The present study conducted research on diagenesis, lithofacies, pore evolution, and relatively high-permeability genesis using thin sections of cast bodies, scanning electron microscopy, cathodoluminescence (CL), X-ray diffraction, physical properties, burial history, and diagenetic evolution. Based on the controlling factors of reservoir current appearance and pore evolution, lithofacies were classified. Based on the reservoir petrologic characteristics, facial rate, and microscopic data, combined with the microcosmic and macroscopic response relationship between sedimentary and diagenetic mineral characteristics, pore types, and reservoir diversity changes, the present features such as mineral, pore structure, and physical properties of the dominant sand body are highlighted. Through pore evolution simulation, the unconsolidated initial porosity of the reservoir is restored (49.55%). The porosity changes after compaction (18.41%), early cementation-metasomatism (9.77%), and dissolution-middle and late cementation (14.93%); apparent compaction rate, apparent cementation rate, and apparent dissolution rate were used to quantify the degree of pore space construction and destruction by diagenesis. In the process of diagenetic facies division, quantitative evaluation of diagenetic intensity is introduced to accurately classify the good and bad reservoir and screen out the reservoir and seepage facies with a high-quality coefficient. There are four diagenetic phases: low-permeability-medium-pore weakly cemented dissolution facies, ultralow-permeability-low-pore medium-compacted medium-cemented dissolution facies, ultralow-permeability-low-pore strong-compacted cemented facies, and ultralow-permeability-ultralow-pore strongly compacted carbonate-cemented facies.

The Lower Cretaceous Baxigai Formation is characterized by fan-delta front deposits and serves as a crucial target for ultradeep tight gas exploration in western China. Consequently, investigating its reservoir characteristics and controlling factors is critical. To characterize these reservoirs, we integrated well logs, core observation and analyses, thin-section petrography, high-pressure mercury injection, and scanning electron microscopy. This approach enabled comprehensive analysis of tight reservoir attributes and their genetic controls. Results show that the Baxigai Formation developed a fan-delta system, with premium reservoirs primarily concentrated in subaqueous distributary channels of fan-delta fronts. Reservoir lithology consists of medium- to fine-grained arkose and lithic arkose, exhibiting well-developed intergranular and intragranular dissolution pores alongside low mineralogical maturity. With average porosity of 2.76% and permeability of 0.24×10−3 μm2, these reservoirs are classified as low-porosity and medium–low-permeability systems. Depositional, diagenetic, and structural factors are the main controls on reservoir quality. Subaqueous distributary channels and mouth bars within the fan-delta system provide favorable conditions for reservoir development. Intergranular dissolution pores formed by feldspar dissolution and organic acid reactions play a key role in enhancing reservoir quality and supporting hydrocarbon generation. Structural fractures play a pivotal role in elevating permeability and establishing effective fracture–pore configurations.

The fast sedimentation rate, complex lithology, and extensive development of interlayers make it difficult to identify the interlayers in sandy conglomerate reservoirs. In response to the problem of unclear identification of interlayers in the sandy conglomerate reservoirs of the Cretaceous Guyang Formation in the west of Hetao Basin. Based on the differences in logging responses of different rock types and physical properties, a comprehensive identification method for multiple logging parameters of interlayer is proposed, which is used to separately identify gravelly interlayer, argillaceous interlayer, calcareous interlayer, and physical property interlayer. Multiple types of interlayers are extensively developed in the research area, mainly consisting of gravelly and argillaceous interlayers. In the sedimentation of fan roots, a large number of gravelly interlayers are distributed, with a large thickness and quantity of interlayers; in the direction of the fan, the hydrodynamic force gradually weakens, causing a gradual decrease in the number of gravel interlayers and a gradual decrease in the overall development of the interlayers; continuing towards the fan edge, there is an increase in the sedimentation of sandy and muddy sediments, with more development of argillaceous interlayers and an increasing trend in the development of interlayers. The overall development of the interlayer shows a trend of decreasing first and then increasing downstream along the sedimentary direction. A logging identification method is proposed for the unique gravelly interlayers in sandy conglomerate reservoirs, which can effectively improve the accuracy of interlayer identification and is of great significance for the efficient development of sandy conglomerate reservoirs.

