Seismic Stratigraphic Interpretation Research Articles

Seismic Stratigraphic Interpretation Based on Unsupervised Validation and Spectral Clustering Sampling

Seismic Stratigraphic Interpretation Based on Unsupervised Validation and Spectral Clustering Sampling

Travel-time seismic tomography for the seismic stratigraphic interpretation of the crust around the San Rafael knickpoint at Coca River, Ecuador

Travel-time seismic tomography for the seismic stratigraphic interpretation of the crust around the San Rafael knickpoint at Coca River, Ecuador

Synthetic seismic-stratigraphic interpretation from a sedimentological forward model in a pre-salt field in the Santos Basin

Forward modelling of sedimentary systems is a method that simulates sedimentation processes over geological time to generate a set of facies distributed in a depositional space. The objective of using forward modelling in this work was to build a 3D facies model from which a synthetic seismic simulation was generated, and then to analyse the relation of seismic-stratigraphic interpretations with the knowledge of the a priori generated sedimentological model. This modelling methodology was applied in a pre-salt field in the Santos Basin, Brazilian offshore, focused on the Barra Velha Formation. The modelling parameters used were: (i) the initial surface of bathymetric depth; (ii) the lake-level variation; (iii) the subsidence map; and (iv) the deposition rates of the facies. Average-constant of acoustic impedance values were assigned to each facies and a synthetic seismic was obtained. With the facies and synthetic models available, it was possible to analyse: (i) the distribution of thicknesses and proportion of facies by region; (ii) the vertical stacking pattern and lateral facies variation; (iii) the Wheeler distance × time diagram; and (iv) the seismic reflector patterns through the seismic facies classification. Through these analyses it was possible to better understand the possibilities and limitations of seismic stratigraphy as an interpretation auxiliary tool in pre-salt carbonate environments.

100,000 years climatic cycles recorded on very high-resolution seismic data from the Santos Basin’s upper slope during the last 800 ka

This study proposes to combine seismic stratigraphic interpretation of very high-resolution sub-bottom chirp profiles acquired along the Santos Basin slope on the Southern Brazilian Margin during the SANBA project to recently published results from five continuous long cores acquired in the Santos Basin (sampling sediments as old as 772 ka with detailed biostratigraphic and chronostratigraphic data). The seismic-core correlation is consistent over the area and shows that 100,000 years cycles’ terminations (G/IG transitions, identified on long sediment cores) do correlate to strong seismic reflectors identified regionally on chirp profiles.In particular, the last eight 100,000 years cycles (down to MIS19) are well-identified throughout the area. Additional higher-resolution sea-level drops or cooling events (e.g., MIS4, MIS7b, MIS9b) can sometimes be distinguished on the chirp profiles but only in areas with sufficiently high sedimentation rates (around 10 cm/ka). At MIS12, we observe a change in seismic architecture with more numerous, more closely spaced seismic reflectors but with smaller amplitudes. According to the available data, this change also corresponds to a change in sedimentation rates (smaller rates before MIS12), which may be related to the mid-Brunhes Transition (at 430 ka) and/or the imprint of 400 ka Milankovitch cycles. Two cores show a specific Nanno Foram Ooze at this transition towards the following Super-interglacial MIS11. This study demonstrates the ability and the reliability of very high-resolution chirp profiles to record continuously the stacking of G/IG climatic cycles on the slope of the Santos Basin despite relatively low subsidence rates on this old passive margin and small direct input from rivers. Therefore, the study points to the continuous feeding of the margin by sediment brought up laterally by currents, most probably mainly Brazilian Current (BC) that follows the shelfbreak down to the South.

