Oil Exploration Research Articles

Reservoir heterogeneities due to diagenesis in Jurassic Samana Suk Formation Kahi section Nizampur Basin North West Himalayas Pakistan

The porosity and permeability determine the reservoir quality of sedimentary rocks, which is fundamentally influenced by both depositional and diagenetic processes. The Jurassic carbonates are targeted in many regions for oil and gas exploration. The current study is carried out to elaborate on the diagenetic alterations and their effect on reservoir properties. A thick outcrop of the Jurassic Samana Suk Formation is studied in the Kahi section of Nizampur Basin Northwest Himalayas, Pakistan, to study and relate the trend of lithological variations and depositional settings. Field investigation revealed that the Samana Suk Formation is extensively distributed in the area and primarily made up of interbedded limestone and dolomite units. The original unaltered limestone has a thick-bedded and oolitic to bioclastic nature. Different types of dolomites have been recognized based on colour contrast and sedimentary features. Moreover, saddle dolomite cement, calcite cementation, and mechanical and chemical compaction have also been observed. The petrographic studies show different types of diagenetic alterations that affected the Samana Suk Formation, including micritization, bioturbation, mechanical and chemical compaction in the form of fractures and stylolites, various calcite cementation, which includes the various cement types that range from isopachous, blocky, granular equant, fibrous, and dog tooth cementation, along with dissolution that occurred in different diagenetic realms. Pyritization was rarely observed. Moreover, different phases of dolomites were identified, ranging in size and shape, i.e., finely crystalline to coarse crystalline and planar euhedral to non-planar anhedral. The stable oxygen isotope values of these dolomites show depletion from original marine signatures and suggest burial-related fault-controlled dolomitization events. Overall, diagenetic processes like dissolution, fracturing and dolomitization increased the reservoir potential. On the contrary, the overburden and cement precipitation result in a decrease in the reservoir properties.

Regional Assessment of Groundwater Contamination Risk from Crude Oil Spillages in the Niger Delta: A Novel Application of the Source-Pathway-Receptor Model

AbstractOnshore oil spills are known for their disastrous environmental impacts and potential to cause lasting damage to underlying groundwater. The Niger Delta is particularly vulnerable to widespread spillages linked to extensive oil exploration, transportation, and theft-related incidents. This research employed a geospatial approach in formulating risk equations, based on the source-pathway-receptor (S-P-R) model using multiple openly available data sets, to assess groundwater contamination risk in the Niger Delta Region (NDR), Nigeria. To develop the overall risk equation, the study combined fourteen thematic data layers including the volume of oil spilled, type of spill, slope, elevation, proximity to spill site, pipeline, oil wells and streams, drainage density, mean annual precipitation and population density. These layers were integrated into source potency, pathway transmissivity, and receptor susceptibility. The NDR was systematically categorized into low, moderate, and high groundwater risk zones. The delineation revealed that high-risk zones predominantly span the central areas, extending from southeast to northwest, effectively encircled by regions of low to medium risk located in both the northern and southern extents of the delta. The efficacy of the risk model was corroborated by existing knowledge. Moderate to high-risk zones were found to be in about 16% of the NDR, revealing previously unknown areas of risk. This spatial configuration underscores a significant gradient in contamination risk across the NDR, with the central corridor emerging as a critical focus for groundwater protection and remediation efforts. In line with UN Sustainable Development Goal (SDG) #6, this study recommends targeted strategies to ensure clean water provision in these identified high-risk areas. By leveraging the S-P-R model within this complex and sensitive ecological area, this research both advances environmental risk assessment and sets a precedent for future large-scale environmental risk assessments utilizing open-source data.

