3D Seismic Survey Research Articles

Multidisciplinary high resolution Geophysical Imaging of Pantano Ripa Rossa Segment of the Irpinia Fault (Southern Italy)

The Irpinia Fault, also known as the Monte Marzano Fault System, located in the Southern Apennines (Italy), is one of the most seismically active structures in the Mediterranean. It is the source of the 1980, Ms 6.9, multi-segment rupture earthquake that caused significant damage and nearly 3,000 casualties. Paleoseismological surveys indicate that this structure has generated at least four Mw ~ 7 surface-rupturing earthquakes in the past 2 ka. This paper presents a comprehensive, high-resolution geophysical investigation focused on the southernmost fault segment of the Monte Marzano Fault System, i.e., the Pantano-Ripa Rossa Fault, outcropping within the Pantano di San Gregorio Magno intramontane basin. The project, named TEst Site IRpinia fAult (TESIRA), was supported by the University of Napoli Federico II to study the near-surface structure of this intra-basin fault splay that repeatedly ruptured co-seismically in the past thousands of years. Our imaging approach included 2D and 3D electrical and seismic surveys, gravimetry, 3D FullWaver electrical tomography, drone-borne GPR and magnetic surveys, and CO2 soil flux assessment across the surface rupture. This multidisciplinary investigation improved our understanding of the basin shallow structure, providing an image of a rather complex subsurface fault and basin geometry. Seismic data suggest that fault activity at the Pantano segment of MMFS is characterized by a near-surface cumulative displacement greater than previous estimations, calling into question earlier assumptions about the timing of its activation. Despite some challenges with our drone-mounted survey equipment, the integrated dataset provides a comprehensive and reliable image of the subsurface structure. This work demonstrates the utility of developing an integrated approach at high-resolution geophysical imaging and interpretation of fault zones with weak morphological expressions.

CHARACTERIZATION OF A FLUVIAL DELTAIC SALT-INFLUENCED SYSTEM FOR CO2 STORAGE USING SEISMIC POST-STACK INVERSION AND SELF-ORGANIZING MAPS IN THE UPPER MIOCENE, ONSHORE LOUISIANA

Basins that have historically been explored for hydrocarbons are now seen through a new perspective for carbon capture and storage. Legacy hydrocarbon reservoirs may now have the potential to become carbon storage targets. The Miocene Sandstone in south Louisiana is a stratigraphic interval that contains favorable zones for carbon storage, and seismic interpretation is a critical tool for characterizing these sands and estimating the amount of possible carbon storage. New workflows leveraging machine learning and seismic inversion can be applied to legacy fields to generate a new estimate for pore space and carbon storage capacity. The study area contains a 3D seismic survey covering 310 mi2 (803 km2) and 16 wells. Using these data, the workflow leverages self-organized maps (SOM) to identify zones of interest both laterally and vertically for carbon storage. SOM provides an uplift in resolution for interpretation compared to single attributes. A model-based acoustic impedance inversion produces porosity information that is used in tandem with SOM outputs. The acoustic impedance results strongly correlate to porosity within the target sands, and the SOM and porosity maps delineate specific sand lobes for potential storage. Wellbore data within the sand lobe align with SOM and inversion results and show rock quality with 26% average porosity and 90 feet gross thickness. The research highlights a project sized target within the middle Miocene containing 10.3 Megatons of estimated CO2 storage. Using SOM and inversion maps in tandem is an effective way for screening an area for carbon storage targets.

Prospects of productive strata of the pre-Jurassic complex of Western Siberia for the discovery and involvement in the development

