Journal of Petroleum Geology最新文献

This study integrates geological (well logs, outcrop), geophysical (2D seismic and gravity surveys), and palynological data to reconstruct the tectonostratigraphic evolution of the Lake Edward Basin (Uganda) and assess its hydrocarbon potential. Results confirm an asymmetric half-graben bounded by major faults to the west and subsidiary faults to the east, with westward-thickening sediments reflecting basement geometry. Seismic interpretation reveals growth strata, fault-controlled depocenters, and structural traps, whereas lithological and wireline data confirm the presence of fluvio-deltaic reservoirs interbedded with local and possible regional seals. With a rift thermal gradient of ∼33–35°C/km, depocenters in the western part of the basin fall within the oil window. The clustering of hydrocarbon seeps on the surface of Lake Edward above the Kasindi–Bantu Fault Zone, coupled with well failure analysis, suggests that lateral hydrocarbon migration from source areas is likely limited, indicating restricted long-distance migration pathways. Although no hydrocarbon discovery has yet been made, the basin exhibits favorable structural and stratigraphic configurations comparable to proven rift plays in the wider Albertine Rift. This work underscores the need for further offshore high-resolution geophysical data acquisition, cross-border data integration, and advanced basin modeling to de-risk the petroleum system and guide future exploration.

Characterizing carbonate reservoirs in the Middle East remains a persistent challenge due to pronounced heterogeneity, complex diagenetic overprints, and facies variability associated with shelf-margin dynamics. This study develops depositional and diagenetic models for major carbonate play types—shelf sheets (inner shelf sheets, sheets proximal to and updip from the carbonate shelf edge, and basinal sheets and wedges), buildups (shelf buildups and downslope buildups), and shelf-margin clinoforms—to improve qualitative interpretation of well-log responses in data-limited settings. Because many legacy wells lack digital log data, interpretations are derived from published values, emphasizing the reproducibility of diagnostic gamma-ray, neutron–density, and sonic motifs across stratigraphic intervals. The resulting framework defines characteristic log signatures for end-member carbonate plays and clarifies how depositional setting and diagenetic evolution govern porosity and reservoir quality. Although limited by incomplete stratigraphic coverage and the absence of direct seismic-to-well calibration, the study provides a regionally consistent qualitative model that enhances understanding of carbonate reservoir architecture across the Arabian Gulf. These models form a foundation for future quantitative analyses integrating modern log suites and, potentially, for artificial intelligence (AI)-assisted approaches to automated facies recognition.

Successfully predicting effective migration pathways can greatly improve the accuracy of trap risk evaluations, increase the drilling success rate, and reduce the costs of exploration in general. Combined with modeling, a total of 47 crude oil samples and 24 source rock samples were analyzed to study oil migration pathways in the Cretaceous Napo Fm M1ss member in the X block in the Oriente Basin of Ecuador. The vitrinite reflectance values of 24 source rock samples show that the source rock in the southwest zone is in the oil maturity window and was capable of supplying oil to the X block. The nitrogenous compound ratios of 1,8-/2,6-dimethylcarbazole and 1,5-/2,7-dimethylcarbazole have a consistent decreasing trend which indicates that oils migrated within the M1ss member from southwest to northeast. Basin modeling of M1ss carrier shows that different oil supply areas have different migration pathways. The migration pathways associated with oil supplies from the southwest region of Block X are restricted to the southwest and central areas. In contrast, those linked to oil supplies from the Fanny fault extend across both the hanging wall and footwall of this fault. Meanwhile, the migration pathways connected to oil supplies from the MariannN and MariannM faults are confined solely to the hanging walls of these two faults. Basin modeling combined with nitrogenous compounds analysis verified the migration pathway distribution in X block which could explain the formation of most accumulations. The traps in the southwest and eastern areas of X block appear to be favorable for future exploration as they are located on a migration pathway.

