Permian Formation Research Articles

Geochemical Characteristic of the Carbonaceous Sediments of the Upper Paleozoic Kuantan Group, Malaysia

The geochemical parameters discussed in this paper are based on an average values of twelve outcrop carbonaceous samples, mainly black shales, were determined using X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) techniques, representative of Charu, Sagor, and Permian formations.The aim of this study is to define and discuss their characteristics, the distribution abundance of major and minor elements, investigation the dominant mineralogical composition and reconstruct the depositional environment for these sediments.The bulk chemical result showed that, the average values of the major elements are 65.83%, 64.82 %, 71.4 % SiO2, 18.27 %, 22.2 %, 15.66 % Al2O3, 1.53 %, 0.99 %, 2.49 % Fe2O3. 4.06 %, 6.25 %, 3.66 % K2O , whereas in the case of the miner elements, the results read values of 524.4 ppm, 758.8 ppm, 446.3 ppm Ba , 366 ppm, 399.3 ppm, 257.3 ppm Rb, 88 ppm, 67.3 ppm, 47.3 ppm Sr , 308 ppm, 288.8 ppm, 327ppm Zr for the Charu, Sagor, and Permian formations respectively. The major oxides reflect the dominant mineralogical composition of quartz and other silicate minerals (e.g. illite, kaolinte, smectite) and deficiency in carbonates.The high Rb/K ratio suggests brackish marine environment or rapid depositions that prevent equilibrium between Rb and K in these study shales and marine environment. The high Rb/Sr ratios of 4.16, 5.89 and 5.44 for the Charu, Sagor, and Permian formations respectively possibly attributed to the lowest contents of Sr content due to reducing environment prevailing during deposition of these sediments.

Geochemical Characteristic of the Carbonaceous Sediments of the Upper Paleozoic Kuantan Group, Malaysia

The geochemical parameters discussed in this paper are based on the analysis of twelve outcrop carbonaceous samples, mainly black shales, using X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) techniques. These samples are representative of the Charu, Sagor, and Permian formations. The aim of this study is to define and discuss their characteristics, the distribution abundance of major and minor elements, investigate the dominant mineralogical composition, and reconstruct the depositional environment for these sediments. The bulk chemical results showed that the average values of the major elements are 65.83%, 64.82%, and 71.4% SiO?; 18.27%, 22.2%, and 15.66% Al?O?; 1.53%, 0.99%, and 2.49% Fe?O?; and 4.06%, 6.25%, and 3.66% K?O for the Charu, Sagor, and Permian formations, respectively. The minor elements recorded values of 524.4 ppm, 758.8 ppm, and 446.3 ppm Ba; 366 ppm, 399.3 ppm, and 257.3 ppm Rb; 88 ppm, 67.3 ppm, and 47.3 ppm Sr; and 308 ppm, 288.8 ppm, and 327 ppm Zr for the Charu, Sagor, and Permian formations, respectively. The major oxides reflect the dominant mineralogical composition of quartz and other silicate minerals (e.g., illite, kaolinite, smectite) and a deficiency in carbonates. The high Rb/K ratio suggests a brackish marine environment or rapid deposition that prevented equilibrium between Rb and K in these shales. The high Rb/Sr ratios of 4.16, 5.89, and 5.44 for the Charu, Sagor, and Permian formations, respectively, are possibly attributed to the low Sr content due to reducing conditions prevailing during the deposition of these sediments.