The article discusses the prospects of productive strata of deposits of the pre-Jurassic complex of Western Siberia for searching, forecasting and involving in the development. Some features of the geological structure of Triassic volcanic-sedimentary deposits and formations of the Paleozoic basement have been identified within the pre-Jurassic complex. The construction of digital geological models of Triassic and Paleozoic formations, which are fundamentally different in the geometry of the internal structure of the hydrocarbon deposits discovered in them, is based on 3D seismic information and its interpretation. In deposits of Triassic and Paleozoic sediments, significant differences in the composition and filtration-capacitive properties of rock reservoirs have been recorded; the principles for creating the structural frameworks of their digital models are also different. 3D seismic data makes it possible to correlate the Triassic strata and identify individual cycles, the boundaries and geometry of which are used to create digital three-dimensional geological models. When creating models of hydrocarbon deposits in Paleozoic formations confined to basement high areas, based on the interpretation of 3D seismic survey materials and analysis of seismic attributes, in combination with information on core, petrophysics and well testing, a forecast is made for the development of areas and strata of increased fracturing of rocks, which are the main inflow strata in production wells. Using the example of individual developed deposits confined to the pre-Jurassic complex in the fields of Western Siberia, the actual results of integrating geological and geophysical information with 3D seismic data are shown. Based on these results not only an assessment of the geological reserves of hydrocarbons was carried out, but also hydrodynamic calculations were conducted to perform history matching, as well as recommendations were made for the locations for drilling wells, their geometry and test strata. The accumulated experience in exploration and development of productive deposits of the pre-Jurassic complex allows us to assess the geometry and features of objects of interest in this interval, select the most informative methods for their mapping and methods for creating digital geological models that are the basis for designing the development.

Three‐dimensional static reservoir modelling of Kareem sandstone reservoir, Tawilla Oil Field, at the southern region of Gulf of Suez, Egypt

The Gulf of Suez, which contains Egypt's oldest oil fields, is one of North Africa's most well‐known oil regions. There are more than 80 conventional oil fields in Egypt's Gulf of Suez, some of which have reservoirs that stretch back to the Precambrian and Quaternary. In close proximity to the southern entrance of the Gulf of Suez is the Tawilla West oilfield. The oil field Tawilla West is believed to consist of rotating fault blocks that descend in a south‐west direction. The main producing reservoirs are the Miocene section reservoirs, the Belayim and Kareem sandstones. The current research is focusing on the structural elements affecting this giant field to update the field structural model using the newly processed 3D seismic survey, the acquired data from newly drilled wells and the associated different logging techniques. The seismic information quality varied from poor to fair. The quality of the interpreted stratigraphic horizons and geological faults was mainly controlled by the seismic information quality. The research used seismic attribute analyses to improve interpretation and incorporate additional features, enabling better hydrocarbon potential identification and characterization of the reservoirs. Several geological structure contour maps and cross‐sections were generated to help in delineating and understanding the reservoir's extension. Based on the detailed correlation study, we were able to detect the faults that affected the structure of the Tawilla West field in detail, define their throw amounts and directions, and identify the missed sections across the studied area. This study introduces an updated model scenario to show the differences and their effect on the field development plan and recommendations. By examining subsurface geologic structural characteristics and evaluating petrophysical data, a 3D static reservoir model was created to resolve structural settings and hydrocarbon trapping, providing detailed information on the field and identifying new opportunities for future development. The research discovered that the updated detailed 3D structural model may support the Kareem Reservoir development plans and encourage drilling, workover and dynamic operations to assign development possibilities in the correct area. According to the established model, there are at least three options in the study's attic areas that might boost oil output and oil reserves for the field while avoiding further failures.

Site selection for a high-level nuclear waste repository in Germany: a short guide

The government agency BGE started a site selection process for a high-level nuclear waste repository in 2017. The first phase of data screening was completed in 2020 and resulted in the identification of search areas covering 54% of the national territory. The actual second phase will be completed by 2027 or later, and the areas for aboveground investigations will be identified. The obligatory nongovernment input is provided by follow-up regional conferences, which are best supported by external scientific expertise. The large amount of text documents and maps and the interactive internet tools such a 3D viewer provide a suitable basis for external evaluation. The rationale is to apply stricter criteria than those used in the first phase to drastically reduce the size of the search area. With this updated set of criteria, the size of the search area can be reduced to 2,662 km2 or 0.7% of the national territory. This size is convenient for detailed aboveground investigations such as high-density 3D seismic surveys.