Despite having promising evidence of hydrocarbons, the Proterozoic Cuddapah Basin in southern India has not been explored adequately for petroleum resources. The present study aims to identify potential regions for hydrocarbons in Cuddapah Basin by integrating various aspects of hydrocarbon exploration. The remote sensing approach involves structural and spectral analyses of multi-sensor satellite data to look for suitable surface manifestations of hydrocarbons. From remote sensing perspective, areas with high lineament density, presence of geomorphic highs and spectrally anomalous regions are mapped as potential hydrocarbon-bearing sites. The sedimentological studies focus on identifying the best suitable reservoirs for hydrocarbon accumulation through detailed analyses of mineralogy, texture and depositional environments. The geochemical aspects cover the surface geochemical prospecting and analysis to pinpoint anomalous areas of soil gas occurrence and potential source rocks. Geophysical studies interpret gravity, magnetic and seismic data to delineate sedimentary thickness and suitable traps for hydrocarbon accumulations. Remote sensing, combined with surface geochemical studies (adsorbed soil gas and microbial analyses), sedimentological, gravity, magnetic and seismic studies point out a promising area for hydrocarbon occurrence in the north-central part of the study area. Detailed sedimentological studies demonstrate Tadpatri, Pulivendla, Vempalle and Gulcheru formations as potential reservoir rocks for the identified promising area. Thick shales and intrusives are envisaged as potential seals. Furthermore, geochemical parameters and the presence of gas seepage reinforce the hydrocarbon potentiality of the mapped region. The study will provide valuable insights into hydrocarbon exploration in Cuddapah and other Proterozoic basins of the world.

The Lower Permian Shanxi Formation in the Eastern Ordos Basin, North China, is a key exploration target for transitional shale gas. Based on facies markers and elemental characteristics, the Shanxi transitional organic-rich shale are divided into estuary shale and lagoon shale. Various techniques (low-temperature N₂/CO₂ physisorption, etc.) are applied to reveal pore structure differences between estuary shale and lagoon shale. The results indicate that the estuary shale exhibit better macroscopic characteristics (organic matter [OM] component, mineral composition, porosity, and gas content) and nanoscale pore structure than those of lagoon shale. The OM enrichment model reveals the differences in OM components, and estuary shale is supplied by both terrestrial and marine OM. During the hydrocarbon generation and evolution process, the marine-origin sapropelinite has the capacity to generate more organic pores. Organic pores still occupy an important position in estuary organic-rich shale. Lagoon shale is greatly influenced by terrestrial sources, with most of the OM components being terrestrial OM, along with is primary OM showing poor pore-forming abilities. Estuary shale reservoir belongs to a pore-fracture type comprising organic pores, inorganic pores, and microfractures, while lagoon shale reservoir is microfractures type.

The Sarvak Formation, a major Cretaceous carbonate reservoir in the Zagros Basin, Iran, exhibits significant heterogeneity controlled by variations in depositional facies characteristics, diagenetic alterations, and accommodation spaces. This study integrates core analysis, petrography, well logs, hydraulic flow units (HFUs), and sequence stratigraphy to unravel multiscale controls on reservoir quality in the Abadan Plain. Petrographic analyses identified eight sedimentary microfacies deposited across shallow to deep settings of a carbonate platform, with diagenetic processes (dissolution, dolomitization, cementation, compaction, fracturing) tightly linked to sequence boundaries and systems tracts. Two third-order sequences (Cenomanian and Turonian) were interpreted, each comprising transgressive and regressive systems tracts (RSTs). Dissolution, concentrated beneath Cenomanian–Turonian and mid-Turonian unconformities in RSTs, generated vuggy and cavernous porosity, correlating with high-quality flow units and pore-size classes (PSCs). Dolomitization, associated with stylolites in mud-dominated facies of transgressive systems tracts (TSTs), enhanced intercrystalline porosity. Cementation and compaction degraded reservoir quality in low-energy facies. Ten HFUs and seven PSCs were classified using flow zone indicator and Winland R35 methods, whereas velocity deviation log subdivided the reservoir into 14 zones in well-A and 9 zones in well-B, highlighting vertical heterogeneity. Fracturing, primarily micro-scale and cement-filled in the Abadan Plain, showed limited permeability impact compared to tectonically active regions. The study establishes predictive links between sequence stratigraphic surfaces and systems tracts, diagenetic processes, and reservoir properties, emphasizing targeting dissolution-prone RSTs beneath unconformities and dolomitized TSTs near maximum flooding surfaces. This integrated approach reduces exploration risk in carbonate reservoirs and provides a framework applicable to analogous basins globally.

