New exploration discoveries in a mature basin: offshore Denmark

2016 ◽  
Vol 8 (1) ◽  
pp. 287-306 ◽  
Author(s):  
Graham Goffey ◽  
Mark Attree ◽  
Paul Curtis ◽  
Fiona Goodfellow ◽  
Jeremy Lynch ◽  
...  
Keyword(s):  
Pore Pressure ◽  
Fault Reactivation ◽  
Hydrocarbon Exploration ◽  
Salt Diapir ◽  
Gas Reservoir ◽  
John 1 ◽  
Incised Valley ◽  
Seal Integrity ◽  
Seal Failure ◽  
Induced Stress

AbstractIn 2011, two discoveries were drilled by PA Resources in the Danish sector. The Broder Tuck 2/2A wells were drilled on a thrusted anticlinal structure, downdip of the apparently small U-1X gas discovery. The wells found an excellent quality gas reservoir within an interpreted Callovian lowstand incised valley containing braided fluvial and marginal-marine sandstones. A top and base seal are provided by mudstones of the over- and underlying transgressive systems tracts respectively. The development of a base seal is key to the presence of a potentially commercial resource downdip of a relatively unpromising old well.The Lille John 1/1B wells were then drilled on a salt diapir on which 1980s wells had encountered shallow oil shows. Lille John 1 found slightly biodegraded 34° API oil in Miocene sandstones at the uncommonly shallow depth of −910 m true vertical depth subsea (TVDSS). The reservoir is full to spill, whilst the trap developed intermittently through latest Miocene–Late Pleistocene times. It is interpreted that a deeper Chalk accumulation temporarily lost seal integrity owing to glacially induced stress or overpressure triggering top-seal failure or fault reactivation during and after latest Pleistocene diapir inflation. The wider hydrocarbon exploration implications of glaciation on stress, pore pressure and trap integrity appear to be underappreciated.

scholarly journals The influence of fault reactivation on injection-induced dynamic triggering of permeability evolution

2020 ◽  
Vol 223 (3) ◽  
pp. 1481-1496
Author(s):  
Elif Cihan Yildirim ◽  
Kyungjae Im ◽  
Derek Elsworth
Keyword(s):  
Pore Pressure ◽  
Fluid Pressure ◽  
Fault Reactivation ◽  
Permeability Evolution ◽  
Fracture Permeability ◽  
Permeability Enhancement ◽  
Pressure Pulses ◽  
Fracture Sealing ◽  
Permeability Increase ◽  
Pressure Driven

SUMMARY Mechanisms controlling fracture permeability enhancement during injection-induced and natural dynamic stressing remain unresolved. We explore pressure-driven permeability (k) evolution by step-increasing fluid pressure (p) on near-critically stressed laboratory fractures in shale and schist as representative of faults in sedimentary reservoirs/seals and basement rocks. Fluid is pulsed through the fracture with successively incremented pressure to first examine sub-reactivation permeability response that then progresses through fracture reactivation. Transient pore pressure pulses result in a permeability increase that persists even after the return of spiked pore pressure to the null background level. We show that fracture sealing is systematically reversible with the perturbing pressure pulses and pressure-driven permeability enhancement is eminently reproducible even absent shear slip and in the very short term (order of minutes). These characteristics of the observed fracture sealing following a pressure perturbation appear similar to those of the response by rate-and-state frictional healing upon stress/velocity perturbations. Dynamic permeability increase scales with the pore pressure magnitude and fracture sealing controls the following per-pulse permeability increase, both in the absence and presence of reactivation. However, initiation of the injection-induced reactivation results in a significant increase in the rate of permeability enhancement (dk/dp). These results demonstrate the role of frictional healing and sealing of fractures at interplay with other probable processes in pore pressure-driven permeability stimulation, such as particle mobilization.

MARGIN-SCALE, BASEMENT-INVOLVED COMPARTMENTALISATION OF AUSTRALIA'S NORTH WEST SHELF: A PRIMARY CONTROL ON BASIN-SCALE RIFT, DEPOSITION AL AND REACTIVATION HISTORIES

1999 ◽  
Vol 39 (1) ◽  
pp. 40 ◽  
Author(s):  
G.W. O'Brien ◽  
M. Morse ◽  
D. Wilson ◽  
P. Quaife ◽  
J. Colwell ◽  
...  
Keyword(s):  
Transition Zone ◽  
Fault Reactivation ◽  
Small Displacement ◽  
Driving Mechanism ◽  
Fracture System ◽  
Primary Control ◽  
North West ◽  
Seal Failure ◽  
Lithospheric Flexure ◽  
Basin Scale

