3D Seismic Data Research Articles

Bottom simulating reflections across the northern Gulf of Mexico slope

Bottom simulating reflections (BSRs) are widely used indicators for natural gas hydrate in reflection seismic data. BSRs, however, are typically studied on a local scale at a single site and less frequently on a large, regional scale. Herein, we map and describe BSRs over a 68,000 km2 area across the northern Gulf of Mexico slope, using publicly released industry-acquired 3D seismic data. We map 74 BSR zones that cover a total area of 2060 km2. To understand the characteristics of these BSR zones, we classify them based on their BSR characteristics in the seismic data (continuous, discontinuous, and clustered) and the geological settings in which they appear (structural, stratigraphic, and venting). The most common type of BSRs are discontinuous BSRs; such BSRs were mapped over ∼60% of the total BSR area. Discontinuous BSRs occur most commonly in structural or stratigraphic settings. Discontinuous BSRs indicate that gas and hydrate are likely concentrated in discrete layers crossing the base of the hydrate stability zone (HSZ). Continuous BSRs occur in 27% of the total BSR area and they primarily occur in venting and stratigraphic settings. At vent sites, hydrate formation likely reduces sediment permeability and focuses fluid flow laterally underneath the base of the HSZ, likely resulting in a continuous BSR along the area of lateral gas flow. Clustered BSRs, chaotic sequences of high amplitude reflections, occur in only 13% of the total BSR area and are only found within structural settings. In addition, the majority of clustered BSR zones are close to paleochannels, suggesting that clustered BSRs may be more common where coarser-grained sediments exist.

3D seismic analysis of complex faulting patterns and fluid escape features and their relation to Late Cenozoic Magmatism in the Bass Basin, offshore SE Australia

Abstract Igneous intrusions in sedimentary petroleum basins are often perceived as having a negative impact on the elements of the petroleum system, though the impact of intrusion-related deformation features on petroleum systems and broader geoenergy applications is not well understood. In this study, we use 3D seismic reflection data to document a variety of deformation styles that are spatially and temporally associated late Cenozoic magmatic activity in the Bass Basin, offshore southeastern Australia; three types of normal fault systems (conjugate faults, concentric faults, radial faults) and fluid escape pipes. These deformation features occur in the overburden up to ∼600 m above underlying igneous intrusions, within the Eocene to Miocene Demons Bluff and Torquay formations. The conjugate faults bound graben and are interpreted to have formed in response to underlying dyke intrusions. The radial faults are interpreted to have formed in response to overburden uplift, though the link between these and associated igneous activity is less clear. We identify 101 fluid escape features that show variation in both the morphology of their surficial depressions and of the seismic reflection characteristics of their infilling deposits. These features are interpreted to be hydrothermal or volcanic vents with underlying pipe-like feeders, depending on their spatial association with adjacent or underlying igneous intrusions. The concentric fault systems are associated with surficial depressions, and quantitative analysis of reflection sags within these depressions suggest that they are a result of subsurface subsidence in response to formation of maar-craters. The intrusion-related deformation features documented in this study may have multiple effects on working petroleum systems, such as providing secondary fluid flow pathways that can either reduce seal integrity, or enabling migration of fluids into shallower reservoirs.

Projection of 4D seismic onto the ensemble observation subspace for data assimilation

Time-lapse (4D) seismic data offer valuable insights into fluid movements and pressure changes within reservoirs, thus aiding the updating of numerical models used in hydrocarbon recovery and geological CO2 storage. However, it is essential to characterize both the uncertainties in the data and the limitations in the forward model to effectively utilize this information. In the context of ensemble-based data assimilation methods, this objective is accomplished through the utilization of the data-error covariance matrix, denoted as Ce. The selection of an appropriate Ce is of paramount importance, as it determines the level of accuracy required to match the data and influences the relative weight assigned to various data sources and prior information during the computation of model updates.Despite significant efforts, the practical estimation of Ce, accounting for both data and model errors, remains a challenging task. This paper presents a novel methodology for estimating Ce within an ensemble-based 4D seismic data assimilation framework. The approach involves projecting observed seismic data onto the subspace defined by predicted data from the prior ensemble and estimating Ce based on the residuals—the difference between observed and projected 4D seismic data. The proposed methodology is tested through application with actual data from three real-world reservoir cases.

