Multiple Seismic Attributes Research Articles

Diacritical Seismic Signatures for Complex Geological Structures: Case Studies from Shushan Basin (Egypt) and Arkoma Basin (USA)

Seismic reflection techniques show an imperative role in imaging complex geological structures and are becoming more acceptable as data interpreting tools in 2D/3D view. These subsurface geological structures provide complex seismic signature due to their geometrical behavior. Consequently, it is extremely difficult to interpret these seismic sections in terms of subsurface configuration. The main goal of this paper is to introduce seismic attributes as a powerful tool to interpret complex geological structures in different geological settings. In order to image these complex geological features, multiple seismic attributes such as coherence and curvature have been applied to the seismic data generated over the Shushan Basin (Egypt) and Arkoma Basin (USA). Each type of geological structure event usually generates a unique seismic “signature” that we can recognize and identify by using these seismic attributes. In Shushan Basin (Egypt), they provide a framework and constraint during the interpretation and can help prevent mistakes during a 3D structural modeling. In Arkoma Basin (USA), the seismic attributes results provide useful information for broader analyses of the complex structural relations in the region where the Ouachita orogenic belt intersects with the southern Oklahoma aulacogen. Finally, complex geological structures provide dramatically diacritical seismic signatures that can be easily interpreted by collaborating conventional seismic interpretation techniques with multiple seismic attributes.

The application of geoelectrical attributes based on crossed square array resistivity sounding data at 'Pudarske Kolibe' site in eastern Serbia

Most of modern geophysical investigations routinely utilize seismic exploration method. 3D seismic and multiple seismic attributes enable the most complete definition of the local geological setting. This paper deals with utilization of crossed-square geoelectrical sounding method, which can be used for a 3D interpretation of resistivity sounding data as well as for defining additional geoelectrical attributes. With crossed-square array, we get a directional independent measurement and multiple geoelectrical attributes (ρm, ρx, n, θ and ξ). A more complete approach towards better interpretation is achieved with maps of five attributes: geometric mean apparent resistivity (ρm), average apparent resistivity (ρx) apparent anisotropy coefficient (n), azimuth of the plane beddings (θ) and a ratio of deviation from homogeneous anisotropic subsurface model (ξ). Multiple geoelectrical attribute maps correspond to depth of investigation of the array, like time and depth slices in seismic method. Horizontal resolution and the depth of investigation are controlled by the size and position of the array. Vertical resolution is, however, limited just like for the usage of any other electrode array in geoelectrical sounding. Combination of depth maps and profile maps enables a 3D interpretation similar to 3D cubes in seismic and recent software enables 3D modelling. The measurements using crossed square array were conducted at site 'Pudarske kolibe' in Eastern Serbia. The goal was to determine and separate 3D calcarinte bodies created in the depositional process, but also the eventual existence of electrical anisotropy in fluvial and shallow see water sediments. Results of investigations revealed the existence of electrical anisotropy with apparent anisotropy coefficient (n) up to the value of 2 and, on the other hand, successfully delineated calcarenite bodies embedded in sedimentary formations present at investigated site.

Analysis on the Applicability of the Post-Stack Seismic Attribute Recognition Method in the Sand Bodies of the River-Way of Fuyang Oil Layer

The later-period structure of Fuyang oil layer is very complex, and the reservoir mainly consists of river-way sand. The form of the reservoir is narrow and distributed differently, so it is very hard to identify. To accurately predict sand bodies, the sand bodies in the river way are comparatively studied using multiple post-stack seismic attributes, and finally a conclusion is made as follows: the reservoir interpretation technology based on frequency possesses a high spatial resolution and can test the spectrum lateral variation caused by different deposits, and then the plane distributions of the river-way and other deposits are described using equifrequent slices, and the combination characteristics of different deposit rhythmic layers are quantitatively analyzed, and also the thickness change of the river-way can be quantitatively analyzed under the ideal condition. Meanwhile, spectrum imaging is implemented using the tuning frequency of the different thickness of the sand bodies, and the reservoir is identified through the spatial changes of amplitude energy, facies values, and frequency attenuation attributes under the different chosen frequency, so that the spatial discontinuity of the deposits is effectively described. Therefore, it can meet the exploration and development needs of the oil field to a certain extent.