Alluvial development during climate fluctuations depicted with spectral decomposition of the Middle Triassic to Lower Jurassic post‐rift succession in the Horda Platform (Norway) and the impact on reservoir properties

AbstractFor the first time, this study presents interpretations of alluvial fans in spectral decomposition RGB Blends, analysed in seismic time slices from the Middle Triassic to Lower Jurassic stratigraphical interval of the Horda Platform (northern North Sea). The time slices record a shifting alluvial fan front, fluvial variability, uplift and erosion and reveals depositional elements that may set the common conception of the geological development of this area during the Early–Middle Mesozoic up for discussion. Results show that the Upper Triassic Lunde Formation in the eastern margin of the Horda Platform was characterized by the deposition of coalesced alluvial fans. A variable extent of the fan front through the Upper Triassic is linked to interplaying allogenic factors: uplifted source areas in the aftermath of Early–Middle Triassic rifting determined sediment availability; climate transitioning from arid to semi‐humid, with increasingly fluctuating precipitation, controlled sedimentation, and run‐off; provenance dictated bulk sedimentology and affected prevailing alluvial processes. An overall retreat of the fan system through the Late Triassic coincided with a significant change in landscape characteristics at the transition into the overlying Statfjord Group. Uplift and initial tilting of the Horda Platform caused landscape degradation and the formation of plateaus and incised valleys, contemporaneous with increased humidity and marine transgression, forming estuaries. The shift in depositional style has implications for reservoir properties, creating complexity and heterogeneity in terms of facies distribution and connectivity, which may benefit potential CO2 storage. Upper Triassic alluvial fan development in the Horda Platform (northern North Sea) depicted through spectral decomposition of seismic time slices Enhanced level of seismic stratigraphic interpretation with RGB blending Impact of allogenic factors on alluvial depositional development Implications of alluvial variability on reservoir properties

ClinoformNet-1.0: stratigraphic forward modeling and deep learning for seismic clinoform delineation

Abstract. Deep learning has been widely used for various kinds of data-mining tasks but not much for seismic stratigraphic interpretation due to the lack of labeled training datasets. We present a workflow to automatically generate numerous synthetic training datasets and take the seismic clinoform delineation as an example to demonstrate the effectiveness of using the synthetic datasets for training. In this workflow, we first perform stochastic stratigraphic forward modeling to generate numerous stratigraphic models of clinoform layers and corresponding porosity properties by randomly but properly choosing initial topographies, sea level curves, and thermal subsidence curves. We then convert the simulated stratigraphic models into impedance models by using the velocity–porosity relationship. We further simulate synthetic seismic data by convolving reflectivity models (converted from impedance models) with Ricker wavelets (with various peak frequencies) and adding real noise extracted from field seismic data. In this way, we automatically generate a total of 3000 diverse synthetic seismic datasets and the corresponding stratigraphic labels such as relative geologic time models and facies of clinoforms, which are all made publicly available. We use these synthetic datasets to train a modified encoder–decoder deep neural network for clinoform delineation in seismic data. Within the network, we apply a preconditioning process of structure-oriented smoothing to the feature maps of the decoder neural layers, which is helpful to avoid generating holes or outliers in the final output of clinoform delineation. Multiple 2D and 3D synthetic and field examples demonstrate that the network, trained with only synthetic datasets, works well to delineate clinoforms in seismic data with high accuracy and efficiency. Our workflow can be easily extended for other seismic stratigraphic interpretation tasks such as sequence boundary identification, synchronous horizon extraction, and shoreline trajectory identification.

Possible geological interpretation of the volcanic seismic facies based on volcanostratigraphy elements: A case analysis of the Yingcheng Formation in the Changling Fault Depression, Songliao Basin, NE China

Volcanic rocks in faulted depressions are one of the most interested areas for hydrocarbon exploration. In a frontier basin exploration, integrated interpretation of the seismic facies of volcanic rocks is a key success. The key information of boundary system and deposited unit in the volcanostratigraphy did not attract sufficient attention during the process of seismic stratigraphic interpretation of volcanic rocks. In this paper, the volcanic rocks of the Yingcheng Formation in the Changling Fault Depression of the Songliao Basin are taken as an example. According to the maximum average slope, the volcanic seismic facies were divided into three types: mounded seismic facies unit (MSFU), tabular seismic facies unit (TSFU), and mounded-tabular seismic facies unit (M-TSFU). MSFU consists of lava dome and simple lava flows, which has fewer reservoir layers, medium to poor reservoir quality with limited extension. The TSFU comprises more complex component of simple lava flow and base surges, and contains more layers, with good-medium reservoir quality and a large reservoir extension. The M-TSFU has numerous reservoir layers with good reservoir quality and a significant reservoir extension, as well as a higher proportion of braided lava flows and pyroclastic flows. Going from the most favorable reservoir targets to the least favorable, the following units were deposited in the Changling Fault Depression: pyroclastic flow, braided lava flow, base surge, simple lava flow, lava dome, and reworked volcanic clastic flow. The study suggested that mounded-tabular facies units are potential favorable exploration targets in the Songliao Basin. This paper provides a technical route for seismic facies interpretation of volcanic rocks and the analysis of favorable volcanic exploration targets in faulted volcanic basins.