Empirical Green’s function analysis of some induced earthquake pairs from the Groningen gas field

We have applied the empirical Green’s function (EGF) method to 53 pairs of earthquakes, with magnitudes ranging from M = 0.4 to M = 3.4, induced by gas production from the Groningen field in the Netherlands. For a subset of the events processed, we find that the relative source time functions obtained by the EGF deconvolution show clear indications of a horizontal component of rupture propagation. The earthquake monitoring network used has dense azimuthal coverage for nearly all events such that wavelet duration times can be picked as a function of source-station azimuth and inverted using the usual Doppler broadening model to estimate rupture propagation strike, distance, and velocity. Average slip velocities have also been estimated and found to be in agreement with typical published values. We have used synthetic data, from both a simple convolutional model of the seismogram and more sophisticated finite difference rupture simulations, to validate our data processing workflow and develop kinematic models which can explain the observed characteristics of the field data. Using a measure based on the L1-norm to discriminate results of differing quality, we find that the highest quality results show very good alignment of the rupture propagation with directions of the detailed fault map, obtained from the full-field 3D seismic data. The dip direction rupture extents were estimated from the horizontal rupture propagation distances and catalogue magnitudes showing that, for all but the largest magnitude event (the M = 3.4 event of 8th January 2018), the dip-direction extent is sufficiently small to be contained wholly within the reservoir.

Time and mechanism of formation of mud volcanoes in the South Caspian basin according to seismic data

There are 277 mud volcanoes located in the South Caspian basin and the Apsheron-Gobustan periclinal trough and the Lower Kura depression that open to it. On land there are 177 mud volcanic structures, from which steam, water, mud, gas and oil are constantly erupting at approximately 500 points. Mud volcanoes located in the Caspian Sea (about 100) also play an important role in the degassing (mainly methane) of the sedimentary layer of the earth’s crust. Based on the results of geological and geophysical research, it has been established that almost all mud volcanoes discovered on the territory of Azerbaijan are associated with hydrocarbon deposits. In the Oligocene – Lower Miocene, mainly in the Maikop time, a thick clayey stratum (Maikop) - source rocks – accumulated in the South Caspian depression. At the end of the Miocene, there was a sharp drop in erosion levels in this basin. As a result of the activity of several river systems (Pleo-Volga, Paleo-Kura, Paleo-Pirsagat, Paleo-Amu Darya) over the Maikop clay deposits, a system of alternating layers of low and high density was formed with a total thickness of sediments of eight kilometers or more. The Maikop clay formations buried under this multilayer system, possessing the properties of a non-Newtonian fluid, created intrusions in the overlying environment, which at subsequent stages of development of the sedimentation basin became eruptive channels of mud volcanoes. The results of research using 3D seismic data made it possible to identify the mechanism of formation of mud volcanism, which, according to the authors, is associated with the migration of hydrocarbons from oil and gas source rocks to reservoir rocks, with the channels of mud volcanoes being considered as the main migration routes. Geological interpretation of seismic data shows that the formation of mud volcanoes in the South Caspian basin supposedly began from the beginning of the Miocene and continued in parallel during subsequent periods of development of the sedimentation basin. As the thickness of the sedimentary cover increased, mud volcanoes periodically became active.