Improvement in facies discrimination using multiple seismic attributes for permeability modelling of the Athabasca Oil Sands, Canada

This study was conducted to develop a reservoir modelling workflow to reproduce the heterogeneous distribution of effective permeability that impacts on the performance of SAGD (Steam Assisted Gravity Drainage), the in-situ bitumen recovery technique in the Athabasca Oil Sands. Lithologic facies distribution is the main cause of the heterogeneity in bitumen reservoirs in the study area. The target formation consists of sand with mudstone facies in a fluvial-to-estuary channel system, where the mudstone interrupts fluid flow and reduces effective permeability. In this study, the lithologic facies is classified into three classes having different characteristics of effective permeability, depending on the shapes of mudstones. The reservoir modelling workflow of this study consists of two main modules; facies modelling and permeability modelling. The facies modelling provides an identification of the three lithologic facies, using a stochastic approach, which mainly control the effective permeability. The permeability modelling populates mudstone volume fraction first, then transforms it into effective permeability. A series of flow simulations applied to mini-models of the lithologic facies obtains the transformation functions of the mudstone volume fraction into the effective permeability.Seismic data contribute to the facies modelling via providing prior probability of facies, which is incorporated in the facies models by geostatistical techniques. In particular, this study employs a probabilistic neural network utilising multiple seismic attributes in facies prediction that improves the prior probability of facies. The result of using the improved prior probability in facies modelling is compared to the conventional method using a single seismic attribute to demonstrate the improvement in the facies discrimination. Using P-wave velocity in combination with density in the multiple seismic attributes is the essence of the improved facies discrimination. This paper also discusses sand matrix porosity that makes P-wave velocity differ between the different facies in the study area, where the sand matrix porosity is uniquely evaluated using log-derived porosity, P-wave velocity and photographically-predicted mudstone volume.

Improved spatial modeling by merging multiple secondary data for intrinsic collocated cokriging

There often exist many secondary data that must be considered in geostatistical reservoir modeling. These include multiple seismic attributes, geological trends and structural controls. It is essential that all secondary data are accounted for when estimating a primary variable (e.g., porosity or water saturation) with the precision warranted by that secondary data type. Characterizing the distribution of primary and secondary variables requires multivariate geostatistical techniques. Collocated cokriging is a common technique in geostatistics to account for multiple data types. This technique, however, has a longstanding problem with variance inflation that leads to problems in histogram reproduction. This paper, analyses an alternative method to collocated cokriging. This method, referred to as intrinsic collocated cokriging (ICCK), is equally simple, but ensures histogram reproduction. To improve practical implementation of ICCK in the case of multiple secondary data a novel merged secondary variable approach is developed in this paper. This approach is aimed at merging all secondary data into a single variable, then implementing ICCK with that single variable. It is shown that the proposed technique yields the same results as would be obtained using all multiple secondary variables simultaneously.

Collocated Cokriging Based on Merged Secondary Attributes

There exist many secondary data that must be considered in in reservoir characterization for resource assessment and performance forecasting. These include multiple seismic attributes, geological trends and structural controls. It is essential that all secondary data be accounted for with the precision warranted by that data type. Cokriging is the standard technique in geostatistics to account for multiple data types. The most common variant of cokriging in petroleum geostatistics is collocated cokriging. Implementations of collocated cokriging are often limited to a single secondary variable. Practitioners often choose the most correlated or most relevant secondary variable. Improved models would be constructed if multiple variables were accounted for simultaneously. This paper presents a novel approach to (1) merge all secondary data into a single super secondary variable, then (2) implement collocated cokriging with the single variable. The preprocessing step is straightforward and no major changes are required in the standard implementation of collocated cokriging. The theoretical validity of this approach is proven, that is, the results are proven to be identical to a “full” approach using all multiple secondary variables simultaneously.

A grand tour of multispectral components: A tutorial

The human interpreter is perhaps the best pattern-recognition engine currently available. Often, interpreting seismic data involves inspection and analysis of multiple seismic attributes. While interpreters are skilled at visualizing complex geologic features in 3D, they are less adept at visualizing a great many attributes at once. Recent software development provides interpreters with the means of corendering three attributes (using a red-green-blue color model) or four attributes (using a hue-lightness-saturation-opacity color model). While analysis of four or more attributes is simple from a mathematical point of view, it is overly taxing on the normal human interpreter who needs to relate these images to the underlying geologic processes.