Impacts of Climate Change on Food Security and Sustainable Water Resources in Nigeria

This study evaluates the impacts of climate change on food security and sustainable water resources in Nigeria. Stratified samples were taken from North Central States of Benue and Plateau, and South-South Cross River State and Akwa-Ibom. These four states are among the thirty six states in Nigeria that have been badly hit by climate change. This study used soft and hardware computer applications including German 12 handheld GPS, and Integrated Land and Water Information System (ILWIS), for data collection. Quantitative and qualitative data were collected for the evaluation. The GIS information software package was used to manipulate and perform feature identification, recognition, classification, calculation, and ground-trotting. A structured questionnaire was also used to collect data on some livelihood activities, the influence of livelihoods activities on water resources, food security, and climate change impacts. Data analysis, found that the forest and water bodies are shrunken. Industrial activities such as oil exploration and exploitation, mining, by Multinational Corporations, illegal mining, grazing, unsustainable farming practices, fishing and hunting for bush meats, bush fire, timber exploitation and deforestation have contributed to climate change. The study recommends climate action and climate diplomacy, building local capacity for resilience, engaging the private sector, partnerships and international assistance.

Meandering streamflows across landscapes and scales: a review and discussion

The study of meandering patterns created by geophysical flows is important for a number of fundamental and applied research topics, including stream and wetland restoration, land management, infrastructure design, oil exploration and production, carbon sequestration, flood-hazard mitigation and planetary palaeoenvironmental reconstructions. This volume, Meandering Streamflows: Patterns and Processes across Landscapes and Scales , contains 13 papers that present field, laboratory and numerical investigations of meandering channels found in distinct environmental and geological contexts and focus on how the interactions of different autogenic and allogenic processes, both in the horizontal and the vertical dimension, affect meander kinematics and the resulting morphology, sedimentology and stratigraphic architecture. In this introductory chapter, we offer an overview of the evolution of scientific research on meandering streams over time, aiming to review and discuss meandering patterns in both fluvial and non-fluvial settings. Additionally, we present a new compilation of data on meander morphological features, drawn from both existing literature and novel sources, encompassing over 8000 meander bends discovered across a diverse array of environments.

Simulation of lower Cambrian oil and gas generation and phase evolution process in ZH1 of Tazhong area

The Lower Cambrian petroleum system in the Tarim Basin has undergone multiple periods of tectonic movements, leading to successive hydrocarbon expulsion events and adjustments. The complex process of hydrocarbon accumulation occurred under deep burial conditions, persisting at depths of nearly 6,000 m over an extended period. This has resulted in the current occurrence of various phases including light oil, condensate, and gas in the deep-ultradeep strata of the Tarim Basin. The intricacies of formation of hydrocarbon accumulations and phase evolution have posed challenges to understanding the accumulation mechanisms and enrichment patterns of the Cambrian in the Tarim Basin, consequently lowering the success rate of oil and gas exploration. Such characteristics of multi-stage accumulation and adjustment are prevalent in deep hydrocarbon systems. Therefore, based on data from Well ZH1 in the Tazhong Uplift, combined with basin simulation, Compositional kinetics model, and PVT performance simulation, this study investigates the hydrocarbon generation and phase evolution processes in the deep hydrocarbon systems of the Tazhong Uplift. The results indicate that Well ZH1 entered the hydrocarbon generation peak during the Late Ordovician, followed by secondary cracking as the predominant hydrocarbon evolution process. Hydrocarbon fluids within the Lower Cambrian reservoir transitioned into the condensate phase towards the end of the Cambrian, with increasing depth resulting in higher gas-oil ratios and a decreasing trend in viscosity and density.

Mesozoic tectonic evolution and dynamic mechanisms of the northern Bozhong depression of the Bohai Bay Basin, eastern China

The northern Bozhong depression of the Bohai Bay Basin in eastern China is an important area for oil and gas exploration in buried hills, which has complex structural styles and evolutionary processes. Based on 3D seismic and drilling data, the features of the Mesozoic structural deformation of the northern Bozhong depression are analyzed, and the tectonic evolution and dynamic mechanisms are also discussed. The complex Mesozoic structural styles of the northern Bozhong depression are composed of compression, strike-slip, and extension structures, which mainly trend in the near E-W, NW, NE, and NNE directions. Triggered by the collision and subduction between the North China, South China and Izanagi plates and associated stress fields of different periods, natures and directions, the northern Bozhong depression has experienced five stages of deformation at the end of the Middle Triassic, the Late Triassic, the Early-Middle Jurassic, the Late Jurassic-Early Cretaceous and the Late Cretaceous. Cyclical tectonic evolution has controlled the development of structural styles of different strikes and natures and the spatial distribution of strata in the northern Bozhong depression, providing an important foundation for hydrocarbon accumulation in buried hills.

