Qualitative time-lapse seismic interpretation of Norne Field to assess challenges of 4D seismic attributes

Time-lapse (4D) seismic analysis plays a vital role in reservoir management and reservoir simulation model updates. However, 4D seismic data are subject to interference and tuning effects. Being able to resolve and monitor thin reservoirs of different quality can aid in optimizing infill drilling or locating bypassed hydrocarbons. Using 4D seismic data from the Maui field in the offshore Taranaki basin of New Zealand, we generate typical seismic attributes sensitive to reservoir thickness and rock properties. We find that spectral instantaneous attributes extracted from time-lapse seismic data illuminate more detailed reservoir features compared to those same attributes computed on broadband seismic data. We develop an unsupervised machine learning workflow that enables us to combine eight spectral instantaneous seismic attributes into single classification volumes for the baseline and monitor surveys using self-organizing maps (SOM). Changes in the SOM natural clusters between the baseline and monitor surveys suggest production-related changes that are caused primarily by water replacing gas as the reservoir is being swept under a strong water drive. The classification volumes also facilitate monitoring water saturation changes within thin reservoirs (ranging from very good to poor quality) as well as illuminating thin baffles. Thus, these SOM classification volumes show internal reservoir heterogeneity that can be incorporated into reservoir simulation models. Using meaningful SOM clusters, geobodies are generated for the baseline and monitor SOM classifications. The recoverable gas reserves for those geobodies are then computed and compared to production data. The SOM classifications of the Maui 4D seismic data seems to be sensitive to water saturation change and subtle pressure depletions due to gas production under a strong water drive.

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Semiquantitative 4D seismic interpretation integrated with reservoir simulation: Application to the Norne field

Interpretation ◽

10.1190/int-2017-0122.1 ◽

2018 ◽

Vol 6 (3) ◽

pp. T601-T611

Author(s):

Juliana Maia Carvalho dos Santos ◽

Alessandra Davolio ◽

Denis Jose Schiozer ◽

Colin MacBeth

Keyword(s):

Simulation Model ◽

Reservoir Simulation ◽

History Matching ◽

Time Lapse ◽

Seismic Signal ◽

Seismic Interpretation ◽

Production Forecast ◽

Seismic Acquisition ◽

Reservoir Simulation Model ◽

4D Seismic

Time-lapse (or 4D) seismic attributes are extensively used as inputs to history matching workflows. However, this integration can potentially bring problems if performed incorrectly. Some of the uncertainties regarding seismic acquisition, processing, and interpretation can be inadvertently incorporated into the reservoir simulation model yielding an erroneous production forecast. Very often, the information provided by 4D seismic can be noisy or ambiguous. For this reason, it is necessary to estimate the level of confidence on the data prior to its transfer to the simulation model process. The methodology presented in this paper aims to diagnose which information from 4D seismic that we are confident enough to include in the model. Two passes of seismic interpretation are proposed: the first, intended to understand the character and quality of the seismic data and, the second, to compare the simulation-to-seismic synthetic response with the observed seismic signal. The methodology is applied to the Norne field benchmark case in which we find several examples of inconsistencies between the synthetic and real responses and we evaluate whether these are caused by a simulation model inaccuracy or by uncertainties in the actual observed seismic. After a careful qualitative and semiquantitative analysis, the confidence level of the interpretation is determined. Simulation model updates can be suggested according to the outcome from this analysis. The main contribution of this work is to introduce a diagnostic step that classifies the seismic interpretation reliability considering the uncertainties inherent in these data. The results indicate that a medium to high interpretation confidence can be achieved even for poorly repeated data.

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4D seismic interpretation in a Nigerian deepwater field

Interpretation ◽

10.1190/int-2014-0198.1 ◽

2015 ◽

Vol 3 (2) ◽

pp. SP11-SP19 ◽

Cited By ~ 2

Author(s):

Oghogho Effiom ◽

Robert Maskall ◽

Edwin Quadt ◽

Kazeem A. Lawal ◽

Raphael Afolabi ◽

...

