Carbon dioxide volume estimated from seismic data after six years of injection in the oil field of Buracica, Bahia

Fast diagnosis of reservoir simulation models based on 4D seismic similarity indicators

A 3D seismic survey in the Green Canyon area of the northern Gulf of Mexico was interpreted for stratigraphy using a sequence stratigraphic analysis. The versatility of the workstation greatly increased our efficiency over manually interpreting 2D seismic paper sections. Compressed black and white variable density displays and narrow band yellow and green instantaneous phase displays were key factors in identifying and interpreting horizons and subtle stratigraphic features. The area-wide autotracking feature allowed the interpreter to pursue other tasks with acceptable map results. The increased spatial resolution of the 3D data over our 2D data grid allowed us to image the detailed geomorphic shape of a deep water Pleistocene slope fan channel/levee system with multiple flattened horizon slices. Lithofacies maps of the lowstand slope fan and prograding wedge were made in much less time than the manual method by using 3D volume attribute maps called reflection heterogeneity and reflection intensity. INTRODUCTION Seismic sequence stratigraphy has developed over the past few years as a significant exploration tool for the oil and gas industry. It is a model-based concept to interpret cyclic stratigraphy and predict lithofacies by integrating well logs, biostratigraphy and seismic data. We sought to extend our 2D interpretation experience to 3D datasets for improved lithofacies predictions through tighter seismic control and utilizing the capabilities of the interactive workstation. Nine federal lease blocks from a Green Canyon 3D seismic survey in the northern Gulf of Mexico were selected in an area where our 2D sequence stratigraphic interpretation could be used as a framework (Fig. 1). Water depths range from 2000'- 3000' in this region of the continental slope. Sequence boundaries were established and dated using seismic data and biostratigraphic data from six nearby wells. An early Pleistocene sequence (1.4- 1.1 million years) with a well developed slope fan was selected to evaluate and demonstrate identification of boundaries, autotracking capabilities and interval mapping, The deepwater sediments are predominantly lowstand slope fan (SF) and prograding wedge (PW) deposits. PRINCIPLES OF SEQUENCE STRATIGRAPHY A sedimentary sequence is composed of a group of genetically related sediments (facies) deposited during one cycle of relative sea level rise and fall. The components are three lowstand depositional complexes (basin floor fan, slope fan, prograding wedge), a transgressive systems tract and a highstand systems tract. Each systems tract and depositional complex has predictable lithofacies for each basin environment. These depositional units have diagnostic well log and seismic reflection characteristics. In addition, biostratigraphic data is used to date the sequences, interpret the paleo-environment and identify condensed section shales within a sequence. Hence, lithofacies can be predicted from an integrated interpretation of well logs, seismic and biostratigraphic data. Further discussions of sequence stratigraphy can be found in Van Wagoner, et al.1, Sangree, et al2, and Barnett3.

Relevance of the work. The paper considers challenging problems related with outlining of intervals with oil and gas presence in the mature Khylly field by use of latest 3D seismic survey techniques in order to gain larger crude resources base. The purpose of this research is to discover the most promising intervals of target horizons with relatively high reservoir properties outlined by 3D seismic data. The subjects of research are 3D seismic survey data, downhole seismic survey – Vertical Seismic Profiling (VSP) and well logging diagrams. The object of research is the Khylly deposit. The paper describes in brief geological and geophysical characteristics, stratigraphic and lithological features of rocks making the section. It is noted that despite repeated surveys by use of various geological and geophysical techniques, the field setting is not thoroughly studied and it has been covered by 3D seismic survey in 2012. Research results. 3D seismic survey applied across Khylly area is resulted in drawing of 4 structural maps for III and I horizons of Productive Series (PS), Akchagyl and Lower Absheron suites. Taking into account the relevance of structural planes of various stratigraphic levels and III horizon of PS being one of the major reference horizons the paper gives description of structural map drawn for this horizon. The detailed velocity model is designed based on VSP data with wide use of velocity analysis data. It has been made clear that Khylly area has block structure and each block has been described in detail. Based on acquired data it has been recommended to drill exploratory well R-1. Conclusion. Processing and interpretation of seismic data are aimed at solving some geological problems; the main task was to obtain results that ensure the study of the geological structure in the seismic survey area, including tracing of seismic horizons, faults and outlining the areas and section intervals which may be of interest due to possible oil and gas presence. VSP data acquired in well 2012 and velocity analysis made it possible to design velocity model of the section under the study, with the use of which the temporary 3D cube was transformed into a depth cube. The quality of seismic data is good and made it possible to solve the tasks set for this research.