This study presents an integrated analysis of organic matter (OM) maturity proxies, including Rock-Eval pyrolysis, vitrinite reflectance, and the spore color standard (SCS), in conjunction with a pre-existing 3D numerical model of the present-day temperature field. Our research, focused on the eastern Polish Outer Carpathians, aimed to unravel the potential distribution of the mature source rocks in the region. Specifically, we sought to verify the timing of maturation (pre- or post-orogenic), delineate extensively uplifted areas, assess the role of the current thermal structure in catagenesis, and understand the origin of thermal anomalies. The 3D thermal model, derived from over 500 well thermal logs, was re-evaluated using isotherm depth maps (80°C, 130°C, and 160°C) to characterize catagenesis stages. The SCS method was introduced as a robust and cost-effective tool for OM maturity determination, offering the unique advantage of tracing multi-sourcing and redeposition. Our findings reveal relatively low maturity in the Silesian and Skole Units, generally mirroring the present-day thermal field. We infer that the mature source rocks responsible for existing hydrocarbon accumulations are likely situated deeper, beneath the basal thrust of the topmost nappes. Localized “hot spots” in the present-day thermal gradient, coinciding with anomalously high OM maturity, indicate irregular heat transfer within the study area. A prominent high heat-flow zone in the southeastern Silesian and Dukla Units (Bieszczady and Bystre Subunit areas) may be linked to significant tectonic uplift or a deep-seated heat source, potentially of magmatic origin. This analysis demonstrates that understanding present-day thermal gradient irregularities can effectively highlight regions of elevated paleotemperatures, indicative of mature source rocks. The presented integration of diverse methods offers a powerful approach for enhanced source rock maturity assessment, benefiting the Carpathian petroleum industry.

This study investigated the microbiological susceptibility of rocks from the Outer Carpathians. We hypothesized that source rocks differ significantly in their ability to be colonized by microorganisms, which in turn may affect the potential use of unconventional techniques for microbial enhancement of gas recovery. To test this, we combined geochemical analyses with the isolation of a hydrocarbon-degrading microbial community and respirometric experiments, in which gas production from rock samples was monitored using an automated system. The results showed that, despite their high hydrocarbon generation potential, rocks of the Menilite Formation may not support microbial activity. In contrast, samples from the Krosno Formation, Upper Istebna Sandstones and Spas-Veřovice Shales displayed much more favourable microbiological properties. The key factors influencing microbial activity in the tested rocks were porosity, total organic carbon and the contents of quartz, aluminosilicates and carbonates.

The drill bit is a crucial device in oil companies, and it is quite expensive. Therefore, studying its mechanical behavior is essential for preserving this device and reducing its maintenance costs. The drilling mud is among the practical things that influence the bit's performance during the drilling operation. This article presents a numerical study of mud rheology in Algerian oil and gas wells using computational fluid dynamics (CFD) analysis. This study aims to optimize the rheological and dynamic properties around the polycrystalline diamond compact (PDC) drill bit of 244 mm diameter in the Algerian borehole. The drilling mud used is a mixture of water, 0.15% of hydroxyethyl cellulose (HEC), and an Algerian bentonite base. The Herschel–Bulkley model has been used to characterize the rheological behavior of this drilling mud because it is a non-Newtonian fluid. The three-dimensional (3D) model of the PDC drill bit was meticulously designed using SolidWorks (version 24, 2016). Additionally, the dynamic behavior of the PDC drill bit in the presence of drilling mud was modeled and simulated using ANSYS Fluent software (version 19.0, 2018). The results indicate that although mud density has minimal impact on annular velocity, it significantly affects the pressure drop across the drill bit. In contrast, the drill bit's rotational speed directly influences annular velocity, which plays a critical role in mitigating stick–slip phenomena. This mitigation is achieved through the enhancement of cuttings transport from the bottom hole to the surface, thereby preventing accumulation around the drill bit, a primary contributor to stick–slip vibrations. These findings support previous studies that have established the influence of mud density on pressure drop and the critical role of rotational speed in mitigating stick–slip phenomena. The numerical results for fluid parameters at the nozzle, obtained using ANSYS Fluent, were validated against established oilfield empirical correlations, demonstrating satisfactory agreement.