scholarly journals Evaluation of the reservoir architectural elements in deepwater turbidites of Niger Delta – a case study from the “AFUN” Field

2021 ◽  
Vol 51 (1) ◽  
pp. 83-108
Author(s):  
Yemisi C. AJISAFE
Keyword(s):  
Seismic Data ◽  
Niger Delta ◽  
Architectural Elements ◽  
Structural Style ◽  
Reverse Faulting ◽  
Thrust Zone ◽  
Detailed Interpretation ◽  
Fault Interpretation

3D post-stack time migrated seismic data and a suite of composite well log data from six wells drilled within the “AFUN” field Niger delta were used to effect a detailed interpretation of the field. This was with a view to delineating architectural elements that control reservoir quality of a deepwater turbidite reservoir. The data analyses were done using the Petrel software. LAS file of logs were imported into the Petrel software as well as SEG.Y. seismic data. Fault interpretation and horizon mapping were based on the well-seismic tie from the generated seismogram. Time and depth structure maps were created. Thirty faults which include growth faults, reverse faults, collapsed crest structure and as well as faults that are synthetic and antithetic to the growth faults were mapped. The growth faults are believed to act as pathways for the updip movement of hydrocarbon from the Akata Formation to Agbada Formation. The structural interpretation showed that the area has been subjected to compressional deformation which resulted in reverse faulting system in toe thrust zone influenced by shale diapirs. The maps revealed contour closures that belong to an anticlinal structure which is forming traps in the reservoirs. The structures are faulted North-South trending rollover anticlines. It has also been shown that the distribution and type of architectural elements i.e. fractures within the fan system have major impact upon the reservoir distribution, continuity and connectivity of sand/shale bodies. The study concluded that structural style and facies architecture are the two fundamental elements that defined the reservoir heterogeneity of the “AFUN” Field.

scholarly journals Fault Interpretation Uncertainties using Seismic Data, and the Effects on Fault Seal Analysis: A Case Study from the Horda Platform, with Implications for CO<sub>2</sub> storage

2021 ◽  
Author(s):  
Emma A. H. Michie ◽  
Mark J. Mulrooney ◽  
Alvar Braathen
Keyword(s):  
Fluid Flow ◽  
Seismic Data ◽  
Growth Models ◽  
Fault Analysis ◽  
Surface Generation ◽  
Co2 Injection ◽  
Line Spacing ◽  
Fault Growth ◽  
Fault Interpretation

Abstract. Significant uncertainties occur through varying methodologies when interpreting faults using seismic data. These uncertainties are carried through to the interpretation of how faults may act as baffles/barriers or increase fluid flow. How fault segments are picked when interpreting structures, i.e. what seismic line spacing is specified, as well as what surface generation algorithm is used, will dictate how detailed the surface is, and hence will impact any further interpretation such as fault seal or fault growth models. We can observe that an optimum spacing for fault interpretation for this case study is set at approximately 100 m. It appears that any additional detail through interpretation with a line spacing of ≤ 50 m adds complexity associated with sensitivities by the individual interpreter. Further, the location of all fault segmentation identified on Throw-Distance plots using the finest line spacing are also observed when 100 m line spacing is used. Hence, interpreting at a finer scale may not necessarily improve the subsurface model and any related analysis, but in fact lead to the production of very rough surfaces, which impacts any further fault analysis. Interpreting on spacing greater than 100 m often leads to overly smoothed fault surfaces that miss details that could be crucial, both for fault seal as well as for fault growth models. Uncertainty in seismic interpretation methodology will follow through to fault seal analysis, specifically for analysis of whether in situ stresses combined with increased pressure through CO2 injection will act to reactivate the faults, leading to up-fault fluid flow/seep. We have shown that changing picking strategies alter the interpreted stability of the fault, where picking with an increased line spacing has shown to increase the overall fault stability. Picking strategy has shown to have minor, although potentially crucial, impact on the predicted Shale Gouge Ratio.

scholarly journals Fault interpretation uncertainties using seismic data, and the effects on fault seal analysis: a case study from the Horda Platform, with implications for CO<sub>2</sub> storage

