Unlocking 4D seismic technology to maximize recovery from the pre-salt Rotliegend gas fields of the Southern North Sea

2017 ◽  
Vol 8 (1) ◽  
pp. 465-471 ◽  
Author(s):  
Jonathan Brain ◽  
Thomas Lassaigne ◽  
Mathieu Darnet ◽  
Peter Van Loevezijn
Keyword(s):  
Travel Time ◽  
North Sea ◽  
Field Tests ◽  
Time Lapse ◽  
Gas Production ◽  
Southern North Sea ◽  
Before And After ◽  
Seismic Acquisition ◽  
Uncertain Time ◽  
4D Seismic

AbstractThe Southern North Sea is a mature gas basin, producing mainly from faulted Permian Rotliegend sandstones. Identifying infill well opportunities in un-depleted or partially depleted blocks in these fields is challenging, particularly if the sealing capacity of faults within a field is uncertain. Time-lapse (4D) seismic monitoring provides an opportunity to identify depleted reservoir blocks by measuring differences in travel time across the producing interval between seismic surveys acquired before and after gas production. 4D seismic field tests were initially performed by Nederlandse Aardolie Maatschappij (NAM) and Shell in 2001. However, the observed travel-time differences proved to be smaller than predicted and any possible signals were too noisy to confidently detect depletion. Since then, advances in seismic acquisition and processing technology have improved the accuracy of 4D measurements and enabled the effective mapping of 4D related gas depletion signals. 4D seismic has now been deployed over a number of fields in the Southern North Sea, and a portfolio of infill opportunities has been identified. In 2015, the first 4D targeted infill well was successfully drilled into a block with limited depletion. This technology represents a breakthrough for operators seeking to maximize hydrocarbon recovery and extend field life in the Rotliegend play of the Southern North Sea.

Time-lapse seismic analysis of overburden water injection at the Ekofisk field, southern North Sea

Geophysics ◽  
2020 ◽  
Vol 85 (1) ◽  
pp. B9-B21
Author(s):  
Filipe Borges ◽  
Martin Landrø ◽  
Kenneth Duffaut
Keyword(s):  
North Sea ◽  
Seismic Data ◽  
Seismic Event ◽  
Seismic Analysis ◽  
Water Injection ◽  
Time Lapse ◽  
Reservoir Compaction ◽  
Southern North Sea ◽  
Stress Changes ◽  
Before And After

On 7 May 2001, a seismic event occurred in the southern North Sea in the vicinity of the Ekofisk platform area. Analysis of seismological recordings of this event indicated that the epicenter is likely within the northern part of the field and its hypocenter lies in the shallow sedimentary layer. Further investigation in this same area revealed a small seabed uplift and identified an unintentional water injection in the overburden. The injection presumably caused the seabed uplift in addition to stress changes in the overburden. To better understand the consequences of this water injection, we analyze marine seismic data acquired before and after the seismological event. The 4D analysis reveals a clear traveltime shift close to the injection well, as well as a weak amplitude difference. We find that these measured time shifts correspond reasonably well with modeled time shifts based on a simple geomechanical model. The modeling also correlates well with the observed bathymetry changes at the seabed and with global positioning system measurements at the platforms. Although no explicit amplitude sign of the seismic event could be detected in the seismic data, the modeled stress changes, combined with the effect of decades of production-induced reservoir compaction, suggest a source mechanism for the far-field seismological recordings of the May 7th event.

The Esmond, Forbes and Gordon Fields, Blocks 43/8a, 43/13a, 43/15a, 43/20a, UK North Sea

1991 ◽  
Vol 14 (1) ◽  
pp. 425-432 ◽  
Author(s):  
F. J. Ketter
Keyword(s):  
North Sea ◽  
Arid Environment ◽  
Gas Production ◽  
Alluvial Fan ◽  
Southern North Sea ◽  
Offshore Installations ◽  
Porosity And Permeability ◽  
Sandstone Formation ◽  
The Uk

