Geological Characteristics and Controlling Factors of Deep Shale Gas Enrichment of the Wufeng-Longmaxi Formation in the Southern Sichuan Basin, China

Lithosphere, Journal Year: 2022, Volume and Issue: 2022(Special 12)

Published: Aug. 1, 2022

Abstract To identify the factors controlling high-quality deep shale gas reservoirs and exploration development potential of Lower Paleozoic marine in Sichuan Basin, sedimentary environment was comprehensively analysed using core thin sections, scanning electron microscopy, gamma ray spectrometry logging, elemental logging data. In addition, geological conditions accumulation effect tectonic processes on preservation are discussed based experimental data mineral composition analysis, geochemical features, reservoir spatial characteristics. (1) The changes from an anoxic water to oxygen-rich oxidizing bottom top Wufeng-Longmaxi Formation southern Sichuan. shows overpressure rich characteristics, namely, high formation pressure (2.0~2.2), porosity (20%~55%), content (4.0~5.0 m3/t). (2) favourable has a higher hydrocarbon generation deposits organic matter siliceous particles. During process, generates large number pores specific surface area, which provides main adsorption space for free adsorbed gas. A biogenic particles provide solid rock support framework reservoir, thereby maintaining excellent physical properties. (3) Late small stratigraphic uplifts result short escape time conditions. Additionally, small-scale faults high-angle intersection between fracture strike geostress direction conducive (4) coefficient, deep-water continental shelf microfacies, relatively stable structure

Language: Английский

---

Pore structure and fractal characteristics of the marine shale of the longmaxi formation in the changning area, Southern Sichuan Basin, China

Frontiers in Earth Science, Journal Year: 2022, Volume and Issue: 10

Published: Sept. 14, 2022

The pore structure is an important factor affecting reservoir capacity and shale gas production. of the Longmaxi Formation in Changning area, Southern Sichuan Basin, highly heterogeneous has a complex structure. To quantitatively characterize shale’s influencing factors, based on whole rock X-ray diffraction, argon ion polishing electron microscopy observations, low-temperature nitrogen adsorption-desorption experiments, characteristics are studied by using Frenkel-Halsey-Hill (FHH) model. research reveals following: 1) pores mainly include organic pores, intergranular dissolution microfractures. size micro-mesoporous. Both ink bottle-type semiclosed slit-type with good openness exist, but observed. 2) self-similarity, conforms to fractal law, shows double characteristics. Taking relative pressure 0.45 (P/P 0 = 0.45) as boundary, surface dimension D sf structural st defined. between 2.3215 2.6117, 2.8424 2.9016. micropores mesopores more complex. 3) mineral components matter have obvious control over shale, samples from different wells show certain differences. positive correlation quartz content negative clay minerals. higher total carbon is, degree thermal evolution, larger dimension. results guiding significance for characterization tight rocks.

Language: Английский

---

Shale pore characteristics and their impact on the gas-bearing properties of the Longmaxi Formation in the Luzhou area

Scientific Reports, Journal Year: 2024, Volume and Issue: 14(1)

Published: July 23, 2024

Abstract Deep shale has the characteristics of large burial depth, rapid changes in reservoir properties, complex pore types and structures, unstable production. The whole-rock X-ray diffraction (XRD) analysis, physical property parameter testing, scanning electron microscopy (SEM) high-pressure mercury intrusion CO 2 adsorption experimentation, low-temperature nitrogen adsorption–desorption testing were performed to study structure marine reservoirs southern Sichuan Basin. results show that deep Wufeng Formation Longyi 1 sub-member Luzhou area is superior Weiyuan terms factors controlling gas enrichment, such as organic matter abundance, gas-bearing thickness. SEM utilized identify six pores (mainly pores). porosities pyrobitumen reach 21.04–31.65%, while solid kerogen pores, siliceous mineral dissolution carbonate are low at 0.48–1.80%. mainly micropores mesopores, with a small amount macropores. total volume ranges from 22.0 36.40 μL/g, an average 27.46 specific surface 34.27 50.39 m /g, 41.12 /g. positively correlated TOC content, minerals, clay minerals. key period for which matches evolution process hydrocarbon generation, capacity, direct indirect cap rocks, Middle Late Triassic present. Areas late structural uplift, uplift amplitude, high formation pressure coefficient favor preserving content production levels.