Keyword(s):

Management Practices ◽

Time Lapse ◽

Seismic Interpretation ◽

Lessons Learned ◽

Water Flooding ◽

Reservoir Architecture ◽

Depositional Settings ◽

Seismic Acquisition ◽

Net To Gross ◽

4D Seismic

To improve the management of a Nigerian deep water field, two vintages of 4D data have been acquired since field start up in 2005. The first Nigerian 4D seismic (monitor-I) in water depths greater than 1000 m was taken in this field in 2008, and the second monitor (monitor-II) was acquired in 2012. Compared to monitor-I, better geometric repeatability was achieved in monitor-II as the lessons learned from monitor-I were incorporated to achieve better results. The final normalized root mean square of monitor-II fast-track volume was 12% compared to 25% for monitor-I. The improved quality is attributed to improvements in the acquisition methodology and prediction of the effects of currents. Seismic interpretation of the field revealed two distinct turbidite depositional settings: (1) An unconfined amalgamated lobe system with low relief, high net-to-gross reservoir sands that exhibit fairly homogeneous water flooding patterns on 4D and (2) an erosional canyon setting, filled with meander belts having a more complex 3D connectivity within and between the channels resulting in a challenging 4D interpretation. The time lapse data were instrumental for better understanding the reservoir architecture, enabling improved wells and reservoir management practices, the identification of infill opportunities, and more mature subsurface models. We evaluated the seismic acquisition and the 4D interpretation of the deepwater 4D seismic data, highlighting the merits of a multidisciplinary collaborative understanding to time-lapse seismic. At present, the value of information of the 4D monitor-II is conservatively estimated at 101 million United States dollars, equivalent to the cost of a well in this deepwater operating environment.

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Step-wise uncertainty reduction in time-lapse seismic interpretation using multi-attribute analysis

Petroleum Geoscience ◽

10.1144/petgeo2020-087 ◽

2021 ◽

pp. petgeo2020-087

Author(s):

Masoud Maleki ◽

Shahram Danaei ◽

Felipe Bruno Mesquita da Silva ◽

Alessandra Davolio ◽

Denis José Schiozer

Keyword(s):

Data Analysis ◽

Interdisciplinary Approach ◽

Time Lapse ◽

Seismic Interpretation ◽

Complex Nature ◽

Engineering Data ◽

Attribute Analysis ◽

Production Regime ◽

Reservoir Simulation Model ◽

4D Seismic

Recently, time-lapse seismic (4D seismic) has been steadily used to demonstrate the relation between field depletion and 4D seismic response, subsequently to have more efficient field management. A key component of the reservoir monitoring is the knowledge of fluid movement and pressure variations. This information is vital to assist infill drillings and a trustworthy source to update reservoir models, consequently improving model-based reservoir management and decision-making process. However, in practice the 4D seismic interpretation of reservoirs with multipart production regime possesses ambiguities through different levels of uncertainty. Complex nature of some 4D seismic signals emphasizes the roles of competing effects, geology, rock and fluid interactions. Hence, a reliable 4D interpretation requires an interdisciplinary approach entailing data analysis and insights from geophysics, engineering and geology. In this research, a step-wise workflow was introduced to reduce uncertainties in the 4D seismic interpretation and provide diagnoses to perform better reservoir surveillance. In parallel, the workflow expresses the use of engineering data analysis to conduct a consistent interpretation and encompasses the 3D and 4D seismic attributes with engineering data analysis. This study is implemented in a Brazilian heavy-oil offshore field where production started in 2013. The field experienced intense production activity up to 2016, making the deep-water field an ideal candidate to explore the challenges in interpreting complex 4D signals. Beyond these challenges, significant understanding of reservoir behavior is obtained and suggestions are made to improve the reservoir simulation model, which could support reservoir engineers with data assimilation applications.