Paleogene-Neogene ring-shaped sedimentary system and reservoir characteristics in the Western depression of the Qaidam Basin

The Paleogene-Neogene strata in the Western Depression of the Qaidam Basin represent a primary focus for oil and gas exploration and development. Influenced by both terrigenous clastic influx and endogenic carbonate deposition, these strata exhibit significant variation in sedimentary systems and reservoir characteristics. This study comprehensively examines the depositional patterns and reservoir properties of the Paleogene-Neogene sequence across the inner, middle, and outer belts of the basin, employing core analysis, thin section petrography, and physical property assessment of reservoirs. Key findings include 1) The development of a concentric sedimentary system in the Western Depression during the Paleogene-Neogene period, characterized by increased carbonate mineral content and decreased clastic material from the periphery to the center of the basin. 2) Varied sedimentary facies associations across different zones, with the outer belt dominated by fan delta and braided river delta deposits, and the middle and inner belts characterized by near-shore shallow lacustrine carbonates and algal mat deposits, and offshore semi-to deep-lacustrine fine sediments, respectively. 3) The outer belt exhibits reservoirs with favorable physical properties and connectivity, while the inner and middle belts show high heterogeneity, indicating potential for lithological traps and shale oil exploration. These insights offer scientific guidance for further investigation into the depositional systems of lacustrine basins in the Western Depression of the Qaidam Basin and for identifying promising reservoirs.

Heavy Metal Pollution in Gas Flare-Impacted Soils: An Assessment Using Pollution Indices in Obunagha, Bayelsa State, Nigeria

Gas flaring is the controlled burning of natural gas which occurs as a result of the activities of oil exploration and exploitation using flare stacks. In Nigeria, gas flaring activities is high and it mainly takes place in the Niger Delta region. The aim of this study was to investigate the bioavailability and concentration of heavy metals pollution of gas flare-impacted soils using pollution indices such as contamination factor, geo-accumulation index and pollution load index. Soil samples were collected with soil auger at depths of 0-15 cm from distances of 200 m, 500 m, 1000 m, 2000 m, and 3000 m away from the flaring point. Flame atomic absorption spectrometry was used to assess the presence of the following heavy metals in the soils: cadmium, chromium, nickel, zinc, copper, and manganese. The findings revealed that Fe (90% bioavailability) had the highest bioavailability among the metals tested in the soils, while Cr (45%) had the lowest. The metals bioavailability decreased in the order of Fe>Mn>Cu>Cd>Ni>Zn>Cr. The geo-accumulation index revealed that the soils were practically uncontaminated by Zn and Cu at all distances, moderately polluted by Cd and Ni at 1000 m and 2000 m and strongly polluted with Cd at a distance of 200 m. The Contamination factor results were consistent with the geo-accumulation index results. The pollutant load index (PLI) was found to be high but decreasing (1.37-0.49) as the distance from the flare point increased, indicating that the research region was polluted. In conclusion, the study's overall findings suggested that the soils were contaminated with heavy metals (particularly Cd) as a result of nearby gas flaring. As a result, the area must be appropriately monitored and managed to prevent future soil contamination by heavy metals to a level that is hazardous to human health.