Language: Английский

---

Lithological Controls on Pore Structure and Their Implications for Deep Shale Gas Reservoir Quality in the Longmaxi Formation, Luzhou area, Southern Sichuan Basin, China

Energy & Fuels, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 11, 2025

This study investigates shale samples from the Longyi1 submember (SM) in Luzhou area of Sichuan Basin. A series experiments, including organic matter content analysis, vitrinite reflectance, whole-rock mineral X-ray diffraction, carbon dioxide adsorption, nitrogen high-pressure mercury intrusion, and argon ion polishing scanning electron microscopy, were conducted to characterize full pore size distribution different phases Longmaxi Formation (LMX FM). The also explores role lithology controlling structure. results show that SM is overmature, with some well sections exhibiting semigraphitization. main lithologies are overmature organic-rich siliceous mixed shale, a small amount semigraphitized shale. Pore analysis reveals mesopores contribute largest proportion volume (PV) (63.3%), followed by micropores (32.7%) macropores (3.9%). Regarding specific surface (SSA), dominate (66.5%), while 33.5% account for only 0.02%. peak diameters ranges 0.3–0.9, 4–15, 20–40 nm, PV ranging 24.7 36.4 μL/g SSA 35.7 50.4 m2/g. LMX FM positively correlated total content, minerals, clay minerals. relatively large volumes pores make it most favorable reservoir phase. top bottom sealing layers create barrier fluid movement Longyi2 primarily composed poorly connected pores, dominated pores. Differences structure between two SMs effect, isolating SM.

Language: Английский

---

Characteristics and distribution of tectonic fracture networks in low permeability conglomerate reservoirs

Scientific Reports, Journal Year: 2025, Volume and Issue: 15(1)

Published: Feb. 18, 2025

Natural fractures (particularly those reshaped by multiple tectonic stages) are of paramount importance for the development tight conglomerate hydrocarbon reservoirs. These not only enhance reservoir pore space but also serve as essential conduits migration. Focusing on Permian Jiamuhe Formation reservoirs in Xiaoguai area Junggar Basin, this study integrates structural interpretation, core observation, and well-log evaluation to elucidate characteristics vertical distribution fractures. A paleotectonic stress field numerical simulation is subsequently employed predict their planar distribution. Results indicate that primarily comprises fracture-type fracture-porosity-type reservoirs, wherein granule pebble conglomerates predominate. Tectonic a pivotal control quality. They predominantly manifest shear formed under compressional stresses, with dip angles exceeding 75°, consistent regionally extensive Such chiefly developed fine conglomerates, gravelly sandstones, heterogeneous sandstones adjacent fault zones, corresponding delta front margin subfacies. Well-log interpretations suggest more pronounced middle upper sections Formation. However, thickness often limited, varies considerably, exhibits marked heterogeneity, limiting straightforward well-to-well correlations. Using finite element software "2D-σ," coupled an elastic constitutive model Mohr-Coulomb failure criterion, we characterized degree rock delineated associated fracture Production data integrated geological analyses facilitated classification zones into three discrete levels. Grade I trending northeast–southwest (NE-SW), subjected northwest–southeast (NW-SE) compressive stresses exhibit high values, large differentials, degrees failure. comparison single-well production outcomes reveals wells intersecting extensively systems generally yield superior oil-test performances, underscoring critical role migration entrapment. The method has thus demonstrated robust reliability predicting Accurate identification instrumental improving exploration success rates optimizing hydraulic fracturing strategies during development.