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Time-Lapse Seismic for Reservoir Management: Case Studies From Offshore Niger Delta, Nigeria

SPE Reservoir Evaluation & Engineering ◽

10.2118/170808-pa ◽

2016 ◽

Vol 19 (03) ◽

pp. 391-402

Author(s):

Sunday Amoyedo ◽

Emmanuel Ekut ◽

Rasaki Salami ◽

Liliana Goncalves-Ferreira ◽

Pascal Desegaulx

Keyword(s):

Case Studies ◽

Niger Delta ◽

Reservoir Management ◽

Time Lapse ◽

Seismic Survey ◽

Elastic Model ◽

Field Development ◽

4D Seismic ◽

The Impact

Summary This paper presents case studies focused on the interpretation and integration of seismic reservoir monitoring from several fields in conventional offshore and deepwater Niger Delta. The fields are characterized by different geological settings and development-maturity stages. We show different applications varying from qualitative to quantitative use of time-lapse (4D) seismic information. In the first case study, which is in shallow water, the field has specific reservoir-development challenges, simple geology, and is in phased development. On this field, 4D seismic, which was acquired several years ago, is characterized by poor seismic repeatability. Nevertheless, we show that because of improvements from seismic reprocessing, 4D seismic makes qualitative contributions to the ongoing field development. In the second case study, the field is characterized by complex geological settings. The 4D seismic is affected by overburden with strong lateral variations in velocity and steeply dipping structure (up to 40°). Prestack-depth-imaging (PSDM) 4D seismic is used in a more-qualitative manner to monitor gas injection, validate the geologic/reservoir models, optimize infill injector placement, and consequently, enhance field-development economics. The third case study presents a deep offshore field characterized by a complex depositional system for some reservoirs. In this example, good 4D-seismic repeatability (sum of source- and receiver-placement differences between surveys, dS+dR) is achieved, leading to an increased quantitative use of 4D monitoring for the assessment of sand/sand communication, mapping of oil/water (OWC) front, pressure evolution, and dynamic calibration of petro-elastic model (PEM), and also as a seismic-based production-logging tool. In addition, 4D seismic is used to update seismic interpretation, provide a better understanding of internal architecture of the reservoirs units, and, thereby, yield a more-robust reservoir model. The 4D seismic in this field is a key tool for field-development optimization and reservoir management. The last case study illustrates the need for seismic-feasibility studies to detect 4D responses related to production. In addition to assessing the impact of the field environment on the 4D- seismic signal, these studies also help in choosing the optimum seismic-survey type, design, and acquisition parameters. These studies would possibly lead to the adoption of new technologies such as broad-band streamer or nodes acquisition in the near future.

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Time-Lapse Seismic Monitoring of Onshore Reservoirs in Niger Delta, Field ‘K’ as a Case Study

Nigerian Journal of Environmental Sciences and Technology - March 2018 ◽

10.36263/nijest.2017.01.0010 ◽

2017 ◽

Vol 1 (1) ◽

pp. 23-27 ◽

Cited By ~ 1

Author(s):

A. Ogbamikhumi ◽

T. Tralagba ◽

E. E. Osagiede

Keyword(s):