Australia's North West Shelf is segmented into four discrete margin-scale compartments which have distinct rift and reactivation histories. Two of the margin segments, the Carnarvon and Bonaparte compartments, are very wide (500–600 km), marginal plateau systems, whereas the other two segments, the Canning and Browse compartments, are narrower and steeper. The boundaries between individual rift compartments appear to be controlled by Proterozoic fracture systems.The Browse-Bonaparte transition zone is a major, northwest-trending Proterozoic fracture system which has a series of igneous intrusions along its length. These intrusions are located where the fracture system is cut by younger, northeast-trending extensional faults. This transition zone is a margin-scale fault relay zone, with intense fault overlap along the transition resulting in the zone being a long-lived, syn-rift high. Moreover, the transition zones between adjacent wide and narrow margins are prime locations for the entry point of siliciclastics into the rift or post-rift margin system. As a result, well-developed channel systems often cut through these boundaries and high quality reservoirs (particularly low-stand fans) are developed.Neogene fault reactivation, associated with convergence of the Australasian and Eurasian plates, is evident along the North West Shelf. The style of this reactivation is, however, closely controlled by the margin- scale architecture. In the Browse and Carnarvon basins, Neogene inversion is common, but at the leading edge of the collisional system, the Bonaparte compartment, the fault style is exclusively extensional. It appears that lithospheric flexure, associated with localised foreland development (i.e. the Timor Trough), has been the driving mechanism for the extensional faulting within the Bonaparte compartment. Crustal convergence seems to have been accommodated completely by thrusting on the northwestern margin of Timor and by foreland formation. In contrast, the Browse and Carnarvon compartments lacked a 'buffering' foreland system and, being adjacent to rigid and thin oceanic crust which transmits stress well over long distances, the inversional stresses were transmitted directly into these compartments.As a result of these margin-scale processes, the Bonaparte compartment is characterised by a thin regional seal (often 100 ms) on Neogene extensional faults—a combination which strongly favours fault seal failure and trap breach. In contrast, the Browse compartment is characterised by thick seals and small displacement Neogene faults, and thus the probability of fault seal failure is much less.

In Situ Stress Field, Fault Reactivation and Seal Integrity in the Bight Basin, South Australia

2003 ◽  
Vol 2003 (2) ◽  
pp. 1-5 ◽  
Author(s):  
Scott D. Reynolds ◽  
Richard R. Hillis ◽  
Evelina Paraschivoiu
Keyword(s):  
Stress Field ◽  
South Australia ◽  
In Situ Stress ◽  
Fault Reactivation ◽  
Seal Integrity ◽  
In Situ Stress Field

In situ stress field, fault reactivation and seal integrity in the Bight Basin, South Australia

2003 ◽  
Vol 34 (3) ◽  
pp. 174-181 ◽  
Author(s):  
Scott Reynolds ◽  
Richard Hillis ◽  
Evelina Paraschivoiu
Keyword(s):  
Stress Field ◽  
South Australia ◽  
In Situ Stress ◽  
Fault Reactivation ◽  
Seal Integrity ◽  
In Situ Stress Field

scholarly journals Impact of in situ stress and fault reactivation on seal integrity in the East Irish Sea Basin, UK

2018 ◽  
Vol 92 ◽  
pp. 685-696 ◽  
Author(s):  
J.D.O. Williams ◽  
C.M.A. Gent ◽  
M.W. Fellgett ◽  
D. Gamboa
Keyword(s):  
In Situ Stress ◽  
Fault Reactivation ◽  
Irish Sea ◽  
Seal Integrity

Sequence stratigraphic controls on reservoir characterization and architecture: case study of the Messinian Abu Madi incised-valley fill, Egypt

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
Mohamed Abdel-Fattah ◽  
Roger Slatt
Keyword(s):  
Reservoir Characterization ◽  
Nile Delta ◽  
Hydrocarbon Exploration ◽  
Incised Valley ◽  
Sequence Stratigraphic ◽  
Valley Fill ◽  
Body Distribution ◽  
Stratigraphic Framework ◽  
Wide Range ◽  
The Impact

