Karyna Rodriguez

The Mid North Sea High (MNSH) consists of a ridge of Paleozoic strata located in the centre of the North Sea between 55° N and 56° N. In 2010, interest in the Permian of the MNSH was revived by the discovery in Quadrant 44 of the Cygnus gas field. This study focuses on the Zechstein carbonates of the MNSH and uses play concepts that draw an analogy with the Zechstein oil and gas fields discovered in Denmark and Poland, and also with the Wissey gas field in Quadrant 53.New 2D seismic establishes the presence of a significant Zechstein reef that blocks the southern entrance of the Jenyon Gap onto the MNSH. Seismic data show that the reef developed in stages and its presence can be inferred from the occurrence of isolated lagoons within the centre of the build-up. The barrier reef's existence explains both the presence of the rare hygroscopic mineral tachyhydrite in the centre of the MNSH and also the observed isopach difference in the Zechstein cycles over the MNSH, as the barrier...

Oriol Ferrer (1), Oskar Vidal-Royo (2), Oscar Gratacós (1), Eduard Roca (1), Josep Anton Muñoz (1), Paolo Esestime (3), Karyna Rodriguez (3), Mary Yazmin Piragauta (1), and Nil Feliu (1) (1) Geomodels Research Institute, Departament de Ciències de la Terra i de l′Oceà, Facultat de Ciències de la Terra, Universitat de Barcelona, Barcelona, Spain (joferrer@ub.edu), (2) Terractiva Consulting SL, Barcelona, Spain , (3) Spectrum Geo Ltd., Woking, Surrey, United Kingdom.

The Durban-Zululand Basin provides an exceptional example of a transform margin that developed during the break-up of Gondwana and the subsequent evolution of the continuation of the Falklands-Aghulas Fracture Zone. The area remains an untested frontier basin with substantial potential for hydrocarbon exploration in particular following the recent discoveries along the East African Margin. Recent acquisition of high fidelity 2D reflection data from offshore Durban and Zululand Basin, in the south-east coast of South Africa, has provided unparalleled new insights into the evolution of the basin, its crustal architecture and structural development. The structural framework mapping of the newly acquired reflection data, coupled with potential field data modelling, illustrates the highly variable nature of the crust in the Durban basin that incorporates a range of crustal types from highly extended crust, allochthonous basement highs to magmatic crust. Understanding the spatial distribu...

Presented here through the interpretation of 2D and 3D seismic data is a suite of 5 linearly distributed trails of fluids escape pipes with pockmarks at their upper terminus. These pipe trails bypass the thick Messinian evaporites, in an area of frontier exploration offshore Lebanon. One of the pipe trails roots to the crest of a prominent pre-salt fold named the Oceanus Structure, while the other 4 pipe trails emanate from a different pre-salt fold named here the Saida-Tyr Structure. The pipes are interpreted to root in Early Miocene sandstone reservoirs analogous to the ‘Tamar’ sands, which are the main reservoir interval in the South Levant Basin following the discovery of >35 Tcf of biogenic methane. The pipe trails are oriented NW-SE and the pockmarks increase in age to the NW, with the first expulsion episode in each trail dated at 1.7 Ma (±0.3 Ma). Each expulsion episode has been systematically offset to the NW, away from the crestal foci of the fold by the flow of the salt, resulting in deformation of the fluids escape pipes in the salt. The outer most deformed pipe in each trail is imaged in 3D seismic data and extends obliquely through the salt at angles of 15°-16° from the pre-salt anticline to directly beneath the first pockmark, demonstrating that the top of the salt and the base of the Pliocene to Recent overburden are coupled. These deformed fluids escape pipes present a natural marker for the deformation through a salt sheet, revealing a Couette flow regime and flow velocities at the top of the salt sheet ranging from 2-4 mm/yr. The 4 pipe trails above the Saida-Tyr Structure presents the first direct calibration for the 3D kinematics of a salt sheet deforming under gravity. Flow orientation above the Saida-Tyr Structure remains consistently parallel over a distance of ~3.5 km, while flow velocities and maximum flow distance in each pipe trail varies by 1mm/yr and 2.5 km respectively. The onset of fluid expulsion from these pipe trails is synchronous with the onset of the most recent phase of extension at the salt basin margins. This means that the deformed fluid escape pipes record the cumulative strain of the salt sheet since the onset of the most recent post-Messinian phase of deformation of the salt in the Levant Basin, and implies a genetic link between the triggers for salt flow and fluid expulsion. Changes in flow direction and flow velocity in the salt can be used to highlight variability in the driving forces of differential loading and marginal uplift and titling around the basin margin, which has implications for migration, fluids expulsion and overpressure.

