NATURAL FRACTURES OF THE SOUTHERN COOPER AND EASTERN WARBURTON BASINS, SOUTH AUSTRALIA

2001 ◽  
Vol 41 (1) ◽  
pp. 201 ◽  
Author(s):  
X. Sun
Keyword(s):  
South Australia ◽  
Open Fractures ◽  
Fracture Density ◽  
Natural Fractures ◽  
High Angle ◽  
Local Structures ◽  
Fracture Systems ◽  
Brittle Sandstone ◽  
Major Fault ◽  
Well Trajectory

A study of the southern Cooper and eastern Warburton Basins has resulted in classifying natural fractures and delineating regional fracture systems and orientations of open and partially open fractures. Firstly, natural fractures have been identified from selected lithological units in 44 wells of the southern Cooper Basin. Open fractures are developed mainly within the brittle Tirrawarra Sandstone. These open fractures are mostly high angle to subvertical, with measured apertures of up to 2 mm. Secondly, natural fractures have been characterised in Warburton Basin cores from 91 wells, 27 of which have dipmeter and/or FMS (Formation Micro- Scanner) logs. Fractures more commonly occur within brittle sandstone, dolomite, grainy limestone and ignimbrite.Two systems of orthogonal, high-angle, regional fracture sets (four fractures) have been identified. They extend across local structures in both basins in South Australia. System I is comprised of a pair of orthogonal fractures, striking NNE–SSW (20–200°) and ESE–WNW (110–290°), while a second pair of orthogonal fracture sets, striking NE–SW (60–240°) and NW–SE (150–330°), characterises System II. Open, steeply dipping SW fractures striking WNW and NW within Systems I and II have been interpreted from core and FMS data in several wells. The results indicate that an optimum well trajectory designed to maximise intersection with open natural fractures should be 200–210° and 240–250°, and possibly also 270–290°. The deviation angle should be 30° from horizontal in the fracture zone due to the high-angle and subvertical fracture dips. A semi-quantitative estimate of fracture density from cores in both basins has been determined: the greatest fracture density is located within major fault zones and structural culminations.

scholarly journals Development of fault and vein networks in a carbonate sequence near Hayl al-Shaz, Oman Mountains

GeoArabia ◽  
2013 ◽  
Vol 18 (2) ◽  
pp. 99-136
Author(s):  
Simon Virgo ◽  
Max Arndt ◽  
Zoé Sobisch ◽  
Janos L. Urai
Keyword(s):  
United Arab Emirates ◽  
Coarse Grained ◽  
Normal Faults ◽  
Structural Elements ◽  
High Angle ◽  
Oman Mountains ◽  
Bedding Planes ◽  
Fracture Systems ◽  
Calcite Veins ◽  
Al Jabal Al Akhdar

ABSTRACT We present a high-resolution structural study on the dip slope of the southern flank of Jabal Shams in the central Oman Mountains. The objectives of the study were: (1) to test existing satellite-based interpretations of structural elements in the area; (2) prepare an accurate geological map; and (3) collect an extensive structural dataset of fault and bedding planes, fault throws, veins and joints. These data are compared with existing models of tectonic evolution in the Oman Mountains and the subsurface, and used to assess the applicability of these structures as analogs for fault and fracture systems in subsurface carbonate reservoirs in Oman. The complete exposure of clean rock incised by deep wadis allowed detailed mapping of the complex fault, vein and joint system hosted by Member 3 of the Cretaceous Kahmah Group. The member was divided into eight units for mapping purposes, in about 100 m of vertical stratigraphy. The map was almost exclusively based on direct field observations. It includes measurement of fault throw in many locations and the construction of profiles, which are accurate to within a few meters. Ground-truthing of existing satellite-based interpretations of structural elements showed that faults can be mapped with high confidence using remote-sensing data. The faults range into the subseismic scale with throws as little as a few decimeters. However, the existing interpretation of lineaments as cemented fractures was shown to be incorrect: the majority of these are open fractures formed along reactivated veins. The most prominent structure in the study area is a conjugate set of ESE-striking faults with throws resolvable from several centimeters to hundreds of meters. These faults contain bundles of coarse-grained calcite veins, which may be brecciated during reactivation. We interpret these faults to be a conjugate normal- to oblique fault set, which was rotated together with bedding during the folding of the Al Jabal al-Akhdar anticline. There are many generations of calcite veins with minor offset and at high-angle-to-bedding, sometimes in en-echelon sets. Analysis of clear overprinting relationships between veins at high-angle-to-bedding is consistent with the interpretations of Holland et al. (2009a); however we interpret the anticlockwise rotation of vein strike orientation to start before and end after the normal faulting. The normal faults post-date the bedding-parallel shear veins in the study area. Thus these faults formed after the emplacement of the Semail and Hawasina Nappes. They were previously interpreted to be of the same age as the regional normal- to oblique-slip faults in the subsurface of northern Oman and the United Arab Emirates, which evolved during the early deposition of the Campanian Fiqa Formation as proposed by Filbrandt et al. (2006). We interpret them also to be coeval with the Phase I extension of Fournier et al. (2006). The reactivation of these faults and the evolution of new veins was followed by folding of the Al Jabal al-Akhdar anticline and final uplift and jointing by reactivation of pre-existing microveins. Thus the faults in the study area are of comparable kinematics and age as those in the subsurface. However they formed at much greater depth and fluid pressures, so that direct use of these structures as analogs for fault and fracture systems in subsurface reservoirs in Oman should be undertaken with care.

