bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved reservoir modelling with time-lapse seismic data in a Gulf of Mexico gas condensate reservoir
Authors: Waggoner J. R. , Cominelli A. , Seymour R. H. , Stradiotti A. 
Published: October 2008

Time-lapse 3D – or 4D – seismic data have been tried in several fields to date, with some good case studies published to demonstrate the utility of the 4D seismic information. While another 4D case study would be useful, this paper describes two novel aspects of a recent application in the Gulf of Mexico. First, the target reservoir contains a gas condensate fluid under primary depletion, so pressure, rather than saturation, changes create the observed 4D acoustic response. Further, the primary impact of the pressure change is to the fluid composition as the initially dense gas phase lightens as condensate drops out below the dew point. The result was a 2.8% change in acoustic impedance predicted in the feasibility study.
Second, the 4D seismic result was used to constrain an optimized history-matching procedure, along with the production data. After describing the method used, the paper will discuss the changes to the reservoir model that resulted. While the results should not be considered unique, they do give some insight intothe structure of the reservoir that should be considered for optimal reservoir management.
Successful application of time-lapse seismic data in Shell Expro's Gannet Fields, Central North Sea, UKCS
Authors: Kloosterman H. J. , Kelly R. S. , Stammeijer J. , Hartung M. , van Waarde J. , Chajecki C. 
Published: October 2008

The Central North Sea contains a large variety of oil and gas fields at different stages of maturity within the life cycle of an asset, at varying depths, in varied geology and at widely differing pressure and temperature conditions. Over the last three years Shell UK Exploration and Production (Shell Expro) has acquired new 3D surveys over many of these fields which, following careful attention to detail in acquisition and processing, have been quantitatively compared to pre-production surveys. Differences between these time-lapse seismic datasets have then been interpreted in terms of changes in reservoir fluid movement and changed pressure/temperature conditions. These interpretations have proven useful for reservoir management by identifying swept versus unswept zones, sealing versus non-sealing faults, efficiency of drive mechanisms and connected volumes to specific wells
Four case studies from the Gannet Development illustrate how these observations have impacted reservoir management and show how application of this relatively new, yet rapidly maturing technology has had a positive impact on the remaining value of these fields. Importantly, the detectability of changes in the reservoir has been seen to be greater than predicted prior to data acquisition. Indeed, 4D seismic data have become an established part of the long-term plans for all of Shell Expro's subsurface assets. With these successes have come fresh challenges and future efforts will focus on reducing costs in proven 4D technology whilst pushing to introduce new techniques for data gathering and for interpretation of large volumes of new information.
4D integrated technologies for deep-water turbidite reservoirs:from petrophysics to fluid flow simulation
Authors: Santos Rogerio A. , Sobrinho Alcides A. , Pinto Antonio C. C. , Dillon Lucia D. , Ritter Gerson L. S. , Silva Eduardo F. F. , Pimentel Marcia B. , Backheuser Yeda , Rosalba Jose F. , Guimarães Marcos A. G. , Prais Fabio , Abreu Carlos E. B. S. , Castellani Ricardo T. , Burns Scott 
Published: October 2008

Petrobras has been developing its 4D seismic technological programme since 1998, focused on the Brazilian deep-water fields in the Campos Basin, and considering the technical, operational and economic challenges involved in the development plan and reservoir management in this environment.
The first step was to align the objectives of the project with the company goals for the following 15 years, in terms of earnings growth, production growth and reserves replacement. This information guided how the 4D reservoir management should be employed: as hedging technology to ensure that production targets would be achieved in several key fields at once, or as a direct technology investment to increase the production of individual, independent fields. The mission of reservoir management for each field involved was understood and new deep-water seismic technologies were developed to face the global operational and economic targets.
3D seismic reservoir monitoring, or 4D seismic study, was defined as an ‘integration of multidisciplinary technologies that includes the time-lapse monitoring of the drainage efficiency, using cores, well logs, seismic data, production history and pressure management’.
Water injection is the preferable recovery method for the deep-water reservoirs in Brazil. Therefore, seismic monitoring should be able to distinguish contrasts of both fluids – injected water and remaining oil – that normally produce small seismic impedance values. This characteristic has brought the first technical challenge: the use of the 3D P-wave surface legacy data from the 1980s and 1990s, when the major fields started production, as 4D base-volumes to be correlated with future recommended 3D seismic data (surface or ocean bottom systems) as 4D monitor-volumes.
In addition to all developed seismic technologies for data processing, a general 4D work flow was designed and the concept of the integrated reservoir model was adapted to relate all such technologies to the reservoir engineering needs and to the field economics, generating reliable 4D images for each reservoir study.
This paper summarizes the multidisciplinary technical integration, including geological and seismic modelling, petrophysical simulations, seismic processing and interpretation, and reservoir simulation. A 4D methodology was implemented to integrate all such technical development and economic analysis, identifying where, when and how seismic monitoring can contribute to the reservoir management. This methodology has been applied to the Campos Basin deep-water reservoir, Rio de Janeiro State, Brazil.
BP's increasing systematic use of time-lapse seismic technology
Authors: Marsh J. Marcus , Whitcombe David N. , Raikes Sue A. , Parr Ronnie S. , Nash Tim 
Published: October 2008