Language: Английский

---

Mineralogical and Lithofacies Controls on Gas Storage Mechanisms in Organic-Rich Marine Shales

Energy & Fuels, Journal Year: 2025, Volume and Issue: unknown

Published: Feb. 12, 2025

Language: Английский

---

Geological characteristics and major factors controlling the high yield of tight oil in the Da’anzhai member of the western Gongshanmiao in the central Sichuan basin, China

Geomechanics and Geophysics for Geo-Energy and Geo-Resources, Journal Year: 2024, Volume and Issue: 10(1)

Published: April 1, 2024

Abstract The Da’anzhai Member limestone in the central Sichuan Basin holds significant importance as a tight oil-producing formation. Despite its crucial role, intricate patterns of hydrocarbon enrichment and elusive geological factors dictating high-yield production have impeded oil exploration development Basin. This study delves into characteristics identifies key influencing production, utilizing comprehensive data derived from cores, thin sections, well logging, seismic studies, tests western Gongshanmiao within Our findings reveal that primary productive strata for are Da 1 (1st Submember Member) 3 (3rd Submembers, characterized by high-energy low-energy shell beach microfacies. kerogen type is sapropelic, ranging mature to highly mature, positioning it moderately good source rock. predominant lithology reservoir consists coquina argillaceous coquina, with secondary dissolved pores, fractures, nano-scale micropores serving spaces. overall represents dense pore-fracture type, featuring low porosity permeability. Critical controlling achieving encompass lithological composition, fracture development, tectonic position, source-reservoir configuration. Notably, substantial thickness, strategic relationship between lower upper rocks contribute significantly unlocking high yields. Additionally, thin-layer emerges potential area realizing increased gas capacity during later stages development. analysis sheds light on dynamics governing Member, offering valuable insights advancing strategies

Language: Английский

---

Editorial: Differences in shale oil and gas reservoirs across various sedimentary environments: theories and applications, volume II

Frontiers in Earth Science, Journal Year: 2025, Volume and Issue: 13

Published: April 22, 2025

Language: Английский

---

Experimental study on the mechanical properties of loess containing tectonic joints

Frontiers in Earth Science, Journal Year: 2025, Volume and Issue: 13

Published: May 12, 2025

This study systematically examines the influence of joints on mechanical properties loess, highlighting impact joint dip angles soil deformation and failure mechanisms. By employing an innovative layered compaction method to prepare jointed specimens, conducting comparative experiments with different simulation materials (wax paper, rice plastic film), a series controlled indoor triaxial compression tests were performed. The key findings are as follows: (1) angle plays decisive role in evolution mode, five typical mechanisms identified based fracture characteristics: shear failure, sliding conjugate sliding-shear sliding-conjugate failure. (2) weakening effect exhibits confining pressure dependency: Under low (50 kPa), specimens demonstrate increased axial displacement reduced strength attenuation ratio. (3) Mechanical parameters significantly influenced by angle: When falls within critical range 60°–75°, both cohesion internal friction reach their minimum values, forming zones weakened properties. (4) A analysis indicates that single-layer due its optimal thickness tensile strength, effectively replicates contact behavior natural surfaces. establishes quantitative relationship between geometric responses, providing experimental basis for engineering geological assessment loess.

Language: Английский

---

Limited distribution of cratonic strike-slip faults in Sichuan basin and their genesis mechanisms

Frontiers in Earth Science, Journal Year: 2025, Volume and Issue: 13

Published: May 14, 2025

Introduction The genesis mechanism of cratonic strike-slip faults in the Sichuan basin is not yet fully resolved, largely due to lack comprehensive characterization fault distribution, which constrains understanding relationship between development and tectonic events. Method In this study, we supplement extensive three-dimensional seismic data from areas beyond central delineate distribution across entire basin. By integrating these findings with regional processes, mechanisms are proposed. Result results reveal that exclusively concentrated Weiyuan area, no such observed elsewhere This spatial restriction suggests their formation was governed by unique evolution Sichuan. Discussion Furthermore, three lines evidence prove multi-stage uplifts played a pivotal role development: (1) Faults varying orientations exhibit distinct periods, aligning uplift phases; (2) Fault correlate bending directions strata induced uplifts; (3) Additional examples analogous Jurassic near foreland front further corroborate link orientation caused processes. region, characterized superimposed multi-phase paleo-uplift evolution, thus serves as focal zone for faults. It also inferred so-called “cratonic strike-slip” system genuine but rather composite normal different periods. attributed tensile strain resulting during study only provides more introduces novel genetic model faults, crucial new ideas improving theory within basins.

Language: Английский

---