Effects of source facies and maturity on individual carbon isotopic compositions of oil

Carbon isotopes have been used extensively in tracing the sources of oil. However, primary source facies and secondary alteration controls on oil isotopic compositions have not been well resolved, resulting in application uncertainties. A case study was undertaken for an alkaline lacustrine oil system in a lower Permian formation in the Junggar Basin, NW China. Results indicate that increasing maturity causes the carbon isotopic composition to become heavier for only short–middle-chain compounds, whereas source facies-related carbon assimilation controls the compositions of short-, middle-, and long-chain compounds. In particular, light-carbon assimilation during organic-matter degradation makes the isotopic composition lighter, whereas heavy carbon from the water mass makes it heavier. Accordingly, oils in this study area were divided into Type U and Type N oils based on individual compound carbon isotopic compositions, reflecting the difference in source facies in a highly saline and reducing stratified water environment. The results provide a better understanding of the controls on carbon isotopes in oil in sedimentary basins, reducing the uncertainty in oil–source correlation and addressing the origin of oil.

ABOUT THE MAIN RESULTS OF DEEP DRILLING IN THE TERRITORY OF THE PREDVERKHOYANSKAYA OIL AND GAS AREA

This article presents the results of drilling wells in the Predverkhoyanskaya oil and gas area, where deep exploratory drilling for oil and gas was started in 1954 at the Kitchan, Sangar and Ust-Vilyu structures pre-pared by the seismic survey in combination with structural core drilling.According to the results of deep drilling in the Predverkhoyanskaya oil and gas area, the section of the sedimentary cover was studied, and ideas about the material composition of the foundation upper part were obtained. The pro-spects of oil and gas potential are evaluated: the reservoir properties are possessed by rocks of the subsalt Nizhnevendsky, Vendian-Lower Cambrian terrigenous and carbonate complex-es, which are associated with industrial oil and gas potential in nearby fields.The following fluid-bearing complexes are distinguished in the sedimentary section of the Preverkhoyanskiy trough: Permian (P), Lower Triassic (T1), Triassic-Lower Jurassic (T2–3–J1), Middle Upper Jurassic (J2-3), Lower Cretaceous (K1).Deposits of the Lower Triassic aquifer complex are deposited on Permian formations. The capacity of the complex is variable, due to the structural features of the Lower Triassicsediments, and it has not been established with-in the Predverkhoyanskiy trough. Thermobaric data were not obtained during the test. Reser-voir pressures are close to hydrostatic. Reser-voir temperatures, as in the Permian complex, increase from west to south-east to the Predverkhoyanskiy trough from 50 °C to 95 °C.The deposits of the Middle-Upper Triassic – Lower Jurassic aquifer complex are more widely developed. During the sampling and test-ing of oil and gas exploration wells, water and gas inflows were obtained from the deposits of the complex, including industrial ones on Ust-Vilyuiskaya, Sobo-Khainskaya Square. The flow rates of water inflows reached 300 m3/day (Sangarskaya 2), gas inflows up to 1800000 m3/day (Ust-Vilyuiskaya area). In the Sobo-Khainskaya 1 well, an industrial gas in-flow was obtained from the interval of 1328–1349 m.The prospects for oil and gas exploration at the Preverkhoyanskaya oil and gas area are associated with its northern part (Setas struc-ture), on which the Setas parametric well No. 1 with a design depth of 4000 m is being laid, and its southern part, where it is advisable to drill 2 parametric wells with a planned depth of 3000 m.

Genesis and Geological Significance of Permian Oilfield Water in the Western Periphery of the Mahu Sag, Junggar Basin, China

Oilfield water contains valuable geological information and plays an important role in petroliferous basins, being closely related to diagenesis, reservoir physical properties, and hydrocarbon preservation conditions. Here we present a case study of oilfield water in Permian formations in the western periphery of the Mahu Sag, Junggar Basin, China. The genesis of oilfield water and its application in oil exploration were investigated through the coupling of tectonic activity, paleoclimate, and water–rock interaction. Volcanic activity provided a rich source of ions, and a hot paleoclimate intensifies the evaporation and concentration of sedimentary water. Tectonic fractures offered channels for water exchange among formations. Water–rock reactions, marked by sodic feldspathization and calcium feldspar dissolution, had profound effects on the oilfield water type and reservoir properties. We established a link between oilfield water and favorable targets for oil exploration. In terms of vertical trends, the Jiamuhe and Upper and Lower Urho formations have strong sealing abilities for hydrocarbon preservation. In the horizontal dimension, areas with high total-dissolved-solid and CaCl2 concentrations, low rNa/rCl, rSO4 × 100/rCl, (rHCO3+CO3)/rCa, and rMg/rCa ratios are favorable for oil exploration.