The Balance Between Lowering Cost and Increasing Capability

Moore’s law (an exponential growth in the number of transistors per integrated circuit) simultaneously delivers both reduced cost and improved capabilities, but most managers focus more aggressively on cost reduction than on capability improvement—and understandably so, as costs continue to drop dramatically for products used in established work processes. This approach leverages Moore’s law to do today—at a lower cost—what your business could do yesterday, and has been doing for 20 years. But inevitably, technology innovators develop and deliver breakthroughs that can fundamentally change the economics of companies dependent upon information technology (IT) to drive their business and profitability. So at some point every industry needs to step back from the focus on reducing cost to ask the question: Can I do things differently in my business today that will substantially improve performance, and materially improve it much more aggressively, than I could ever achieve by saving another 10% on a cheaper personal computer? By grasping new technologies, often at the same or reduced cost compared to legacy systems, the industry can reap both financial savings and vastly increased computational capabilities. Energy companies that have decided to take advantage of both curves of Moore’s law are enjoying increased efficiency, production, and profits. Improving Performance In the mid-1980s, the geophysical work process changed from working with paper sections and maps to interpreting seismic data and automatically creating the resultant maps on computers. Although the movement to computers was a significant breakthrough because it allowed data to be viewed and understood much more quickly, the memory capacity of those early computers was so limited that the industry went from using multiple seismic attributes in the interpretation to only one: amplitude. The task of loading a second attribute to the process was difficult and time-consuming, and there was no effective way of simultaneously viewing multiple attributes. So additional attributes often were not incorporated. Fast forward 20 years, and there is an established standard work process in which seismic interpreters, having entered the workplace after the transition to computers, work predominantly with only a single attribute. The computing capabilities of 2005, in contrast to 20 years ago, can take us back to where we were before the ubiquitous introduction of work stations, where multiple simultaneous attributes can be used in the standard work process but are now visualized and analyzed together in a common volumetric digital image. For example, last year, SGI and Landmark Graphics conducted a technology breakthrough using a data set loaned by Marathon Oil. Using Landmark’s Geoprobe interpretation software running on an SGI visualization system, the team successfully demonstrated how a 400 gigabyte volume could be visualized and analyzed in real time. This was a multiattribute volume that allowed the interpreter to look at the amplitude volume corendered with a continuity volume, pro-viding a high-resolution view of key faults and stratigraphic discontinuities in the volume.

Detection of fluid migration pathways in seismic data: implications for fault seal analysis

AbstractA new and efficient method for fault seal analysis using seismic data is presented. It uses multiple seismic attributes and neural networks to enhance fluid migration pathways, including subtle features that are not detectable using single attributes only. The method may be used as a first estimate of fault seal or to calibrate results from other techniques. The results provide information about which faults and fault segments are sealing or leaking. Fluid flow along individual faults appears to be focused along zones of weakness, and fault seal research should thus be focused on finding such weak locations within fault zones, a task that is best done using three‐dimensional (3D) seismic data. Under certain conditions, it is suggested that fluids migrate along fault planes by a diapiric fluid flow mechanism. The results assist in calibrating the bulk hydraulic properties of faults and rock formations and can be used in basin modelling.

Implementation of volume interpretation in revealing upside potential in a mature field, the sangatta oilfield: A case study

The Sangatta field is a shallow, medium sized oilfield, located in prolific Kutai Basin and was discovered in 1939. Field production begun at 1972. Primary production derives from Mid Miocene fluviodeltaic reservoir. Three deep exploratory wells drilled on crestal position in mid 70's failed to encounter reservoir quality rock and paleontologically exhibited deeper marine environment. Following conventional structural interpretation based on 3D shot in 1993, a comprehensive 3D volume interpretation was conducted recently. This new method facilitating combination between conventional 3D interpretation with the power of visualization, which enable interpreting of simultaneous multiple seismic attributes as single object that improve degree of confidence. This method eventually has revealed subtle seismic signature that can be interpreted as volumetrically significant geologic body that possess reservoir quality and becoming an attractive exploration target. Further to this study, 4 deep exploratory wells are scheduled to be drilled during this year drilling campaign.

The attribute explosion

Webster's defines “attribute” as an inherent characteristic; a word describing a quality. Robert Sheriff (in The Encyclopedic Dictionary of Exploration Geophysics, 3rd edition ) defines “seismic attribute” as a measurement based on seismic data, such as envelope amplitude (“reflection strength”), instantaneous phase, instantaneous frequency, polarity, velocity, dip, dip azimuth, etc. This special section on seismic attributes extends the classical definition of seismic attribute technology; i.e., most of the papers describe not only seismic attributes but sophisticated workflows and techniques using multiple seismic attributes that are integrally related to the geology and/or calibrated to reservoir properties. While seismic attributes are one of the most routine technologies exploited in geoscience interpretation and analysis of 3D seismic data, researchers at major oil companies, geoscience …

3-D seismic detection of undrilled prospective areas in a mature province, South Marsh Island, Gulf of Mexico