Summary East Africa conjugate margin evaluation has led to a greater understanding of source rock deposition and distribution as well as a detailed analysis of the similarities and differences in stratigraphic evolution offshore Somalia, Madagascar, Seychelles and West India. The transform nature of Jurassic rifting explains the differences in crustal architecture across the basins and the presence of isolated salt basins. This study also provides a good framework for play type identification in the four margins with large structural and stratigraphic traps identified and strong evidence for oil.

The discovery of Kudu gas-condensate accumulation and recent wells drilled offshore in the Namibian margin have successfully de-risked source rock presence and maturity (Hodgson and Intawong, 2013). Both the acquisition of an extensive 2D seismic dataset in 2012 and a recently acquired cross-border survey 2015 off¬shore Namibia and South Africa have facilitated the evaluation of source rock maturity distribution for the Early Aptian and Cenomanian-Turonian source rocks along this margin (Figure 1). Conventionally, we have no tools to interrogate heat flow and geothermal gradient in an undrilled basin and have to rely on extrapolation from offset wells, imposing models on a structural interpretation of the basin margin. Near-surface geotherm estimation derived from seismic measurement of the thickness of a gas hydrate accumulation with respect to the water depth found in the Luderitz Basin has been employed as a preliminary approach for the initial evaluation of source rock maturity ...

The emergence of pre-salt exploration in the past 30 years has resulted in a significant addition to world oil reserves since the first pre-salt discovery offshore Angola in 1983. Among the most successful deep water pre-salt exploration plays is the Campos Basin offshore Brazil, where a milestone achievement of 800,000 bpd production level was achieved just 8 years after the first pre-salt well was drilled in 2006. The Yucatan Basin offshore Mexico represents one of the last significant pre-salt exploration provinces yet to see any significant exploration activity. In this paper we illustrate evidence of an extensive pre-salt layer using newly acquired long-offset 2D seismic data. We distinguish between sub-salt and pre-salt prospects in the Yucatan Basin by illustrating images of pre-salt horst and graben rift structures and preand synrift deposits, which have been proven as potential source and reservoir rocks elsewhere. Sub-salt plays are also in evidence in the northeastern Cam...

The recent glut of giant oil and gas hydrocarbon discoveries on the North West African coast (Figure 1) began in 2014 with the SNE-1 discovery by Cairn in Senegal. This play-making well targeted Albian sandstones and Aptian carbonates in a structural trap, at the eroded edge of the Early Cretaceous platform margin. There are a number of interesting play elements at work in this play that require definition so that a model can be extracted and reused elsewhere along the margin in the chase for analogue traps. Where we will end up is Guinea Bissau, Senegal’s southern neighbour, where the plays is as yet unexplored yet appears to have an even more promising potential, but first – SNE. The SNE discovery has been presented to the industry by operator and partners several times over the last few years, including a presentation at the recent HGS PESGB African conference by Wytze de Boer et al. of Cairn Energy (Geophysics of the SNE Field, Senegal, HGS PESGB 16th African Conference, 2017). ...