Application of modern seismic attributes in the characterisation of mass transport deposits: Orange Basin, South Africa

Abstract The southern Orange Basin is structurally complex, with a tectonic history dating back to the Late Jurassic to Early Cretaceous. Mass movement events triggered by gravity and tectonic activities have resulted in the deposition of mass transport deposits (MTDs) on the seafloor. These MTDs have been documented as contributors to geohazards, posing risks to underwater infrastructure. Evidence of MTDs has been observed in 3D seismic surveys in the southern portion of the Orange Basin. However, limited studies have explored the geomorphological expression of MTDs using seismic attributes to delineate their shape, size, and anatomy in this region. The MTDs in the study area exhibit features such as basal shear surfaces (BSS), grooves, ramps, and striations. Four distinct mass transport packages were interpreted, primarily within the extensional regime, in the study area. These MTDs, spanning the Neogene to Coniacian periods, have thicknesses ranging from 300 m to 500 m. The MTDs are generally chaotic with semitransparent reflections. MTD D, being the largest, exhibits a maximum thickness of about 500 m and extends approximately 30 km in width.

Characteristics of the structure and hydrocarbon prospectivity of the deeply buried strata in the eastern Precaspian basin

The article examines the geological structure and oil and gas prospects of the pre-salt complex in the eastern Precaspian Basin (PB). Based on the synthesis and comprehensive analysis of geological exploration (GE) results and the analysis of geological-geochemical criteria for hydrocarbon potential, the oil and gas geological zoning has been updated, and effective directions for GE have been identified. The justification of a new hydrocarbon resources base within the eastern PB margin can be ensured by further investigating of the deeply buried Devonian-Middle Carboniferous horizons in the known petroleum plays, as well as within the less explored Sakmar-Kokpektinsky segment of the Ural fold-and-thrust belt. Within the productive KT-I and KT-II formations, there is an unrealized hydrocarbon potential at depths of 5-6 km. Using the example of the Bozoba West area, the oil and gas prospects of the Visean-Bashkirian and Lower Permian strata are examined, highlighting the significance of faults as elements of the hydrocarbon system. The applied set of 3D seismic survey data and deep drilling allowed for the interpretation of deep seismic sections, up to depths of 7.0-7.5 km. The Middle-Upper Devonian strata are considered prospective but have not been extensively explored by deep drilling. To establish a new hydrocarbon resource base within the eastern Precaspian Basin margin, it is recommended to conduct advanced regional seismic surveys and parametric exploration drilling.

3D Structure of Low‐Angle Normal Faults and Tectono‐Sedimentary Processes of Nascent Continental Core‐Complexes in the SE South China Sea

AbstractThis contribution explores the formation and evolution of hyper‐extended basins, associated with the early stage of core complex formation, controlled by low‐angle normal faults active at <30°. Based on a high‐resolution industrial 3D seismic reflection survey along the southern margin of the South China Sea (SCS) (Dangerous Grounds), we mapped and analyzed the 3D geometry of low‐angle normal fault systems and the related stratigraphy. Two main hyper‐extended basins were documented, filled by up to 6 km of sediments including pre‐ to post‐rift sequences. The observed normal faults on depth migrated seismic sections show an average dip angle of <30° and appear planar, characterized by continuous reflections with no clear steepening at depth and sole‐out on distinct decollement levels. Detailed fault surface mapping reveals the occurrence of km‐scale corrugations together with large wavelength undulation. The formation of these hyper‐extended basins is associated with polyphased syn‐rift infill during the development of the low‐angle normal faults. The first syn‐rift sequence appears as chaotic and discontinuous packages that has been dismembered and fragmented during the activity of low‐angle normal faults. The second syn‐rift package shows unexpected sedimentary wedges developing successively toward the footwall and the hangingwall. This geometry results from the interplay between the main low‐angle normal fault and antithetic faults defining a so‐called extensional fishtail. The deep structure of these basins shows nascent domes with limited evidence of magmatism. Eventually, these basins likely capture the earliest stage of core complex development in the proximal margin of the southern SCS.