Detecting hypogenic karst features in the northeastern Delaware Basin, west Texas: Applications of Full Tensor Gradient (FTG) gravity data

Extensive karst development in carbonate and evaporate strata often occur in the Upper Permian formations of the Delaware Basin, west Texas. Subsurface karst feature detection is essential since they may cause severe drilling geohazards. In order to detect subsurface karst features, we present an interpretation approach that integrates high-resolution, high-precision airborne full tensor gradiometry (FTG) gravity data, structural interpretations, density and lithological variations derived from well logs, and published seismic refraction data, with regional cross sections to produce a geologically plausible 3D FTG model in the northeastern Delaware Basin. Both traditional gravity (Tz) and FTG (Tzz) density inversions were carried out on three shallow sedimentary layers of the Ochoan-lower Permian section, demonstrating the subtle density distribution in these strata. Detailed low-density karst boundaries were then interpretated by making use of the intrinsic properties of the gradient components, Txz and Tyz, which are: 1) edge detectors, because anomaly maxima and minima are located directly over source boundaries, and 2) indicators of the direction of density change across these boundaries. Source boundaries, or faults, mapped from these components were integrated and combined with regional geology and measured densities to verify existing faults, infer new faults, and predict probable locations and shapes of karst cavities in the southwestern and northeastern parts of the study area. Our results show that the central and southwestern parts of the study area may represent higher drilling risks due to an increase in shallow karst geohazards. This interpretation approach may be used to detect fault systems and geometries of low-density or high-density source geobodies worldwide.

Petrophysical evaluation of the Lower Permian formation as a potential reservoir for CO2 - EGS – Case study from NW Poland

Petrophysical evaluation of the Lower Permian formation was performed on the basis of the results of laboratory tests of rocks including pore space investigations using the Mercury Injection Capillary Pressure (MICP) method, the pore space saturation measurements by the Nuclear Magnetic Resonance (NMR) method, and measurements of the thermal conductivity coefficient by FOX series heat flow meters based on the one-dimensional Fourier equation. Three types of rocks: sandstones, conglomerates and effusive, sampled from the Ośno IG-2 well located in the Gorzów Block (NW part of Poland) were analysed. 42 core samples from the depth interval of 3212–3659 m bgl were tested. The results provide a wide range of information about the sample, primarily such parameters as pore size distribution, effective porosity and permeability, bulk density, sketal density, and thermal conductivity. The aim of the study was to determine the relevance of Lower Permian formation as a geothermal reservoir for CO2 – EGS - Enhanced Geothermal Systems, which use carbon dioxide instead of water as working medium. Although worldwide research on such systems has been going on for many years, so far it has not been realized on a commercial scale. Moreover, to date there are no EGS installations in Poland. The ongoing research aims to bring the construction of the first pilot installation in Poland closer. Effusive rocks were characterized by lower value differentiation and relatively high lambda values (average 1.77–1.81 W/mK for dry samples, 2 W/mK for fully saturated and 2.1 W/mK for a mixture of water and CO2), average effective porosity of 7.92% and permeability of 0.055 mD. Sandstones have the highest thermal conductivity values (1.87 W/mK at 20 °C, 1.87 W/mK at 50 °C, 1.82 W/mK at 100 °C and 1.79 W/mK at 150 °C), average effective porosity 5.56%, and permeability of 0.133 mD. For the conglomerates, the lowest values of thermal conductivity were obtained (average value for water-saturated sample equal 1.7 W/mK and for dry sample 1.4 W/mK). The average value of effective porosity for conglomerates is 7.66% and the permeability is 0.141 mD. The results indicate that the studied rocks have suitable parameters as a geothermal reservoir for CO2-EGS, especially effusive rocks. These parameters are similar to those of reservoir rocks for the EGS installation in Groß Schönebeck, as well as all types of rocks are classified primarily as petrothermal EGS.