This paper focuses on the most effective approach to defining additional resources using 3-D seismic as the sole data source. Although this example is from a densely drilled province, such a seismic-based approach is often used in frontier areas with sparse well coverage, in step-out regions around known production, can be used for a “quick look” evaluation of existing properties, and for real-time interpretation of newly acquired data. This approach—integrating multiple seismic attributes and interpretation methods—refined the structural framework and detected undrilled prospective areas in a mature province in the Gulf of Mexico. Coherency technologies refined the fault interpretations. Surface mapping identified structural highs, and stratal-surface techniques were used to evaluate seismic stratigraphic facies. The study area covered approximately 350 square miles of coastal waters just south of Marsh Island, Louisiana (Figure 1). Data consisted of two merged 3-D surveys, Outer Continental Shelf (OCS) 310 and State Lands (SL) 340 that cover six productive offshore fields: Starfak, Tiger Shoal, Mound Point, Amber Complex, Lighthouse Point, and North Lighthouse Point. Figure 1. Tiger Shoal area in Vermilion Block 50 offshore Louisiana. Sur-rounding fields and the outline of the two major 3-D seismic surveys are indicated. The area is in the Oligocene-Miocene detachment province of the northern Gulf Coast continental margin—a region generally characterized by large-displacement, dominantly down-to-the-basin, listric growth faults that sole on a regional detachment zone above the Oligocene section. Regional deformation is a product of salt mobilization. The faults originate in the autochthonous Jurassic Louann Salt or in the detachment zone represented by a salt weld that formerly contained a thick, allochthonous salt body. A characteristic feature of this province is the thickness (typically exceeding three miles) of deltaic and shelf sediments above the detachment zone. This remarkable stacking of deltaic/shelf sandstone reservoirs helps make this province one of the world's …

ABSTRACT: A new approach to predict log properties from seismic data using multiple seismic attributes and neural networks

ABSTRACT: A new approach to predict log properties from seismic data using multiple seismic attributes and neural networks

ABSTRACT: The combined use of visualization and multiple seismic attributes for cycle time reduction and risk minimization

ABSTRACT: The combined use of visualization and multiple seismic attributes for cycle time reduction and risk minimization

Using Bayesian simulations to predict reservoir thickness under tuning conditions

Mapping reservoir thickness from 3-D seismic data is a difficult task when the seismic response is dominated by tuning effects. Deterministic solutions may be considered when the acoustic properties of the reservoir and the encasing material are nearly constant. When the acoustic properties are highly variable, the dispersion of points observed in the tuning curves precludes a deterministic approach, and a statistical method is preferred. In this study, we apply a recently developed nonlinear Bayesian simulation technique to map the thickness of a reservoir associated with an intrusive rock. In contrast to linear geostatistical techniques such as cokriging, this method handles complex nonlinear relationships between thickness and multiple seismic attributes.

Abstract: Estimation of Sand/Shale Ratio in Interbedded Formations Using Neural Network Processing of Multiple Seismic Attributes

Abstract: Estimation of Sand/Shale Ratio in Interbedded Formations Using Neural Network Processing of Multiple Seismic Attributes

Seismic attribute inversion for velocity and attenuation structure using data from the GLIMPCE Lake Superior experiment

A simultaneous inversion for velocity and attenuation structure using multiple seismic attributes has been applied to refraction data from the 1986 GLIMPCE Lake Superior experiment. The seismic attributes considered include envelope amplitude, instantaneous frequency, and travel time of first arrival data. Instantaneous frequency is converted to t* using a matching procedure which approximately removes the effects of the source spectra. The derived seismic attributes are then used in an iterative inversion procedure referred to as AFT inversion for amplitude, (instantaneous) frequency, and time. Uncertainties and resolution of the velocity and attenuation models are estimated using covariance calculations and checkerboard resolution maps. A simultaneous inversion of seismic attributes from the GLIMPCE data results in a velocity model similar to that of previous studies across Lake Superior. A central rift basin and a northern basin are the most prominent features with an increase in velocity near the Isle Royale fault. Although there is an indication of the central and northern basins in the attenuation model for depths greater than 4 km, the separation is not evident for shallower depths. This may result from microfractures masking compositional variations in the attenuation model for shallower depths. Attenuation Q values range from approximately 60 near the surface to near 500 at 10 km depth. A relationship between inverse Q and velocity of Q−1=0.0210–0.0028*v was found with a correlation coefficient of −0.96. This suggests a nearly linear, inverse relationship between Q−1 and velocity beneath Lake Superior which supports previous laboratory results. The inverted velocity and attenuation models provide important constraints on the lithology and physical properties of the Midcontinent rift beneath Lake Superior.

3-D Petrophysical Properties from Seismic Data

This interpretation technique uses a seismic workstation to estimate combinations of rock types, porosities, fluids, and pressures from three-dimensional (3-D) seismic data. It displays the information as clouds in a 3-D volume. Data inputs are post- and prestack seismic attributes, and a combination of well-log curves. The display of petrophysical properties relative to the 3-D seismic structure allows a geoscientist to hypothesize a combination of petrophysical properties of a zone in the subsurface and observe the resulting spatial distribution of that combination in the 3-D survey volume. The spatial pattern changes as the geoscientist sweeps across a range of combinations of petrophysical properties. Clouds appear where the combination produces the observed responses of multiple seismic attributes. A data set from the Gulf of Mexico shows the applications of the technique to identify gas-saturated reservoirs.