Synchrosqueezing voices through deep neural networks for horizon interpretation

Horizon picking is a crucial element in reservoir characterization, but it remains a labor-intensive process. Manually interpreting horizons across thousands of vertical seismic slices in a 3D seismic survey significantly increases the time and labor required for this task. Although several automated methods for extracting the horizons in seismic images have been developed, their effectiveness can be hampered by interruptions in lateral continuity, such as faults and noise. In addition, closely spaced horizons pose a challenge, making it even more difficult to recognize their exact position. To track the horizons through a 3D seismic volume, other seismic attributes extracted from the 3D seismic data must be used. We suggest using spectral voice components together with the original seismic amplitudes to track the surfaces of the target horizons. We generate the time-frequency spectrum using a high-resolution method, namely the synchrosqueezing wavelet transform (SWT), and the real part of the complex SWT spectrum is the voice component. We import the spectral voice component and the seismic amplitude into a neural network. A deep convolutional neural network is used to track the horizon surfaces within a 3D seismic volume. We evaluate this application on a field seismic data set where closely spaced thin layers are located within a complex faulted formation with noisy seismic data with a low signal-to-noise ratio. The integration of the amplitude and phase within the attribute of the voice component indicates that it improves the quality of the generated horizons, especially compared with using the seismic amplitude only for this task. An example from field data demonstrates the ability of our method to accurately delineate the horizons across fault surfaces and in the immediate vicinity of unconformities. This exceeds the current limits of the existing methods for horizon detection.

Time-lapse imaging of shallow water coastal regions using a portable ultra-high-resolution 3D seismic survey system: a case study from offshore Pohang, South Korea

Time-lapse imaging of shallow water coastal regions using a portable ultra-high-resolution 3D seismic survey system: a case study from offshore Pohang, South Korea

The magma plumbing system of the Northern Carnarvon Basin, offshore Australia: multiscale controls on basin-wide magma emplacement, and implications for petroleum exploration

Abstract The Northern Carnarvon Basin (NCB) located on Australia's North West Shelf hosts an extensive (∼40 000 km 2 ) intrusive igneous complex related to Mesozoic rifting and break-up. Using an extensive suite of modern 3D seismic reflection surveys, we have mapped this intrusive system across the NCB. We identify three predominant intrusion morphologies: stacked sheets of large interconnected sill intrusions (up to ∼170 km long) and smaller (8–30 km long) isolated, strata concordant intrusions, which often interact with normal faults emplaced into deltaic sedimentary rocks, and variably sized (10–40 km long) saucer-shaped intrusions emplaced into marine shales, spread across seven zones (geographically constrained groups of intrusions of a specific morphology). We consider the zones’ margin-parallel orientation, suggesting control by subcrustal extensional processes during rifting, and the variation in intrusion morphology between these zones, suggesting a dominant control by host rock mechanical properties. We integrate previous work with our observations, constraining emplacement to between the Kimmeridgian and Valanginian, coinciding with key phases of margin evolution. Finally, we assess the impact of this intrusive complex on local petroleum systems. There is likely little to no adverse impact on source rock maturation or reservoir contamination by CO 2 , but there is a spatial dissociation between the location of groups of intrusions and the gas fields, particularly in the Exmouth Plateau. This suggests that migrating hydrocarbons may be blocked, baffled and/or redirected by emplaced igneous rocks.

Analysis of Reservoir Properties and Quantification of Hydrocarbon Volumes Within LK Field, Niger Delta, Nigeria

This work analyzes and estimates the qualities and volumes of hydrocarbons in the identified reservoirs (Thin Sand and Sand B) of the LK field in the Niger Delta, Nigeria. The LK field is a promising hydrocarbon reservoir located at the border of the Greater Ughelli Depobelt in the Niger Delta Basin. The data utilized encompassed a 3D seismic survey, which was analyzed to delineate faults, identify stratigraphic horizons, and generate maps illustrating the time and depth structures within the subsurface. Well log data, including gamma ray, resistivity, and density/neutron measurements, were analyzed to evaluate and describe the petrophysical characteristics of the subsurface rock formations. The Thin Sand reservoir unit contains natural gas, while the Sand B reservoir is divided into two separate zones: the first zone (Z1) contains natural gas, and the second zone (Z2) contains oil. For Sand B, Z1, and Z2, the gross thicknesses are 13.16m and 57.46m, net thicknesses are 11.32m and 45.39m, NTGs are 0.86 and 0.79, shale volumes (Vsh) are 0.13 and 0.21, effective porosities (?e) are 0.28 and 0.21, water saturations (Sw) are 0.11 and 0.39, and hydrocarbon saturations (Sh) are 0.89 and 0.61, respectively. For the Thin Sand reservoir, the gross thickness is 6.00m, net thickness is 4.74m, NTG is 0.79, Vsh is 0.21, ?e is 0.23, Sw is 0.12, and Sh is 0.88. The stock tank oil initially in place (STOIIP) in the Sand B, Z2 reservoir is estimated to be 46.8 million barrels, with a recoverable oil volume of 9.4 million barrels, assuming a 20% recovery factor. The stock tank gas initially in place (STGIIP) is estimated at 10.4 billion cubic feet (Bcf) in the Thin Sand reservoir and 30.6 Bcf in the Sand B, Z1 reservoir, with recoverable gas volumes projected at 8.3 Bcf and 24.5 Bcf, respectively, assuming 80% recovery factors. After estimating the volume of hydrocarbons in the known reservoirs, significant and economic amounts of gas and oil for commercial purposes were discovered. However, this research study faces challenges such as uncertainty, unreliability, and varying scales due to different origins within the field. Further research using unconventional computational tools together with high-resolution simulating software is needed to produce more detailed and accurate results.

