PreviousNext No AccessInterpretationJust-Accepted ArticlesIntroduction to special section: Recent advances in reservoir characterizationAuthors: Runhai FengDongfang QuSatinder ChopraSixue WuAndrey KlimushinKlaus MosegaardChingWen ChenKenneth BredesenRunhai FengAramco Asia, China. E-mail: [email protected]., Dongfang QuRamboll, Denmark. E-mail: [email protected]., Satinder ChopraSamiGeo, Canada. E-mail: [email protected]., Sixue WuBP, UK. E-mail: [email protected]., Andrey KlimushinRFD, USA. E-mail: [email protected]., Klaus MosegaardUniversity of Copenhagen, Denmark. E-mail: [email protected]., ChingWen ChenGeophysical Insights, USA. E-mail: [email protected]., and Kenneth BredesenGEUS, Denmark. E-mail: [email protected].https://doi.org/10.1190/int-2024-0603-spseintro.1 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InReddit FiguresReferencesRelatedDetails Just-Accepted ArticlesPages: 1-47ISSN (print):2324-8858 ISSN (online):2324-8866 publication data© 2024 Society of Exploration Geophysicists and American Association of Petroleum GeologistsPublisher:Society of Exploration GeophysicistsAmerican Association of Petroleum Geologists HistoryPublished Online: 04 Jun 2024 CITATION INFORMATION Runhai Feng, Dongfang Qu, Satinder Chopra, Sixue Wu, Andrey Klimushin, Klaus Mosegaard, ChingWen Chen, and Kenneth Bredesen, (), "Introduction to special section: Recent advances in reservoir characterization," Interpretation 0: 1-2. https://doi.org/10.1190/int-2024-0603-spseintro.1 Plain-Language Summary PDF Download Metrics Loading ...

Numerous studies have demonstrated the capability of supervised deep learning techniques for predicting geological features of interest from seismic sections, including features that are difficult to identify using tradi-tional interpretation methods. However, the successful application of these techniques in practice has been limited by the difficulty of obtaining a large training data set where the seismic data and corresponding ground truth labels are well-defined. Manually creating large amounts of labels requires a heavy workload, and the uncertainty of the interpretation and labeling process decreases the model's ability for making accurate pre-dictions. Using the chalk-flint sequence scenario onshore Denmark as an example, we have developed a novel workflow for predicting subresolution thin layers from seismic sections. It entails generating large quantities of synthetic training data with high-quality labels using stochastic geological modeling, training a convolutional neural network based on the synthetic data set, and applying it to real seismic data. This is, to our knowledge, the first example of using deep learning to predict subresolution thin layers from seismic data based on geo-statistically generated training images. It is shown that a neural network trained on synthetic data can predict a realistic number of subresolution flint layers from the real seismic data that have been collected from the Stevns region in Denmark, which has value for the understanding of the overall geological characteristics of succession and engineering applications such as construction site evaluation.

Interference and inherent resolution limitations are well-recognized problems in reflection seismic data and have over time led to misinterpretations. Acquisition of seismic data containing a broad range of frequencies, including high frequencies, does not solve this problem but merely moves the problem to a finer scale. Forward seismic modeling of known geological scenarios is a valuable tool for studying anticipated seismic responses of successions with a given set of geological and/or rock physical characteristics and for predicting interpretational challenges. The objective of this paper is to demonstrate that interbedded strata with contrasting physical properties and variable thickness can result in interference effects resembling faults and fractures. We conduct finite-difference-based seismic forward modeling on a conceptual geological model derived from outcropping chalk sections in SE Denmark, and present possible pitfalls that may hamper interpretation of seismic data acquired from strata with similar characteristics. The result has significance for characterization of e.g., geothermal sites, potential CO2 storage targets, groundwater reservoirs and hydrocarbon exploration sites, in which proper imaging of faults and fractures from seismic is an essential task.

Outcrops are valuable for analogous subsurface reservoirs in supplying knowledge of fine-scale spatial heterogeneity pattern and stratification types, which are difficult to obtain from subsurface reservoir cores, well logs or seismic data. For petrophysical properties in a domain where the variations are relatively continuous and not dominated by abrupt contrasts, the spatial heterogeneity pattern can be characterized by a semivariogram model. The outcrop information therefore has the potential to constrain the semivariogram for subsurface reservoir modelling, even though it represents different locations and depths, and the petrophysical properties may differ in magnitude or variance. However, the use of outcrop-derived spatial correlation information for petrophysical property modelling in practice has been challenged by the scale difference between the small support volume of the property measurements from outcrops and the typically much larger grid cells used in reservoir models. With an example of modelling the porosity of an outcrop chalk unit in eastern Denmark, this paper illustrates how the fine-scale spatial correlation information obtained from the sampling of outcrops can be transferred to coarser-scale models of analogue rocks. The workflow can be applied to subsurface reservoirs and ultimately improves the representation of geological patterns in reservoir models.

