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Fifth EAGE Eastern Africa Petroleum Geoscience Forum
- Conference date: March 30, 2021 - April 1, 2021
- Location: Online
- Published: 30 March 2021
23 results
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Applied Geoscience Project
By V. OjoSummaryImportance, economic impacts, result in part of the world and possible solutions on geoscience
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Reservoir Delineation and Characterization in the Northern Orange Basin, using Genetic Inversion and Seismic Attributes
By R. AfricaSummaryFor this study two geophysical techniques were implemented to delineate potential hydrocarbon reservoirs and perform reservoir characterization in the Northern Orange Basin, Offshore South Africa. The aim of this study is to use seismic attributes with genetic inversion to delineate potential reservoir distribution and quality within the study area. Petrophysical properties use to characterize reservoir quality were porosity (F) and volume of shale (Vsh).
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Integrated Studies Intrigue to Mineral Prospectivity. Applicability to Kikombo, Dodoma, Tanzania.
More LessSummaryDetailed prospecting studies were carried out in Kikombo, Dodoma, Central Tanzania to examine the possible mineralization zones through delineating subsurface structures and characterizing geochemical distribution of various elements by integrating the results of the methods applied. The prospecting methods utilized include geological methods, regional aeromagnetic survey, local ground magnetic survey, airborne gravity survey, induced polarization survey and geochemical survey. Geological observation shows the area’s underneath geology to be composed of tonalitic — orthogneiss rock types whose regolith is composed of brown sand which is light as well as reddish. Gravity survey results suggest high gravity anomaly to most of the occupied area. Aeromagnetic surveys reveal high magnetic anomaly to most of the occupied area with NE-SW structural trending patterns. Local ground magnetic survey reveals to lack prominent structures (faults) that are deep and localized, however, the shallow structures were revealed showing similar trend of NE -SW. The depth to the magnetic anomaly of various methods employed goes up to 494.1 m. IP results indicate high resistive and chargeable bodies at the basement with some faults striking NE-SW. Geochemical survey shows the concentration of elements such as As, Au, Ca, Cr, Cu, Fe, K, Mg, Mn, P, S, Ti, V, Zn and Zr while suggesting a strong positive correlation of Mn and Cu.
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Analysis of the Regional Sediment Distribution along the East Coast, South Africa during Gondwana Break up and its Hydrocarbon Potential
By S. DavidsSummaryThe frontier east coast offshore South Africa has an active petroleum system that is proven with only four offshore wells in the Durban basin. This paper is part of a regional evaluation conducted at the Petroleum Agency SA and highlights the sediment distribution pattern and the potential of the area. The importance of the hinterland is essential in understanding the sediment source to sink evolution of the southern African offshore. The potential sediment sources from the hinterland includes Jurassic coarse to fine grained sandstones, mudstones, siltstone and shales. The newly acquired non-exclusive seismic data was the primary seismic data source used. The results from the seismic mapping produced isopach maps for the Lower Cretaceous, Mid Cretaceous, Upper Cretaceous and the Cenozoic. The Agency’s 1D basin modelling study demonstrated that hydrocarbon potential exists within the vast study area. Thermal modelling has demonstrated that hydrocarbons have been generated from various stratigraphic levels within this frontier basin provided suitable source rocks are present. However, the lack of good quality source rocks at the existing wells in shelfal locations means that the presence of source rocks in more favorable palaeo bathymetric positions currently remains hypothetical.
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Seismic Reveals Potential New Deep Source Rocks off the Western and Eastern Margins of South Africa
Authors A. Fielies, J. Salomo and C. Van BloemensteinSummaryTwo potential source rocks have been identified and mapped using recently acquired seismic data along the South African margin. One of these overlies transitional crust along the passive margin off the west coast, and the other overlies oceanic crust along the transform margin of the east coast. This study aims to draw inferences on both source rocks and their hydrocarbon potential, and their significance for petroleum exploration along the South African margin.