Improving the Drilling Parameter Optimization Method Based on the Fireworks Algorithm.

The rate of penetration (ROP) is a manifestation of drilling efficiency, and optimizing drilling parameters is an important way to improve it. To achieve a low ROP for a Permian formation in a certain oil and gas field, three single wells in this formation were selected for optimization. An improved fireworks optimization algorithm was proposed for drilling parameter optimization. We first established the objective function that predicted the ROPs for the three wells. The objective function employed a multilayer perceptron neural network as the optimization adaptation function. We then optimized four controllable parameters (weight on bit, rotary speed, pump discharge, and pump pressure) and improved the fireworks algorithm with an adaptive number of various factors. This improvement enhanced the debugging performance of the fireworks algorithm during optimization. The results indicated that the improved fireworks algorithm has significantly enhanced search performance, and the optimum ROPs for the three wells were increased by 38.55, 78.30, and 60.15%, which provides a reference for the controllable parameter setting in the area.

COMPOSITIONAL FEATURES AND AGE OF ALKALINE GRANITES OF THE INGUR MASSIF, WESTERN TRANS-BAIKAL AREA

The Ingur alkaline granite massif and the associated Zr-Nb occurrence make up part of the largest Mongolian-Trans-Baikal alkaline granitoid provinces. The massif is composed of arfvedsonite, biotite, and alaskite granites. High content of HREE determines the low La/Ybn (2–7) value and a negative europium anomaly (Eu/Eu*≈0.17). They are depleted in Ba, Sr and enriched in Nb, Ta, Zr, Hf and Y. According to their geochemical properties the rocks of the massif belong to the A-type granites. The rare-metal mineralization of the Ingur granites mainly involves zircon, bastnäsite, monazite, and xenotime. The U-Pb age determined by SHRIMP II with zircon from arfvedsonite granites (272 Ma) indicates the Late Permian formation.

Scandium prospects in the Yakutian Diamond Province

Prerequisites and signs of scandium deposits in the ancient weathering crusts and in the oxidation zones in the Upper Paleozoic strata in West Yakutia are defined and substantiated. The prerequisites include: the presence of scandium sources—basic rocks, kimberlites and carbonatites; the spread of the ancient formation and ground oxidation which conditions migration of scandium; the presence of weathering crusts of the Carboniferous and Mesozoic ages, with alkaline and adsorptive barriers which concentrate scandium; good prospecting at depths up to 100 m. These prerequisites govern the relevance of the research as there is a possibility of scandium recovery from ore by in-situ leaching. Ancient oxidation in the strata and in the fractures in the gray-colored Сarboniferous–Permian formations and in the underlying weathering crusts is detected in the Ulakhan-Kurung-Yuryakh area of the Malaya Botuoba region in the Yakutian Diamond Province. Ancient epigenetic processes are confirmed by zonal limonitization and clarification of primary gray-colored rocks, and by redistribution of uranium, vanadium and gallium with the increased background contents of V and Sc. The X-ray fluorescence analyses performed in the Malaya Botuoba, Middle Markha and Ygyatta diamond-bearing regions revealed areal concentrations and promising scandium ore occurrences in the ancient weathering crusts and in the Late Paleozoic formations. In the weathering crust, in Suldyukar kimberlites, scandium concentrations exceed 100 ppm and feature high (up to 0,n%) contents of V, Co, Ni, La and Ce. The outstanding concentrations of scandium are found in the Triassic–Jurassic Dyakhtar clayey rocks representing a derivative weathering crust in the Nakyn diamondiferous field.