Early Cretaceous rift basins of northeastern Brazil illustrate key three-dimensional geometries of intracontinental rift systems, controlled mainly by the basement structures. These basins were formed and then abandoned during the early extension associated with the north-south-propagating separation of South America and Africa. During the early Neocomian, extensional deformation jumped from the easternmost basins (group 1: Sergipe Alagoas and Gabon basins; group 2: Reconcavo, Tucano, and Jatoba basins) to the west, forming a series of northeast-trending intracratonic basins (group 3: Araripe, Rio do Peixe, Iguatu, Malhada Vermelha, Lima Campos, and Potiguar basins). The intracratonic basins of groups 2 and 3 consist of asymmetric half-grabens separated by basement highs, transfer faults, and/or accommodation zones. These basins are typically a few tens of kilometers wide and trend northeast-southwest, roughly perpendicular to the main extension direction during the early Neocomian. Preexisting upper crustal weakness zones, like the dominantly northeast-southwest-trending shear zones of the Brazilian orogeny, controlled the development of intracrustal listric normal faults. Internal transverse structures such as transfer faults (Reconcavo basin and onshore Potiguar basin) and accommodation zones (onshore Potiguar basin and Araripe basin) were also controlled by the local basement structural framework. Transverse megafaults and lithostructural associations controlled the three main riftmore » trends. The megashear zones of Pernanbuco (Brazil)-Ngaundere (Africa) apparently behaved like a huge accommodation zone, balancing extensional deformation along the Reconcavo-Jatoba/Sergipe Alagoas-Gabon trends with simultaneous extension along the Araripe-Potiguar trend. The Sergipe Alagoas-Gabon trend and the Potiguar basin represent the site of continued evolution into a marginal open basin following early Neocomian deformation.« less

Modern three-dimensional (3D) seismic data assist not only in delineating reservoir geometry, but also in predicting porosity and lithology variations away from well control. This case study of an oil-producing channel sand in the Taber/Turin area, Alta., Canada illustrates the improvement in reservoir characterization achieved with an integrated approach incorporating both well and seismic information.

P054 An Integrated Project Design for a 3D seismic exploration survey in the Burgos basin Mexico Summary 1 MARCELO BENABENTOS * FRANCISCO ORTIGOSA* CHU-CHING-LI** TIM BROOKS ** The exploration and development plan for the Reynosa Monterrey block in the Burgos basin Mexico included the acquisition of new 3D seismic surveys and the reprocessing of the existent 3D seismic data. In January and February of 2004 Repsol-YPF and WesternGeco conducted an Integrated Project Design study with the following objective: to determine the optimum acquisition and processing parameters for two 3D seismic surveys. Based on this study in the summer and fall

In some oilfield where 3D seismic survey has been done, the deeper structure cannot be discovered for poor deep seismic data. Layer stripping technique applied both seismic and gravity data is a solution, but it cannot get satisfied processing effect because the horizontal variation of formation density is ignored. To improve the gravity survey effect in 3D seismic survey area, this paper presents the formation separation technique. Based on 3D seismic depth data and the transformed density data from 3D seismic velocity data, the upper formation's gravity effects are calculated and removed from Bouguer gravity and then the formation‐separated gravity‐anomaly was obtained, which mainly reflects the deeper geological structure. In block XX, the seismic data of shallow formations are excellent but that of top of basement are poor. The formation‐separated gravity‐anomaly processed under the control of 3D seismic data fits well with the known seismic interpretation and wells. It makes the geological interpretation more reliable

Southern Ordos Basin contains plentiful oil and gas shale resources in the Mesozoic and Upper Paleozoic. It is known that the surface in this region is covered by thick loess layers with severe variations in tomography, thickness and velocity. The adverse surface conditions result in complex statics problems and heavy scattering noise and also cause serious absorption of high-frequency energy. Conventional seismic surveys obtain poor quality seismic data, which could hardly be used to obtain information about gas shale reservoirs. In order to study strong heterogeneous gas shale reservoirs and improve the success rate of horizontal wells, a new 3D seismic survey was acquired in the typical loess plateau area by using the WesternGeco UniQ integrated point-receiver land seismic system. The new survey is designed as full-azimuth, high-density, point-source/point-receiver in order to fully sample the seismic wavefield and avoid the irreversible signal damage caused by conventional field array techniques. By taking advantage of the benefits of UniQ seismic data, targeted data processing sequence is given to resolve the specific complicated statics and noise attenuation problems. Compared with the previously acquired 2D crooked line high-resolution seismic data in the gullies, the result of UniQ seismic data exhibits significant improvement both in the single-to-noise ratio (SNR) and the image quality of target layers. This indicates that the UniQ seismic data will be more feasible to facilitate gas shale characterization.