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Hydrocarbon Seep Hunting: Soil Gas Geochemical Sampling Application in the Karoo Basin, South Africa
Authors Z. Mowzer and C. MotsoalediSummaryGeochemical soil sampling is an important method for determining if there are hydrocarbons present within the soil, the extent of the seepages and if there have been any contamination within the groundwater aquifers (Field Sampling procedures manual; 2005; Abrams et al. 2009). The study focuses on the baseline geochemical soil sampling study within the area of Beaufort West and three wells (AB1/65, KA 1/66 and VR 1/66) to delineate the volatile and semi-volatile organic compounds present within the soil surrounding the shale gas onshore acreage. Historical data on the above-mentioned wells reveals dry gas throughout most of the lithological logs. However, this is speculative at best as these results are informed by cuttings within the stratigraphic sections, this research will aim to address the gaps within the dataset and ascertain the validity of the hydrocarbon source.
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Stratigraphic Forward Modelling in Albert Lake as a Tool for an Integrated Understanding of Basin Sedimentary Infilling
Authors G. San Miguel, N. Vilasi-Marmier, M. Bez, S. Veillard, N. Buratti, M. Rousseau, A. Ahmed, M. Stankoff and J.L. RubinoSummaryHydrocarbon exploration over the Ugandan side of the Albert Graben is still within main operators’ program. The 2019 second Ugandan Bid Round reoffered several blocks that requires further evaluation of the proven petroleum system. In these areas, exploration is mainly driven by potential fields methods and sparse 2D seismic data, locally complemented with precious 3D seismic data. Hence, integrating of surface and subsurface data at regional-scale in an overall source-to-sink study remains crucial (i.e. detrital geochemical studies, tectono-stratigraphic analyses associated to an age model built up by combining sedimentological and biostratigraphical outcrop studies). This work illustrates an integrated update of the sedimentary basin infill of Albert Graben developed thanks to multi-disciplinary regional synthesis. The results can be used for defining the reservoir-presence risk as well as the distribution of the source rock-type (terrigenous to lacustrine end-members) expected in the deepest and potentially matured part of the basin for petroleum system modelling.
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Regional Aquifer Characterization in the Buliisa Area – Uganda.
Authors L. Cedric, L. Cantegrel, L. Carcione and E. GaucherSummaryThe purpose of this paper is to detail the multidisciplinary approach employed to understand the hydrostatic and regionally common aquifer within the hydrocarbon bearing reservoirs in the Buliisa Area (Tilenga Project) of the Lake Albert in Uganda. The results of the study led to a better definition of the free water depth having consequences in the low case resources considerations and having impact in the development perimeter of the Tilenga project.
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Adoption of a Standardized Checklist for Quality Checking Geomodelling Workflows for a Green Field in the Albertine Graben, Uganda
Authors J. Ecau, A. Nyombi and A. Aya O’BialeSummaryA KPI based standardized model checklist therefore enables timely and thorough evaluation of Geomodels based on the key inputs, workflows (modelling approach) and their likely impact on subsurface uncertainties and resources. This therefore enables the PAU to effectively communicate its key findings with the Licensees thus streamling the Authority’s regulatory functions related to monitoring subsurface operations.
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Identification of Bypassed Oil in Carbonate Buildup Reservoir at Mature Field with Integration of Saturation Log and Cement Bond Quality
Authors I.K. Barus, H. Sipahutar, A. Sukmatiawan, A. Amperianto and G. SucahyoSummaryThe SK field operated by Pertamina EP is a mature field with RF of 41%. The main producing formation is a reef build-up carbonate reservoir. The production data shows significantly increasing water-cut, which was much faster than the cumulative production. Along with the available Fractional Flow data, this shows promising chance of production optimization. There are several key contributing factors for the water production in the SK field, i.e. water channeling behind casing due to poor cement bond, uneven production of the wells leading to varying water rise and water coning. Several efforts have been performed to optimize production, namely: identification of the potential of bypassed oil in the wells by evaluating current saturation evaluation through downhole surveillance, estimation of current water contact and cement bond improvement. Production optimization so far has been successfully achieved through comprehensive effort starting with the screening process of candidate wells, the evaluation of cement bond quality, the wellsite execution for bypassed oil evaluation and bypassed oil production. From the total of seventeen wells, fourteen wells were successfully re-perforated and put on production with incremental gain of approximately 10000 BOPD. Success rate of bypassed oil identification and production of bypassed oil is roughly 82%.