Visualization experiment of multi-stage alternating injection acid fracturing

Permian formation reservoir in the Sichuan Basin has the characteristics of high temperature(153 °C), strong heterogeneity, thin thickness, low porosity and low permeability(0.8 mD). In the early stage, gelling acid fracturing was mainly used to increase gas production, but the effect was not good, and the average daily production of gas wells after fracturing was 20000–30000 m3. The acid fracturing operation of Permian formation reservoir is faced with the problems of fast acid rock reaction speed under high temperature and low conductivity of acid etching fracture under high closing pressure. In view of the above technical problems, we carried out the visual test experiment of alternating injection acid fracturing. The fingering behavior of steering acid, gelling acid, and fracturing fluid is evaluated through experiments, and gelling acid is polymer gels. Through the experiment, it is clear that in order to achieve a good acid fingering phenomenon, the viscosity ratio should be increased to 20:1, the injection displacement is 50–70 ml/min, the controlled injection series are level 4–5, and the proportion of design acid dosage is 0.3. It can be seen from the 3D rock scanning diagram that with the increase of injection stages, the corrosion ability of acid to fractures is significantly enhanced. Multi-stage alternating injection acid fracturing technology has achieved good application effect in Permian formation of Sichuan Basin. The average gas production of the wells is 1.5 times higher than that of the gelling acid fracturing technology.

Effects of Deep Fluids on Middle Permian Dolomite of the Western Sichuan Basin

Deep fluid activity is closely related to carbonate reservoir transformation as well as oil and gas accumulation. The large-scale deep fluid activity caused by Emeishan large igneous province (ELIP) brought a lot of deep material and energy to Sichuan Basin and changed the paleogeothermal and geochemical field of the region they flowed through, which had an important impact on the formation of the Middle Permian dolomite reservoir in Western Sichuan. Through comprehensive analyses of petrographic, geochemical, and fluid inclusion data from two drill cores and three outcrop sections of the Middle Permian Formation in the Western Sichuan Basin, the dolomitizing fluid, dolomite genesis, and effect of deep fluid were discussed. The dolomite was divided into four types which are matrix dolomites (Md1, Md2, and Md3) and cement dolomites (Cd). Among them, the Md1 was formed in penecontemporaneous seawater by seepage reflux dolomitization, while Md2 was formed in heated Permian seawater through thermal convection. In the northwest of the study area, the Md3 and Cd were formed by higher-temperature thermal convection without hydrothermal. In the southwest of the study area, the lower δ13C value and Sr contents, higher Mn contents and 87Sr/86Sr ratios, and positive Eu anomalies as well as much higher Th and salinity values of inclusions show that hydrothermal participated in the dolomitization, forming the Md3 and Cd through structure-hydrothermal dolomitization and the thermal convection of seawater mixed with hydrothermal. The deep fluid activities of ELIP provided both the material source (Mg2+) for the dolomitization process and the migration motive power for the dolomitization fluid. From the southwest to northwest, with the deep fluid activity decreasing, the abundance of Md3 and Cd, which are closely related to the hydrothermal solution, reduced.

Evaluation of the Accumulation Conditions and Favorable Areas of Shale Gas in the Upper Palaeozoic Marine-Continental Transitional Facies in the Daning-Jixian Area, Ordos Basin