Supplementary Table S3. SHRIMP U–Pb geochronological data of single zircon for two-mica monzonitic granites.

Diagenetic fluids is one of the most important reservoir modifiers, their differences can result in various petrography, storage capacity, and geochemical characteristics, so clarifying the diagenetic fluids is vital for understanding dolostone origin. Dolomitization is an important genetic type of dolostone reservoir, the fluid properties differ in different dolomitization, which may lead to reservoir storage capacity changes. Therefore, the identification of dolomitization fluid properties is critical for deeply understanding of dolomitization process and predicting storage capacity. Two types of dolostone are developed in submember Ma55 of Majiagou Formation in northwestern Ordos Basin, with obviously different petrological characteristics and reservoir properties. On the basis of petrological studies such as core and casting thin section observation and cathodoluminescence analysis, the diagenetic fluid properties of these two dolostone are characterized by geochemical analytical methods such as major and trace element tests. The results show that Type-1 dolostone is mainly composed of micritic dolomite, showing micritic structure and algae-rich lamina structure, and accompanied by evaporite minerals and moldic pores. This type of dolostone has a various Mn content, weak to medium cathodoluminescence intensity, high contents of TiO2, Al2O3, K2O+Na2O, Li, and U, and lower content of TFe2O3. The type-2 dolostone is composed of fine-grained dolomite with obvious residual texture of primary limestone, clear brim, and cloudy center structure, accompanied by the existence of intergranular pores. Most of this kind of dolostone have medium-strong cathodoluminescence, higher TFe2O3 content and lower TiO2, Al2O3, K2O+Na2O, Li, and U contents. Moreover, both the two types of dolostone have similar Fe/Ca and Mn/Ca ratios, and a low and concentrated CaO content, whose composition is similar to that of stoichiometric dolomite. The comprehensive analysis shows that the diagenetic fluid of Type-1 dolostone is mainly a high salinity fluid existed in plaster and calcareous sediments in a near surface environment with low temperature. The diagenetic fluid of Type-2 dolostone may be a high salinity brine formed by evaporation and concentration of seawater with normal salinity. The research results will provide a significant theoretical basis for the evaluation of dolostone reservoir quality and the prediction of favorable areas of reservoir distribution.

The parameters of grain size, contents of silica, kaolinite, hydromica, calcite, and a geological time of tight sandstone reservoirs in Upper Paleozoic in Ordos basin were researched thoroughly, and the impact of the diagenetic evolution process of different sandstone types on porosity and throats was analyzed, based on the quantitative statistics from thin sections, measurements of porosity and permeability, and conventional and constant-rate mercury injection tests. We not only build the evolution of porosity through process-oriented numerical simulations during the geological time but also establish effect-oriented numerical simulations between porosity and different diagenesis parameters. Furthermore, we set up a fitting relationship between diagenetic factors and pore throats in different gas-bearing reservoirs. Differentiation results in the evolution of porosity and a pore-throat system of sandstone types have clear characteristics, such as lithic quartz sandstones of the He 8 Member in the Sulige area and quartz sandstones of the Shan 2 Member in the Yulin area. The fitting results show that the main factors influencing the evolution of porosity and a pore-throat system are grain size and siliceous cement, which can also be validated by the measured data on two gas-bearing intervals. The results are important to a deep understanding of the relationship between the reservoir continuing to experience porosity and permeability evolution and the timing of petroleum charging into the reservoir and can also be applied elsewhere as a quick means in high grading areas of risks during field development.