Use of resistivity and density borehole image logs to identify and distribute facies in the Pikka unit — A case study from the Nanushuk Formation, North Slope, Alaska

Over the past few decades, the North Slope of Alaska has yielded several major hydrocarbon discoveries in the deltaic topsets of the Brookian Nanushuk Formation. Together, the Nanushuk topsets and genetically related foreset and bottomset beds of the Torok Formation comprise part of a giant clinothem system that prograded across the Colville Foreland Basin during the lower Cretaceous (the Aptian through the Cenomanian). The Nanushuk Topset Play contains stratigraphically trapped hydrocarbons within multiple fairways trending roughly north to south along the basin’s extent. Inside the Pikka Unit, the Nanushuk Formation represents a shelf-edge delta and attached shoreface system, defined primarily from sedimentological interpretations of conventional cores integrated with 3D seismic reflection data and well-log motifs. In this study, we build a structural and stratigraphic framework for the Nanushuk reservoir across the Pikka Unit through integrated observations of the borehole image logs, seismic data, and core. In the described workflow, the boundaries delimiting dip zones interpreted in the wells are correlated to higher order stratigraphic cycles within the Nanushuk clinothem zone. These boundaries are observed in seismic profiles and provide the basis of the structural framework. In addition, core facies interpretations are calibrated to CT-scan data to establish each facies character and vertical distribution within the wells. In the absence of core data, core-calibrated borehole images are instrumental in guiding sedimentological and structural interpretations. This extrapolation is dependent on the image log quality and resolution. The calibrated facies interpretations are applied to wells without core data and guided by seismic amplitude interpretation to extrapolate reservoir presence and distribution across the area.

Paleogene to Neogene sequence stratigraphy and deepwater depositional systems in Kribi-Campo/Rio-Muni margin (Offshore Cameroon-Equatorial Guinea Margin)

2D seismic data and Gamma Ray logs were interpreted to document the Tertiary deepwater depositional system observed in the southern part of the Kribi-Campo sub-basin and the northern part of the Rio Muni basin, both basins separated by the Campo high. The sedimentary filling of both basins occurred with cyclicity during the Tertiary. The Paleogene filling exhibits at least three Seismic Unit Packages (SUP1 to SUP3) interpreted as some Feeder Channels-Lobe Complexes (FCLC). The units with Mass Transport Complexes (MTCs) are low amplitude and chaotic to transparent seismic facies. They are interpreted as mud-rich complexes. The units related to FCLC, features high to moderate amplitude with shingled oblique progradational clinoforms. The Neogene filling is dominated by some submarine Leveed-Channels Complexes associated to Lobes (LCCL) with low to moderate amplitude and concave-up mounded configuration. The well log analysis revealed three main electrofacies namely, shale, siltstone, and sandstone that were deposited in various depositional environments. Shale lithology are underlined by irregular, bell and bow gamma ray log motifs which may be deposited in inner shelf, tidal channels and channel-levees systems that are associated with transgressive to regressive depositional sequences. Sandstone and siltstone lithology are typified by funnel and cylindrical gamma ray log motifs that are deposited in prograding marine shelf fans and slope channels. Influenced by the high slope of paleotopography around the Campo High, the submarine channel-levee are confined to a western part of Kribi-Campo sub-basin. The FCLC shows large planar distribution, while the MTC are poorly structured.

An artificial intelligence workflow for horizon volume generation from 3D seismic data

Horizon-based subsurface stratigraphic model building is a tedious process, especially in geologically complex areas where seismic data are contaminated with noise and thus are of weak and discontinuous reflectors. Seismic interpreters usually use stratal (proportional) slices to approximately inspect 3D seismic data along seismic reflectors yet to be interpreted. We introduce an artificial intelligence workflow consisting of three deep learning steps to provide a conditioned seismic image that is easier to interpret, a stratigraphic model that outlines major formations, and moreover a relative geologic time volume that allows us to automatically extract an infinite number of horizons along any seismic reflectors within a seismic cube. Depending on the availability of interpreters, the proposed workflow can either run fully unsupervised without human inputs or using sparse horizon interpretation as constraints to further improve the quality of extracted horizons, providing flexibility in both efficiency and quality. Starting from only seismic images and a few key horizons interpreted on very sparse seismic lines, we demonstrate the workflow to generate a stack of complete horizons covering the entire seismic volume from offshore Australia.