Heavy Metal Pollution in Gas Flare-Impacted Soils: An Assessment Using Pollution Indices in Obunagha, Bayelsa State, Nigeria

Gas flaring is the controlled burning of natural gas which occurs as a result of the activities of oil exploration and exploitation using flare stacks. In Nigeria, gas flaring activities is high and it mainly takes place in the Niger Delta region. The aim of this study was to investigate the bioavailability and concentration of heavy metals pollution of gas flare-impacted soils using pollution indices such as contamination factor, geo-accumulation index and pollution load index. Soil samples were collected with soil auger at depths of 0-15 cm from distances of 200 m, 500 m, 1000 m, 2000 m, and 3000 m away from the flaring point. Flame atomic absorption spectrometry was used to assess the presence of the following heavy metals in the soils: cadmium, chromium, nickel, zinc, copper, and manganese. The findings revealed that Fe (90% bioavailability) had the highest bioavailability among the metals tested in the soils, while Cr (45%) had the lowest. The metals bioavailability decreased in the order of Fe>Mn>Cu>Cd>Ni>Zn>Cr. The geo-accumulation index revealed that the soils were practically uncontaminated by Zn and Cu at all distances, moderately polluted by Cd and Ni at 1000 m and 2000 m and strongly polluted with Cd at a distance of 200 m. The Contamination factor results were consistent with the geo-accumulation index results. The pollutant load index (PLI) was found to be high but decreasing (1.37-0.49) as the distance from the flare point increased, indicating that the research region was polluted. In conclusion, the study's overall findings suggested that the soils were contaminated with heavy metals (particularly Cd) as a result of nearby gas flaring. As a result, the area must be appropriately monitored and managed to prevent future soil contamination by heavy metals to a level that is hazardous to human health.

The meteoritic record of Arabia

Meteorites provide a wealth of information about the origin of the Earth and the Solar system. Systematic searches have proved successful in cold and hot desert areas. Meteorite finds are favoured in areas with light-coloured surfaces stable over tens of thousands of years and in hyper-arid climates. The deserts of Arabia are well suited for the search for meteorites. Following the first finds by explorers in the 1930s' and during oil exploration in the 1950s', a significant number of finds have been recorded from Oman since 1999 with >4000 meteorites currently recorded. Exploratory searches in Saudi Arabia have also shown significant potential for meteorite discoveries. A collaborative Omani-Swiss search project was initiated in 2001 and 23 search campaigns since have yielded more than 7300 samples, including meteorites from the Moon and Mars and,37 strewn fields. Arabia has the potential to become one of the key regions for meteorite recovery and future research. Only three confirmed (Wabar, Saqqar, Jebel Waqf as Suwwan), several suspected and some dubious impact structures have been reported. The Wabar impact locality in Saudi Arabia features impact craters in dune sands, shocked and melted sand and finds of several large meteorites.

Ecoanatomical Affiliation of Halophyte in Hydrocarbon Polluted Sites in Parts of Bodo Coastal Creeks, Rivers State, Nigeria

The increasing demand for energy supply and revenue has led to an ever increasing oil exploration and exploitation in parts of the Niger Delta, Nigeria. This has also led to an increase in hydrocarbon pollution leading to the destruction of the plant and animal ecosystems in parts of Rivers State. This study was aimed at investigating the impact of hydrocarbon pollution on the stem and root anatomy of a special group of plants- “Halophytes” present in polluted and unpolluted areas of Bodo Creek, Gokana in Ogoni land Rivers State. The result reveal diverse structural aberrations and challenges involving the species inability to pick up stains thereby limiting the clarity of focus, conversion of air/intercellular spaces into vacuoles filled with oil, rearrangement of the vascular bundles, thickening of the sclerenchyma cells, damage of vital parts of stem and root tissues as well as shrinkage and detachment of cortex from the epidermis leading to the reduction of the air compartments. All these are the anatomical distortion associated with the impact on hydrocarbon pollution on the internal structures of these halophytes when compared with the structures of sections in the controlled unpolluted site.

Seismic Prediction Technology for Channel Sand Body of Fuyu Oil Layer in Xinmin Area, Southern Songliao Basin

The Fuyu reservoir in Xinmin area is a delta plane-front facies deposit, and the channel sand body in this area is the main reservoir of oil and gas. Due to the complex sedimentary environment, the sand body shows great variation in thickness and distribution. In this study, the method of combining well vibration, model forward modeling and stratum slicing are used to predict the sandstone bodies of different thickness successfully. Especially for the thin sand body with a thickness of less than 5 meters, this study found that the GR curve can effectively distinguish sandstone and mudstone through the intersection analysis of logging curves, and applied the GR curve co-simulation inversion technology to perform fine characterization. In addition, the study also reveals that the northeastward twisting fault zone in Xinmin area is a favorable accumulation area of the reservoir, which provides a new direction for oil and gas exploration. This study not only improves the accuracy of sandstone prediction, but also provides a valuable reference for oil and gas exploration under similar complex geological conditions.