AbstractUnderstanding sequence stratigraphy architecture in the incised-valley is a crucial step to understanding the effect of relative sea level changes on reservoir characterization and architecture. This paper presents a sequence stratigraphic framework of the incised-valley strata within the late Messinian Abu Madi Formation based on seismic and borehole data. Analysis of sand-body distribution reveals that fluvial channel sandstones in the Abu Madi Formation in the Baltim Fields, offshore Nile Delta, Egypt, are not randomly distributed but are predictable in their spatial and stratigraphic position. Elucidation of the distribution of sandstones in the Abu Madi incised-valley fill within a sequence stratigraphic framework allows a better understanding of their characterization and architecture during burial.Strata of the Abu Madi Formation are interpreted to comprise two sequences, which are the most complex stratigraphically; their deposits comprise a complex incised valley fill. The lower sequence (SQ1) consists of a thick incised valley-fill of a Lowstand Systems Tract (LST1)) overlain by a Transgressive Systems Tract (TST1) and Highstand Systems Tract (HST1). The upper sequence (SQ2) contains channel-fill and is interpreted as a LST2 which has a thin sandstone channel deposits. Above this, channel-fill sandstone and related strata with tidal influence delineates the base of TST2, which is overlain by a HST2. Gas reservoirs of the Abu Madi Formation (present-day depth ∼3552 m), the Baltim Fields, Egypt, consist of fluvial lowstand systems tract (LST) sandstones deposited in an incised valley. LST sandstones have a wide range of porosity (15 to 28%) and permeability (1 to 5080mD), which reflect both depositional facies and diagenetic controls.This work demonstrates the value of constraining and evaluating the impact of sequence stratigraphic distribution on reservoir characterization and architecture in incised-valley deposits, and thus has an important impact on reservoir quality evolution in hydrocarbon exploration in such settings.

Improving hydrocarbon exploration with pore pressure assisted earth-model building

2018 ◽  
Vol 6 (3) ◽  
pp. SG41-SG47
Author(s):  
Yangjun (Kevin) Liu ◽  
Michael O’Briain ◽  
Cara Hunter ◽  
Laura Jones ◽  
Emmanuel Saragoussi
Keyword(s):  
Pore Pressure ◽  
Initial Velocity ◽  
Model Building ◽  
Rock Physics ◽  
Velocity Model ◽  
Hydrocarbon Exploration ◽  
Earth Model ◽  
Well Control ◽  
Physics Model ◽  
Rock Physics Model

In shale-dominated clastic lithology environments, a rock-physics model relating velocity and pore pressure (PP) can be calibrated and used to convert velocity to PP properties. The crossvalidation between velocity and overpressure, which follows the geology, can be used to better understand the model, help to build an initial velocity model, and allow selecting tomography solutions with more confidence. The velocity model developed using this approach is more plausible and more suitable for subsequent PP analysis. We highlight the application of this method in areas with poor seismic illumination and insufficient well control.

HYDROCARBON CHARGE HISTORY OF THE NORTHERN LONDONDERRY HIGH: IMPLICATIONS FOR TRAP INTEGRITY AND FUTURE PROSPECTIVITY

2001 ◽  
Vol 41 (1) ◽  
pp. 483
Author(s):  
M.P. Brincat ◽  
G.W. O’Brien ◽  
M. Lisk ◽  
M. De Ruig ◽  
S.C. George
Keyword(s):  
Stress Field ◽  
Shear Failure ◽  
Fault Reactivation ◽  
Field Analysis ◽  
Northern Province ◽  
Oil Accumulation ◽  
Seal Integrity ◽  
History Of ◽  
Sar Data ◽  
Migration Pathways

Re-appraisal of the oil charge history of the northern Londonderry High has identified numerous palaeo-oil columns of up to 80 m in height. An integration of the oil charge history, stress field analysis and contemporary seepage data allows a subdivision of the well results into three distinct provinces. These each have distinct charge histories that reflect differences in potential source kitchens and all have been adversely affected by the Neogene collision of the Australian and Southeast Asian plates. Traps located on the northern and northeastern Londonderry High have experienced high oil charge rates at the Mesozoic level, with nearly all valid traps showing evidence of prior oil accumulation. Breaching of these oil columns in the Neogene appears to be related to the orientation of the contemporary stress field, which promotes shear failure on the faults reliant for seal. Present day hydrocarbon migration indicators, such as Synthetic Aperture Radar (SAR) data show differences in seepage response between the northern and northeastern Londonderry High, with prolific current day seepage restricted to the northern province. Rapid subsidence associated with plate collision has accelerated maturation in the northern province to create these strong seepage anomalies over this region. The absence of seepage over the breached oil columns of the northeastern province indicates that either, oil charge has ceased to this area or that hydrocarbon leakage is episodic in nature.In contrast, results from the northwestern province show no evidence of prior oil accumulation, despite many wells having tested valid traps. These data point to either a lack of connected oil migration pathways or an impoverished source kitchen for liquid hydrocarbons. Low levels of seepage in the northwestern Londonderry High detected by the SAR data are minor compared with other parts of the Timor Sea and consistent with migration continuing at the current day. The overall prospectivity for fault bound traps in the study area appears to be low, due to extensive fault reactivation producing low fault seal integrity. Stratigraphic plays that do not rely on faults for seal, particularly in the northern and northeastern provinces, represent an alternative play concept at the Jurassic level. At shallower levels in the Cretaceous, subtle four-way dip closed structures are often enhanced by the reactivation process and could be ideally positioned to receive remigrated oil from breached Jurassic oil accumulations.

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