scholarly journals 3D finite-element modeling of effective elastic properties for fracture density and multiscale natural fractures

2021 ◽  
Vol 18 (4) ◽  
pp. 567-582
Author(s):  
Shikai Jian ◽  
Li-Yun Fu ◽  
Chenghao Cao ◽  
Tongcheng Han ◽  
Qizhen Du
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Elastic Properties ◽  
Least Square ◽  
P Wave ◽  
Fracture Density ◽  
Equivalent Stiffness ◽  
Natural Fractures ◽  
Effective Elastic Properties ◽  
Element Modeling

Abstract Natural fractures are usually multiscale in size, orientations and distribution, resulting in complex anisotropic characteristics. Analytical methods for quantifying the associated effective elastic properties are based on some assumptions, such as dilute fracture concentration and regular-shaped fractures, which do not occur in actual reservoirs. Here, we conduct anisotropic finite-element modeling of effective elastic properties of complex fractured rocks using the least-square fitting method. The algorithm is developed for a 3D case and validated by classical effective medium theories for models with different fracture densities. The results of the 3D numerical method agree well with the theoretical predictions at low fracture density. The model also considers the interactions among fractures to calculate equivalent stiffness tensors at high fracture density. Three 2D fracture models are simulated to demonstrate the basic behavior of stress interactions and their effect on the overall elasticity under different fracture densities. We applied the developed model to 3D natural fractures built from a real outcrop, and we found that the fracturing pattern significantly affects the effective anisotropy properties. The resultant P-wave phase velocities as functions of the incidence angle and frequency are anisotropic. This study provides a great potential to calculate equivalent stiffness tensors and anisotropic properties of 3D multiscale natural fractures.

The Stratigraphy of Pre-Tertiary Economic Basement in South Jambi B Block, South Sumatra Basin

2021 ◽  
Keyword(s):  
Significant Contribution ◽  
Fracture Network ◽  
Natural Fracture ◽  
Fracture Density ◽  
The South ◽  
The North ◽  
Fracture Intensity ◽  
Parent Rocks ◽  
Major Fault ◽  
Essential Function

As one of the most promising plays, the Pre-Tertiary basement play holds a significant contribution to the latest success of exploration efforts in the South Sumatra Basin, which then includes the South Jambi B Block. Yet, the natures of the Pre-Tertiary unit in this block remains unsolved. Lithology variability, spatial irregularity, genetic ambiguity, and different reservoir characteristic are indeterminate subjects in the block are the main focus here. The ultimate goals of this study are to better characterize the unit and gain more understanding in calibrating the remaining potential. Based on this study, The Pre-Tertiary units are mainly originated from layered marine-deltaic sedimentary parent rocks with carbonate, intruded by spotty granite where the concentration of each parent rocks varies at the north, the middle, and southern part. Secondly, both lithology heterogeneity and natural fracture density create distinctive reservoir deliverability at each structure. The storage concept is an essential function of natural fracture intensity and diversity, supported by matrix porosity that varies across a different succession of lithology. Lastly, this study observes that major fault orientation is essential in constructing the fracture network. Evidence from several image logs across the study area concludes that most of the interpreted fractures are oriented subparallel to the major faults. The northern belt area is relatively affected by NW-SE Neogene structure, where the southern area is recognized to be affected by both Neogene compression and pre-existing Paleogene structure.