Seismic Prediction Technology for Channel Sand Body of Fuyu Oil Layer in Xinmin Area, Southern Songliao Basin

The Fuyu reservoir in Xinmin area is a delta plane-front facies deposit, and the channel sand body in this area is the main reservoir of oil and gas. Due to the complex sedimentary environment, the sand body shows great variation in thickness and distribution. In this study, the method of combining well vibration, model forward modeling and stratum slicing are used to predict the sandstone bodies of different thickness successfully. Especially for the thin sand body with a thickness of less than 5 meters, this study found that the GR curve can effectively distinguish sandstone and mudstone through the intersection analysis of logging curves, and applied the GR curve co-simulation inversion technology to perform fine characterization. In addition, the study also reveals that the northeastward twisting fault zone in Xinmin area is a favorable accumulation area of the reservoir, which provides a new direction for oil and gas exploration. This study not only improves the accuracy of sandstone prediction, but also provides a valuable reference for oil and gas exploration under similar complex geological conditions.

TECHNOLOGICAL SOLUTIONS FOR DRILLING USING FLEXIBLE TUBING – UP-TO-DATE WORLD EXPERIENCE AND PROSPECTS FOR RUSSIA

The article presents an analytical review of modern technologies for using flexible tubing to perform complex technological operations aimed at increasing oil recovery, exploration and repair of wells, and construction of lateral and horizontal wellbores. The authors have been most interested in the technology of underbalanced coiled tubing drilling, since it has the potential to increase oil production while maintaining or minimizing drilling costs without drilling complications while ensuring operational safety.The experience of a foreign company in coiled tubing drilling is reviewed, positive results and growth points are highlighted. Solutions for the implementation of coiled tubing drilling in Russian conditions are proposed to reduce the costs of constructing horizontal wells and additional hydrocarbon production during the drilling process. Preparatory work is underway to conduct pilot-industrial research of the proposed technology.

Regression analysis and its application to oil and gas exploration: A case study of hydrocarbon loss recovery and porosity prediction, China

In oil and gas exploration, elucidating the complex interdependencies among geological variables is paramount. Our study introduces the application of sophisticated regression analysis method at the forefront, aiming not just at predicting geophysical logging curve values but also innovatively mitigate hydrocarbon depletion observed in geochemical logging. Through a rigorous assessment, we explore the efficacy of eight regression models, bifurcated into linear and nonlinear groups, to accommodate the multifaceted nature of geological datasets. Our linear model suite encompasses the Standard Equation, Ridge Regression, Least Absolute Shrinkage and Selection Operator, and Elastic Net, each presenting distinct advantages. The Standard Equation serves as a foundational benchmark, whereas Ridge Regression implements penalty terms to counteract overfitting, thus bolstering model robustness in the presence of multicollinearity. The Least Absolute Shrinkage and Selection Operator for variable selection functions to streamline models, enhancing their interpretability, while Elastic Net amalgamates the merits of Ridge Regression and Least Absolute Shrinkage and Selection Operator, offering a harmonized solution to model complexity and comprehensibility. On the nonlinear front, Gradient Descent, Kernel Ridge Regression, Support Vector Regression, and Piecewise Function-Fitting methods introduce innovative approaches. Gradient Descent assures computational efficiency in optimizing solutions, Kernel Ridge Regression leverages the kernel trick to navigate nonlinear patterns, and Support Vector Regression is proficient in forecasting extremities, pivotal for exploration risk assessment. The Piecewise Function-Fitting approach, tailored for geological data, facilitates adaptable modeling of variable interrelations, accommodating abrupt data trend shifts. Our analysis identifies Ridge Regression, particularly when augmented by Piecewise Function-Fitting, as superior in recouping hydrocarbon losses, and underscoring its utility in resource quantification refinement. Meanwhile, Kernel Ridge Regression emerges as a noteworthy strategy in ameliorating porosity-logging curve prediction for well A, evidencing its aptness for intricate geological structures. This research attests to the scientific ascendancy and broad-spectrum relevance of these regression techniques over conventional methods while heralding new horizons for their deployment in the oil and gas sector. The insights garnered from these advanced modeling strategies are set to transform geological and engineering practices in hydrocarbon prediction, evaluation, and recovery.