Semi-Supervised Seismic Stratigraphic Interpretation Constrained by Spatial Structure

Seismic stratigraphic interpretation plays an important role in geophysics and geoscience. Recently, deep learning has been widely applied to seismic stratigraphic interpretation. These deep learning-based stratigraphic interpretation methods have shown greater potential than traditional methods. Despite the promising results achieved by deep learning-based methods, it is still necessary to enhance their generalization capabilities and the reasonability of stratigraphic interpretation. Therefore, we propose a semi-supervised deep learning-based method to improve the accuracy and reasonability of interpretation results. First, we quantitatively describe the correlation of adjacent seismic data using the dynamic time warping algorithm. The correlation of all seismic data can be regarded as the spatial structure of seismic data. The interpretation results of seismic data should conform to such spatial structure. Then, we train a deep learning model to interpret seismic stratigraphic units under the constraints of seismic spatial structure. The performance of the proposed seismic stratigraphic interpretation method is evaluated on the Netherlands F3 data. We build two scenarios to interpret the stratum: 1D scenario for the one seismic profile and 2D scenario for the whole seismic volume. The results on the field data demonstrate that the proposed method has better generalization ability and the interpretation results are more reasonable. Therefore, the proposed method can be a useful tool for seismic stratigraphic interpretation.

Seismic Stratigraphic Interpretation Based on Deep Active Learning

Seismic stratigraphic interpretation plays an important role in geophysics and geosciences. Recently, deep learning has been explored for seismic stratigraphic interpretation. However, deep learning-based interpretation methods usually require sufficient labeled samples. This is often too hard to be satisfied in field seismic interpretation. In this paper, we propose a deep active learning-based method to address this issue. Active learning typically exploits prediction uncertainty to reduce labeling effort. We found that uncertainty of prediction is easily obtained in the field of seismic interpretation. Since adjacent seismic images are very similar, they should have similar predictions. When the model performs poorly, the predictions of adjacent images will differ significantly. Thus, the uncertainty can be easily obtained by measuring the similarity of the predictions of adjacent seismic images. Then, data with the highest uncertainty is annotated by geological expert and used for the next round of training. For few-shot active learning, initial models obtained by different initial training sets are quite different. We combine deep clustering and uncertainty sampling to select initial training datasets, with which a good initial model can be obtained. To improve generalization, we introduce a random thin plate spine transformation to simulate changes of terrain. We apply the proposed method to the F3 field seismic data. The results demonstrated that the proposed method can effectively improve performance of learned seismic interpretation network with very limited labeled samples.

High-resolution sequence stratigraphy of complex gas reservoirs: Patao and Dragon fields, offshore Venezuela

