Seismic Applications Throughout the Life of the Reservoir

ECLIPSE, FrontSim, MultiWave Array and RFT (Repeat Formation Tester) are marks of Schlumberger.

Journal of Petroleum Science and Engineering, 2018

The Sawan Gas Field is one of the most promising gas fields of Middle Indus Basin in Pakistan with a cumulative production of 850 BCF. In the reservoir interval, the thin shale sequence is interbedded and dispersed resulting in extreme heterogeneity. Consequently, conventional seismic amplitude interpretation fails to delineate the sand-shale facies distribution. In this case study, the depositional facies of the reservoir C-sand interval with the integration of electrofacies analyses, historical production data, and seismic attribute analyses using 3D seismic and well log data were analyzed for prospect evaluation and field development plan to achieving maximized production. The electrofacies analyses show that the reservoir C-sand interval falls in funnelshaped, bell-shaped, and cylindrical-shaped trends. The obtained results suggest deposition of Csand in proximal delta front to pro-delta settings with medium to fine grain pore size distribution. Conversely fine grained lime mud, silt, and shale with poor-sorting fall in the irregular-shaped trend which suggests deposition in pro-delta settings. C-sand interval was evaluated using multiple seismic attributes including relative acoustic impedance, root mean square amplitude, envelope, sweetness, instantaneous frequency, structural smoothing, and phase shift. The results of all the seismic attributes demarcate the transitional boundary between the delta front sand facies and pro-delta sandy-shale facies. The calibration of electrofacies analysis with 3D seismic attributes indicates an appropriate agreement between them. This study effectively predicted the spatial distribution of sweet spots in the heterogeneous reservoir using 3D seismic attributes analysis, which can provide valuable guidance for the development of the area.

Geological Society, London, Special Publications, 2003

Integrated structural analyses of seismic and various well data are necessary to optimize hydrocarbon reservoir characterization. However, there are many published examples from the oil and gas industry where single data types are analysed but not integrated. This may lead to erroneous interpretations and drainage strategies. As illustrated by an example from the area around well 34/10-B-12 in the North Sea Gullfaks Field, integrated structural interpretation should typically utilize all available seismic surveys, well log correlation data, dipmeter data and core data. Interpretation of seismic data helps in the understanding of large-scale structural and stratigraphic geometries. Time-lapse (4D) seismic helps to identify changes in reservoir properties caused by injection and production. Well log correlation data are used to document variations in zonation thickness caused by sedimentological or structural changes. Dipmeter data tie observations of bedding orientation from seismic data to subseismic scale. Core data represent the most detailed (millimetre to metre scale) data available and can yield information on rock properties as well as sedimentological and (micro)structural features. Small-scale deformation structures such as deformation bands and fractures can typically be identified and characterized. In addition, it is possible from unorientated cores to find the orientation of bedding and deformation structures. This information is compared to observations from dipmeter data, well log correlation data and seismic data to improve the interpretation.

Marine and Petroleum Geology, 2001

All seismic data contain a mixture of signal and noise. In detailed reservoir characterisation, it is commonly dif®cult to distinguish between real features and seismic artefacts. This is especially a problem when interpreting seismic attribute maps. Such maps are widely used tools during reservoir description, but serious pitfalls exist, which may lead to erroneous interpretations and fatal development plans for oil ®elds. A recent interpretation of seismic attribute maps from a seismic survey collected across Gullveig, an oil ®eld located in the northern North Sea, has been used to illustrate how small faults can be recognised and mapped from such maps. We applied available well data (including core data) and two seismic surveys from the same area, and present convincing evidence that the vast majority of linear features seen on the seismic attribute maps are, in fact, seismic artefacts and not faults. The data from Gullveig are furthermore supplemented by observations from the nearby Gullfaks Field and discussions on the topic of seismic noise. We use these observations and discussions to stress the importance of using all available data to guide and quality control the structural interpretation of attribute map features before utilising such interpretations as input to reservoir modelling or well planning. q