Solid Earth ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 1259-1286
Author(s):  
Emma A. H. Michie ◽  
Mark J. Mulrooney ◽  
Alvar Braathen
Keyword(s):  
Fluid Flow ◽  
Seismic Data ◽  
Growth Models ◽  
Fault Analysis ◽  
Surface Generation ◽  
Co2 Injection ◽  
Line Spacing ◽  
Fault Growth ◽  
Fault Interpretation

Abstract. Significant uncertainties occur through varying methodologies when interpreting faults using seismic data. These uncertainties are carried through to the interpretation of how faults may act as baffles or barriers, or increase fluid flow. How fault segments are picked when interpreting structures, i.e. which seismic line orientation, bin spacing and line spacing are specified, as well as what surface generation algorithm is used, will dictate how rugose the surface is and hence will impact any further interpretation such as fault seal or fault growth models. We can observe that an optimum spacing for fault interpretation for this case study is set at approximately 100 m, both for accuracy of analysis but also for considering time invested. It appears that any additional detail through interpretation with a line spacing of ≤ 50 m adds complexity associated with sensitivities by the individual interpreter. Further, the locations of all seismic-scale fault segmentation identified on throw–distance plots using the finest line spacing are also observed when 100 m line spacing is used. Hence, interpreting at a finer scale may not necessarily improve the subsurface model and any related analysis but in fact lead to the production of very rough surfaces, which impacts any further fault analysis. Interpreting on spacing greater than 100 m often leads to overly smoothed fault surfaces that miss details that could be crucial, both for fault seal as well as for fault growth models. Uncertainty in seismic interpretation methodology will follow through to fault seal analysis, specifically for analysis of whether in situ stresses combined with increased pressure through CO2 injection will act to reactivate the faults, leading to up-fault fluid flow. We have shown that changing picking strategies alter the interpreted stability of the fault, where picking with an increased line spacing has shown to increase the overall fault stability. Picking strategy has shown to have a minor, although potentially crucial, impact on the predicted shale gouge ratio.

scholarly journals Investigation of geophysical challenges in land seismic data acquisition in Nigeria: case study of parts of the Niger Delta region

2021 ◽  
Vol 11 (2) ◽  
pp. 587-599
Author(s):  
C. N. Onwubuariri ◽  
L. S. Al-Naimi ◽  
B. I. Ijeh ◽  
T. I. Mgbeojedo ◽  
M. U. Igboekwe ◽  
...  
Keyword(s):  
Seismic Data ◽  
Niger Delta ◽  
Weather Conditions ◽  
Seismic Exploration ◽  
Noise Interference ◽  
Niger Delta Region ◽  
Cloudy Weather ◽  
Seismic Acquisition ◽  
Seismic Data Acquisition

AbstractGeophysical analysis was carried out to evaluate the challenges encountered in land seismic exploration within the study area. This analysis cuts across various stages in land seismic acquisition. These stages include the following: the availability of the prospect map as originally planned by the prospect owners—the client, the desk study and planning of this map by the seismology section (planning seismologist) for acquisition convenience and the field implementation of the acquisition which the survey, drill and recording (preloading, shooting, swath move, line check, LAUX crew and recording platform) sections carried out. The challenges observed included environmental challenges, noise interference, weather conditions (statics or electrostatics interference), line break, faulty equipment, wrong detailing, cake or expired explosives, poor or compromised supervision, security and permit challenges. These challenges are peculiar to Nigeria due to inadequate implementation of policies that guide human settlements and activities. Nigeria is within the climate region where most at times it is very impossible to control natural events like cloudy weather, rainfall, thundering and lightening. As such, the problem of static charges interfering with acquired seismic data becomes inevitable, mostly during the rainy season. Almost total dependency on imported technology and lack of readily available experienced manpower also contribute to these challenges, most especially when it has to do with proper inspection of equipment and materials required for the acquisition and supervision processes. Approaches to follow to minimize the observed challenges were equally highlighted.