This study focuses on the organic-rich mud shale in the Upper Palaeozoic transitional facies in the southeastern margin of the Ordos Basin. It systematically analyzes the shale gas accumulation conditions of the organic-rich mud shale in the Lower Permian Shanxi-Taiyuan Formation, including the thickness, distribution, organic matter type and content, thermal maturity, reservoir space, gas-bearing property, and rock brittleness. The results show that the thick dark mud shale contains a high organic matter content, is a suitable kerogen type for gas generation, and exhibits moderate thermal evolution, providing excellent conditions for hydrocarbon accumulation. Residual primary pores formed by shale compaction, secondary pores formed by organic matter hydrocarbon generation, clay mineral transformation and dissolution, and fractures provide suitable reservoir spaces for shale gas. The shale in the study area has a higher gas content than the shale strata in the marine basins of the United States. In addition, the content of brittle minerals such as quartz is higher, and Poisson’s ratio is lower, facilitating the subsequent transformation. The accumulation conditions indicate the high potential of the study area for shale gas exploration and development. The geological analogy method is used to compare the study area with five major shale gas basins in the United States. The results indicate that the shale gas resources of the Shanxi-Taiyuan Formation in the study area are in the range of 2800– 3200 × 10 8 m3. The primary controlling factors affecting shale gas reservoirs in this area are the abundance of organic matter, thermal maturity, shale thickness, and quartz content. Favorable areas are predicted based on these factors.

Forecast of Economic Tight Oil and Gas Production in Permian Basin

We adopt a physics-guided, data-driven method to predict the most likely future production from the largest tight oil and gas deposits in North America, the Permian Basin. We first divide the existing 53,708 horizontal hydrofractured wells into 36 spatiotemporal well cohorts based on different reservoir qualities and completion date intervals. For each cohort, we fit the Generalized Extreme Value (GEV) statistics to the annual production and calculate the means to construct historical well prototypes. Using the physical scaling method, we extrapolate these well prototypes for several more decades. Our hybrid, physico-statistical prototypes are robust enough to history-match the entire production of the Permian mudstone formations. Next, we calculate the infill potential of each sub-region of the Permian and schedule the likely future drilling programs. To evaluate the profitability of each infill scenario, we conduct a robust economic analysis. We estimate that the Permian tight reservoirs contain 54–62 billion bbl of oil and 246–285 trillion scf of natural gas. With time, Permian is poised to be not only the most important tight oil producer in the U.S., but also the most important tight gas producer, surpassing the giant Marcellus shale play.

Application of Indicator Kriging to hydraulic head data to test alternative conceptual models for spring source aquifers

Hydraulic head distributions can inform spring source-water characterisation by determining whether aquifers meet the thresholds required to sustain spring flow. Assessing hydraulic head data can be challenging in areas where data are sparsely distributed and subject to variable measurement uncertainty. Geostatistical methods can be used to estimate hydraulic head values at unmeasured locations with quantitative uncertainty estimates. While these methods have been applied extensively for hydraulic head estimation in management contexts, no studies have used these approaches for spring source-water conceptual model testing. In this study, an investigation into the hydraulic head distribution was conducted through the application of Ordinary Indicator Co-Kriging. Interpolated hydraulic head estimates were used to quantitatively assess the plausibility of source-aquifer conceptual models for the Doongmabulla Springs Complex (DSC), Queensland, Australia. The results offer insights into the likelihood of alternative source aquifers having adequate head to support flow to eight springs within the DSC. Probabilities of adequate head to support the springs ranged from 0.03 to 0.12 for the Permian Formations, compared to <0.01 to 0.49 for the Triassic Formations. Analyses indicated that the Triassic Formations are more likely to have adequate hydraulic head to support spring flow. However, significant uncertainty exists in the conceptual model assessment due to hydraulic head measurement scarcity, particularly in the vicinity of the springs. These findings have important implications given that the Permian Formations will be dewatered by the operation of the nearby Carmichael coal mine. The techniques employed here can inform conceptual model uncertainties arising from the interpretation of sparsely distributed hydraulic head datasets, a major benefit over traditional interpolation methods.