Discovery and petroleum geological significance of delta in the third member of Oligocene Lingshui Formation in southern Baodao Sag, Qiongdongnan Basin, South China Sea

Based on the 3D seismic data and the analysis and test data of lithology, electricity, thin sections and chronology obtained from drilling of the Qiongdongnan Basin, the characteristics and the quantitative analysis of the source-sink system are studied of the third member of the Upper Oligocene Lingshui Formation (Ling 3 Member) in the southern fault step zone of the Baodao Sag. First, the YL10 denudation area of the Ling 3 Member mainly developed two fluvial systems in the east and west, resulting in the formation of two dominant sand transport channels and two delta lobes in southern Baodao Sag, which are generally large in the west and small in the east. The evolution of the delta has experienced four stages: initiation, prosperity, intermittence and rejuvenation. Second, the source-sink coupled quantitative calculation is performed depending on the parameters of the delta sand bodies, including development phases, distribution area, flattening thickness, area of different parent rocks, and sand-forming coefficient, showing that the study area has the material basis for the formation of large-scale reservoir. Third, the drilling reveals that the delta of the Ling 3 Member is dominated by fine sandstone, with total sandstone thickness of 109–138 m, maximum single-layer sandstone thickness of 15.5–30.0 m, and sand-to-strata ratio of 43.7%–73.0%, but the physical properties are different among the fault steps. Fourth, the large delta development model of the small source area in the step fault zone with multi-stage uplift is established. It suggests that the episodic uplift provides sufficient sediments, the fluvial system and watershed area control the scale of the sand body, the multi-step active fault steps dominate the sand body transport channel, and local fault troughs decide the lateral propulsion direction of the sand body. The delta of the Ling 3 Member is coupled with fault blocks to form diverse traps, which are critical exploration targets in southern Baodao Sag.

Isopach Map of Mishrif Formation in Nasiriya Oil Field by Using 3D Seismic Data

The current study included interpretations of the three-dimensional seismic Data for the Nasiriya oil field implemented by the Oil exploration company in 2010 with a planned surface coverage area of 1273 km². The Nasiriyah field is located in southern Iraq within the Dhi Qar Governorate, about (10) km northwest of the governorate center (Nasiriyah), and the Muthanna governorate is located in the northwestern part of the field, which is approximately (15) km west of the governorate center (Samawah). The information from the wells (well velocity survey, formation depths, logs) was relied upon and entered into the seismic cube data to capture the top of the Mishrif Formation. In addition is to pick the top of the Rumaila Formation, which represents the bottom of the Mishrif Formation. The top and bottom Mishrif reflectors were picked, interpreted, and tracked within the region. The reflector's two-way time (TWT), velocity, and depth maps showed structural closure features in the center of the area, and the general direction of the closure is thenorthwest–southeast. The structural maps showed a general tendency towards the northeast. The isopach map showed that the thickness values of the Mishrif Formation increased to the west and northwest while the thickness decreased toward the east and southeast.

Application of Generalized Reciprocal Method on 2D Seismic Refraction Data in Mt. Manglayang, West Java

The imaging of shallow subsurface structures, weathered rock thickness and velocity propagation distribution of the rocks can be identified by seismic refraction. This method is one of the geophysical exploration methods utilizing refracted wave once it reaches the boundary of subsurface layer. In this research we used the generalized reciprocal method (GRM) as one of the robust processing methods in analyzing subsurface data. This method was chosen due to its accuracy in interpreting shallow subsurface layer with highly undulating refractors by determining time velocity analysis, XY optimum distances, and time depth analysis, then, the expected depth values can be achieved. The acquisition of data for this research was conducted using 13 geophones with forward and reverse sources, the data were then picked to get travel time values and inverted to obtain real geological setting of the earth. The results were interpreted as 2 layers, the first layer had a velocity distribution of 499.289 m/s which was identified as a weathered layer with a thickness of about 4.74 meters, whereas the second layer was interpreted as clay rock with velocity distribution of 1270.433 m/s with the thickness reached up to 16 meters.
 Keywords: generalized reciprocal method, 2D seismic refraction

Unveiling the transtensional geodynamics of Cenozoic depocenter changes in the Andaman sea: Seismic evidence for the existence of the East Sagaing Fault and the Andaman Basin Central Fault Zone in the Tanintharyi region