Journal of African Earth Sciences, 2019

An integrated 3-D seismic data, suite of eleven well logs and checkshot data from Fabianski field, Coastal Depobelt, Niger Delta basin Nigeria were analysed and interpretations carried out using relevant algorithm models in the Petrel workstation for detailed 3-D structural and seismic attribute analysis. The method adopted involves well log interpretation for identification of reservoirs tops and base, well correlation for determination of lateral continuity of the reservoirs, seismic structural mapping, seismic attribute analysis, lead(s)/prospect(s) mapping and risk assessment. Twenty-three (23) faults were interpreted to offset the stratigraphic packages within the field at different seismic horizons. These faults created structures that are favourable for hydrocarbon trapping and accumulation. Three reservoirs have been identified: FAB-1, FAB-2 and FAB-3. Correlation of the reservoirs across five wells along depositional dip shows that the reservoirs are laterally continuous with varying thicknesses at well points. FAB-1 reservoir was studied in detail because it corresponds to a seismic flat spot identified in seismic volume. Four prospects were identified within the FAB-1 reservoir based on structural contour closures: FAB-1 southern prospect, FAB-1 northern prospect, FAB-1 northeastern prospect and FAB-1 northwestern prospect. Only FAB-1 southern prospect shows evidence of hydrocarbon accumulation. FAB-1 southern reservoir is characterized by localized bright amplitudes of root mean square (RMS) and envelope attributes which indicates porous and fluid filled lithologies; constant drop-off high frequencies of instantaneous frequency (12 Hz to 25 Hz), and very bright localized high values of sweetness attribute indicative of hydrocarbon saturated sand. Positive values of apparent polarity attribute validate the presence of hydrocarbons in the southern prospect. Spectral decomposition analysis shows that the FAB-1 southern reservoir is better imaged by a frequency range of 15 Hz to 25 Hz. It is therefore concluded that spectral decomposition techniques integrated with seismic attributes can unravel subtle indications that are not independently conclusive, and delineate hydrocarbon charged reservoir geometry and structural discontinuities within complex tectonic settings.

Journal of Applied Sciences 23(1):34-46, 2023

Characterizing fracture properties in naturally fractured reservoirs poses a significant challenge. While well-testing remains valuable, it often fails to provide precise descriptions of these properties. Bridging this gap requires the integration of geological expertise to enhance fracture assessment. This study addresses the limitations of well-test analysis and explores the application of Conventional Image Logs in structural, fracture, and geomechanical analysis. However, effectively combining these applications with well-test analysis on a field scale reveals a substantial knowledge gap. A critical challenge in this context is the absence of a defined procedure for calculating the variable "σ," a crucial parameter for simulating fractured carbonate reservoirs using image log fracture density. Integrating geological knowledge is essential to reduce uncertainties associated with well-test analysis and provide more accurate characterizations of fracture properties. Image log data processing emerges as a valuable avenue for gaining insights into the static attributes of naturally fractured reservoirs. This study focuses on Characterizing fractures using data from ten image logs and Developing a more accurate simulation model through the interpretation of images, with a particular emphasis on OBM imaging. The main goals of this fracture study revolve around establishing correlations between fracture densities well by well within the simulation and enhancing the accuracy of the simulation model by incorporating fracture data from image logs. Borehole imaging tools such as FMI/FMS and OBMI-UBI play a pivotal role in identifying significant structural features, including faults, fractures, and bedding. Fine-tuning fracture parameters during the history matching process, while potentially time-consuming, significantly impacts other historical match parameters. Consequently, the reliability of reservoir simulation results, predictions, and recovery enhancement strategies hinges on the precision of fracture properties and their distribution within the model. Recent advances in interpretation techniques have expanded the horizons of image interpretation, enabling the creation of more accurate simulation models for fractured reservoirs using fracture data obtained from image logs. The overarching goal of this project is to comprehensively evaluate a fractured reservoir field by integrating data from ten individual wells. Keywords: Well-testing, fracture evaluation, Image log data, fracture density, simulation sensitivity analysis.