Optimum well trajectory design in a planned well in Blacktip field, Australia: a case study

2010 ◽  
Vol 50 (1) ◽  
pp. 535 ◽  
Author(s):  
Vamegh Rasouli ◽  
Zachariah Pallikathekathil ◽  
Elike Mawuli
Keyword(s):  
Strength Properties ◽  
Earth Model ◽  
Trajectory Design ◽  
Lower Section ◽  
Principal Stresses ◽  
Stress Anisotropy ◽  
Major Fault ◽  
Well Trajectory ◽  
Mechanical Earth Model ◽  
Well Data

A geomechanics study carried out in the Blacktip field, offshore Australia led to optimum wellbore deviation and azimuth to minimise drilling-associated instability problems near a major fault in the field. Elastic and strength properties of the formations and magnitude of principal stresses in the field were estimated from a mechanical earth model (MEM) based on offset well data. The direction of the minimum horizontal stresses was predicted from formation microresistivity image (FMI) logs available in offset wells. The MEM results were calibrated using results from laboratory experiments, well tests and drilling incidents from drilling reports. The MEM showed that formations at the lower section of the well are very competent and have high uniaxial strength; however, most of the failures in the form of breakouts observed from calliper and image logs were in this interval. Therefore, obtaining a good match between the model and observed failures required a large stress anisotropy to be considered for the lower section of the wellbore. Further investigations demonstrated that this is because the wellbore trajectory at deeper depth gets closer to the major fault plane, and this large stress anisotropy is due to the stress redistribution near the fault. The data from offset well was mapped into the planned trajectory, and the selection of the optimum trajectory and a stable mud weight window for the appropriate section led to successful drilling of the deviated well.

A SEISMIC MODEL OF FAULTS IN THE COOPER BASIN

1984 ◽  
Vol 24 (1) ◽  
pp. 421
Author(s):  
R. J. Gray ◽  
D. C. Roberts
Keyword(s):  
Hanging Wall ◽  
South Australia ◽  
Shadow Zone ◽  
Seismic Line ◽  
Seismic Section ◽  
Seismic Modelling ◽  
Geological Cross Section ◽  
Major Fault ◽  
Seismic Lines ◽  
Cooper Basin

A synthetic seismic section was modelled to help in the interpretation of Cooper Basin seismic lines which cross major faults and exhibit shadow zones.A major fault bounding the northwest flank of the Packsaddle Structure in the Merrimelia-Innamincka Farmout Block in South Australia was selected for modelling. A geological cross-section postulated on the basis of wells on either side of the fault was fed into the seismic modelling package AIMS (Advanced Interpretive Modelling System — licensed by Geoquest International Inc.) to produce a synthetic seismic line. This synthetic line provided a realistic match with an actual seismic line across the fault. Pre-stack migration of the actual seismic data is suggested to provide additional evidence for the reliability of the model.The shadow zone in the synthetic section is caused by dipping events in the fault shadow zone created by compaction of the Toolachee and Patchawarra Formations along the hanging wall of the fault plane. The dipping events cause reflected energy to be detected outside the fault zone. The large component of compaction within the Permian section is largely ascribed to thick coal horizons. The possibility of petroleum traps in the hanging wall of the fault is inferred and drilling is recommended.

Use of seismic attributes and open-hole log data to characterize production variability in a fractured carbonate play: A case study from Madison County, Texas

2019 ◽  
Vol 7 (1) ◽  
pp. T167-T178
Author(s):  
Courtney Beck ◽  
Anna Khadeeva ◽  
Bhaskar Sarmah ◽  
Trey Kimbell
Keyword(s):  
Natural Fracture ◽  
Good Prediction ◽  
Fracture Density ◽  
Natural Fractures ◽  
Well Performance ◽  
Log Data ◽  
Well Production ◽  
Well Completion ◽  
Madison County ◽  
Fractured Carbonate

Understanding natural fracture systems is key for tight carbonate plays, in which production is dependent on secondary interconnected porosity networks. Locating geographic areas and stratigraphic sections with high natural fracture density and optimizing well locations and perforations to connect these fractures can enhance well performance and asset value. There is substantial production variation in the Cretaceous stacked carbonate play in East Texas, despite similarities in well completion and perforated intervals. Petrophysical property models did not explain the significant variation in well production; therefore, we have developed a multidisciplinary workflow combining seismic and log data with the goal of identifying faulting and natural fractures and understanding their effect on production. We used seismic discontinuity to map faults as the main indicator of presence of fractures. We calibrated triple combo logs with an image log to generate an indicator curve to identify natural fractures. The fracture indicator curve provided a good prediction of where natural fractures may occur, and discontinuity maps revealed a good correlation to well production. Furthermore, we concluded that drilling too closely to large faults negatively impacted production and correlated with increased water production. The workflow developed here can be used to optimize well placement in the stacked carbonate play of Madison County, Texas, and it can be applied to other fractured carbonate reservoirs.