Summary The outcrop Maastrichtian chalk forms important reservoir for groundwater in Denmark and potential analogue for hydrocarbon reservoirs in the North Sea. This paper presents a workflow for variogram inference and modeling of porosity of outcrop chalk with different bedding architectures, integrating knowledge and data from exposed outcrop sections, borehole and seismic. The resulting high-resolution models can be upscaled to any larger scale of interest, and provide the corresponding geostatistical properties regarding spatial distribution of chalk properties, which could constrain offshore reservoir modeling and geostatistical seismic inversion.

Summary Interpretation of seismic responses from subsurface fault zones is hampered by the fact that the geological structure and property distributions of fault zones can generally not be directly observed. This shortcoming curtails the use of seismic data for characterizing internal structure and properties of fault zones, and has instead promoted the use of interpretation techniques which tend to simplify actual structural complexity by rendering faults as lines and planes rather than volumes of deformed rock. Facilitating correlation of rock properties and seismic images of fault zones would enable active use of these images for interpreting fault zones, which in turn would improve our ability to assess the impact of fault zones on subsurface fluid flow. The present study employs a combination of 3D fault zones models, based on empirical data, and 2D forward seismic modeling to investigate the link between fault zone properties and seismic response. A comparison of spatial statistics from the geological models and the seismic images was carried out to study how well seismic images render the modelled geological features. Our results show the feasibility of extracting information about fault zone structures from seismic data by the methods employed.

This paper addresses seismic imaging of fault zones and analysis of the seismic data with the use of the fault facies model developed at Uni Research CIPR. Simulated and ideal seismic images were produced to generate a statistical ensemble of realizations of this model. The comparative analysis presented in this paper is focused on the statistical characteristics of the initial geological model and its seismic images. This paper analyzes cross-correlations between seismic images and ideal seismic images. The method proposed makes it possible to establish an exact correspondence between the initial fault facies models and the seismic images of these models.

Interpretation of seismic responses from subsurface fault zones is hampered by the fact that the geologic structure and property distributions of fault zones can generally not be directly observed. This shortcoming curtails the use of seismic data for characterizing internal structure and properties of fault zones, and it has instead promoted the use of interpretation techniques that tend to simplify actual structural complexity by rendering faults as lines and planes rather than volumes of deformed rock. Facilitating the correlation of rock properties and seismic images of fault zones would enable active use of these images for interpreting fault zones, which in turn would improve our ability to assess the impact of fault zones on subsurface fluid flow. We use a combination of 3D fault zone models, based on empirical data and 2D forward seismic modeling to investigate the link between fault zone properties and seismic response. A comparison of spatial statistics from the geologic models and the seismic images was carried out to study how well seismic images render the modeled geologic features. Our results indicate the feasibility of extracting information about fault zone structure from seismic data by the methods used.

Access to 3D descriptions of fault zone architectures and recent development of modeling techniques allowing explicit rendering of these features in reservoir models, provide a new tool for detailed implementation of fault zone properties. Our aim is to assess how explicit rendering of fault zone architecture and properties affects performance of fluid flow simulation models. The test models use a fault with a maximum 100 m displacement and a fault damage zone with petrophysical heterogeneity caused by the presence of deformation bands. The distribution pattern of deformation bands in fault damage zones is well-documented, which allows generation of realistic models. A multiscale modeling workflow is applied to incorporate these features into reservoir models. Model input parameters were modulated to provide a range of property distributions, and the interplay between the modeling parameters and reservoir performance was analyzed. The influence of deformation-band damage zone on reservoir performance in the presence of different fault core transmissibility-multipliers was investigated. Two configurations are considered: one in which the fault terminates inside the model domain, representing a case in which the fluid can flow around the fault, and one in which the fault dissects the entire model domain, representing a case in which the fluid is forced to cross the fault. We observed that the impact of deformation-band fault damage zone on reservoir performance changes when the fault core transmissibility multiplier is changed. Reservoir performance is insensitive to changing damage zone heterogeneity in a configuration in which flow can move around the fault. Where flow cannot bypass the fault, the influence of fault damage zone heterogeneity on reservoir performance is significant even when the fault core transmissibility multiplier is low.