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Evaluation of the Coalbed Methane Prospectivity of the Ermelo Coalfield (Amersfoort Project Area), Main Karoo Basin, South Africa
Authors X. Schalkwyk and T. ThovhogiSummaryThe evaluation of the coalbed methane (CBM) potential of the Ermelo Coalfield in the Mpumalanga Province of South Africa. Previous studies done by the Agency revealed that the coals vary in rank from high volatile bituminous to medium bituminous and considered favourable for the occurrence of CBM due to the presence of extensive coal deposits and adequate depths for CBM development and preservation. The primary objective of this study is to identify play fairways and assess the petroleum geology and hydrocarbon potential in the Permian coal-bearing Karoo-aged basin. The Ermelo Coalfield is located in the extensive Permian age coals of South Africa’s Main Karoo Basin with the most significant coal seams contained within the Ecca Group. The coalfield is considered highly prospective for coalbed methane and also gassy sandstone overlying the coal horizons. Gas contents have been reported in studies associated with previous mining attempts but no actual measured gas contents are available. The Agency adopted a three-stage process that involved gathering and evaluating the quality of existing borehole data for evaluating the CBM resource potential of the basin. Generally, exploration borehole locations, lithology descriptions, and coal composition (proximate analysis) data are available for the Ermelo coalfield. Because direct gas content data is lacking for the Ermelo coalfield, the gas storage capacity (gas content) was estimated by the indirect method of Kim (1977) which calculates dry, ash-free gas storage capacity of bituminous coal from proximate analysis using temperature, pressure and depth data.
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Shale Gas Resource Assessment of the Organic-rich Ecca Group Shale of the Karoo Basin: Prospective Area Delineation and Resource Estimation
By S. AdamsSummaryAssessment of the shale gas resource potential of the southern Main Karoo Basin in South Africa.
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Exploiting the Geothermal Potential of East Africa for Energy Diversification and Sustainability
Authors K. Ndyamuhaki, O. Ssembataya and J. BalingaSummaryThe East African region is a major bearer of geothermal potential in the world. However, even with this blessing, the region still suffers from energy deficiency as it still depends on mainly hydro electric power. This is because very little of this potential, if at all; in some countries,has been developed. This can only be reverted if substantial investment is made into geothermal exploration and development. Geothermal power has numerous advantages over other sources of power as it is not affected by drought and climatic variability, has the highest availability (capacity factor) at over 95 %, is green energy with no adverse effects on the environment, and is indigenous and readily available in the region, unlike most thermal energy that relies on imported fuel. This makes geothermal a very suitable source for base-load electricity generation in the region. Therefore, it is high time the regional countries harnessed their geothermal potential.
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Hunt for Oil in Offshore Angoche, Mozambique
By D. RatheeSummaryInterpretation of seismic data combined with petroleum systems modeling highlights the exploration potential of the Angoche for liquid hydrocarbons. Turbidite systems have been quite actively depositing sediments in deep offshore since late Jurassic, but high sediment rates are observed from late cretaceous onwards. Upper Cretaceous-Lower Tertiary is dominated by basin floor fans whereas onshore African uplift during the Priabonian significantly increased clastic input. We can see vertical incision of the channel systems during Mid to late Tertiary in the form of stacked channel complexes. Since the mid Miocene, the southward propagation of the East African Rift has destabilized the margin resulting in slope failure systems and mass transport deposits acting as the main form of sediment supply in more recent times. Numerous leads are identified at various stratigraphic intervals. These are mapped out and supported by AVO analysis (Class II & III) and PSM study. Cretaceous source rocks are modeled to be expelling oil even to present day, which would be indicative that the Angoche basin is more oil prone. Upper & lower Cretaceous intervals reach critical moment in Palaeocene & Miocene respectively. The next-round of drilling campaigns in Mozambique over the Angoche area will provide further necessary data to conclude the oil or gas debate.
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Oil & Gas Exploration in Brazil using the Magnetotelluric Method: An Example for East Africa
Authors P. De Lugao and B. KriegshaeuserSummaryWe have successfully helped to introduce the magnetotelluric (MT) method in the workflow for the exploration of oil&gas in Brazil and strongly suggest that the MT method can be used in the frontier onshore areas of East Africa. The MT method is used to uncover the potential of frontier onshore basins and also to delineate prospects in the mature basins. The MT method is a powerful frequency domain electromagnetic technique that provides a resistivity model of the subsurface of the earth at depth. MT data acquisition is fast, environmentally friendly and provides the structural and stratigraphic information needed to explore onshore basins. In recent years, the magnetotelluirc (MT) method was considered by the National Petroleum Agency (ANP) of Brazil as a valuable exploration tool and was added to the list of methods that account for the Exploratory Program (PEM).