Summary Geologic sequestration by carbon dioxide injection into saline aquifers and others is one of the promising options to mitigate global climate changes. Elastic parameters are fundamental in estimating rock properties, fluid saturation and pore pressure in carbon dioxide injection and 4D seismic survey efficiently provides spatial and temporal changes of elastic parameters as well as baseline parameters. 4D seismic survey data, collaboratively acquired by Japex in 2003 and 2005 on the area of onshore RITE/METI carbon dioxide injection test site in Japan, were analysed incorporated with repeated time-lapse logging data matched in scale by the current method. In this study, 1) newly built the most probable full-scale baseline and monitor elastic wave velocity model of the 4D seismic survey in the depth domain using time scale adjusted and calibrated 4D AI cube in the time domain and 2) examined the feasibility of nonlinear elastic wavefield inversion of synthetic 4D seismic data assuming regular 3D geometry, though the original 3D was covered by irregular geometry, with common smoothest quasi-linear initial macro-velocity model for baseline and monitor surveys. Results of non-linear elastic wavefield inversion (FWI) with frequency-cascade scheme successfully showed estimates of 4D elastic wave velocity changes at excellent quality and accuracy.

3D seismic fault detection using the Gaussian process regression, a study on synthetic and real 3D seismic data

Interactions of CO2 with formation waters, oil and minerals and CO2 storage at the Weyburn IEA EOR site, Saskatchewan, Canada

Seismic 4D analysis is a model for integrating different disciplines in the oil and gas industry, such as seismic, petrophysics, reservoir engineering, and production engineering. Two 3D seismic surveys were conducted in the studied area with low repeatability of the recordings: the baseline survey in 1994 and the monitoring survey in 2014. A full 4D seismic co-processing of the baseline and monitor surveys was performed for both surveys starting with the field tapes. The 4D seismic co-processing improved poor seismic acquisition repeatability and 4D seismic attributes such as NRMS and predictability showed that. 4D time-trace shift was also performed, using the baseline survey as a reference to measure the time shifts between the baseline survey and the monitor survey at 20-year intervals. Dynamic 4D trace warping was followed by seismic 4D inversion to compare the 4D difference in the seismic inverted data with the difference in seismic amplitude. The seismic inversion helped overcome noise, multiple contamination, and differences in dynamic amplitude range between the baseline and seismic monitoring measurements. Applications of machine learning in the geosciences are growing rapidly in both processing and seismic interpretation. We then examined the relationship between well logs and seismic volumes by predicting a volume of log properties at the well locations of the seismic volume. In this method, we computed a possibly nonlinear operator that can predict well logs based on the properties of the adjacent seismic data. We then tested the Deep Forward Neural Network (DFNN) on six wells to adequately train and validate the machine learning approach using baseline seismic inversion data and monitoring data. The objective of trying such a supervised machine learning approach was to predict the density and porosity of both the baseline seismic data and the monitoring seismic data to verify the accuracy of the 4D seismic inversion.

This study explores the application of data-driven modeling and prediction in reservoir characterization and simulation using seismic and petrophysical data analyses. Different aspects of the application of data-driven modeling methods are studied, which include rock facies classification, seismic attribute analyses, petrophysical properties prediction, seismic facies segmentation, and reservoir dimension reduction. The application of using petrophysical well logs to predict rock facies is explored using different data analytics methods including decision tree, random forest, support vector machine and neural network. Different models are trained from a set of well logs and pre-interpreted rock facies data. Among the compared methods, the random forest method has the best performance in classifying rock facies in the dataset. Seismic attribute values from a 3D seismic survey and petrophysical properties from well logs are collected to explore the relationships between seismic data and well logs. In this study, deep learning neural network models are created to establish the relationships. The results show that a deep learning neural network model with multi-hidden layers is capable to predict porosity values using extracted seismic attribute values. The utilization of a set of seismic attributes improves the model performance in predicting porosity values from seismic data. This study also presents a novel deep learning approach to automatically identify salt bodies directly from seismic images. A wavelet convolutional neural network (Wavelet CNN) model, which combines wavelet transformation analyses with a traditional convolutional neural network (CNN), is developed and demonstrated to increase the accuracy in predicting salt boundaries from seismic images. The Wavelet CNN model outperforms the conventional image recognition techniques, providing higher accuracy, to identify salt bodies from seismic images. Besides, this study evaluates the effect of singular value decomposition (SVD) in dimension reduction of permeability fields during reservoir modeling. Reservoir simulation results show that SVD is valid in the parameterization of the permeability field. The reconstructed permeability fields after SVD processing are good approximations of the original permeability values. This study also evaluates the application of SVD on upscaling for reservoir modeling. Different upscaling schemes are applied on the permeability field, and their performance are evaluated using reservoir simulation.