Integration of Advanced Borehole Sonic and Resistivity Image Analysis for Fracture and Stress Characterisation - Implications to Carbon Sequestration Feasibility

2021 ◽  
Author(s):  
Debashis Konwar ◽  
Abhinab Das ◽  
Chandreyi Chatterjee ◽  
Fawz Naim ◽  
Chandni Mishra ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Horizontal Stress ◽  
Open Fractures ◽  
Earth Model ◽  
Natural Fractures ◽  
Mechanical Earth Model ◽  
Induced Fractures ◽  
Maximum Horizontal Stress ◽  
Fracture Stability ◽  
Resistivity Image

Abstract Borehole resistivity images and dipole sonic data analysis helps a great deal to identify fractured zones and obtain reasonable estimates of the in-situ stress conditions of geologic formations. Especially when assessing geologic formations for carbon sequestration feasibility, borehole resistivity image and borehole sonic assisted analysis provides answers on presence of fractured zones and stress-state of these fractures. While in deeper formations open fractures would favour carbon storage, in shallower formations, on the other hand, storage integrity would be potentially compromised if these fractures get reactivated, thereby causing induced seismicity due to fluid injection. This paper discusses a methodology adopted to assess the carbon dioxide sequestration feasibility of a formation in the Newark Basin in the United States, using borehole resistivity image(FMI™ Schlumberger) and borehole sonic data (SonicScaner™ Schlumberger). The borehole image was interpreted for the presence of natural and drilling-induced fractures, and also to find the direction of the horizontal stress azimuth from the identified induced fractures. Cross-dipole sonic anisotropy analysis was done to evaluate the presence of intrinsic or stress-based anisotropy in the formation and also to obtain the horizontal stress azimuth. The open or closed nature of natural fractures was deduced from both FMI fracture filling electrical character and the Stoneley reflection wave attenuation from SonicScanner monopole low frequency waveform. The magnitudes of the maximum and minimum horizontal stresses obtained from a 1-Dimensional Mechanical Earth Model were calibrated with stress magnitudes derived from the ‘Integrated Stress Analysis’ approach which takes into account the shear wave radial variation profiles in zones with visible crossover indications of dipole flexural waves. This was followed by a fracture stability analysis in order to identify critically stressed fractures. The borehole resistivity image analysis revealed the presence of abundant natural fractures and microfaults throughout the interval which was also supported by the considerable sonic slowness anisotropy present in those intervals. Stoneley reflected wave attenuation confirmed the openness of some natural fractures identified in the resistivity image. The strike of the natural fractures and microfaults showed an almost NE-SW trend, albeit with considerable variability. The azimuth of maximum horizontal stress obtained in intervals with crossover of dipole flexural waves was also found to be NE-SW in the middle part of the interval, thus coinciding with the overall trend of natural fractures. This might indicate that the stresses in those intervals are also driven by the natural fracture network. However, towards the bottom of the interval, especially from 1255ft-1380ft, where there were indications of drilling induced fractures but no stress-based sonic anisotropy, it was found that that maximum horizontal stress azimuth rotated almost about 30 degrees in orientation to an ESE-WNW trend. The stress magnitudes obtained from the 1D-Mechanical Earth Model and Integrated Stress Analysis approach point to a normal fault stress regime in that interval. The fracture stability analysis indicated some critically stressed open fractures and microfaults, mostly towards the lower intervals of the well section. These critically stressed open fractures and microfaults present at these comparatively shallower depths of the basin point to risks associated with carbon dioxide(CO2) leakage and also to induced seismicity that might result from the injection of CO2 anywhere in or immediately below this interval.

3D Digital Outcrop Model analysis of fracture networks: insights from the Mt. Vettore Fault Zone.

2021 ◽  
Author(s):  
Riccardo Inama ◽  
Yuri Panara ◽  
Niccolò Menegoni ◽  
Filippo Carboni ◽  
Giovanni Toscani ◽  
...  
Keyword(s):  
Fault Zone ◽  
Central Italy ◽  
Structural Evolution ◽  
Fracture Network ◽  
Geometrical Parameters ◽  
Fracture Density ◽  
Coseismic Slip ◽  
Major Fault ◽  
Mapping Techniques ◽  
Digital Outcrop