Faults play a key role in reservoirs by enhancing or restricting fluid flow. A fault zone can be divided into a fault core that accommodates most of the displacement and a surrounding damage zone. Interpretation of seismic data is a key method for studying subsurface features, but the internal structure and properties of fault zones are often at the limit of seismic resolution. We have investigated the seismic response of a vertical fault zone model in sandstone, populated with fault facies based on deformation band distributions. Deformation bands reduce the porosity of the sandstone, and they condition its elastic properties. We generate synthetic seismic cubes of the fault facies model for several wave frequencies and under realistic conditions of reservoir burial and seismic acquisition. Seismic image quality and fault zone definition are highly dependent on wave frequency. At a low wave frequency (e.g., 10 Hz), the fault zone is broader and no information about its fault facies distribution can be extracted. At higher wave frequencies (e.g., 30 and 60 Hz), seismic attributes, such as tensor and envelope, can be used to characterize the fault volume and its internal structure. Based on these attributes, we can subdivide the fault zone into several seismic facies from the core to the damage zone. Statistical analyses indicate a correlation between the seismic attributes and the fault internal structure, although seismic facies, due to their coarser resolution, cannot be matched to individual fault facies. The seismic facies can be used as input for reservoir models as spatial conditioning parameters for fault facies distributions inside the fault zone. However, relying only on the information provided by seismic analyses might not be enough to create high-resolution fault reservoir models.

Summary Presented paper addresses to a problem of the seismic analysis of fault damage zones. Statistical approach is applied by employing fault facies modelling technique which allows the detailed description of complex structure of fault damage zone. At that, the geometry and spatial distribution of petrophysical properties inside fault zone are described by categorical random fields. The comparison of main statistical properties of original facies model and the corresponding seismic images is carried out. Our study allows to estimate the resolution accuracy of seismic modelling for fault zone characterization.

Summary Access to 3D descriptions of fault zone architectures and recent development of modelling techniques allow explicit rendering of these features in reservoir models. Implementing detailed fault zone architectures in reservoir models is computationally expensive, particularly on field-scale, and should not be employed without due consideration. However, it remains to be established under which circumstances the addition of these features would significant influence production simulation. The objective of the present study was to test the sensitivity of reservoir performance to fault zone architectures, and thereby provide guidelines for when incorporating detailed fault zone structure in a reservoir simulation model would be meaningful or not. Flow simulations were performed on a set of models with varying fault zone property distributions and at different scales. Varying the spatial distribution of fault zone properties and upscaling them both influence reservoir response in different ways, depending on whether flow can circumvent the fault zone or not.

Seimic data represent a largely untapped source for characterising of fault zones. The key for using it lies in linking fault zone structure and properties to seismic response. The recent development of outcrop-based fault zone models allows this links to be studied. A seismic imaging procedure for fault zones, using multicomponent surface data generated for statistical fault facies models, is presented and discussed. It is based on a specific imaging procedure, which consists in a weighted summation of multicomponent multishot/multioffset data and spectral filtering of seismic data. The imaging procedure presented here is capable of resolving details inside the fault zone, which opens up for using seismic data to characterize sub-surface faults.

Fault damage zones in porous sandstones commonly exhibit networks of deformation bands reflecting crushing and reorganization of grains associated with small-scale, localized displacement. Deformation bands introduce anisotropic, order-of-magnitude reduction of effective permeability, which will affect fluid flow in reservoir rocks. We here present a method for incorporating these features in industrial-type reservoir models. The method involves the use of a three-dimensional fault zone grid generation technique that allows property modeling on a discrete high-resolution fault zone grid without refining the entire reservoir model. Deformation band data from 106 outcrop scan lines of fault damage zones were classified into discrete fault facies defined according to deformation band density. The distributional pattern of fault facies in the data exhibits recurrent spatial relationships, which could be reproduced using truncated Gaussian simulation in the modeling process. The frequency distribution of deformation band density for each facies was analyzed, and average density values were assigned to each facies for calculating cell permeability. Permeability anisotropy was handled by approximating the relationship between deformation band densities in different directions based on published high-resolution fault zone maps and cross sections. Fluid-flow simulations were carried out on several damage zones models, and results were benchmarked against models with conventional fault rendering without damage zones. Simulation results show that flow paths, remaining oil distribution, and reservoir responses in models incorporating damage zones deviate from models employing conventional fault representation without damage zones, and these differences increase as deformation band permeability decreases.