AbstractThe three separate fields, Esmond, Forbes and Gordon form the Esmond Gas Complex in Quadrant 43 in the UK Southern North Sea. The Bunter Sandstone Formation is the reservoir in each of the separate, seismically defined, simple, anticlinal structures. The Bunter Sandstone correlates well across the three structures and is composed of a 400-500 ft thick interval containing individual channel sandstones deposited in an arid environment on an alluvial fan. Porosity and permeability are controlled by original texture and by subsequent diagenesis. Reservoir communication within the Bunter reservoir is good though locally tortuous.First gas production started in July 1985. Four offshore installations have allowed gas to be produced at full contract (plateau) rates of 200 MMSCFD without major interruption. Ultimate sales gas reserves are approximately 530 BCF.

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

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.

4D seismic interpretation in a Nigerian deepwater field

2015 ◽  
Vol 3 (2) ◽  
pp. SP11-SP19 ◽  
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.

Multiwell 3D distributed acoustic sensing vertical seismic profile imaging with engineered fibers: CO2CRC Otway Project case study

Geophysics ◽  
2021 ◽  
Vol 86 (6) ◽  
pp. D241-D248 ◽  
Author(s):  
Alexey Yurikov ◽  
Konstantin Tertyshnikov ◽  
Roman Isaenkov ◽  
Evgenii Sidenko ◽  
Sinem Yavuz ◽  
...  
Keyword(s):  
Low Cost ◽  
Optimal Solution ◽  
Time Lapse ◽  
Local Area ◽  
Seismic Profile ◽  
Enhanced Backscattering ◽  
Seismic Acquisition ◽  
Vsp Data ◽  
4D Seismic

The 4D surface seismic monitoring is a standard method for reservoir surveillance during the production of hydrocarbons or CO2 injection. However, land 4D seismic acquisition campaigns are often associated with high cost and disruptions to industrial operation or agricultural activities in the area of acquisition. An alternative technique for time-lapse monitoring of the subsurface is the 3D vertical seismic profiling (VSP), which becomes particularly attractive when used with distributed acoustic fiber-optic sensors (DAS) installed in wells. The advantages of 3D DAS VSP include its relatively low cost, minimal footprint on the local area during acquisition, and superior spatial resolution compared to the resolution of geophones. The potential of this technique is explored by processing and analyzing multiwell 3D DAS VSP data acquired at the CO2CRC Otway Project site in Victoria, Australia. The DAS data were recorded using an engineered fiber with enhanced backscattering cemented behind the casing of five wells. The data from each well are processed individually using the same processing flow and then migrated using a 3D migration code tailored to DAS data. Having DAS along the full extent of multiple wells ensures adequate seismic coverage of the area of CO2 injection. The migrated images provide detailed information about the subsurface up to 700 m away from a well and up to 2 km depth. The images are consistent with previously acquired geophone VSP and surface seismic data. The quality of the 3D DAS VSP imaging is comparable or superior to the quality of conventional imaging using geophone data. Therefore, 3D DAS VSP is a demonstrably optimal solution for reservoir monitoring.

scholarly journals Review Article: Storm Britta in 2006: offshore damage and large waves in the North Sea

2015 ◽  
Vol 3 (9) ◽  
pp. 5493-5510 ◽  
Author(s):  
A. J. Kettle
Keyword(s):  
North Sea ◽  
Structural Damage ◽  
Impact Damage ◽  
Gas Production ◽  
Wave Impact ◽  
Southern North Sea ◽  
The North ◽  
The North Sea ◽  
Southern Norway ◽  
Insight Into