Following experimental success in the application of 4D technology in the Magnus and Foinaven fields and the delivery of commercial value from the application of time-lapse seismic (4D) studies in the Forties and West of Shetland fields and in the Pompano Field in the Gulf of Mexico, BP has embarked on the systematic use of 4D monitoring in its NW Europe operations to enhance value in the light of an increasing production challenge. Within the past two years, 12 datasets have been acquired over 19 fields of varied reservoir age, type and property. Although specific questions differ from field to field, in all cases a major objective is to influence the location and design of infill wells.
Useful time-lapse information has been gained from post-stack matched ‘legacy’ surveys of varying data quality. However, it is clear that more value is added by custom-designed 4D surveys: seismic quality and repeatability are critical to the successful delivery of reliable time-lapse seismic monitoring. Integration of seismic data with dynamic data is still relatively ‘low-tech’ and further benefits will be gained by improvement in this area.
The paradigm is shifting to a position where 4D monitoring in the North Sea is the rule rather than the exception. Now that there is clear evidence of added value in the most obvious target reservoirs, surveys are being carried out in areas that are technically more challenging – and the early results indicate that these too will be of real commercial benefit. Use of 4D data is also being progressed in other regions, including the Gulf of Mexico, and application in other basins around the world is being planned. On the technology development front, BP is seeking continuous improvements in acquisition and processing, both in quality and turnaround time, and richer integration with production and conventional well-based surveillance data. The ultimate goal is for effective reservoir management based on a range of surveillance methods.
Seismic characteristics of fluid leakage from an underfilled and overpressured Jurassic fault trap in the Norwegian North Sea
Authors: Teige Gunn M. G. , Hermanrud Christian 
Published: October 2008

Pre-drill estimates of hydrocarbon column heights are often uncertain, particularly where filling to structural spill point is questioned. Identification of locations where vertical leakage is concentrated can allow more reliable hydrocarbon column height predictions. The locations of vertical leakage were sought on seismic data over an underfilled and overpressured trap (35/10-2) in the Norwegian North Sea. It was hoped that one single location or one single narrow leakage zone coinciding with the gas–water contact would be found. If such a location or zone existed, it was expected to be in or above a fault plane, as leakage in the 35/10-area is thought to mainly result from shear failure along faults.
The investigation found a zone with pronounced dimming above a triple fault intersection bounding the 35/10-2 structure. This zone stretches further downdip and is positioned above a fault plane. The shallowest part of this zone intersects the top of the reservoir at the depth of the proven gas–water contact. These observations suggest that a discrete leakage zone, of which the shallowest part controls the column height of the structure, has been identified and that the column height is limited by leakage resulting from shear failure. The occurrence of similar seismic features over undrilled structures can lead to safer assessments of hydrocarbon column heights, especially if the observations are consistent with the general knowledge of stress state and leakage processes in the area.
Hydrocarbon leakage processes and trap retention capacities offshore Norway
Authors: Nordgård Bolås Hege M. , Hermanrud Christian 
Published: October 2008

Associations between high overpressures and sparse hydrocarbon occurrence are commonly ascribed to hydrocarbon leakage through pressure-induced fractures in the cap rock. However, several hydrocarbon traps in the North Viking Graben area in the North Sea still contain abundant commercial volumes of hydrocarbons at very high pore pressures. By contrast, a majority of the overpressured structures at the Halten Terrace further to the north have leaked hydrocarbons, even at considerably lower overpressures.
A selection of wells in the North Viking Graben and the Halten Terrace areas was investigated to find possible explanations for these observations. Distinct regional differences emerged, as the emptied reservoirs at the Halten Terrace generally have higher retention capacities than the overpressured discoveries in the North Viking Graben area. Thus, there appears to be a lack of any clear relationship between structures emptied of hydrocarbons and low retention capacities, which could be expected if pressure-induced fracturing of the cap rock was the main process of the hydrocarbon leakage.
The regional differences in retention capacities were mainly attributed to different leakage processes in the two basins. Stress history variations are suggested to be the main controlling factor of these leakage processes.
The influence of intraplate structural accommodation zones on delineating petroleum provinces of the Sub-Andean foreland basins
Authors: Jacques John M. 
Published: October 2008

