CALIBRATING PREDICTIONS OF FAULT SEAL REACTIVATION IN THE TIMOR SEA

2002 ◽  
Vol 42 (1) ◽  
pp. 187 ◽  
Author(s):  
S.D. Mildren ◽  
R.R. Hillis ◽  
J.Kaldi
Keyword(s):  
Shear Failure ◽  
Fault Analysis ◽  
Vertical Stress ◽  
Fault Reactivation ◽  
Power Relationship ◽  
Fault Rock ◽  
Seal Integrity ◽  
Timor Sea ◽  
Stress Profiles ◽  
Sea Area

Predictions of the likelihood of fault reactivation for five fault-bound prospects in the Timor Sea are made using the FAST (Fault Analysis Seal Technology) technique. Fault reactivation is believed to be the dominant cause of seal breach in the area. Calculations are made using a stress tensor appropriate for the area, a conservative fault-rock failure envelope and the structural geometries of each prospect. A depth-stress power relationship defines the vertical stress magnitude based on vertical stress profiles for 17 Timor Sea wells.Empirical evidence of hydrocarbon leakage at each trap is used to investigate the accuracy of the fault reactivation-based predictions of seal integrity. There is a good correlation between evidence of leakage and the risk of reactivation predicted using the FAST technique. Risk of reactivation is expressed as the pore pressure increase (ΔP) that would be required to induce failure. This study allows the fault reactivation predictions to be calibrated in terms of risk of seal breach. Low integrity traps are associated with ΔP values less than 10 MPa, moderate integrity traps correspond with values between 10 and 15 MPa and high integrity traps correspond with values greater than 15 MPa. Faults with dip magnitudes greater than 60° in the Timor Sea area are likely to have a high risk of reactivation and shear failure is the most likely mode of reactivation.

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.

scholarly journals Modelling fault reactivation with characteristic stress-drop terms

2019 ◽  
Vol 49 ◽  
pp. 1-7 ◽  
Author(s):  
Martin Beck ◽  
Holger Class
Keyword(s):  
Induced Seismicity ◽  
Shear Failure ◽  
Fault Reactivation ◽  
Mechanical Responses ◽  
Flow Processes ◽  
Failure Event ◽  
Characteristic Values ◽  
Shear Slip ◽  
Stress Drops ◽  
Characteristic Stress

Abstract. Predicting shear failure that leads to the reactivation of faults during the injection of fluids in the subsurface is difficult since it inherently involves an enormous complexity of flow processes interacting with geomechanics. However, understanding and predicting induced seismicity is of great importance. Various approaches to modelling shear failure have been suggested recently. They are all dependent on the prediction of the pressure and stress field, which requires the solution of partial differential equations for flow and for geomechanics. Given a pressure and corresponding mechanical responses, shear slip can be detected using a failure criterion. We propose using characteristic values for stress drops occurring in a failure event as sinks in the geomechanical equation. This approach is discussed in this article and illustrated with an example.

Development, Evolution, and Episodic Charge History of Pop-up Structures in Southeast Abu Dhabi, UAE

2021 ◽  
Author(s):  
Jose Manuel Guevara ◽  
Mary Grace Jubb ◽  
Abdulla Seliem ◽  
Hilario Camacho ◽  
Jorge Mario Lozano
Keyword(s):  
Classification Scheme ◽  
Strike Slip ◽  
Abu Dhabi ◽  
Structural Deformation ◽  
Fault Rock ◽  
Seal Integrity ◽  
Exploratory Wells ◽  
And Migration ◽  
Step Over

Abstract The main goal of this paper is contributing to the understanding to the structural geology, development, and evolution of traps associated with strike-slip restraining bend and restraining step-over structures as a key petroleum system element in southeastern Abu Dhabi. We introduce a preliminary classification scheme for these relatively small, low-relief features defined here as pop-up structures. These structures represent different evolutionary stages of strike-slip restraining bends formed along prominent WNW-trending strike-slip fault systems in southeastern Abu Dhabi. The proposed classification scheme was summarized as a chart to illustrate the correlation between the degree of structural deformation and seal integrity, and estimates the likelihood of finding multiple, vertically stacked, productive reservoirs. It also leads to a more detailed discussion on others important characteristics of pop-up structures and provides a better understanding of sealing mechanisms such as fault juxtaposition, fault throw analysis, fault slip tendency, fault rock processes, and the role of the development of hybrid flower structures in the area. We will also show a simple case study based on two exploratory wells that targeted two pop-up structures with different degrees of deformation in southeast Abu Dhabi. This case study illustrates the complex relationship between pop-up evolution, timing of trap formation, seal integrity, trap preservation, and multiple petroleum generation and migration events. Pop-up structures are linked to multiple episodes of trap and seal evolution, where several episodes of hydrocarbon migration, charge, and leaking of hydrocarbons may occur.