The Andaman Sea, situated at the highly oblique convergent boundary of the Indian and the Sunda Plates in the eastern Indian Ocean, has been shaped by transtensional geodynamics throughout the Cenozoic and has given rise to the formation of fault systems in the Andaman back-arc region. Out of these faults, the Sagaing Fault system exists as the active transform boundary between the Burmese and Eurasian Plates. The East Sagaing Fault, which runs through the Gulf of Martaban in the Andaman Sea, is a critical component of this Sagaing Fault system in fostering the transtensional regime and contributing to the opening of the Andaman Sea as a pull-apart basin. In contrast, the Andaman Basin Central Fault Zone, previously misinterpreted as the South Sagaing Fault, is an inactive fault system that experienced deformation until the Middle Miocene and is currently concealed beneath the East Andaman Basin. This temporal disparity in the Andaman Basin Central Fault Zone and East Sagaing Fault activity patterns has led to uncertainty regarding their existence within the Tanintharyi region of the Andaman Sea. To address this uncertainty, 2D and 3D seismic data interpretations were used to explore the distribution of faults, including the presence and extent of these two faults in the Tanintharyi region. Through a comparative analysis of the structural characteristics of the East Sagaing Fault in the northern part, and the Andaman Basin Central Fault Zone in the southern part of the Andaman Sea, this study presents compelling evidence confirming the existence of both faults in the Tanintharyi region with their structural implications. The innovative discoveries in this article contribute to a deeper understanding of Cenozoic depocenter changes in the Tanintharyi region, substantiating the significance of these two faults in transtensional geodynamics and allowing for a comprehensive examination of geodynamic evolution in the Andaman Sea region.

Influence of sedimentary processes and fault tectonics on the evolution of submarine canyons in the East Andaman Basin: Insights from high-resolution seismic data analysis

The Andaman Sea Basin, a well-known back-arc spreading centre and a mature petroliferous basin, presents a unique and complex scenario for understanding the interplay of sedimentary processes and fault tectonics on seafloor geomorphology evolution, particularly in the eastern shelf region. This study, using high-resolution 3D seismic data and published exploratory well-seismic interpretation results, aims to establish a comprehensive stratigraphic framework for the Tanintharyi region, spanning the Lower Miocene, Middle Miocene, Upper Miocene, Pliocene, and Quaternary. A submarine canyon system was identified and investigated along the Tanintharyi continental slope within the East Andaman Basin, comprising thirteen slope-confined canyons arranged predominantly in an east-west vertical slope orientation. By analysing seismic reflection features, five distinct seismic facies have been identified, including basal lag (BL), slump and debris-flow deposits (SDFDs), canyon confined sheets (CCSs), laterally inclined packages (LIPs), and channel-levees (CLs). The evolution of this canyon system, a vital focus of this study, can be categorised into three phases based on the morphology and sedimentary structures observed: canyon initiation, canyon extension, and erosion-sedimentation. The findings of this study highlight the critical controlling role of faults in canyon evolution, with the intensity of fault activity displaying a negative correlation with canyon size, indicating the direct impact of faults on geomorphological changes. In addition, the geomorphological changes induced by fault activity have resulted in changes in sediment supply, dispersal, and sedimentation rates, thus significantly impacting the spatial distribution and dimensions of slope-confined canyons within the East Andaman Basin, with far-reaching implications.

Fracture analysis in borehole images from BM-C-33 area, outer Campos Basin, Brazil