Abstract. The Britta storm of 31 October–1 November 2006 was a severe autumn storm that was particularly damaging for shipping and coastal flooding from storm surge effects along the southern North Sea. The main low pressure of the storm propagated from Scotland to southern Norway on 31 October, leading to a system of strong north winds that moved southward across North Sea over an 18 h period. A progression of ship and offshore platform difficulties were registered from the northern part of the North Sea from late on 31 October and culminated near the coasts of Germany and the Netherlands early on 1 November with a series of ship emergencies linked with large waves. In two separate incidents, unusually high waves broke the bridge windows of ships and necessitated emergency rescues, and a Dutch motor lifeboat experienced a triple capsize. In the southern North Sea, several gas production and research platforms experienced wave impact damage. The FINO1 offshore research platform, near the Dutch–German border, experienced some of the worst storm conditions with some structural damage. Its meteorological and oceanographic instrumentation give a unique profile of the severe met-ocean conditions during the storm. Two Waverider buoys at FINO1 and the nearby Dutch coastal site of Schiermonnikoog recorded groups of large waves at different times during the storm. These reports give insight into a little-reported rogue wave phenomenon that sometimes accompanies the "ground sea" conditions of the worst storms of the area.

4D PLANNING AND EXECUTION STRATEGIES FOR AUSTRALIAN RESERVOIR MONITORING PROJECTS

2006 ◽  
Vol 46 (1) ◽  
pp. 67
Author(s):  
A.S. Long ◽  
M. Widmaier ◽  
M.A. Schonewille
Keyword(s):  
Time Lapse ◽  
Seismic Signal ◽  
Reservoir Simulations ◽  
Reservoir Models ◽  
Processing Strategies ◽  
Reservoir Monitoring ◽  
Seismic Acquisition ◽  
4D Seismic ◽  
Interactive Visualisation ◽  
Time Acquisition

Time-lapse (4D) reservoir monitoring is in its infancy in Australia, but is on the verge of becoming a mainstream pursuit. We describe the 4D seismic acquisition and processing strategies that have been developed and proven elsewhere in the world, and customise those strategies for Australasian applications.We demonstrate how a multidisciplinary pursuit of real-time acquisition and processing Quality Control (QC) is an integral component of any 4D project. The acquisition and processing geophysicists must be able to understand all the factors contributing to the 4D seismic signal as they happen. Such an understanding can only arise through rigorous project QC and management using interactive visualisation technology. In turn, the production geologists and reservoir engineers will then receive 4D seismic products that can be robustly and confidently used for the construction of accurate reservoir models and the pursuit of reliable reservoir simulations and forecasts.

scholarly journals Effects of an area closed to fisheries on the composition of the benthic fauna in the southern North Sea

2007 ◽  
Vol 64 (5) ◽  
pp. 899-908 ◽  
Author(s):  
Gerard C. A. Duineveld ◽  
Magda J. N. Bergman ◽  
Marc S. S. Lavaleye
Keyword(s):  
North Sea ◽  
Benthic Fauna ◽  
Gas Production ◽  
Adult Survival ◽  
Exclusion Zone ◽  
Arctica Islandica ◽  
Southern North Sea ◽  
Production Platform ◽  
Amphiura Filiformis ◽  
Living Species

Abstract Duineveld, G. C. A., Bergman, M. J. N., and Lavaleye, M. S. S. 2007. Effects of an area closed to fisheries on the composition of the benthic fauna in the southern North Sea. – ICES Journal of Marine Science, 64: 899–908. The effects of fishery exclusion on the composition of the macrofauna were determined by comparing the fishery-exclusion zone around a gas production platform in the southern North Sea (Frisian Front) with nearby regularly fished areas. A Triple-D dredge was used, in addition to a standard box corer, to collect the relatively rare and larger species. Multivariate analysis showed greater species richness, evenness, and abundance of mud shrimps (Callianassa subterranea, Upogebia deltaura) and fragile bivalves (Arctica islandica, Thracia convexa, Dosinia lupinus, Abra nitida, Cultellus pellucidus) in the Triple-D samples from the exclusion area. Although box cores did confirm the higher abundance of both mud shrimps in the exclusion zone and demonstrated greater densities of the brittlestar Amphiura filiformis, they did not clearly reveal the distinctness of the exclusion zone. This is attributed to the large proportion of small, short-living species in the samples and the relative scarcity of vulnerable larger species common to all the box core samples. There was no evidence of greater recruitment in the relative small exclusion zone, despite its positive effect on adult survival. The observation that the fishery affects deep-living mud shrimps may point to consequences for the functioning of the benthic ecosystem other than simple loss of biodiversity.

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