Tracing the Provenance of the Devonian Limestone of Telen River, East Kalimantan

H. Witkamp found an outcrop with Devonian Limestone in East Kalimantan in 1925. In 1989, an expedition run by Institute of Technology Bandung (ITB) reinvestigated the outcrop and concluded that the Devonian Limestones in Telen River were boulders within a Permian formation. This paper gives a wider overview on the distribution of Devonian rocks in Asia Pacific region and discusses their possible origin.Based on the distribution map of Devonian rocks in the region, the Devonian limestone in Borneo is very isolated. The closest Devonian limestones are about more than 2000 km away. Probably the Devonian limestone in Telen River has been separated away from its origin by significant tectonic movement. There are several theories and models related to the formation history of this area, which makes it very complex. To understand the origin of these limestones, the geology needs to be restored to their time and place of deposition of the Devonian limestone.

Refining the depositional model of the lower Permian Carynginia Formation in the northern Perth Basin: anatomy of an ancient mouth bar

The late early Permian coincided with a short-lived cold episode in Western Australia, which occurred long after the demise of late Paleozoic ice sheets, and is manifested by conspicuous dropstones in corresponding marine strata. In the northern Perth Basin, this time interval is represented by the Carynginia Formation, which has long been regarded as a record of low-energy marginal-marine sedimentation. The low-diversity body-fossil content and impoverished trace-fossil assemblages in the formation were recognised as evidence of low salinities, low dissolved-oxygen levels and high suspended-sediment concentrations presumably related to freshwater influxes into a restricted basin. However, sedimentary facies indicative of river processes have yet to be documented to explain the sedimentological and paleontological character of the formation. This study examines an overlooked sandstone-rich interval of the Carynginia Formation in the Irwin Sub-basin, a marginal half graben faulted against crystalline basement of the Yilgarn Craton and forming part of a series of late Paleozoic intracratonic rift basins in Western Australia. Facies analysis indicates that the lower part of the interval is dominated by storm-generated deposits containing extraformational pebbles and boulders. These deposits are interpreted as recording lower-shoreface sedimentation under the influence of seasonal sea ice, and constitute a shallower, sandstone-rich equivalent of mudstone-prone strata that otherwise characterise the Carynginia Formation. The upper part of the interval consists of river-borne deposits representing friction-dominated deposition of a river-mouth bar, the first direct record of deltaic sedimentation in the Carynginia Formation. The stratal organisation of mouth-bar bedsets is likely the result of successive sediment-laden pulses related to seasonal floods in a shallow marine basin, and the autogenic evolution of the mouth-bar complex in response to fluctuating river discharge and compensational stacking. Formative runoff events were arguably responsible for reductions in salinity and the introduction of turbid buoyant plumes into the shallow sea that were adverse to faunal development. A fluvial influence may explain the sedimentary character and fossil content of coeval mudstone-prone formations in Western Australian rift basins, especially in the vicinity of cratonic margins. KEY POINTS The lower Permian (late Artinskian–Kungurian) mudstone-prone Carynginia Formation in the northern Perth Basin has long been regarded as the record of low-energy, marginal-marine conditions in a cold-water seaway. The low-diversity fossil content in the lower part of the formation indicates stressed physico-chemical conditions influenced by freshwater, sediment-laden influxes. The described mouth-bar deposits are the first direct evidence of deltaic sedimentation in the Carynginia Formation, demonstrating that river outflows likely controlled water chemistry and impacted faunal development.

Organic geochemical characteristics and gas prospectivity of Permian source rocks in western margin of Songliao Basin, northeastern China