Many clastic wedges prograding from the coast in Africa’s passive margin basins display extraordinary gravity-driven collapse structures described variously as gravity-driven linked systems, fold and thrust belts or megaslides (Butler and Turner, 2010, Scarselli et al 2016). These features form relatively slowly and are distinct from instantaneous collapse submarine landslides or Mass-Transport Complexes (MTC) that reflect sudden catastrophic shelf collapse in response to seismicity, gas hydrate destabilization or high sedimentation rates. Megaslides occur on giant scales from hundreds to thousands of square kilometres in extent, and are characterized by up-dip listric growth fault rollover systems in extensional zones, and a corresponding down-dip shortened section comprising multiple imbricate toe thrust faults and duplexes often referred to as foldand thrust belts (FTB’s). Separating the structured material from largely undeformed coherently bedded strata below, is a zone of plan...

The outbreak of hostilities between new unconventional oil supply and giant legacy oil production represents a violent threat to the sustainability of the conventional oil exploration industry. Coruscations from this battle starkly illuminate the explorer's paradox: an imperative to focus on plays that have low risk and huge potential, whilst having to seek these within mature basins on well explored conti- nental shelves. Where can we find sufficient prospects with dramatic enough scale to compete in the unconventional vs legacy giant wars? Using 2D seismic acquired in the last two years on the Atlantic margins, we will examine the play systematics that manifest in Ultra-Deep Water (UDW) low risk prospects on a scale hitherto unimagined that will ultimately win conven- tional's fight back to be the futures energy supplier of choice. Background Since the invention of marine seismic in the 1950s, oil explor- ers have been on a journey through a wilderness of hope, lay- ing ba...

With the recent Zaedyus-1 well oil discovery in French Guiana and the recent oil discoveries in the offset conjugate margin area in Africa (Sierra Leone-Liberia), it is no surprise that explorers are looking to continue this success into the Foz do Amazonas Basin of Brazil. Foz do Amazonas is the most northerly of the Brazilian equatorial margin basins with an area of 282,909 km², and water depths ranging from 50 m to greater than 3000 m. In this under-explored frontier basin, exploration drilling has been confined to the shelf, with 95 exploration wells drilled and ten of these with hydrocarbon shows. The 11th Exploration Licence Round focused on the potentially large reservoirs in distal Late Cretaceous/Palaeogene deep-water turbidite plays, following successful wells drilled in French Guiana. There are strong indicators for the presence of hydrocarbon-bearing reservoirs shown in recent publications, based on newly available data (Rodriguez et al., 2014). This study complements so...

Exploring in frontier basins carries with it the challenge of identifying and derisking hydrocarbon play elements where well data and consequently, lithological and stratigraphic information is often sparse to absent. In this setting, seismic data will typically be the only source of information available to identify potential play fairways and derisk the corresponding petroleum system elements. Until recently, the exploration focus of seismic interpretation has predominantly been on developing methodologies to identify structure, traps and reservoir rather than interrogate source rocks. Geophysical deconstruction of the data again focuses on categorizing hydrocarbon-bearing reservoirs, including AVO/AVA (Amplitude vs Offset/Angle) analysis, bright spot/dim spot and flat spot identification. Yet the lack of focus on source is curious as, particularly in frontier basins, the ability to derisk presence and effectiveness (total organic carbon percentage (TOC%) and maturity) of a viable...

Tertiary clastic sequences within the Veracruz Basin of Mexico have been prolific hydrocarbon producers for many decades. However, during the last few years, production has declined. Several fields have recently been restudied to evaluate behind-pipe and deepening possibilities and new exploration opportunities in the area. This paper focuses on a multi-disciplinary integrated reservoir characterization study of Novillero Field in the Veracruz Basin. Novillero Field, discovered in 1966, has produced about 59 BCF of gas from calcareous turbidites and mudstone-rich debris flows. Reprocessing of 2D seismic in 1996-97 and the generation of synthetic seismograms permitted the integration of seismic and sequence stratigraphy, AVO analysis, biostratigraphy, well and core data, petrophysical analysis, and production data that resulted in a complete reservoir model based on all available data. This study led to the identification of several opportunities in the field area. Working on a commo...