Laboratory study of cyclic underground hydrogen storage in porous media with evidence of a dry near-well zone and evaporation induced salt precipitation

Large-scale storage of ‘green’ hydrogen is essential in our quest to transition to renewable energy sources and achieve the net-zero emission targets. As such, Underground Hydrogen Storage (UHS) in geological porous media, such as in depleted oil and gas fields or saline aquifers, provides a cost-effective solution to store such large volumes of hydrogen (H2) to buffer seasonal fluctuations in renewable energy supply and demand. Due to the novelty of the topic, many research gaps persist, but we focus on H2 transport characteristics in the subsurface, hydrogen recoverability during cyclic operations, chemical interactions, and acoustic velocity as an indicator of H2 saturation. In this study, we investigate UHS using a triaxial core-flooding experiment to address the above-mentioned research gaps by replicating field operations in the laboratory setup at representative subsurface conditions. Unstable displacement due to immiscible two-phase flow led to early H2 breakthrough at 18% of H2 saturation, ultimate H2 saturation of 36% and withdrawal efficiency of 78% during the first cycle. However, cyclic charging and discharging led to an eventual H2 withdrawal efficiency as high as 95%. Observed chemical interactions during our 3-day experiments were negligible, but our results also indicated a strong potential for evaporation-induced salt precipitation after injection of dry H2 gas, leading to decreased reservoir porosity and permeability over time. Our ultrasonic measurements confirmed the sensitivity of P-wave velocity to H2 saturation, which decreased by 3.5% when the H2 saturation increased to 36%. This indicates that H2 plume and leaks in UHS should be possible to monitor using 4D seismic surveys. Our results help to better understand H2 flow, storage, and transport during cyclic UHS. The results indicate that H2 withdrawal efficiency increases as the UHS reservoir matures and provides evidence of a dry near-well zone and evaporation induced salt precipitation in a UHS reservoir.

Post-stack 3D merging to fast-track regional interpretation – offshore Otway Basin case study

Ideally when combining legacy 3D seismic surveys, differences in acquisition parameters warrant full pre-stack reprocessing from field data. However, there are occasions where this is not possible due to time, financial or data access constraints; a valuable alternative is post-stack merging and enhancement of existing migrations. This case was to produce a regularised and seamless 3D dataset of the highest possible quality, for the offshore Otway Basin, within 2 months. The input migrated volumes varied by data extent, migration methodology, angle range and grid orientation. Fourteen input volumes totalling 8092 km2 were post-stack merged and processed to produce a continuous and consistent volume, enabling more efficient and effective interpretation of the region. The surveys were regularised onto a common grid, optimised for structural trends, prior to survey matching. A mis-tie analysis algorithm, applied over a time window optimised for interpretation of key events, was used to derive corrections for timing, phase and amplitude, using a reference. This was followed by time-variant spectral and amplitude matching to improve continuity between volumes. Additional enhancements including noise removal and lateral amplitude scaling were also applied. The final merged volume offers significant uplift over the inputs, providing better imaging of structure and events and dramatically improving the efficiency and quality of interpretation. This enables rapid reconnaissance of the area by explorers.