Attributes: New Views on Seismic Imaging -- Their Use in Exploration and Production: 31st Annual, 2011

Seismic data have often played a significant, and sometimes dominant role in previous Bob F. Perkins conferences, such as in last year's conference on seismic geomorphology. Nevertheless, the last conference to address the role of seismic attributes was held in 1996. The advancement in algorithm development, 3D multiattribute visualization, interpretation workflows, and more quantitative reservoir characterization during this 15-year interval has been astounding. This year's conference, "Attributes: New Views on Seismic Imaging-Their Use in Exploration and Production," gathers some of the world's foremost attribute software developers, service providers, and oil-company practitioners under one roof at the same time. The Perkins conference provides a unique opportunity for such an attribute forum. It is small enough, with only one session at a time, to provide a great deal of interaction, particularly at meals and breaks. Yet it is large enough to allow the participation and input of the greater seismic interpretation community. You will find the quality and technical content of the papers provide the feel of a "technical workshop," whereby experts can compare and contrast state-of-the-art innovations with their expert peer group. However, we have instructed the authors that the intended GCSSEPM audience will be primarily practicing geologists and geophysicists, and to pitch their papers and presentations appropri-

Pure and Applied Geophysics, 2017

Thin hydrocarbon reservoir facies pose resolution challenges and waveform-signature opportunities in seismic reservoir characterization and prospect identification. In this study, we present a case study, where instantaneous frequency variation in response to a thin hydrocarbon pay zone is analyzed and integrated with other independent information to explain drilling results and optimize future drilling decisions. In Morrison NE Field, some wells with poor economics have resulted from well-placement incognizant of reservoir heterogeneities. The study area in Clark County, Kanas, USA, has been covered by a surface 3D seismic reflection survey in 2010. The target horizon is the Viola limestone, which continues to produce from 7 of the 12 wells drilled within the survey area. Seismic attributes extraction and analyses were conducted with emphasis on instantaneous attributes and amplitude anomalies to better understand and predict reservoir heterogeneities and their control on hydrocarbon entrapment settings. We have identified a higher instantaneous frequency, lower amplitude seismic facies that is in good agreement with distinct lithofacies that exhibit better (higher porosity) reservoir properties, as inferred from well-log analysis and petrographic inspection of well cuttings. This study presents a pre-drilling, data-driven approach of identifying sub-resolution reservoir seismic facies in a carbonate formation. This workflow will assist in placing new development wells in other locations within the area. Our low amplitude high instantaneous frequency seismic reservoir facies have been corroborated by findings based on well logs, petrographic analysis data, and drilling results.

Handbook of Mathematical Geosciences, 2018

In the oil industry, exploratory targets tend to be increasingly complex and located deeper and deeper offshore. The usual absence of well data and the increase in the quality of the geophysical data, verified in the last decades, make these data unavoidable for the practice of oil reservoir modeling and characterization. In fact the integration of geophysical data in the characterization of the subsurface petrophysical variables has been a priority target for geoscientists. Geostatistics has been a key discipline to provide a theoretical framework and corresponding practical tools to incorporate as much as possible different types of data for reservoir modeling and characterization, in particular the integration of well-log and seismic reflection data. Geostatistical seismic inversion techniques have been shown to be quite important and efficient tools to integrate simultaneously seismic reflection and well-log data for predicting and characterizing the subsurface lithofacies, and its petro-elastic properties, in hydrocarbon reservoirs. The first part of this chapter presents the state of the art and the most recent advances of geostatistical seismic inversion methods, to evaluate the reservoir properties through the acoustic, elastic and AVA seismic inversion methods with real case applications examples. In the second part we present a methodology based on seismic inversion to assess uncertainty and risk at early stages of exploration, characterized by the absence of well data for the entire region of interest. The concept of analog data is used to generate scenarios about the morphology of the geological units, distribution of acoustic properties and their spatial continuity. A real case study illustrates the this approach.

Proceedings of the 4th Unconventional Resources Technology Conference, 2016

The URTeC Technical Program Committee accepted this presentation on the basis of information contained in an abstract submitted by the author(s). The contents of this paper have not been reviewed by URTeC and URTeC does not warrant the accuracy, reliability, or timeliness of any information herein. All information is the responsibility of, and, is subject to corrections by the author(s). Any person or entity that relies on any information obtained from this paper does so at their own risk. The information herein does not necessarily reflect any position of URTeC. Any reproduction, distribution, or storage of any part of this paper without the written consent of URTeC is prohibited.