In the BM-C-33 area, divided into the Raia Manta and Raia Pintada development areas, reservoirs are arranged into three structural highs: Gávea, Seat, and Pão de Açúcar. These reservoirs consist of pre-salt limestones deposited on volcanic sequences and underwent complex diagenetic evolution. Successive post-depositional processes, including silicification, affected original mineral assemblage, modified pore textures, and caused intense fracturing. Based on borehole image logs (BHI), wireline data from four wells, and 2D and 3D seismic data, this study details natural fracture acoustic and resistivity properties. It also discusses the relationship of faults, fractures, and vugs with diagenetic and tectonic processes. The authors used the data to divide the pre-salt section (Cabiúnas and Macabu formations) into three informal stratigraphic units. The analysis of interpreted fractures within these units suggests that major fracturing occurred due to regional tectonic stress, with local aspects like structural positioning interfering. The results of the fracture analysis imply a direct relationship between fracturing and silicification. Additionally, fracture density, vug volume distribution, and the presence of dissolution features like enlarged fractures limited to specific units imply stratigraphic control on fluid percolation. Finally, the study examines structural particularities in BM-C-33 area that potentially impacted intensity and extension of diagenetic alterations.

Interaction between magmatism and polygonal faults revealed by three-dimensional seismic data in the Zhongjiannan Basin, South China Sea

The features of magmatism and polygonal faults are unveiled through a comprehensive analysis of high-resolution and reprocessed three-dimensional (3D) seismic data covering 1200 km2 in the Zhongjiannan Basin, South China Sea. These structures influence the hydrocarbons formation and migration, and the interaction between them is significant for hydrocarbon exploration. We identified magmatic bodies, including eight volcanoes, fifty sills, and a single igneous diapir, are mainly developed in three stages: 27.9–23 Ma (between T70 and T60), around 11.6 Ma (T40), and after 5.3 Ma (T30). The polygonal faults, characterized by linear, polygonal, and radial configurations, are extensively distributed within Miocene and Quaternary sediments. In the platform, polygonal faults manifest linear or polygonal attributes, while in the basin floor, they show a polygonal shape. Particularly, above volcanoes and the igneous diapir, the polygonal faults exhibit radial configurations. However, among volcanoes, few polygonal faults are discerned based on the coherence attribute slice. The controlling factors influencing the distribution of polygonal faults are the lithological disparity, temperature, and pressure. Radial fault formation is promoted by volcanoes and igneous diapir through differential compaction. The resultant vertical pathways formed by volcanoes and overlying radial faults play a crucial role in adjusting pressure differentials or water discharges. Consequently, these pathways disrupt the requisite conditions for the formation of polygonal faults among volcanoes. In the basin floor, magma intrusion occurs along the planes of polygonal faults, giving rise to inclined, spoon-shaped, and bowl-shaped sills. As weak zones, polygonal faults worked as connectors for sills at different depths. Hence, pre-existing polygonal faults are considered pathways facilitating magma migration from the lower Miocene to Pliocene strata, ultimately contributing to sill formation in shallow sediments. This study advances our understanding of the intricate interaction between polygonal faults and magmatism within sedimentary basins.

Structural and seismic attribute analysis of the Paleocene carbonate reservoir from the Balkassar Field, Potwar Plateau, Pakistan

The structural and seismic properties of the Paleocene carbonate reservoir are re-evaluated, using 3D seismic data multi-attributes, to improve reservoir prediction accuracy rarely documented earlier. This study highlights a number of relevant post-stack seismic attributes for understanding the structural setup and seismic properties of a carbonate reservoir. The structural analysis was carried out using seismic interpretation, combined with multi-attribute analysis for prospect actualization and generation of a 3D structural model to determine the structural aspect. The structural interpretation reveals the presence of faults and an asymmetrical anticlinal structure demonstrating a four-way closure, confirming compressional tectonics. The high amplitude anomaly (-6 to 12) combined with the RMS attribute (23 to 32) suggests bright spots in the Paleocene carbonate reservoir and gas saturated zone, the variance attribute (0.05 to 0.03) highlights the presence of two major faults, and the lower instantaneous frequency demonstrates the presence of hydrocarbons. The attribute results indicate that the Lockhart Limestone possesses good reservoir potential as revealed by DHI (bright spot), gas saturated zone and a trapping mechanism supported by four-way structure closure in the region and can help to understand analogous carbonate reservoirs in similar geological settings around the world.