Insights into the depositional setting for the Gippsland Basin from modern basin-wide 3D datasets

The Gippsland Basin is a prolific hydrocarbon basin, with gas and oil initially discovered in the Barracouta (1965) and Kingfish (1967) fields. Historically the basin was covered with a patchwork of legacy 3D seismic surveys acquired from 1980 to mid-2000s, shot with old technology resulting in sub-optimal imaging of the subsurface. CGG reprocessed 10,190 km2 of legacy 3D data as part of their ReGeneration project in 2018 and in 2020 acquired 8751 km2 of long offset, deep tow and undershot seismic data. With these data sets, Woodside has been able to extract images of the regional depositional systems through the basin’s evolution. These observations range in scale from interpretation of individual channels and channel belts to the distribution of the major shoreface systems and marine fans.

The Rafael gas-condensate discovery – a potential game-changer in the Canning Basin

The Rafael 1 exploration well discovered an abnormally high-pressured gas-condensate pool in the Kimberley region in late 2021. Data supports a minimum gross gas column of 165 m at the well location trapped within a large faulted four-way closure in a dolomite reservoir sequence with strong similarities and age equivalent to the oil-bearing Ungani Dolomite reservoir in the Ungani Field. A successful production test in March 2022 resulted in sustained natural flows of gas and condensate to surface. The presence of thick sandstones of the Anderson Formation and a complete Laurel section beneath the Meda Unconformity were unexpected based on the pre-drill interpretation. Serendipitously, it provided the perfect geological setting for a significant hydrocarbon accumulation and emphasised the need to consider multiple geological scenarios when evaluating prospects to capture the full range of uncertainties and potential pool sizes. Although the range in size of the contingent resources is wide and requires further drilling for refinement, the Rafael 1 discovery could be one of the most significant onshore gas discoveries since Waitsia 1 and provides impetus and incentive for continued exploration in the basin. Several pathways for commercialisation have been identified linked to the resource size. A comprehensive appraisal program is underway including the recently completed acquisition of a 200 km2 3D seismic survey to optimally locate wells, and plans for drilling to reduce uncertainty and support the first phase of development based on a low case contingent resource that could underpin the energy needs of the Kimberley region.

3D Geometry and Slip Distribution in the Long Beach Earthquake Gate, Newport–Inglewood Fault, Los Angeles, California

ABSTRACT We present a new, 3D representation of the Long Beach restraining bend system along the Newport–Inglewood fault (NIF), Los Angeles, California. The NIF is an active strike-slip system that cuts over 60 km through densely populated metropolitan Los Angeles and poses one of the greatest deterministic seismic hazards in the United States (California Division of Mines and Geology, 1988). Part of the NIF sourced the 1933 M 6.4 Long Beach earthquake, which claimed ∼120 lives and remains one of the deadliest events in California history (Barrows, 1974; Hauksson and Gross, 1991). The event is thought to have arrested at Signal Hill within the Long Beach restraining bend, which is formed by a left step in the NIF (Hough and Graves, 2020). Events that rupture through Signal Hill could generate larger (M ≈7) events that pose a significant hazard to urban Los Angeles. Our analysis integrates a diverse range of datasets, including over 4200 fault and horizon penetrations from 243 wells, 2D seismic reflection surveys, field maps, machine-learning-based tomography studies, and the U.S. Geological Survey QFaults surface traces. We show that the fault system in Long Beach has three main strike-slip segments connected by orthogonal reverse faults. The strike-slip faults are nonvertical and nonplanar, merge at depth, and extend through the seismogenic crust. The Long Beach restraining bend system presents numerous rupture pathways and arrest points that NIF earthquakes may follow. We apply a novel, map-based restoration to quantify how much total slip has passed through each of the fault segments. About 375 m of total slip is partitioned into the three main fault strands, including the Reservoir Hill fault (≈75 m), the Northeast Flank fault (≈120 m), and the Cherry Hill fault (≈209 m). This slip partitioning informs our understanding of the tendency of ruptures to involve different fault segments or arrest at specific junctures.