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3D Seismic Evidence for the Beira High as a Continental Fragment
By S. SuttonSummaryA new 3D seismic dataset over part of the Beira High has revealed details of internal basement geometry, early volcanic deposits, the top basement unconformity, and an early carbonate platform. Internal seismic reflection geometries within the basement appear much more consistent with continental than with oceanic crust. Extensive volcanic features appear to be largely subaerial. The 3D seismic facilitates map view analysis of the top basement unconformity and immediately overlying deposits, clearly showing that the basement has undergone subaerial rather than submarine erosion, and is overlain by a rimmed carbonate platform. These geological lines of evidence complement the earlier geophysical measurements, and support the hypothesis that at least part of the Beira High is a fragment of continental crust that was sufficiently buoyant, during the Early to Middle Jurassic opening of the Indian Ocean, to be emergent or nearly emergent, even though the present day water depth is on the order of 1 to 2 kilometers.
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The Brulpadda Discovery and Accelerated Follow-up de-risking in a Complex Environment
Authors W. Gordon Canning, C. Scheffer, M. Zweigert, E. Bof, M. Rousseau, A. Bourgeois, A. Perchoux, G. Sterbecq, G. Loir and J.M. BugeatSummaryThe Brulpadda discovery Operated by Total (45%) in early 2019 has been part of a long journey of technical expertise, engineering collaboration and R&D integration in order to execute the well in only 61 days with 4% WoW in such an environment.
The Brulpadda well is the first well drilled in the Deep Offshore of South Africa and tested the
Paddavissie Play within the Outeniqua Basin. The well was drilled on 2D data supported by AVO with further follow-up potential already mapped on the trend.
In order to accelerate follow-up exploration a post discovery 3D seismic survey had already been prepared prior to Brulpadda well spud enabling first shot less than a month after P&A of well operations. A Fast Track 3D volume allowed preparation of a follow-up drilling program scheduled to start in Q2 2020 utilising the proven capabilities of the DSS.
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Reviving the Cretaceous Deep Water Clastics Plays of Southern Namibia
Authors J. Bijkerk, S. Dekker, M. Poupon, J. Reijs, K. Van Toorenenburg and P. LambregtsSummaryThe Orange Basin, offshore South Africa and Namibia forms a major Cretaceous depocenter that has only been significantly explored on the shelf with exploration currently shifting to deep water blocks. Shell is currently evaluating PEL39, a Namibian deep water block located outboard of the Orange River. This study focuses on the facies indicating the interplay of gravity and contour currents, their methods of interaction, and their potential implication for reservoir development based on the newly acquired 3D seismic. Some turbidite reservoir levels show development of large-scale sediment waves. These wave fields are the most prominent seismic features hinting at contouritic influence and can span 10’s of kilometres and have thicknesses of 100’s of metres, with individual crests spaced several kilometres apart. They indicate a synchronous interaction between gravity and contourite currents and highlight similarities to the sedimentology of the Coral Field in the Rovuma Basin. At present, Shell and JV partners Kosmos and NAMCOR are evaluating the clastic play fairway on two newly acquired seismic surveys (∼7500 km2) in preparation for an exploration drilling campaign in the upcoming years.
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2D Coda Attenuation Analysis in Sub-Basaltic Regions from Active Sources
By K. AsenaSummaryMainstream seismology adopts the use of passive as opposed to active seismic waveforms to evaluate seismic attenuation parameters, often depicting lateral variation in attenuation as well as changes in attenuation with depth. Despite the successful and widespread use of attenuation parameters in characterising the earth’s lithosphere, active seismic datasets are yet to be adopted in imaging reservoirs. In this study, the potential of using seismic reflection data acquired within the North-Eastern Atlantic margin was investigated. This study aims to transfer knowledge from the numerous seismic attenuation research applied to volcanoes and earthquakes and adapting it to the oil and gas industrial setting. Stacked signals were adopted in the analysis with optimal parameters established to investigate the capability of the dataset to quantify attenuation. A multiple scattering model was adapted assuming the contributions due to intrinsic absorption were dominant over scattering effects within a large lapse times. The frequency dependent models were jointly interpreted using the images of seismic sections, well data and the documented regional geology of the underlying rock sequences. This non-invasive method utilizes already acquired seismic data and any inferred conclusion from the analysis can be upscaled from the rock to reservoir scales.