The stratigraphic complexity of near-shore depositional systems, together with the occurrence of submarine mass-failure deposits in the area of the Patao and Dragon fields, represents a challenge for devising a development plan for the gas reservoirs identified in the area. The high drilling costs in offshore areas and the sparse knowledge in this frontier basin require an integration of all available data to optimize the development of production projects. This work aims to refine the geological model, particularly with respect to understanding the complexity of the sedimentary deposits in this area and its impact on the exploitation of the associated reservoirs. The Patao and Dragon fields belong to the Carupano Basin, offshore northeastern Venezuela, and contain hydrocarbon accumulations mostly trapped in late Miocene and early Pliocene clastic reservoirs. Existing well data in the area are still relatively scarce, but provide valuable calibration of the available seismic data. This study involves the construction of a sequence stratigraphic framework, based on the integration of sedimentological and petrophysical studies, vertical proportion curves of lithofacies (VPC), seismic-stratigraphic interpretation, petro-acoustic characterization, and reservoir analysis, which enable the identification of stratigraphic units and the correlation between wells. Seven systems tracts have been identified, including the FSST3 (falling-stage systems tract 3) and TST3 (transgressive systems tract 3) which host the most prolific gas reservoirs in the area, comprised of coalescent sands with distinctive rocks properties. There is evidence that the FSST3 is affected by syn-depositional submarine mass movement that distorted the sedimentary architecture and the internal structure of the deposits. These considerations, as well as the identification of potential permeability barriers associated with marine flooding surfaces, allowed the establishment of different scenarios of hydraulic unit configuration, key for the evaluation of these gas reservoirs in terms of their storage capacity and subsequent production.

Intelligent seismic stratigraphic modeling using temporal convolutional network

Deep learning (DL) has stimulated the intelligent processing and interpretation of seismic big data for oil and gas exploration in the past decade. In the applications to seismic stratigraphic modeling, most DL algorithms utilize a combination of ‘convolution + pooling’ to extract spatial features from seismic volume or images, which, however, may lead to a loss of the fine-grained information endowed in seismic time-series records inevitably. Here, we proposed a novel scheme for intelligent seismic stratigraphic interpretation based on temporal convolution network (TCN). The purpose of using TCN is to implement a trace-by-trace segmentation of lithologies by extracting spatio-temporal correlation of seismic record from a small amount of well log labels or manually interpreted geological profiles, thereby building a 3-D subsurface stratigraphic model. The proposed TCN model for seismic stratigraphic interpretation is trained, validated, and tested using the Netherlands F3 seismic dataset. The results suggest that, with a limited number of either manual interpretation profiles or well logs information, the proposed TCN algorithm can produce a highly accurate and laterally continuous 3-D stratigraphic model. Specifically, the mean pixel accuracy of prediction results of the above two schemes (compared to the real model) has achieved 98.23% and 96.09%, respectively. In addition, comparing TCN to the widely used encoder-decoder convolutional neural networks for seismic strata interpretation shows the outperformance of TCN scheme in terms of training time, model size, and prediction accuracy, while also revealing that the proposed TCN model can well identify thin strata in complex seismic data.

Episodic postglacial deltaic pulses in the Gulf of Cadiz: Implications for the development of a transgressive shelf and driving environmental conditions

Abstract The postglacial sea-level rise after the Last Glacial Maximum provided ideal conditions to study the transgressive sedimentary response to sudden shelf flooding driven by different rates of sea-level rise. In this study, a high-resolution seismic stratigraphic interpretation and sedimentological analysis were conducted on data from the northern Gulf of Cadiz continental shelf (SW Iberian Peninsula), in order to: 1) understand the succession of sedimentary processes during each shelf flooding episode and 2) explore the significance of variable rates of sea-level rise, sediment fluxes, and climatic conditions on the development of postglacial deposits. Four backstepping seismic postglacial transgressive units (PTUs; 4 to 1 from oldest to youngest) that are linked to the retreating mouth of the Guadiana River were interpreted. Together, these seismic units display a wedge-shape geometry, are located over the inner to middle shelf, and overlie a regional unconformity formed during the Last Glacial Maximum. Each PTU can be divided into several sub-units with distinctive seismic facies that have a similar stratigraphic organization. Each PTU contains lower sub-units that are composed of low-angle tangential-oblique clinoforms. The clinoforms are locally topped by a channelized sub-unit. The distal and/or lateral parts of the clinoforms are occasionally buried by sheet-like semitransparent subunits. The uppermost sub-units are present over the proximal and central parts of each seismic unit and are also sheet-like. PTUs can also be subdivided and described sedimentologically. Fine-grained sands with intercalated silty layers dominate the lower part of each PTU (lower clinoform sub-units). The upper part of each PTU (upper sheet-like sub-units) is characterized by reworked facies, composed of highly fragmented bioclasts within a mixture of silt and coarse to medium sand. Finally, mud deposits occur as a sediment drape over the PTUs. The internal structure of each PTU reveals several phases of development under a general process of transgressive submergence in which both coastal and marine deposits were formed and eventually preserved. The initial phase involved the development of coarse-grained deltas in shallow water, which were locally eroded by a network of distributary channels. In a transitional phase, the infilling of distributary channels and the offshore export of fine-grained sediments is related to a change in sediment sources, possibly triggered by enhanced hydrodynamic processes. The final phase involved the reworking of fluvio-deltaic sediments by shoreface processes to generate a sediment sheet. Age correlation with a suite of postglacial sea-level curves indicates that the formation of the postglacial transgressive deposits is bracketed between 14 ka and 9 ka. The studied deposits are related to a period of reduced sea-level rise, culminating in the Younger Dryas event (two oldest PTUs), and to phases of enhanced sea-level rise, such as Meltwater Pulse (MWP) 1B (two youngest PTUs). In spite of high rates of sea-level rise over MWP-1B, each PTU exhibits progradation and preservation of much of the delta. The preservation of progradational deltaic units is likely caused by increased sediment supply during progradational pulses. We suggest that those pulses of enhanced sediment fluxes during MWP-1B were strongly driven by the overall climatic conditions in the southwest of the Iberian Peninsula, probably resulting from enhanced rainfall runoff during humid periods and scarce land vegetation cover.