Northern Houtman Sub-basin prospectivity—preliminary results

2016 ◽  
Vol 56 (2) ◽  
pp. 577
Author(s):  
Irina Borissova ◽  
Chris Southby ◽  
George Bernardel ◽  
Jennifer Totterdell ◽  
Robbie Morris ◽  
...  
Keyword(s):  
Seismic Data ◽  
Source Rocks ◽  
Large Igneous Province ◽  
The North ◽  
Structural Style ◽  
Igneous Province ◽  
Line Spacing ◽  
History Of

In 2014–15 Geoscience Australia acquired 3,300 km of deep 2D seismic data over the northern part of the Houtman Sub-basin (Perth Basin). Prior to this survey, this area had a very sparse coverage of 2D seismic data with 50–70 km line spacing in the north and an industry grid with 20 km line spacing in the south. Initial interpretation of the available data has shown that the structural style, major sequences, and potential source rocks in this area are similar to those in the southern Houtman and Abrolhos sub-basins. The major difference between these depocentres, however, is in the volume and distribution of volcanic and intrusive igneous rocks. The northern part of the Houtman Sub-basin is adjacent to the Wallaby Plateau Large Igneous Province (LIP). The Wallaby Plateau and the Wallaby Saddle, which borders the western flank of the Houtman Sub-basin, had active volcanism from the Valanginian to at least the end of the Barremian. Volcanic successions significantly reduce the quality of seismic imaging at depth, making it difficult to ascertain the underlying thickness, geometry and structure of the sedimentary basin. The new 2D seismic dataset across the northern Houtman Sub-basin provides an opportunity for improved mapping of the structure and stratigraphy of the pre-breakup succession, assessment of petroleum prospectivity, and examination of the role of volcanism in the thermal history of this frontier basin.

Stochastic inversion by trace matching for carbonate reservoir property prediction: A Mishrif Reservoir case study

2019 ◽  
Vol 38 (1) ◽  
pp. 27-34 ◽  
Author(s):  
Sara R. Grant ◽  
Matthew J. Hughes ◽  
O. J. Olatoke ◽  
Neil Philip
Keyword(s):  
Seismic Data ◽  
Carbonate Reservoir ◽  
Inversion Process ◽  
Reservoir Properties ◽  
Stochastic Inversion ◽  
Large Numbers ◽  
Well Data ◽  
Established Technique

Estimation of reservoir properties and facies from seismic data is a well-established technique, and there are numerous methods in common usage. Our 1D stochastic inversion process (ODiSI), based on matching large numbers of pseudowells to color-inverted angle stacks, produces good estimations of reservoir properties, facies probabilities, and associated uncertainties. Historically, ODiSI has only been applied to siliciclastic reservoir intervals. However, the technique is equally suited to carbonate reservoirs, and ODiSI gives good results for the Mishrif Reservoir interval in the Rumaila Field in Iraq. Of course, a thorough awareness of the quality of all input well data and detailed validation of the parameters input to the inversion process is crucial to understanding the accuracy of the results.

scholarly journals Carbonaceous schists of the Main Central Thrust zone as a source of graphite: a case study from the Kali Gandaki valley, west Nepal

1970 ◽  
Vol 14 ◽  
pp. 9-14 ◽  
Author(s):  
Lalu Prasad Paudel
Keyword(s):  
Flake Graphite ◽  
X Ray Diffraction ◽  
Main Central Thrust ◽  
X Ray ◽  
Potential Sources ◽  
Thrust Zone ◽  
Carbonaceous Rocks ◽  
Graphitic Material

Petrological study and X-ray diffraction analysis were carried out to identify the content and quality of graphitic material inthe carbonaceous schist from the Main Central Thrust zone in the Kali Gandaki valley, west Nepal. The study shows that thecarbonaceous schists contain more than 15-30% graphite. They contain both amorphous and flake graphite with variable grainsize. As graphite is being mined commercially in rocks containing even <5% graphite worldwide, carbonaceous rocks of the MainCentral Thrust zone can be a potential sources of commercial graphite in Nepal.DOI: http://dx.doi.org/10.3126/bdg.v14i0.5431Bulletin of the Department of Geology Vol.14 2011, pp. 9-14

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