The Permian in western margin of Songliao Basin is a strategic potential field of oil and gas resources in northeastern China, but the systematic researches since few boreholes were drilled up to Permian strata, as well as there is a lack of seismic and well-logging data. This paper presents the lithological composition of the Permian Formations on the basis of regional geological survey in western margin of Songliao Basin. A total of 60 mudstones and shales were collected to evaluate the organic geochemical and petrophysical characteristics and gas prospectivity of Permian source rocks. The Permian is composed of Shoushangou, Dashizai, Zhesi and Linxi Formation, which represent large sets of mudstones and shales, which are mainly deposited in a weakly to strongly reducing marine environment. The primary organic matter precursors in Permian were lower aquatic organisms such as zooplankton and algae, while a few samples of Linxi Formation indicate mixed sources of lower aquatic organisms and terrigenous higher plants. The Permian gas–prone source rocks are at over–mature stage with vitrinite reflectance Ro% = 2.01%–3.14% and mainly classified as fair to good quality and type II–III kerogens, and generally have a tricyclic terpane distribution pattern of C21>C23>C20, but Shoushangou Formation and Linxi Formation have subordinate patterns of C21>C20>C23 and C23>C21>C20, respectively. The residual organic matters in Permian source rocks have CH4 yields up to 24.34 mg/g∙TOC at EASY%Ro = 4.45%, which indicate the possibility of secondary gas generation at Ro% = 2.0%–3.5%. The pores and fractures are developed in Permian source rocks with widths of 5.28–18.64 μm, and mean values of porosity and permeability are 2.17% and 0.0043 × 10−3 μm2, respectively. The source–reservoir–cap rock assemblages in Carboniferous–Permian and Mesozoic sedimentary sequences are included in situ and near–source accumulation in Permian, and long–distance migration and accumulation in underlying Carboniferous and overlying Triassic, Jurassic and Cretaceous. The Permian system can be regarded as a potential gas exploration target in the western margin of Songliao Basin.

Hydrasperman pteridosperm ovules from the Permian of China: palaeoecological and palaeobiogeographic implications

ABSTRACT Hydrasperman pteridosperms (seed ferns) were widespread and diverse in Carboniferous equatorial wetlands of Euramerica, and although present in Permian equatorial wetlands in Cathaysia, little is known about their ovules (unfertilised seeds) from this phytogeographical realm. Hydrasperman ovules are recognisable from their distinctive pollen chamber organisation, but those previously noted from the Permian floras of Cathaysia are imperfectly characterised and require further study to confirm their affinity and identity. Here we document the hydrasperman ovule Conostoma cf. kestospermum from coal-balls in the early Permian aged Taiyuan Formation of North China for which preliminary findings were previously published in a Chinese language book on the coal-ball floras of China. We provide additional information on the organisation and structure of the ovules and for the first time consider their palaeoecological and palaeogeographical significance. We conclude that significant taxonomic filtering occurred in the migration of wetland plant species between Euramerica and Cathaysia in the late Pennsylvanian, with the majority of hydrasperman pteridosperms going extinct in Euramerica at the end of the Carboniferous as a result of habitat loss and climate change. The few hydrasperman genera and species that persisted into the Cathaysian flora were relicts and a minor component of Permian equatorial wetland floras.

Depositional environment of clastic sedimentary rocks in Viet Phuong mine at Loc Thanh ward, Loc Ninh district, Binh Phuoc province

After the last Permian formation of limestone, the Southeast region of Viet Nam was covered with a series of clastic sedimentary rocks of Triassic (Vu Khuc, 2000). This region was classified with the sequential rhythm from coarse to fine, including conglomerate, sandstone, and claystone. According to some previous research, this series of sediments belonged to a molasse facies, the marine sedimentary facies characterized by claystone, siltstone containing lime, arranging in rhythm with conglomerate and sandstone (greywacke, arkose). This paper aimed to more precisely elucidate the sedimentary environment of this debris set, Viet Phuong mine. Regarding the texture of sedimentary rocks (Folk, 1974), the sediment was in the sub-mature stage, the moderate sortting (So = 1.15), the particle shape was nearly square, the kurtosis was from -0.19 to +0.4. For tidal environment, sedimentary structures also contributed to the above theory with the characteristic structures of hering-bone cross stratification, convoluted, Convolute Bedding and Flame structures and the presence of Ichnofacies Asterosoma (Cruziana) and Diplocraterion (Skolithos)…Thus, the sediment of Viet Phuong mine was identified with two types of depositional environments: estuary and tide dominated delta from bottom to top.