<p>In the last years, several studies investigated the Mt. Vettore Fault Zone (MVFZ), activated during the 2016 Central Italy seismic sequence. Research has focused mainly on aftershocks and mainshock locations, coseismic slip and surface cracks, while an accurate study of the fracture network in the MVFZ was never conducted.</p><p>In this study we present a fracture analysis performed using very high resolution (0.5 – 5 cm) Digital Outcrop Models (DOMs) that developed by Unmanned Aerial Vehicle (UAV)-based digital photogrammetry. The UAV gave the possibility to investigate outcrops with dimensions up to hundreds of metres high and wide, and acquire big and precise fracture data using 3D digital automatic and manual mapping techniques. To investigate the structural variability of the MVFZ fracture network, we realized several DOMs located in different positions, along and around the major fault. All the selected outcrops are formed by Calcare Massiccio Fm., which better records brittle deformation in the study area.</p><p>This analysis aimed to better understand the MVFZ fracture network, including mechanics, kinematics and local structural evolution. In particular, it allowed to determine: 1) the main sets of fractures; 2) the geometrical parameters of the fracture network (e.g. fracture density, persistence, roughness and aperture); 3) the relative timing of the main tectonic brittle events. The preliminary analysis of the DOMs suggests a variability of the fracture network parameters over the MVFZ, especially for what concerned fracture set orientation and density. </p><p> </p><p> </p>

Characteristics of Fracture and Fractured Reservoir of Hailaer Basin Budart Group

2013 ◽  
Vol 316-317 ◽  
pp. 826-829
Author(s):  
Cui Ju Feng ◽  
Wei Lin Yan
Keyword(s):  
Oil And Gas ◽  
Low Permeability ◽  
Fractured Reservoir ◽  
Fracture Density ◽  
High Angle ◽  
Pore System ◽  
Reservoir Evaluation ◽  
Angle Fracture ◽  
Conventional Logs ◽  
Huge Challenge

The output of fracture pool is over half of the entire outout of oil and gas,and fracture pool is one of the important fields of oil inhancing yield in 21st Century. Fractured reservoir evaluation is always a huge challenge for the oil exploration and development. Budart Group of Sudert district in Hailaer Basin is a reservoir that has very low porosity、very low permeability、double pore system and it is rich of fracture. The paper summarized Hailaer Basin Budart Group reservoir’s characteristics, especially fractures’s characteristics in conventional logs,fracture’s parameters,such as fracture density,dip,width and filling and illustrate the response of low angle fracture and high angle fracture in logs.

Determination of target-oriented parameters for computation of curvature attributes

2018 ◽  
Vol 6 (2) ◽  
pp. T485-T498 ◽  
Author(s):  
Lee Hunt ◽  
Bahaa Beshry ◽  
Satinder Chopra ◽  
Cole Webster
Keyword(s):  
Positive Curvature ◽  
Time Windows ◽  
Window Size ◽  
Parameter Selection ◽  
Fracture Density ◽  
Natural Fractures ◽  
Deep Basin ◽  
Seismic Line ◽  
Curvature Estimates ◽  
Seismic Volumes

The application of curvature attributes on seismic horizons or 3D seismic volumes has been discussed in the literature in several ways. Such discussion largely ignores the detail of parameter selection that must be made by the working interpreter or the expert processor. Parameter selection such as window size and filtering methods for seismic curvature estimates have not been extensively compared in the literature and have never been validated using quantitative ground truthing to log or drilling data. Of even greater relevance to the interpreter is the lack of discussion of curvature parameters as they are relevant to interpretive and operational concerns. We focus on the seismic most-positive curvature attribute, its parameterization, and filtering for the overpressured tight sand target in the Falher F formation of the deep basin of Alberta, Canada. This sand has numerous natural fractures that constitute an occasional drilling hazard due to mud losses. Various parameterizations on horizon- and volume-based curvature extractions are made and examined in the context of the drilling results of four horizontal wells, one of which has image log fracture density along the lateral portion of the well. We compared different lateral (and vertical where applicable) window sizes in the initial curvature estimates, as well as different postcurvature filtering approaches including unfiltered, Gaussian-filtered, and Fourier-filtered products. The different curvature attribute estimates have been evaluated by way of map comparisons, cross-section seismic line comparisons, and correlations with the upscaled fracture density log data. We found that our horizon-based estimates of positive curvature suffered from mechanical artifacts related to the horizon picking process, and the volume-based methods were generally superior. Of the volume-based methods, we found that the Fourier-filtered curvature estimates were the most stable through smaller analysis windows. Gaussian-filtering methods on volumetric curvature gave results of varying quality. Unfiltered volumetric curvature estimates were only stable when very large time windows were used, which affected the time localization of the estimate. The comparisons give qualitative and quantitative perspective regarding the best parameters of curvature to predict the key properties of geologic target, which in this case are the potentially hazardous natural fractures within the overpressured Falher F sandstone.

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