity, which in turn are considered in the context of both local and regional paleoenvironmental trends and events. The greatest depositional depths during the latest Kimmeridgian–earliest Tithonian are documented by the occurrence of pseudonodular limestones. A Tithonian shallowing trend is demonstrated via the increasing size and roundness of cyanoids, while the final (?)emergence and erosion in the South Tatric Ridge is documented by earliest Cretaceous disconformities. This process might have been related to both falling sea-level during the major eustatic regressive cycle and tectonic uplift caused by the mutually related (re)activation in the Neotethyan Collision Belt and rifting in the Ligurian-Penninic-Vahic Oceans. The highest lithogenic influx (although still low; max 0.5% of Al content) during the Late Kimmeridgian is considered as associated with relatively humid climate conditions, whereas a subsequent decreasing trend is thought to result from aridification during the latest Kimmeridgian–earliest Tithonian. Ultimately, deposition in the High-Tatric zone was affected by both large-scale environmental perturbations characteristic of the latest Jurassic (climate changes, variations in seawater pH, monsoonal upwelling, lithogenic input, etc.), as well as local sedimentary controls, predominantly the oxygenation state of bottom waters and tectonic movements. Supplementary Material 1

Indonesia is one of the largest coal producers in the world, one of its coal-producing basins is the Central Sumatra Basin. The Korinci Formation is a formation with economic coal deposits in the Central Sumatra Basin that formed in the Late Miocene with depositional environments in the form of fluvio-deltaic, paludal, and continental that are widespread in the basin so that the formation of this area is controlled by wetlands where organic material accumulates. Coal samples were taken from IUP PT Bukit Asam Peranap using ply-by-ply sampling method, followed by organic petrographic analysis and geochemical analysis consisting of proximate and ultimate analysis. Results of organic petrographic analysis and geochemical analysis showed dominant vitrinite abundance ranging from 58.65-71.74 (% vol), liptinite between 21.10-32.41 (% vol), inertinite between 5.69-11.62 (% vol), mineral matter ranging from 0.18-1.75 (% vol), ash content data ranging from 1.13-19.38 (% wt air dry basis), and sulfur content data ranging from 0.22-0.76 (% wt, dry ash free). Maceral content of Korinci Formation coal does not show significant changes, almost all coal samples have high humotellinite content (>30% vol.), high humodetrinite (>20% vol.), and high liptinite content (>25% vol.). Based on the maceral assemblage, Korinci Formation coal microfacies can be divided into four groups, such as: (1) humotellinite-rich group, (2) humodetrinite-rich group, (3) humotellinite-liptinite-rich group, (4) humotellinite-inertinite-rich group. Korinci Formation coal did not experience extreme changes, but the difference in macerals composition each coal layer can indicate a certain event. Korinci Formation coal formed in dry forest swamp with limnic condition and build up by aquatic and herbaceous plants.