Interpretation Of Seismic Attributes Research Articles

High-dimensional co-occurrence matrix: A new tool for 3D seismic target visualization and interpretation

The interpretation of seismic attributes has been developed for more than 40 years, but it still cannot be fully matched with the study of geologic sedimentology. There are two main bottlenecks. One is that almost no attributes can completely characterize amplitudes from a 3D perspective. Another is the influence of wavelets (frequency and phase). Accordingly, a new volumetric attribute extraction technique is presented for solving these two problems as much as possible. A high-dimensional co-occurrence matrix (HCM), as a statistical representation of the spatial structural relationship between data points, can be one of the solutions to extracting 3D attributes. By considering the global spatial distribution, the HCM fixes the directional distortion of the existing co-occurrence matrix methods and effectively suppresses vertical wavelet illusions. By realizing a rapid transformation of seismic data to 3D geologic target visualizations, this method does not rely heavily on structural information such as dip and azimuth and becomes a convenient bridge from seismic to geologic interpretation. We have applied the methodology to channel delineation in a 3D seismic survey acquired in Ordos, China. The results indicate that the attribute volume extracted from HCM expresses the geologic target convincingly and eliminates the illusions caused by the wavelets. The deposition history of the channels could be observed continuously through geologic time.

An evaluation of the impact of shot and receiver lines spacing on seismic data quality – the Wierzbica 3D AGH seismic experiment

An attempt was made to describe the quality of the stacked seismic data semi-quantitatively with respect to the spacing of shot and receiver lines. The methods used included: signal-to-noise ratio calculation, seismic-to-well tie accuracy, wavelet extraction effectiveness and reliability of semi-automated interpretation of seismic attributes. This study was focused on the Ordovician-Silurian interval of the Lublin Basin, Poland, as it was considered as a main target for the exploration of unconventional hydrocarbon deposits. Our results reconfirm the obvious dependency between the density of the acquisition parameters and data quality. However, we also discovered that the seismic data quality is less affected by the shot line spacing than by comparable receiver line spacing. We attributed this issue to the fact of the higher irregularity of the shot points than receiver points, imposed by the terrain accessibility. We have also proven that the regularity of receiver and shot point distributionis crucial for the reliable interpretation of structural seismic attributes, since these were found to be highly sensitive to the acquisition geometry.

Depositional settings and history of the Lower Miocene Fleming Group, Refugio County, Texas, as defined using seismic geomorphology

Abstract A study of the Lower Miocene Fleming Group in Refugio County, Texas from 3-D seismic and wireline-log data documents continuous strandplain and associated lower-coastal-plain fluvial systems along a wave-dominated shoreline. This study delineates and characterizes, through the interpretation of seismic attributes and seismic geomorphology maps from 15 horizons, three principal styles of stratal patterns: (1) parallel and subparallel, strike-continuous sets of beach ridge and swale deposits within a strandplain system that prograded at least 12 km, (2) sinuous channel belts in a coeval mixed-load meanderbelt system, and (3) acoustically dim, nearly featureless seismic attribute patterns that record homogenous and topographically subdued, shallow-marine mudstones associated with transgressive marine deposits and flooding surfaces. Holocene depositional analogs for these Lower Miocene sandy strandplain deposits include the Nayarit coastline in Mexico, whereas the lower coastal plain between Galveston and Corpus Christi, Texas serves as an appropriate analog for mixed-load meanderbelt systems. The Lower Miocene coastline in Refugio County consists of a regressive phase that was punctuated by two transgressive phases. These episodes of marine transgression correspond to the Anahuac Formation and the Marginulina A shale, respectively. Succeeding events record complex, amalgamated beach-ridge deposits and coeval fluvial-channel systems that exhibit patterns of channel migration, erosion, incision, and downdip fusion of channel belts. This study concludes that potential reservoir geometries and architectures in the Lower Miocene succession are much more complex than previously inferred, the result of rapidly fluctuating and evolving strike-fed shoreline systems and contemporaneous fluvial dip-dispersal systems, some manifested by shore-parallel trends confined in swales. Improved reservoir-development strategies in this prolific hydrocarbon-bearing play should be guided by distribution of sandy depositional elements and the paleogeographic setting.

Constraining 3D facies modeling by seismic-derived facies probabilities: Example from the tight-gas Jonah Field

Seismic reservoir characterization is usually based on the interp retation of seismic attributes that relate to the geological feature or reservoir property of interest. If we are interested in fault geometries, a variety of geometric attributes can be used to map the details of fault distributions and constrain discontinuities and flow barriers in geological and flow-simulation models. If we are interested in reservoir properties, however, the usual approach is to estimate seismic attributes that are qualitatively related to such properties. The interpretation of the attribute focuses on the identification of “good” and “bad” areas depending on how the attribute relates to the property of interest.

Borehole seismic: what does it bring to the understanding of the reservoir?