The Sub-Andean foreland region is summarized in a series of palaeogeographical maps. Various time-slices show important basin-forming processes and the extent and evolution of principal depositional elements. Based on spatial and temporal changes in palaeodepositional setting, the Sub-Andean region can be subdivided longitudinally into a number of tectonostratigraphic domains. The differential amount of subsidence between two adjacent tectonostratigraphic provinces or sub-provinces has been taken up across, complex, broad, transverse, transcontinental accommodation zones, which probably represent the multiphase reactivation of pre-existing fault systems in the underlying basement. Two predominant sets of basement lineaments are recognized: ENE–WSW and NW–SE. Both sets of lineaments occur as major structural anisotropies throughout the basement rocks of South America, providing zones of weakness, which were repeatedly reactivated and, at least in part, controlled: (a) the geometry of inter- and intra-cratonic rifting; (b) rates of subsidence and uplift along the Andean depositional axis; (c) the position of basin-bounding and intra-basinal highs/arches; (d) the structural geometry of the Andean Deformation Zone, correlating with changes in deformational style and major deflections; and (e) the location of magmatism.
Based primarily on source rock age, it is suggested that these transverse, structural accommodation zones had a profound effect on source rock distribution and hydrocarbon occurrence; subdividing the Sub-Andean region into five petroleum provinces/megasystems: a ‘Northern’ Late Cretaceous (La Luna Formation and equivalents); a ‘Western’ Late Palaeozoic–Early Mesozoic (Permian and Upper Triassic to Lower Jurassic source rocks); a ‘Central’ Palaeozoic (Late Devonian and Silurian); an ‘Eastern’ Tertiary; and a ‘Southern’ Mesozoic.
Well test simulation through Discrete Fracture Network modelling in a fractured carbonate reservoir
Authors: Casciano Claudio , Ruvo Livio , Volpi Bruno , Masserano Franco 
Published: October 2008

A Discrete Fracture Network (DFN) model was used to simulate the results of a production test carried out in a well drilled in a tight, fractured carbonate reservoir. Several static DFN models, depicting different geological scenarios, were built based on data from well logs, core analyses, PLT surveys and structural geology studies. Each of these models underwent a validation procedure, consisting of the simulation of the production test. The comparison between the simulated results and the actual data identified the scenario whose results most closely matched the actual well behaviour.
In order to compensate for the lack of geological data, an iterative loop was performed between the static model and the dynamic simulation. Constraints-added flow simulations provided new information for use in modifying the DFN model, resulting in a step-by-step updating of the static model itself. Finally, a geologically sound model accurately matching the results of the production test was obtained. The final DFN model was used to calculate the equivalent petrophysical parameters that were transferred to the corresponding region of the full field dual-porosity fluid flow model.
The controversy concerning stratigraphic architecture of channelized reservoirs and recovery by waterflooding
Authors: Larue D. K. , Friedmann Francois 
Published: October 2008

There is a subtle controversy in the petroleum industry regarding the relationship between reservoir architecture and recovery efficiency from petroleum reservoirs. Stratigraphers tend to believe that facies architecture and geometric shapes strongly govern recovery, whereas engineers stress factors such as permeability heterogeneity and anisotropy. To understand the relationship between architecture and recovery better, a suite of conceptual models of different channelized clastic reservoir architectures was constructed and pore-volume replacement waterflood simulations were performed on each. Three 11-member suites of models were constructed at net: gross values of 35%, 60% and 85%. The reservoir architecture features that were varied were channel width to thickness, thickness, sinuosity, stacking patterns, orientation and reservoir element type (point bar vs. channel). The three sets of models appear visually very different from a reservoir architecture standpoint. Permeability and porosity were simulated using geostatistical techniques but share the same conditioning population. The same water saturation, well count (110 acre spacing), fluid properties and relative permeability were used in each waterflood simulation. In this situation, in which the only significant variable was reservoir architecture, only a few percent spread in recovery was noted for each net: gross suite. Variation in recovery efficiency can be shown to be associated with reservoir connectivity, which is generally high for all models but shows some variation. Additional studies were made to address the influence of well count, mobility ratio, permeability heterogeneity and geostatistical seed number on recovery efficiency.
Two stratigraphic factors are shown to influence recovery efficiency: reservoir connectivity and permeability heterogeneity. Both factors influence the volumetric sweep efficiency of reservoirs. Models that appear to be visually different, but have similar connectivity, well count and permeability heterogeneity, have similar sweep efficiencies and, therefore, recovery efficiencies. The practical importance of this observation for development studies is that building and flow-simulating suites of models with different reservoir architectures may not help to characterize recovery uncertainty unless the models are constructed to emphasize differences in sweep efficiency.
Exhumation of the Corrib Gas Field, Slyne Basin, offshore Ireland
Authors: Corcoran D. V. , Mecklenburgh R. 
Published: October 2008