PETROPHYSICAL ANALYSIS AND SEISMIC STRATIGRAPHY INTERPRETATION TO DETERMINE HYDROCARBON RESERVOIR IN TARAKAN BASIN, BUNYU ISLAND WATERS

Tarakan Basin area of Bunyu Island Waters is known to have hydrocarbon potential with complex geological structures. This study aims to determine reservoir characterization and to obtain prospect of hydrocarbon reservoir zones based on petrophysical and seismic stratigraphy analysis with reference to Well DDS-1 and 2D seismic Line S88. Petrophysical analysis results 3 zones that have potential as hydrocarbon reservoirs. Based on petrophysical quantitative analysis, Zone 1 has values of 52.25% for shale volume, 18.48% for effective porosity, 39.84% for water saturation and 13.03 mD for permeability. Zone 2 has values of 54.66% for shale volume, 10.27% for effective porosity, 40.9% for water saturation and 1.14 mD for permeability. Zone 3 has values of 49.22% for shale volume, 9.33% for effective porosity, 56.33% for water saturation and 0.22 mD for permeability. Out of these three reservoir zones in Well DDS- 1, Zone 1 has the prospect of hydrocarbons which is supported by the net pay value. Based on seismic stratigraphy interpretation, the reservoir zone is correlated to the Tabul Formation, which comprises calcareous clay and limestone.

Seismic-stratigraphic interpretation and modeling of offshore synrift and postrift Cretaceous sequences in the Kribi-Campo subbasin, southern Cameroon

Seismic-stratigraphic interpretation and modeling of offshore synrift and postrift Cretaceous sequences in the Kribi-Campo subbasin, southern Cameroon

A 2D Seismic Reflection and Interpretation Study of the Khan Al-Baghdadi area within the Palaeozoic Era (western Iraq)

This research deals with a 2D seismic structural and stratigraphic interpretation of Khan Al-Baghdadi area which is located in the western part of Iraq in Anbar governorate. Two main seismic reflectors are identified within the Silurian and Ordovician; these are the Hot_shale_1 within Akkas Formation and the Top Khabour Formation, which were deposited during the Paleozoic, based on synthetic seismogram of Akk_3 well near the study area. Time, depth, and velocity maps show the presence of two anticline structures trending east-west and located on the west side of the study area. The first is the Tulul structure (here denoted as A) and the second is denoted as B. Also, the maps show the increase in time towards the eastern side of the study area. The general slope of the reflectors is towards the southeast and the increase in the thickness of formations is gradually to the southwest and the northwest sides of the study area. The direct hydrocarbon indicator (DHI) was identified as sand lenses and flat spots on the studied reflectors, when applying seismic attributes like the instantaneous phase and the instantaneous Frequency), which give indicators of potential hydrocarbon accumulations. The primary reservoir in the study area is sandstone within the Khabour Formation, while the source and seal rocks are in the Hot_shale within Akkas Formation. They are interpreted to be present throughout Akkas Field, as gas-condensate accumulations, 100 km to the west of the study area and demonstrate the viability of the Paleozoic petroleum system in the Western Desert of Iraq.