Assessing the Helium Potential of Variscan Batholiths: Insight From Corsica Island

AbstractMost of the current helium (He) reserves originate from fortuitous discoveries, mainly made during oil and gas exploration in sedimentary basins. As helium generation depends on U and Th α‐decay, old geological provinces gather key ingredients for high He accumulation. However, numerous He‐rich springs have also been documented in much younger rocks, such as Variscan granites (320–250 Ma). These latter discoveries question the current exploration guidelines and require revisiting some of the longstanding paradigms. Here, is investigated He migration along a major fault rooted in the Corso‐Sardinian batholith (France). Two thermal springs, Caldanelle and Guagno‐Les‐Bains, show significant outgassing activities of crustal sourced He with concentrations up to 1.45 vol% and flow rates of 110 m3 STP 4He/year. Besides He, the gas phase is dominated by N2 (≈98 vol%) and minor CH4. Based on a survey employing multidisciplinary methodologies, it is revealed that (a) Variscan rocks represent efficient 4He source rocks, (b) the main source of He comes from the underlying Eo‐Variscan basement, (c) A deeply rooted fault and dense fractures networks drain the He, (d) the helium loss is limited, (e) faults and fractures may act as partial traps, and finally (f) the presence of an efficient trap could promote a He‐rich reservoir with high flux but low reserves. In that sense, young post‐orogenic granites represent promising helium plays. The geological context in which Caldanelle and Guagno‐Les‐Bains are embedded is ubiquitous in European Variscan batholiths. This case study is therefore intended to serve as a guide for helium exploration and to provide insights into helium behavior within a Variscan geological context.

Oil-and-gas potential of the northeast Predpatom trough

This article discusses the geological structure and prospects of the oil and gas potential in the northeastern part of the Predpatom trough. The materials of the study included geological findings from deep drilling and data from direct geochemical studies conducted in recent years. It describes the specific features of the structural plans of the upper versus the lower part of the geological cross-section. It is assumed that deep drilling in the area of the Ulugur structure has not reached the target productive horizons in the autochthonous part of the section. After acquiring more recent seismic data, there is a proposal to drill a deeper exploratory well in the area. As another priority target for oil and gas exploration, a potential zone of Vendian clastic deposits wedging on the southwestern slope of the Suntar uplift has been identified. A forecast has been made for the distribution of lithological traps stacked with well-sorted granular Vendian reservoirs in the northern parts of the Ergedzheysky and Ulugursky license areas. In the allochthonous part of the section, the potential for oil and gas content in carbonate deposits from the Vendian and Lower Cambrian periods is highlighted in reservoirs formed by secondary processes. It is assumed that thrust deformations could lead to the circulation of aggressive solutions, resulting in the formation of secondary fractured cavernous reservoirs. Subsequently, hydrocarbon accumulations may migrate and accumulate within these reservoirs. Good gas prospects were also noted in the upper part of the section, where gas deposits were confirmed in newly discovered fields. The results of direct geochemical testing of the Ulugur and Ergedzheysky license areas are presented, enabling the preliminary delineation of promising zones and areas in the studied territory. At the same time, narrow elongated geochemical anomalies are associated with the prospects of the allochthonous part of the section, while isometric anomalies are linked to the autochthonous part of the section. The need to consolidate all available geological and geophysical information on the Pre-Atomic deflection within the framework of case studies is noted.