The Huashan Group preserves Neoproterozoic volcanic‐sedimentary sequences in the northern Yangtze Block and is an ideal target for determining the provenance and characteristics of Neoproterozoic sedimentary basins and the Precambrian crustal evolution of the Yangtze Block. Here, we report LA‐ICP‐MS detrital zircon U–Pb–Hf isotopes from four metamorphic clastic rock samples in the Huashan Group. Detrital zircons ages yield four major peaks at ca. 2,670, 2,040, 940, and 840 Ma and five subordinate peaks at greater than or equal to ca. 2,850, 2,490, 1,840, 1,600, and 1,240 Ma. The provenance of the Huashan Group includes Archean to mid‐Neoproterozoic magmatic rocks, and reworked sedimentary rocks from the northern Yangtze Block. The Huashan Group was deposited from ca. 830 to 800 Ma and represents sedimentation accompanying the development of a mid‐Neoproterozoic continental rift basin in Yangtze Block associated with the breakup of the Rodinia supercontinent. Hafnium isotope analyses of detrital zircon from the Huashan Group suggest that most crustal growth in the northern Yangtze Block occurred during the Late‐Mesoproterozoic and early to Middle Neoproterozoic and crustal reworking occurred from the Archean to the Neoproterozoic.

Since the Quaternary period, tectonic uplift and river erosion in the northeastern Ordos Basin (northwest China) have exhumed numerous coal seams, creating the conditions for the development of coal fires following their spontaneous combustion or other types of ignition (e.g., lightning strikes). Coal fires activity is testified by the widespread occurrence of combustion metamorphic rocks. In this study, thin section analyses, scanning electron microscopy, X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma mass spectrometry (ICP-MS) were used to investigate in detail the mineralogical and geochemical characteristics of combustion metamorphic rocks in the Jurassic succession of the northeastern Ordos Basin. The samples collected in localities distributed over an area of about 8000 km2 were analyzed to determine their mineral association, revealing the presence of tridymite, cristobalite, mullite, and cordierite that are typically produced in pyrometamorphic reactions. XRF and ICP-MS analyses revealed that combustion metamorphic rocks are iron-enriched. Investigations in the study area also highlighted the occurrence of a peculiar, porous, and permeable white sandstone that appears often associated with clinkers or coal seams. It is composed of quartz and feldspar grains and cemented by kaolinite. It is here suggested that the white color of this sandstone could be due to coal fire-related kaolinization of a sandstone protolith produced by the acidic low-temperature hydrothermal circulation of rain waters during times of coal fire activity.

The first, third and fifth members (henceforth referred to as T(3)x(1), T(3)x(3) and T(3)x(5), respectively) of the Upper Triassic coal-bearing Xujiahe Formation black shale are among the most significant hydrocarbon source rocks in the Sichuan basin. Here, we present geochemical data for the Upper Triassic black shales from core from Well LD-1 to determine their paleoenvironmental conditions, paleoweathering, provenance transitions and tectonic setting. The V/(V + Ni) vs. U/Th, V/Cr vs. U/Th and Ni/Co vs. U/Th bivariate plots and the TFe-TOC-TS (total Fe-total organic carbon-total Sulphur) ternary diagram indicate that the synsedimentary redox regime of almost all the shale samples was oxidizing. Ba/Al, Sr/Al and P/Ti data combined with quantitative biogenic Ba data indicate that moderate-high primary paleoproductivity levels prevailed during deposition. The Sr/Cu ratio and C-value combined with the sedimentary features are indicative of warm-humid climate conditions. The Ti/Al deposition rate proxy and decompacted sedimentation rate are positively correlated with the total organic carbon (TOC) content. According to our multiproxy approach, black shale development in the Xujiahe Formation was mainly controlled by the primary productivity level, foreland basin setting, high tectonic subsidence and sedimentation rate and exhibited a limited correlation with water column redox conditions. Through the compilation and calculation of various weathering indices for the Xujiahe black shale, we suggest that caution must be taken when inferring paleoclimate characteristics based on the chemical index of alteration (CIA) because of the influence of multiple nonweathering factors. Provenance-sensitive elemental ratios (Th/Sc vs. Zr/Sc and Co/Th vs. La/Sc) indicate that the elastic contribution to Xujiahe black shales was of a predominantly felsic character. The black shales exhibit a transition from T(3)x(1), T(3)x(3) and T(3)x(5), whereby T(3)x(1) was primarily sourced from the Proterozoic to early Paleozoic strata of the Qinling orogeny, T(3)x(3) was primarily sourced from the Neoproterozoic complex in the Longmen Shan, and T(3)x(5) was primarily sourced from the Songpan-Ganzi flysch strata, which contributed recycled material because of folding and strong southeastward thrusting.