Testing normal fault growth models by seismic stratigraphic architecture: The case of the Pliocene‐Quaternary Fucino Basin (Central Apennines, Italy)

AbstractNormal faults grow either by radial propagation and segment linkage or by accruing displacement without a proportional increase in fault length. To test these competing models of fault growth, a novel 2D seismic stratigraphic interpretation of the recent Fucino Basin of the central Apennines (Italy) has been performed. The Fucino is a major Pliocene‐Quaternary non‐marine ‘extensional collapse basins’, developed immediately after the Apenninic compressional strain had locally abated, and bounded by seismogenic faults that generate strong (Mw = 6–7) and destructive earthquakes. The Fucino is an overall dual polarity half‐graben, built around two border fault systems: the northern one lies along the east‐northeast striking Avezzano‐Bussi regional fault‐zone; the other, south‐eastern trending, bounds the basin to the east. Two separate fault‐driven depocentres of fluvio‐lacustrine sequences (maximum thicknesses of ~1,750 m) are present. One is associated to the northern border faults, with mainly Late Pliocene activity; the second is to the hanging‐wall of the eastern border‐faults and reveals a stepwise Pleistocene‐Recent activity. Tectonic depocentres have migrated clockwise through time, and new‐born fault systems have developed at the south‐eastern basin periphery (Gioia dei Marsi area). This, together with the progressive accumulation of throw in time without significant fault lengthening, suggests that the model of fault growth by segment linkage is not the best explanation for this basin. Instead, the stepwise onset and growth of the Fucino extensional collapse faulting, and its ongoing earthquake hazard, may have been promoted by polyphase inversion tectonics of inherited deep‐seated zones of weaknesses (e.g. Avezzano‐Bussi Line).

Neogene Development of the Terror Rift, Western Ross Sea, Antarctica

AbstractThe Terror Rift is a 350 km‐long, 50–70 km‐wide, north‐trending deep basin in the western Ross Sea, adjacent to the Transantarctic Mountains. The Terror Rift lies within the broader Victoria Land Basin, which experienced 100 km of a mid‐Cenozoic extension. New fault and post‐29 Ma seismic stratigraphic interpretations were developed using all the seismic reflection data available from the Antarctic Seismic Data Library System and were correlated to all the scientific coreholes. A new 3D velocity model was used for depth conversions. Depth‐converted seismic profiles are used to image the faulting along the rift margins. Two segments of steep normal‐separation faults, which are connected by a broad anticline, border the eastern margin, whereas steep to sub vertical faults, combined with a stratal dip, produce the relief present at the western margin. The overall geometry of the Terror Rift shows an asymmetric half‐graben structure with a main bounding fault that dips alternatively eastward and westward in the southern and in the central parts, until it becomes a symmetric graben in the north. Both the eastern and western faults were active since at least 29 Ma in the southern and central Terror Rift and at least since 21 Ma in the north. This fault activity appears to have continued within the whole Terror Rift into post‐Miocene time, as suggested by the significant component of post‐Miocene vertical slip. The measurements of large sedimentary rock thicknesses changes over time between the rift shoulders and the deepest part of the basin and agree with the continuous faulting and relative subsidence in the southern Terror Rift that occurred between 29 and 13 Ma. These changes differ from several published papers that proposed that no significant tectonic activity occurred between 23 and 13 Ma. Despite the growth of the Terror Rift basin, the extension after 21 Ma was only ∼2–4 km across offshore mapped faults in the Terror Rift, and this minor extension agrees with a published plate tectonic study that suggests that the Terror Rift was a transtensional dextral transform boundary between 26 and 11 Ma. Therefore, the Terror Rift may have changed from an orthogonal rift into a transtensional transform boundary after 26 Ma, with the faulting after 11 Ma considered to be intraplate deformation.