Deep-ocean channel-wall collapse order of magnitude larger than any other documented

Submarine channels are the largest conveyors of sediment on Earth, yet little is known about their stability in the deep-ocean. Here, 3D seismic data from the deep-ocean Hikurangi channel-levee system, offshore New Zealand, reveal the largest channel-wall failure yet documented. Collapse of both channel-walls along a 68 km stretch created a mass-transport deposit of 19 km3, containing 4 km long blocks. Channel-walls typically collapse piecemeal, but here synchronous failure of both channel-walls and landslide erosion of the seafloor is documented, requiring a new process model for channel-wall failure. Mass-failure on this scale poses an under-appreciated risk to seafloor infrastructure both within channels and over regions extending twice the channel width into their overbank. Hitherto, channel-wall failures of this size are unrecognised in abyssal plains; its scale changes our understanding of how channel-levee systems are constructed and how they conduct sediment, carbon and pollutants into the deep-ocean.

The complex interaction between channel–levee systems and mass transport complexes in the Pliocene–Quaternary Rakhine Basin, offshore Myanmar

Channel–levee systems (CLSs) and mass transport complexes (MTCs) are prevalent in deep-water basins, yet their interplay remains enigmatic. This study uses high-resolution 3D seismic data to investigate the architecture of CLSs and MTCs, aiming to explore how CLSs influence the distribution of MTCs in the Rakhine Basin, Bay of Bengal. Two models are built to illustrate the interaction between CLSs and MTCs. In the first model, large-scale aggradational CLSs created unfilled relief in their overbank environments, which acted as spatially confined topography for subsequent mass-wasting deposits. In this model, the interaction between large-scale CLSs and confined MTCs controls the distribution of confined MTCs. In the second model, laterally migrating CLSs do not create such prominent topographic relief in their overbank environments. This characteristic renders them inconsequential in influencing the distribution of subsequent mass-wasting processes. Consequently, spatially extensive MTCs develop within unconfined settings. This configuration gives rise to lithological traps, which might be common and represent potential drilling targets on continental margins. This study could contribute to a better understanding of the interplay between CLSs and MTCs and have some enlightenment on looking to provide some insight into the search for lithological traps in the Rakhine Basin.

Gas hydrate in the North Carnarvon Basin, offshore Western Australia

Analysis of hydrate systems across basins is not common, as most studies are focused on smaller sites. Using petroleum industry well and seismic data, we identify natural gas hydrate accumulations across the entire North Carnarvon Basin, offshore Western Australia. Out of 120 wells, 52 wells have evidence for gas hydrate, though hydrate is distributed throughout the hydrate stability zone in low concentrations. In addition, we do not observe a connection between the presence of hydrate in wells and deeper thermogenic gas reservoirs. From 3D seismic data, we observe bottom simulating reflections (BSRs) are very rare. In addition, while faults are common across the basin, shallow bright spots, which indicate shallow free gas, are uncommon. Based on all these observations from well and seismic data, we argue that hydrate across the North Carnarvon Basin formed predominantly from in-situ gas that is microbial in nature.

Prediction and effectiveness study of fracture distribution based on an artificial neural network technology and production performance data detection method: a case study of Ordovician carbonate formation in the Tahe oilfield, Tarim Basin

To solve the difficulty of predicting the spatial distribution of fracture linear density and clarify the controlling influence of tectonic factors on the effectiveness of fractures. This article combines core, conventional logging, imaging logging, and 3D seismic volume data and uses artificial intelligence neural network technology combined with the sequential Gaussian method to establish a linear density volume prediction model for fractures in the study area. In addition, production dynamic data are applied to verify the effectiveness of the fractures. The results show that the artificial intelligence neural network technique is highly applicable with an accuracy of up to 76.8% in predicting the fracture linear density. The fracture linear density is controlled by tectonic activity, and the fracture linear density increases sharply in the areas adjacent to the main faults, the fracture superposition site, and the intersection site of multiple faults, with the fracture linear density reaching 8.65 fractures per meter in study areas. The effective distance of fracture connectivity is mostly concentrated between 550 and 670 m. When the difference in fracture density along the structural ridge is between 2 and 4 fractures/meter, the effectiveness of the fractures is strong.