Slope Fan Deposit Distal massive transport complex Distal massive transport complex With a record $1.4 billion bid total, Brazil’s 11th licensing round was a significant event for the region’s oil industry. High priority for many oil companies was the Foz do Amazonas Basin, offshore northern Brazil. A year before the exciting events of the 11th round, Spectrum acquired over 21,000 km of 2D seismic, gravity and magnetics data in this area, providing a regional grid and a suite of seismic data to evaluate the exploration potential of the basin. This evaluation continues into 2015 with the addition of new seismic analysis and collaborations with these remote sensing tools. The integration of seismic data with other tools and methodologies has greatly enhanced the understanding of this frontier area. Foz do Amazonas Basin: Latest Exploration Enhances Prospectivity

The outbreak of hostilities between new unconventional oil supply and giant legacy oil production represents a violent threat to the sustainability of the conventional oil exploration industry. Coruscations from this battle starkly illuminate the explorer’s paradox: an imperative to focus on plays that have low risk and huge potential, whilst having to seek these within mature basins on well explored continental shelves. Where can we find sufficient prospects with dramatic enough scale to compete in the unconventional vs legacy giant wars? Using 2D seismic acquired in the last two years on the Atlantic margins, we will examine the play systematics that manifest in Ultra-Deep Water (UDW) low risk prospects on a scale hitherto unimagined that will ultimately win conventional’s fight back to be the futures energy supplier of choice.

The shallow offshore in south Gabon has been explored for more than 50 years, highlighting the potential for oil discoveries.However, exploration of the sub-salt syn-rift section requires an advanced support that only modern, regionally consistent 3D seismic data can provide. Such support was the objective of a large-scale multi-client 3D seismic programme, representing a collaboration between Spectrum Geo Ltd and the Gabonese Hydrocarbon Authorities (Direction Generale des Hydrocarbures (DHG)), which commenced in December 2016. This survey acquired 11,500 km2 of 3D seismic data in the ‘Gryphon Area’ – the shallow offshore of Mayumba and Sette Cama, west of the Olowi Field, in a range of water depths from 20 to 1000 m (Figure 1). Advanced and accurate modelling allowed for the survey specifications to be tailored to the geological setting and the exploration targets. The previous geological and geophysical exploration was taken as background information to develop the new subsurface...

The first encounter of the Pre-Salt Aptian ‘Microbialite’ carbonate reservoirs (the Barra Velha Fm) in 2005, in the Parati field, Santos Basin, was followed by additional discoveries such as the multi-billion barrel Lula (Tupi) field. Now, nearly 30 more discoveries have been made in the basin such as Libra and Sapinhoa, with recoverable reserves estimated as >30 BBOE, according to ANP. In addition, discoveries have been made in the adjacent Campos Basin, including the Pao de Acucar field (Viera de Luca et al., 2017), where the same unit is known as the Macabu Fm., and also in the Kwanza Basin, West Africa (Saller et al., 2016). After deposition in a late rift setting, the Barra Velha Fm and its equivalents were buried by more than 1 km of marine origin evaporites of the Ariri Fm and its equivalents, as the Albian Ocean seeped and poured into the basin.

F I R S T B R E A K I V O L U M E 3 6 I J U N E 2 0 1 8 6 3 is deposited below the lower limit of permafrost. In contrast, slow seepage of thermogenic methane to the surface can be observed in deep water settings, where methane hydrate will be deposited most commonly below the seafloor or can travel up faults to accumulate as hydrate mounds on the seafloor (Figure 1). The phase diagram in Figure 2 shows the range of temperatures and pressures at which methane hydrate is stable. With an increasing geotherm under a relatively constant pressure within the methane hydrate stability zone (red line in Figure 2), methane hydrate will change phase to methane gas as the temperature increases. This happens in deep water settings as the temperature of the sedimentary column increases with burial depth. Depending on the geothermal gradient, methane hydrate will change phase to methane gas (also known as free gas) at different depths. In deep water offshore settings, the methane hydrate zone thi...