Seismic Data ◽

Acoustic Impedance ◽

Niger Delta ◽

Rock Physics ◽

Time Lapse ◽

Seismic Survey ◽

Impedance Change ◽

Data Set ◽

Reservoir Fluid ◽

4D Seismic

Field ‘K’ is a mature field in the coastal swamp onshore Niger delta, which has been producing since 1960. As a huge producing field with some potential for further sustainable production, field monitoring is therefore important in the identification of areas of unproduced hydrocarbon. This can be achieved by comparing production data with the corresponding changes in acoustic impedance observed in the maps generated from base survey (initial 3D seismic) and monitor seismic survey (4D seismic) across the field. This will enable the 4D seismic data set to be used for mapping reservoir details such as advancing water front and un-swept zones. The availability of good quality onshore time-lapse seismic data for Field ‘K’ acquired in 1987 and 2002 provided the opportunity to evaluate the effect of changes in reservoir fluid saturations on time-lapse amplitudes. Rock physics modelling and fluid substitution studies on well logs were carried out, and acoustic impedance change in the reservoir was estimated to be in the range of 0.25% to about 8%. Changes in reservoir fluid saturations were confirmed with time-lapse amplitudes within the crest area of the reservoir structure where reservoir porosity is 0.25%. In this paper, we demonstrated the use of repeat Seismic to delineate swept zones and areas hit with water override in a producing onshore reservoir.

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3D DAS-VSP Illumination Modeling for CO2 Plume Migration Monitoring in Offshore Sarawak, Malaysia

10.2118/207842-ms ◽

2021 ◽

Author(s):

Pankaj Kumar Tiwari ◽

Zoann Low ◽

Parimal Arjun Patil ◽

Debasis Priyadarshan Das ◽

Prasanna Chidambaram ◽

...

Keyword(s):

Dynamic Simulation ◽

Seismic Velocity ◽

Time Lapse ◽

Carbonate Reservoir ◽

Fiber Optic Sensor ◽

Co2 Injection ◽

Storage Site ◽

Plume Migration ◽

Co2 Plume ◽

4D Seismic

Abstract Monitoring of CO2 plume migration in a depleted carbonate reservoir is challenging and demand comprehensive and trailblazing monitoring technologies. 4D time-lapse seismic exhibits the migration of CO2 plume within geological storage but in the area affected by gas chimney due to poor signal-to-noise ratio (SNR), uncertainty in identifying and interpretation of CO2 plume gets exaggerated. High resolution 3D vertical seismic profile (VSP) survey using distributed acoustic sensor (DAS) technology fulfil the objective of obtaining the detailed subsurface image which include CO2 plume migration, reservoir architecture, sub-seismic faults and fracture networks as well as the caprock. Integration of quantitative geophysics and dynamic simulation with illumination modelling dignify the capabilities of 3D DAS-VSP for CO2 plume migration monitoring. The storage site has been studied in detailed and an integrated coupled dynamic simulation were performed and results were integrated with seismic forward modeling to demonstrate the CO2 plume migration with in reservoir and its impact on seismic amplitude. 3D VSP illumination modelling was carried out by integrating reservoir and overburden interpretations, acoustic logs and seismic velocity to illustrate the subsurface coverage area at top of reservoir. Several acquisition survey geometries were simulated based on different source carpet size for effective surface source contribution for subsurface illumination and results were analyzed to design the 3D VSP survey for early CO2 plume migration monitoring. The illumination simulation was integrated with dynamic simulation for fullfield CO2 plume migration monitoring with 3D DAS-VSP by incorporating Pseudo wells illumination analysis. Results of integrated coupled dynamic simulation and 4D seismic feasibility were analyzed for selection of best well location to deploy the multi fiber optic sensor system (M-FOSS) technology. Amplitude response of synthetic AVO (amplitude vs offsets) gathers at the top of carbonate reservoir were analyzed for near, mid and far angle stacks with respect to pre-production as well as pre-injection reservoir conditions. Observed promising results of distinguishable 25-30% of CO2 saturation in depleted reservoir from 4D time-lapse seismic envisage the application of 3D DAS-VSP acquisition. The source patch analysis of 3D VSP illumination modelling results indicate that a source carpet of 6km×6km would be cos-effectively sufficient to produce a maximum of approximately 2km in diameter subsurface illumination at the top of the reservoir. The Pseudo wells illumination analysis results show that current planned injection wells would probably able to monitor early CO2 injection but for the fullfield monitoring additional monitoring wells or a hybrid survey of VSP and surface seismic would be required. The integrated modeling approach ensures that 4D Seismic in subsurface CO2 plume monitoring is robust. Monitoring pressure build-ups from 3D DAS-VSP will reduce the associated risks.

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