When thinking about what we need for a more comprehensive approach to reservoir description and management, the range of information is large and various. The objective is always to improve our ‘vision’ of the geological setting, including a precise rock-type characterization and a good understanding of hydrocarbon flow paths. Each of these elements of the reservoir is determined with a varying level of uncertainty. Today, there is general agreement that integration of competences in business units is the optimal way to take the full benefit of technology breakthroughs in each individual discipline. Borehole seismic is identified as being critical to increasing the quality and the reliability of processing and interpretation of surface seismic data. If until recently, borehole seismic applications were focused on seismic calibration using vertical seismic profiles (VSP) and sometimes on imaging when surface seismic defaulted, today the link to well data is growing stronger. Since not all disciplines involved in reservoir management can work at the same scale, this raises the problem of scale and model compatibility between the respective disciplines. Here again borehole seismic can play a key role. This is becoming possible because advances have been made in a variety of techniques and methods leading to applications such as multi-walkaway and 3D-VSP, 4C and 4D-VSP, single-well and crosswell acquisitions, amplitude variation with offset (AVO) calibration, and scale change. Moreover, improvements in technology make the acquisition and processing cost-effective. Multilevel, three- or four-component receiver strings and permanent seismic sensors are examples of a continued development of operationally efficient hardware. New borehole seismic techniques such as 4D-VSP or the improvement in more mature ones such as crosswell seismic, offer new images of the reservoir. Although these images may be spatially limited, they are usually of a higher resolution than surface seismic and can offer significant benefit for reservoir management and monitoring. This paper illustrates the benefits of borehole seismic with three case studies, illustrating (1) how we can include uncertainties in the VSP imaging process and its impact on structural interpretation of a North Sea reservoir, (2) why AVO calibration using a walkaway technique is mandatory for a better prediction and interpretation of seismic attributes in terms of lithology and fluid content and (3) 4D walkaway and passive seismic surveys using fibre-optic seismic permanent sensors for monitoring an onshore gas storage.

3-D Visualisation and Interpretation of Seismic Attributes Extracted from Large 3-D Seismic Datasets: Sub-regional and Prospect Evaluation, Deepwater Nigeria: ABSTRACT

3-D Visualisation and Interpretation of Seismic Attributes Extracted from Large 3-D Seismic Datasets: Sub-regional and Prospect Evaluation, Deepwater Nigeria: ABSTRACT

3-D Visualisation and Interpretation of Seismic Attributes Extracted from Large 3-D Seismic Datasets: Subregional and Prospect Evaluation, Deepwater Nigeria: ABSTRACT

High resolution 3-D visualization of horizon interpretation and seismic attributes from large 3-D seismic surveys in deepwater Nigeria has greatly enhanced the exploration team`s ability to quickly recognize prospective segments of subregional and prospect specific scale areas. Integrated workstation generated structure, isopach and extracted horizon consistent, interval and windowed attributes are particularly useful in illustrating the complex structural and stratigraphical prospectivity of deepwater Nigeria. Large 3-D seismic volumes acquired over 750 square kilometers can be manipulated within the visualization system with attribute tracking capability that allows for real time data interrogation and interpretation. As in classical seismic stratigraphic studies, pattern recognition is fundamental to effective depositions facies interpretation and reservoir model construction. The 3-D perspective enhances the data interpretation through clear representation of relative scale, spatial distribution and magnitude of attributes. In deepwater Nigeria, many prospective traps rely on an interplay between syndepositional structure and slope turbidite depositional systems. Reservoir systems in many prospects appear to be dominated by unconfined to moderately focused slope feeder channel facies. These units have spatially complex facies architecture with feeder channel axes separated by extensive interchannel areas. Structural culminations generally have a history of initial compressional folding with late in extensional collapse and accommodationmore » faulting. The resulting complex trap configurations often have stacked reservoirs over intervals as thick as 1500 meters. Exploration, appraisal and development scenarios in these settings can be optimized by taking full advantage of integrating high resolution 3-D visualization and seismic workstation interpretation.« less

Blanket 3-D Coverage-Its Successful Application in Exploring a Mature Area, Central Dutch Offshore

In the K and L blocks of the Dutch sector of the southern North Sea, the Rotliegende Sandstone forms the main objective. Drilling started in 1968, and to date 36 Rotliegende gas fields have been discovered in Nederlandse Aardolie Maatschappij (NAM) operated acreage with volumes in place ranging between 2 and 50 x 10[sup 9]m[sup 3]. Approximately 70% of these fields were discovered using two-dimensional seismic, but as exploration progressed an increasing number of wells were found water bearing. The main cause of failure is lack of structural integrity, due to high Rotliegende fault density and highly variable overburden dominated by Zechstein salt and Chalk grabens. Three-dimensional (3-D) seismic acquisition started in 1981 but at first was typically limited to small production surveys covering existing gas fields. In 1986, acquisition of block-wide exploration 3-D surveys began. This has resulted in a present-day coverage of some 5000 km[sup 2], representing 95% of NAM-operated central offshore K and L blocks. Interpretation of these surveys revealed many undrilled structures, inspiring a second phase of exploration drilling with a high success ratio of 80%. As drilling activity progressed in the earliest covered blocks, however, a number of structurally conclusive dry wells were drilled, andmore » remaining individual prospects are small. Therefore, a third exploration phase now has started, concentrating on hydrocarbon habitat reviews making use of detailed 3-D interpretation of seismic attributes. The reconstruction of tectonic history and and updated charge model are expected to lead to an improved definition of remaining potential in these mature blocks.« less