The Corrib Gas Field contains in excess of 10
12
SCF (28.3×10
9
Sm
3
) of gas in place in a Triassic fluviatile sandstone reservoir, sealed by late Triassic evaporites and trapped in a relatively simple, but underfilled, NE–SW-trending anticlinal structure. In contrast, the post-Triassic overburden manifests a more complex evolution with indications of flipped polarity, extensional faulting on a crestal detachment structure during the Jurassic, succeeded by alternate episodes of burial and exhumation from the Early Cretaceous onwards. Compactional, thermal and stratigraphic frames of reference have been used to assess the magnitude and timing of the principal exhumation episode, which occurred during the early Cretaceous. Large uncertainty is associated with exhumation estimates derived from individual techniques, but stratigraphic analysis and seismic interpretation support the conclusion that kilometre-scale (800–1700 m) exhumation and erosion of the Jurassic overburden has occurred in the Corrib area. A number of post-Aptian re-burial and exhumation events also occurred but are unlikely to have exceeded the earlier maximum burial of source, reservoir and seal rocks achieved during the Late Jurassic. Continued local extensional reactivation of the listric detachment structure, post-Aptian, has resulted in a pattern of heterogeneous exhumation within the field area. However, the severely attenuated post-rift stratigraphic record throughout the Slyne Basin suggests that long-wavelength processes, such as mantle hotspot activity and shoulder uplift linked to the rifting and thermal subsidence of the Rockall Basin, were the primary drivers of exhumation in the Corrib area during the Cretaceous-Tertiary period.
Sequence stratigraphic-based analysis of reservoir connectivity: influence of depositional architecture – a case study from a marginal marine depositional setting
Authors: Ainsworth R. Bruce 
Published: October 2008

This case study of the Sunrise and Troubadour fields (offshore northwest Australia) concentrates on the impact of primary depositional architecture on reservoir connectivity via a sequence stratigraphic-based, 3D reservoir modelling approach. The marginal marine reservoir is composed of fluvial-dominated and wave-dominated depositional environments. The succession is divided into six sequences and 12 systems tracts. Each systems tract is subdivided into parasequences which form the basic building blocks of the 3D model. The connectivity of sandbodies within each parasequence, systems tract and sequence were calculated when the models were palinspastically restored to a depositional datum.
The findings indicate that depositional connectivity trends within a sequence stratigraphic framework are predictable. Connectivity trends can be related directly to depositional and stratigraphic trends and to position in the sequence stratigraphic hierarchy. Therefore, with a good understanding of depositional settings and high resolution sequence stratigraphic subdivision of strata, predictions of depositional connectivity trends at all stratigraphic hierarchical levels can be made. All connectivity trends at sequence and systems tract stratigraphic hierarchical levels remained the same when the area of the model was reduced by a factor of four and the volume of the model was reduced by truncation below the gas–water contact. Hence, the relationships between the stratigraphic trends and the connectivity trends for the thicker stratigraphic units can be said to be scale invariant.
Three-dimensional reservoir models currently provide the best means of quantitatively assessing and predicting reservoir connectivity. However, in low fault density settings, initial screening of reservoir connectivity can be made using connectivity indicators calculated from simple parameters derived from well data such as ‘Thickness divided by Sand/Shale ratio’.
Productivity evaluation of hydraulically fractured gas-condensate reservoirs
Authors: Zheng Shi-Yi , Zhiyenkulov Murat , Yi TongChun 
Published: October 2008

This study describes an application of a compositional single well simulator to analyse well tests in gas-condensate reservoirs. An important aspect of this application for gas-condensate well tests is accurate fluid property prediction during the multi-phase flow regime, which occurs in the near-well region. The simulator can also be used to understand the impact of liquid drop-out and fracture flow on well productivity.
Hydraulic fracturing improves the economics of wells drilled in tight reservoirs. However, the operation involves a significant amount of expenditure. In recent years this technique has also been used to stimulate gas-condensate reservoirs by creating a flow conduit through the condensate banking near the well. Thus, it is crucial to keep a fracture as small as possible. In practice it has been proved that a short, wide fracture can provide much higher production than the traditionally pursued narrow, long fracture.
The workflow in this study contains compositional simulation of a single well in a tight gas-condensate reservoir, which is used to generate transient pressure data for well test analysis and interpretation to predict multi-phase flow behaviour, and to analyse productivity impairment due to condensation. Simulation models were then further modified to study the impact of various hydraulic fractures on the well productivity index (PI), which is defined as the ratio of production rate (constant) divided by the pressure drop across the reservoir. PIs for fractured cases are compared with respect to the non-fractured base case. Streamline simulation of the fractured gas-condensate reservoir was also included in the study to allow visualization of the flow profile in and around the hydraulic fracture.