Oil Economy and Society of Nigeria’s Niger Delta Region, 1956-2019

This paper studies the oil economy with a particular focus on the Nigeria’s Niger Delta Region. It argues that since the discovery and exploration of oil in commercial quantities in the Region, it has become both a blessing and a curse. It is a blessing because it has provided wealth to the people and government of the region. Some indigenes of the Nigeria Delta are owners of the oil wells others are employed to work with the oil multi-national companies like Chevron, Texaco, Shell Petroleum Development Company, Agip Oil Company, et cetera. The exploration of oil in the area under review is also a curse because it has negatively affected plants and animals (that is the destruction of flora and fauna); it has destroyed the ecosystem of the area. Using survey and documentary methods of data collection; the paper reveals that despite the discovery and exploration of oil in the said region, Nigeria’s Delta Region has remained one of the underdeveloped regions of the country. This is to say that the impact of the oil industry on the economy and society of the people is marginally felt. Based on the foregoing, these policy options are made. The government should give immediate attention to the indigenes of the region where crude oil is being extracted from. This will reduce the unrest in that region. The government should establish an institution that will ensure that the multinational oil companies are socially responsible to their host communities. Environmental pollution and the adverse effects on the host communities of oil exploration sites in the Niger Delta is an important issue that requires urgent and prompt attention because petroleum production forms the major natural-based resources on which the country depends. Therefore, Policymakers of the various oil exploration companies should realize that there is a need to protect the health, safety, and welfare of these communities. The communities and the inhabitants have to be well protected and some of the health and safety measures, which members of the company staff benefit, should be extended to members of the host communities to improve their standard of living.

MA_W-Net-Based Dual-Output Method for Microseismic Localization in Strong Noise Environments

With the continuous depletion of conventional oil and gas reservoir resources, the beginning of exploration and development of unconventional oil and gas reservoir resources has led to the rapid development of microseismic monitoring technology. Addressing the challenges of low signal-to-noise ratio and inaccurate localization in microseismic data, we propose a new neural network MA_W-Net based on the U-Net network with the following improvements: (1) The foundational U-Net model was refined by evolving the single-channel decoder into a two-channel decoder, aimed at enhancing microseismic event localization and noise suppression capabilities. (2) The integration of attention mechanisms such as the convolutional block attention module (CBAM), coordinate attention (CA), and squeeze-and-excitation (SE) into the encoder to bolster feature extraction. We use synthetic data for evaluating the proposed method. Comparing with the normal U-net network, our accuracy in seismic recordings with a signal-to-noise ratio of −15 is improved from 78 percent to 93.5 percent, and the average error is improved from 2.60 m to 0.76 m. The results show that our method can accurately localize microseismic events and denoising processes from microseismic records with a low signal-to-noise ratio.

Paleo-Sedimentary Environment and Formation Mechanism of the Organic-Rich Shale of the Permian Lucaogou Formation, Jimsar Sag, Junggar Basin, China

The Jimsar Sag is an important shale oil exploration target area in the Junggar Basin, northwestern China. The Permian Lucaogou Formation, with a thickness of 200–300 m, is the primary exploration target. High-frequency variation in lithology is a typical feature of the Lucaogou Formation, reflecting the fluctuation of the depositional environment and organic matter enrichment. The evolution of the depositional environment and accumulation mechanism of organic matter still need to be elucidated for the Lucaogou Formation. High-resolution sampling of the entire Lucaogou Formation was applied to a 248 m long core from Well JX in the Jimsar Sag to examine the depositional environment and organic matter enrichment. The findings unveiled that the Lucaogou Formation was deposited under a hot and arid climate, within the confines of a closed saline paleo-lake, where sediments endured an extended period of anoxic conditions, displayed periodic oscillations in paleo-temperature and paleo-salinity values over time, alongside a continuous rise in paleo-water depth. The predominant source lithology of the Lucaogou Formation is felsic igneous rock. Small-scale transgression and hydrothermal sedimentation occurred during the deposition of the Lucaogou Formation. The prevailing hot climate and enduring reducing environment fostered ideal circumstances for the enrichment of organic matter in the Lucaogou Formation. Due to different sedimentary environments and enrichment mechanisms, organic matter is enriched in two modes in the Lucaogou Formation.