Seismic Stratum Segmentation Using an Encoder–Decoder Convolutional Neural Network

As an essential step in reservoir characterization, seismic stratigraphic interpretation is often dependent on the development of powerful computer-based interpretation tools that can simulate the intelligence of experienced interpreters. With the success of machine/deep learning applications in many aspects of geoscience in recent decades, geophysicists have become more dedicated to exploring seismic big data in a smarter and more sophisticated way to better image subsurface reservoirs/structures. In this paper, a specific U-shaped fully convolutional network (U-Net) is established for automatic seismic stratigraphic interpretation. Specifically, this task is formulated as a semantic segmentation problem by identifying strata at the pixel level and classifying each pixel in the image into a specific stratum category. An experiment using the Netherlands F3 seismic dataset suggests that, compared with previously established deep learning models requiring a large number of training sets, the proposed U-Net method can achieve high evaluation indicators and better stratum segmentations in the case of a limited training set. During the test, the proposed U-Net model outperforms the Bayesian neural network (BNN) model for seismic stratum segmentation with regard to the training time, prediction speed, and segmentation accuracy. These results indicate the great potential of using U-Net-based deep learning for intelligent seismic stratigraphic interpretation.

Seismic stratigraphy analysis of main controlling factors of Lower Wuerhe Formation reservoir in Manan area

Fan delta sedimentary reservoirs developed in the Lower Wuerhe Formation of the Manan Slope in the Mahu Sag of the Jungger Basin have good prospects for oil and gas exploration and development. In order to clarify the high-quality reservoir system and the distribution range of the reservoir plane, a seismic stratigraphic interpretation of the Lower Wuerhe Formation is carried out in combination with geology, logging and 3D seismic data. The Lower Wuerhe Formation is divided into three stratigraphic series, a total of 8 four-level sequences, and 8 water body lifting cycles. Through seismic wave group and sedimentary evolution analysis, combined with pseudo-acoustic impedance amplitude and production test analysis, the high-quality oil-bearing reservoirs of the Lower Wuerhe Formation are mainly the third member of the Lower Wuerhe Formation. Oil-bearing reservoirs are mainly controlled by sedimentary facies belts caused by the ups and downs of water bodies. The well-developed oil-bearing reservoirs are developed in the fan delta plain-fan delta front-shore shallow lake sedimentary system.

Quantitative seismic-stratigraphic interpretation of the evaporite sequence in the Santos Basin

On the account of the absence of modern analogues, the interpretation of evaporite-bearing basins relies extensively on seismic and well data. Recent studies describe the intrasalt kinematic, geometries and compositions, relating the change of reflection patterns in seismic data to variations in evaporite sequences. However, these interpretations are only qualitative. This study describes a step further in proceeding from qualitative to quantitative interpretation of an evaporite-dominated interval. It integrates geophysical and geological foundations by combining rock physics, seismic inversion and statistical techniques to deliver seismic-driven facies volume of the evaporite sequence in the Santos Basin, offshore Brazil. Synthetic seismogram demonstrate the ambiguities and uncertainties in relating the seismic amplitude to salt types. Rock-physics analysis indicates that acoustic impedance is an effective differentiator of salt types in comparison to seismic amplitude. Therefore, we perform seismic inversion to transform interface property into layer property. The acoustic impedance volume mitigated significantly the risk of seismic interpretation in the salt sequence. The Bayesian classification integrates acoustic impedance and rock-physics analysis to deliver the seismic-driven facies volume, which categorizes bittern salts, halite and anhydrite. This enables the refinement of the seismic-stratigraphic interpretation of intrasalt sequences of the Ariri Formation based on the sedimentary cycles of evaporites. Additionally, we calculate proportion maps to evaluate the spatial variability of salt deposition. We observe an increase in bittern salts and anhydrite proportions from the bottom to the top of the sequence. The comparison between well-based and seismic-based proportions testifies to the quantitative potential of seismic data. The approach provides quantitative analysis of the evaporite sequence and can be applied to other salt-bearing basins.