THE REGIONAL GEOLOGY OF THE BONAPARTE GULF TIMOR SEA AREA

1974 ◽  
Vol 14 (1) ◽  
pp. 77 ◽  
Author(s):  
Robert A. Laws ◽  
Gregory P. Kraus
Keyword(s):  
Late Cretaceous ◽  
Late Jurassic ◽  
Oil And Gas ◽  
Upper Jurassic ◽  
Structural Configuration ◽  
Structural Pattern ◽  
Source Areas ◽  
Timor Sea ◽  
Early Palaeozoic ◽  
Sea Area

The present structural configuration of the Bonaparte Gulf-Timor Sea area is essentially the result of Mesozoic and Tertiary fragmentation of a once relatively simple Permo-Triassic Basin. A northwest-southeast Palaeozoic structural grain in the southeastern portion of the area resulted from early Palaeozoic faulting, possibly tied to aborted rift development. This faulting effectively controlled sedimentation throughout the Phanerozoic. Pronounced northeast-southwest Jurassic to Tertiary structural trends dominate the central and northern area, paralleling the present edge of the continental shelf and swinging south southwest into the northern extension of the Browse Basin. Post-Palaeozoic epeirogenies which had the greatest effect on the regional structural pattern occurred in the mid-Jurassic, Early Cretaceous, within the Eocene and in the Plio-Pleistocene.The Kimberley and Sturt Blocks flanking the basin to the south and east constituted the most important source areas for clastic sedimentation throughout the Phanerozoic. Periodic contributions during the Mesozoic were derived from a postulated source to the northwest in the vicinity of the present-day Timor Trough.The maximum thickness of Phanerozoic sediments present within the Bonaparte Gulf-Timor Sea area exceeds 50,000 ft (15,000 m). Early Palaeozoic to Carboniferous evaporites, carbonates and clastics are unconformably overlain by a thick sequence of Permian deltaic sediments in the southeastern Bonaparte Gulf Basin. This is succeeded by a Triassic to Middle Jurassic transgressive-regressive clastic sequence, grading northwestward to marginal marine and marine clastics and carbonates. The Permian to mid-Jurassic sediments are unconformably overlain by Upper Jurassic sands and shales, mainly fluvial in the southeast and north, becoming more marine westward. These clastics are everywhere succeeded by a monotonous sequence of Cretaceous shales and shaly limestones followed by a generally north to northwesterly thickening wedge of Tertiary carbonates and minor elastics.Hydrocarbon shows have been noted offshore in rocks of Carboniferous, Permian, Late Jurassic, Late Cretaceous and Eocene age. Porous clastics in conjunction with thick and laterally-extensive, organically-rich shales are present within the Palaeozoic and Mesozoic sequences. These sediments, in association with fault- and diapir-related anomalies and stratigraphic plays, combine to make certain provinces of the Bonaparte Gulf-Timor Sea area prospective in the search for viable oil and gas reserves.

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

High resolution imaging of fault reactivation in long-lived extensional setting: a case study from the Exmouth Plateau (NW Australia)

2020 ◽  
Author(s):  
Nico D'Intino
Keyword(s):  
High Resolution ◽  
Confining Pressure ◽  
Data Interpretation ◽  
Fault Analysis ◽  
Fault Reactivation ◽  
Normal Faults ◽  
3D Seismic ◽  
Exmouth Plateau ◽  
Northern Carnarvon Basin ◽  
Nw Australia

<p>Extension in rift zones and passive margins often occur by multiphase normal faulting which usually accommodates several episodes of lithosphere stretching by brittle deformation. In these settings, pre-existing normal faults may reactivate but also new-formed structures may nucleate, with multiple orientations and deformational styles. The various modes of fault growth and nucleation are strongly influenced by several parameters (including orientation and geometry of pre-existing discontinuities, stress orientation and magnitude, strain rates, confining pressure, etc..) with the lithostratigraphy controlling the brittle or ductile litho-mechanic behavior of each unit.</p><p>In this work, we interpreted and analyzed an industrial 3D seismic volume acquired in the Exmouth Plateau, (Northern Carnarvon Basin – offshore NW Australia), where pre-existing Mesozoic normal faults were reactivated during the Cenozoic and controlled the nucleation and growth of the new-formed overlying fault segments. The peculiarity of this system is that the two sets of faults are separated by a ductile interval of shales. The latter acted as decollement level and promoted the formation of prominent faulted anticlines in the overlying brittle sequence; these forced folds are poorly documented in other extensional settings while are common where salt layers are present. In this study, the high-resolution techniques adopted for seismic data interpretation aimed to understand the geometries of faults and their interactions in fine detail. The results of fault analysis suggest that the use of high-quality 3D seismic volumes is very useful to unravel the complex and subtle spatial variability and also the displacement pattern of faults with a limited amount of fault-throw.</p>

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