Volumetric data for scientific purposes and applications are made increasingly available with novel modes of acquisition and modelling, which need to be visualised in order to understand the data and derive structured insight. Various methods for volume visualisation exist, while a persisting challenge is the interaction and delineation of object of interest within the data. Transfer functions, commonly used in medical visualisation, are the established means of interaction, which are cognitively challenging to setup and understand. This article presents new approaches for the coupled visualisation of volumetric data and their statistical derivatives to support the interactive data exploration. The presented techniques improve the means of volumetric data exploration in scientific disciplines and application cases for which established transfer function techniques are inadequate, such as structuraland petroleum geology.

Our study focusses on seismic analysis of fault damage zones. A model containing a fault zone populated with fault facies is used as input to seismic forward modeling and imaging. A statistical comparison of the geological input model and the resulting seismic images was carried out, and the link between fault zone model parameters and seismic resolution studied. Our study demonstrates the potential of systematically using detailed geological 3D models of fault zone structures and properties to understand seismic responses from subsurface fault zones.

The internal structure and petrophysical property distribution of fault zones are commonly exceedingly complex compared to the surrounding host rock from which they are derived. This in turn produces highly complex fluid flow patterns which affect petroleum migration and trapping as well as reservoir behavior during production and injection. Detailed rendering and forecasting of fluid flow inside fault zones require high-resolution, explicit models of fault zone structure and properties. A fundamental requirement for achieving this is the ability to create volumetric grids in which modeling of fault zone structures and properties can be performed. Answering this need, a method for generating volumetric fault zone grids which can be seamlessly integrated into existing standard reservoir modeling tools is presented. The algorithm has been tested on a wide range of fault configurations of varying complexity, providing flexible modeling grids which in turn can be populated with fault zone structures and properties.

在“相-势耦合”控藏模式的基础上,融合“源控论”思想,提出“源-相-势耦合”控藏作用定量模型,并利用该模型对东营凹陷南坡金8——滨188井剖面的成藏过程进行了研究.结果表明:根据成藏期“源-相-势耦合”指数的分布,确定了金8——滨188剖面Ⅰ类、Ⅱ类和Ⅲ类有利区；Ⅰ类有利区成藏最有利,从成藏期开始到现今都具备优越的成藏条件；Ⅱ类有利区成藏较有利,在成藏期的大多数时间都具备优越的成藏条件；Ⅲ类有利区至少在成藏期内的一段时间具备优越的成藏条件.在金8——滨188井剖面缓坡带的滩坝砂具有最高的“源-相-势耦合”指数,是Ⅰ类有利区；位于坡底的浊积岩透镜体、同沉积断层上升盘构造圈闭以及缓坡带的三角洲具有好的“相”和“势”,是Ⅱ类有利区；位于坡底的深部滩坝砂在超压对油气的驱动下也可以成藏,是Ⅲ类有利区.

The Paleogene "Red Bed", the alternative strata for oil and gas exploration in the South Slope of the Dongying Depression, refers to a set of red clastic sediments of the lower 4th member of the Shahejie Formation and the 1st member of the Kongdian Formation. And it has important significance to study the controlling factors on oil and gas accumulation and the accumulation modes for guiding the deep-layer oil and gas exploration in the area. In this paper, according to the statistics of oil and gas static characteristics, analysis of oil original types, study of pathway system and recovery of oil and gas accumulation, the controlling factors on the Red Bed oil and gas accumulation were summarized as follows: source rock controlling oil and gas distribution, physical features of reservoir bed controlling trap oiliness, faults controlling oil and gas source and trap conditions, and nose structural zone controlling oil and gas migration and enrichment zone. Based on these studies, three accumulation modes for the Paleogene Red Bed in the research area were built: joints of source rock and reservoir bed acting as lateral pathway for oil and gas accumulation, faults acting as vertical pathway for oil and gas accumulation, and high pressure of deeper depression resulting in oil and gas flowing downward to form accumulation.

Faults are volumetric in nature and can cause complex fluid flow inside the fault zone because of its special fault zone architecture and different petrophysical properties from the host rock. Thus explicit fault zone modeling is important for capturing the fluid flow inside and through the fault zone precisely. Generation of a refined volumetric fault zone grid is the first step to perform explicit fault zone modeling. An algorithm for generating volumetric fault zones has already been implemented in Havana, however this algorithm failed to generate continuous top and bottom surfaces for the fault zone. This lead to internal discontinuities in the fault zone grid, and made it hard to run flow simulations on the grid. We now present an improved version of the algorithm that works well on complex faults and indicate the capability of explicit fault facies modelling of real field cases.