Strong ocean current influences a marine seismic survey and forces the streamer off-course from the survey line. The sideway drift of the streamer results in that the reflection data are no longer distributed in common midpoint gathers along the survey line but become swath distribution on one side of the ship track. This effect is known as “streamer feathering” which degrades the profile image of the 2D processed seismic data. However, if we have long streamer or closely spaced parallel 2D seismic survey lines, we may turn this deleterious effect into a good opportunity to generate 3D seismic volumes with swath distributed reflection data. We present two case studies in which 2D seismic data were collected offshore eastern Taiwan where the strong Kuroshio Current heavily influenced the ship speed and caused large streamer feathering. The first case is a large-offset 2D seismic profiling data collected using a 6-km long streamer. We processed the swath part of the reflection data in 3D that not only avoids the inappropriate smearing effect in 2D data processing but also generates a 3D seismic volume to help the seismic interpretation. In the second case, we adjusted our 2D survey strategy when realizing that strong Kuroshio Current was causing significant streamer feathering, and collected a set of closely spaced parallel 2D seismic lines. This multi-swath dataset covers a broad area which enables us to generate a 3D seismic volume. Since our datasets are not real 3D seismic data, we have tailored our processing flows to deal with different data configurations and limitations of each dataset. Our results show that not only we have enhanced 2D seismic images of the originally-interested survey lines, but also provide information on 3D geometry of the geological features imaged. The benefits and limitations of utilizing the streamer feathering effect to generate 3D seismic volumes from 2D seismic profile data are reported. Overall, this approach is a considerable way to handle 2D seismic data with large streamer feathering for both avoiding unreliable 2D seismic images and obtaining information on 3D geometry of the geological features imaged.

Five petroleum provinces are known on the eastern Brazilian continental margin: Reconcavo, Sergipe-Alagoas, Espirito Santo, Potiguar, and Campos. Analysis of the petroleum habitat in these areas differentiates five petroleum reservoir systems: Late Jurassic, Neocomian, Aptian, Albian-Santonian, and Late Cretaceous-Tertiary. These systems are associated with five stages in the tectono-sedimentary evolution of the Brazilian coastal basins. 1. In the Late Jurassic petroleum reservoir system the reservoir rock is a fluvial blanket sandstone deposited during the prerift intracratonic stage. The petroleum migrated from Neocomian shales and was trapped by faulted blocks or unconformities on the crest of regional highs. The Agua Grande and Dom Joao fields in the Reconcavo basin, as well as the Caioba field in the offshore part of the Sergipe basin, are typical examples of this system. 2. The Neocomian petroleum reservoir system is associated with the deltaic-lacustrine depositional suite of the rift-valley stage. The oil is trapped in arched structures within regional depressions which have subsided along major fault trends. The Miranga and Aracas fields in the Reconcavo basin are the best examples. Minor stratigraphic fields such as Candeias in the Reconcavo basin also belong to this system. 3. The Aptian petroleum reservoir system is associated with the evaporitic stage. The petroleum was generated in euxinic shales and accumulated in conglomerates and sandstones. The traps are broad and gentle paleogeomorphic highs or structures contemporaneous with the evaporitic section. The Carmopolis and Riachuelo fields in the Sergipe-Alagoas basin are typical examples. 4. The Albian-Santonian petroleum reservoir system is associated with sandstones and carbonate rocks of the shallow-marine proto-oceanic stage. The oil accumulations are sealed in faulted blocks and paleogeomorphic traps. The Garoupa and Namorado fields in the Campos basin are examples. 5. The Late Cretaceous-Tertiary petroleum reservoir system is in turbidites of the open-oceanic stage. The oil fields are stratigraphic-trap type and the source rocks are continental-slope shales of the Calumbi Member and Urucutuca Formation. The Guaricema field in the offshore part of Sergipe basin and the Fazenda Cedro field in Espirito Santo basin are good examples of this system.