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Determination of Reservoir Properties of the Semliki Basin Using Rock Physics Templates
Authors J. Nakajigo and J.M. KiberuSummaryRock physics plays an important role in reservoir characterization as it links seismic properties to reservoir properties. The Semliki basin is located in the Albertine Graben in the western arm of the East African rift valley. The study demonstrated the application of rock physics modelling whereby two rock physics models were developed namely; Constant Cement model and unconsolidated model. Rock Physics Templates (RPTs) developed by using model parameters to analyse reservoir properties. The four zones identified on the RPT, are interpreted as gas sand, brine sands, shaly sands and shales. The shales indicate decreasing acoustic impedance with increasing Vp/Vs ratio interpreted as laminated shales. To examine the effects of Vp, Vs and impedance, fluid replacement modeling (FRM) was carried out. It was observed that P-wave, density, water saturation, fluid density, fluid modulus, increases on replacing gas with water at all percentages (50% and 100%). However, Swave decreases while bulk modulus matrix, shear modulus matrix and matrix density remained constant. This is because S-wave is insensitive to fluid and the other parameters remain constant because replacing gas with water does not increase the matrix.
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Local Content Legislative Framework in Kenya
Authors L. Obwogo, L. Koiyo, J. Waringa and A. OmarSummaryThis paper analyses the provisions as well as strengths and weaknesses of the Petroleum Exploration and Production Act of 1986 with regard to Local Content Requirements. Specifically, it outlines various challenges faced by upstream Kenyan contractors as a result of the old legislation that hindered their effective participation in the sector. It then compares and analyses the facelift on Local Content Requirements outlined therein in overcoming the weaknesses of the 1986 Act. In addition, various risks — to Government, IOCs and the Local communities — are outlined.
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Where next offshore East Africa? Mega-regional seismic dataset highlights new play potential
Authors N. Hurst and P. BellinghamSummaryThe offshore East African margin has proven a rich exploration province over the last 10 years. We use a mega-regional integrated seismic dataset stretching from Northern Kenya to the Angoche Basin, Mozambique to highlight new play potential across the region.
In Kenya, we demonstrate two distinct provinces in the offshore, separated by the Davie-Walu Ridge. To the north, the system is dominated by a narrow shelf and steep slope with gravitational deformation prevalent. To the south the Tembo trough presents a confined recently deformed system with multiple trapping geometries with clastic and carbonate targets.
Intense recent deformation and structural inversion has created the uplifted areas of Zanzibar and Pemba islands. We show how this deformation presents likely trapping geometries and targets. Outboard tectonism along the Davie Fracture Zone has resulted in several Lower Cretaceous structures upon which potential reservoir systems onlap or cover.
In the Comoros, our investigation focuses on the potential for Cretaceous and Palaeogene deep-water sand systems charged by Lower Cretaceous source rocks. Multiple, large low relief structures provide significant volume potential.
The Angoche Basin, Mozambique provides the last area of discussion. We show some of the potential reservoir and trap architectures in the thick post rift section of this basin.
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Reconstruction of Sediment Routing into the South African Cape Basin for Reservoir Quality Predictions
Authors K. Van Toorenenburg, M.W. Blakeley, C.R. Carvajal and J.F. BijkerkSummaryThe Cape Basin is an underexplored depocentre that forms part of the greater Orange Basin, situated offshore on Southern Africa’s Atlantic Margin. This study assesses reservoir quality based on offset well data to underpin the current exploration effort in block 5/6/7. The work includes a reconstruction of regional sedimentary pulses and drainage evolution, and updated core descriptions of offset exploration and DSDP wells. The results are used as input for reservoir-quality models.
Lower Cretaceous post-rift basin floor fans in the Cape Basin are likely sourced from Table Mountain Group quartzites of the Agulhas Arch, forming the down-slope equivalent to the shelfal sands in well C-B1. Away from diagenesis related to phreatic water, these fans are expected to have good reservoir quality. Outboard well DSDP 361 shows regionally extensive organic-rich shales, providing close access to charge when extended into the Cape Basin. Marine pelagic shales and sediment waves would serve as a seal over closures in the basin. The reconstruction of sediment routing presented here helps to de-risk the reservoir play element in the Cape Basin.
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