A remarkable property of the Argentine Basin, located in the Atlantic west of Argentina, is that within its 450,000 km2 of extent – not one exploration well has been drilled. Compared to the world’s other continental passive margins, this makes it the most unexplored high potential basin on Earth. Partly this is owing to a lack of modern seismic data in this basin, with exploration previously focused on rifts that lie on the continental shelf. Yet also it is unexplored because of the lack of industry access to the area in the last 10-15 years since deep water drilling technologies have become widely available. However, this is all about to change. The Argentine government is opening the area to international exploration investment, at the same time as a new 35,000 km 2D seismic programme is being acquired by Spectrum in 2017 (Figure 1). This survey aims to reveal the fundamentals of multiple oil-prone hydrocarbon systems in the basin, which include Pre-Atlantic rift plays, syn-rift ...

Exploration in Somalia began onshore in the 1950s with the drilling of several onshore wells, but no notable economic discoveries. Tragically, the collapse of the Government in 1991 ushered in a long period of political instability, where Somalia remained inaccessible to exploration companies for 25 years. During this time, the majority of Somalia’s legacy geological and geophysical data were lost, or destroyed.

Global exploration has seen a dramatic upturn in 2018, with close to 4 billion barrels of oil equivalent discovered in the first half of the year alone, and many exciting wildcat wells still to come. Although the oil price slide of 2014 changed the industry, with the focus now on commerciality and risk reduction, it is of interest that most of the new discoveries this year have been made in commercially challenging deep water. The reason for this is that our industry has been exploring shallow-water oil-prone basins since the invention of marine seismic methods in the 1950s, and they appear now to be ‘mature’ and depleted in material low-risk opportunities. Indeed the future of shallow-water exploration has been portrayed as binary: either mopping up around what we know or exploring new frontiers. However, in South Gabon we challenge the established idea that after 50 years of exploration the basin is mature, by revealing a new generation of prospectivity with modern 3D acquisition ...

We present an integrated geological and geophysical study conducted during the acquisition and processing of extensive 3D Multi-Client seismic campaigns offshore Gabon. These campaigns resulted in two distinct surveys, the first of 11.500 km2 in the southern shelf, and a second of 5500 km2 to the north, offshore Libreville (Figure 1). The acquisition parameters and survey design were planned with seismic illumination studies, long offset streamers were utilised and the data was processed with a modern broadband sequence (Esestime et al., 2017). The surveys presented various imaging challenges, from shallow water multiples to shallow high velocities, carbonate and salt. The Gabonese Authorities for Hydrocarbon (DGH) provided a comprehensive well dataset, including geological markers, logs and checkshot data. These penetrated both pre-salt and post-salt sections, and provided valuable data during all stages of the velocity model building, especially for the southern part of the area. ...

A s exploration evaluations for the 28th UK Licensing round draw to a close, the industry can reflect on the fierce competition for acreage in the Dinantian (Early Carboniferous) play at the northern margin of the Southern Gas Basin. First gas production from the Breagh Field in October 2013, confirming the commerciality of the play, prompted a regional play-fairway study which was quickly followed by the acquisition of a dense 2D seismic programme (Figure 1) in 2013. Intended to define the prospectivity of the Base Permian, this survey has imaged the intra-Carboniferous remarkably well allowing, for the first time, the potential of this sequence to be mapped and evaluated with confidence. Furthermore, post-salt charge modelling and seismic AVO-modelling reveal prospects at higher stratigraphic levels, indicating multi-level exploration potential in an exciting new play-fairway.