Assimilation of Geophysics-Derived Spatial Data for Model Calibration in Geologic CO2 Sequestration

Summary Uncertainty in geological models usually leads to large uncertainty in the predictions of risk-related system properties and/or risk metrics (e.g., CO2 plumes and CO2/brine leakage rates) at a geologic CO2 storage site. Different types of data (e.g., point measurements from monitoring wells and spatial data from 4D seismic surveys) can be leveraged or assimilated to reduce the risk predictions. In this work, we develop a novel framework for spatial data assimilation and risk forecasting. Under the U.S. Department of Energy’s National Risk Assessment Partnership (NRAP), we have developed a framework using an ensemble-based data assimilation approach for spatial data assimilation and forecasting. In particular, we took CO2 saturation maps interpreted from 4D seismic surveys as inputs for spatial data assimilation. Three seismic surveys at Years 1, 3, and 5 were considered in this study. Accordingly, three saturation maps were generated for data assimilation. The impact from the level of data noise was also investigated in this work. Our results show increased similarity between the updated reservoir models and the “ground-truth” model with the increased number of seismic surveys. Predictive accuracy in CO2 saturation plume increases with the increased number of seismic surveys as well. We also observed that with the increase in the level of data noise from 1% to 10%, the difference between the updated models and the ground truth does not increase significantly. Similar observations were made for the prediction of CO2 plume distribution at the end of the CO2 injection period by increasing the data noise.

Развитие методики 3D-сейсморазведки в арктическом регионе

This article discusses the technological aspects of developing a methodology for detailed seismic surveying using the 3D method in the Russian Arctic. The primary aim is to enhance the economic efficiency of the exploration stage in oil and gas field development. The paper highlights the significance and substantiates the advantages of 3D seismic surveys that make it possible to drill production wells without the need for exploratory drilling. It is established that the principal impediment to technological advancements in seismic surveying within Arctic regions is the restrictive policies of Western nations, which primarily take the form of sanctions. Factors influencing the economic efficiency of seismic surveying include the quality of fieldwork management and workers' professional skills, both of which can catalyze the evolution of seismic survey techniques. The article presents an illustrative case of detailed seismic surveys conducted on the Gyda Peninsula. An innovative seismic survey technique is introduced, and an integrated indicator, which is grounded in criteria reflecting the quality of work, is proposed and employed for an objective assessment of economic efficiency. The proposed methodology has been successfully tested, proving its advantages, and the results obtained are of value for the sector of seismic surveying. It is proposed that the methodology should be used by geophysical companies deploying high-density seismic survey methods to find new hydrocarbon fields in northern territories.

Algorithm for Surface Wave Suppression on 2D Seismic Data Using the Slant Karhunen–Loeve Transform in a Time-Frequency Domain

Abstract —Surface waves are the main source of coherent noise in land seismic survey, and their suppression is one of the main stages of common depth point data processing designed to improve the quality of tracking primary reflections on time sections. In practice, noise reduction is carried out using procedures from modern software based on numerical modeling of waveforms. However, they are too resource-intensive and have a large number of subjectively customizable parameters. The known algorithms have a common drawback: either the energy of reflected waves is distorted in an interference zone with a noise wave or the noise suppression quality is unsatisfactory. The current research is aimed at improving the filtering algorithm in a time-frequency domain using the slant Karhunen–Loeve transform in order to overcome these limitations, to increase the accuracy and rate of its software implementation, and also to test it when processing profile field data from land-based 2D seismic surveys. The algorithm is modified by developing a new method for determining static corrections for surface wave hodograph rectification in a time-frequency domain and by the application of preprocessing in which the reflected wave signal is removed preliminarily. These and other modifications ensure faster calculations and improve the quality of surface wave interference suppression. In addition, the slant Karhunen–Loeve transform is accelerated by parallelizing calculations across logical processor cores. In this paper, the algorithm is described in detail, its significant advantage over the standard methods of bandpass filtering and F–K filtering is shown, and the results of processing the field data obtained by the SWANA procedure (Geovation 2.0) and by the slant Karhunen–Loeve transform. The result obtained by the slant Karhunen–Loeve transform is superior to the SWANA procedure in terms of the surface wave filtering quality and has only four adjustable parameters (SWANA has 20 parameters)