Sunday 28 November
Session 1: Regional, Sub-Regional and Localized Intraformational Seals with Field Analogues
Regional, sub-regional and localized intraformational seals play a vital role while exploring for new hydrocarbon prospects and/or developing producing fields. For example, the analysis of a exploration target depends on how thick an oil column, a certain identified seal can trap before it leaks. Likewise, the petrophysical properties and thickness of an intraformational seal define its ability to form a barrier to flow in geological and production scales. Generally, the potential and impact of the intraformational seals depend on their areal extent, thickness, capacity, geometry and integrity.
This session will discuss Oman’s intraformational seals comparing them to different field analogues from various sedimentary basins which will provide a better appreciation of their potential impact on field exploration and development.
Monday 29 November
Session 2: Sequence Stratigraphic Framework, Facies and Relationships to Seal Occurrences
Sequence stratigraphy provides an excellent framework within which to integrate many scales of observations of physical, chemical and biological attributes necessary to understand seal rock occurrences across the spectrum of depositional settings. The seal rock might be deposited in the wide range of depositional environments, ranging from lacustrine trough marine shelf to bathyal. A stratigraphic unit is not a cap rock unless it seals an underlying reservoir; thus, the ideal seal rocks should occur in stratigraphic association with reservoirs. This condition is liable to be met in many types of depositional settings, particularly associated with Transgressive and Late Highstand System Tracts (transgressive marine shales on gently sloping siliciclastic shelves or evaporitic deposits in regressive supratidal sabkhas and in evaporitic interior basins).
This session will discuss the use of sequence stratigraphy framework and depositional settings associated with hydrocarbon seal occurrences, with examples from the Middle East. Furthermore, the session will address the expression of depositional sequences in seal rocks on seismic, well-log, core, and outcrop data.
Tuesday 30 November
Session 3: Hydrocarbon Seal Architecture and Capacity in Carbonate, Evaporite and Clastic Sequences
Seals are key elements of any petroleum system. Their importance is usually overlooked during the evaluation of the potential hydrocarbon accumulation. The effectiveness of seals depends on several factors. The most important is the thickness, continuity, and high capillary entry pressure. The typical lithology of seals in the Middle East includes shale, silt, salt, and anhydrite formations. In terms of their architecture, they can be created by vertical lithological stratifications and lateral lithological variation or porosity degradation. Additionally, faults and fractures can act as seals by impeding fluid flow. In the Arabian Peninsula, potential seals include deformation bands, and hydrodynamically-aided stratigraphic and fault rocks.
Assessment of seals using a rigorous strategy is vital in the appraisal phase. However, production and injection-related activities might alter seals hydrocarbon retention characteristics, and therefore, must be incorporated in all stages of the field development plans.
Session 4: Static (Capillary) and Dynamic Sealing Capacity and Hydrocarbon Retention
The current understanding is that a capillary pressure change between a seal and a carrier bed (or reservoir) is the main factor responsible for the trapping. Top and lateral seals are often assumed to be static, with a fixed seal threshold determined by capillary properties. They prevent the migration of hydrocarbons out of traps and commonly comprise fine-grained rocks, which have much reduced porosity compared to the reservoir rocks. A capillary seal act as a perfect seal for hydrocarbons until the hydrocarbon buoyancy pressure exerted by the increasing column, exceeds the top seal capillary entry pressure, at which point leakage will take place. In this way, the trappable hydrocarbon column buoyancy pressure is always limited by the seal capillary threshold pressure.
This session will discuss the importance of the static (capillary) and dynamic sealing capacity and different elements that contribute to making seals effective, such as lithology, their brittle-ductile nature, the hydrocarbon column length, the pressure regime, geomechanics impacts and trap type. Understanding and predicting hydrocarbon seals is typically a multidisciplinary task requiring geosciences and engineering to collaborate on both dynamic and static data.
Wednesday 1 December
Session 5: Integration of Petrophysical, Rock Mechanics, Seismic and Engineering Data for Hydrocarbon Seal Assessment
Seals are fundamental element of any hydrocarbon accumulation. And despite their clear importance, they often remain the least studied and integrated element of petroleum system. Elements that contribute to making seals effective, such as lithology, their brittle-ductile nature, the hydrocarbon column length, pressure regime and trap type should be integrated when assessing seal effectiveness.
Both vertical and lateral seals must be identified when exploring for subtle and stratigraphic traps, including fault bound accumulation whether or not the fault has a sealing potential. Quantification of effective seals and an ability to predict seal capacity before investment is key to safe and successful exploration.
In terms of seal assessment, understanding and predicting hydrocarbon seal is typically a multidisciplinary task requiring geosciences and other subsurface engineers to collaborate on both dynamic and static data.
Seismic data, special core analysis, petrophysical evaluation, geochemical, pressure and production data can all be integrated. In addition, top seal ductility and brittleness, seal integrity and capacity, fluid pressures recorded in a compartmentalized accumulation can all contribute to a good assessment of the hydrocarbon seal.
Seals control migration pathways into traps. A trap may be empty not because a fault leaked once-trapped hydrocarbons but because a fault sealed and prevented hydrocarbons from migrating into a trap and filling it in the first place. Similarly, top seals can restrict vertical migration into shallow traps and control the vertical and lateral distribution of hydrocarbons within a basin.
Thursday 2 December
Session 6: The Impact of Structural Geology & Geomechanics on Hydrocarbon Seals
In exploration environments risking traps are related to fault, top seals and trap geometry, these also imposes greater uncertainty on characterization compared to later life cycle of the field development. On the other hand, in the production environments; characterization of compartmentalization or fluid segregation possibly caused by fluid flow during production is required. This have implications on reserve estimates, and effective production strategies.
From Basinal and regional perspective, knowing and honoring the structural geology history and deformation style provides an insight to critically define the potential targets in working play to target exploration prospects and leads, where it can provide an effective sealing or seals that would leak resulting in shallow reservoirs to fill, for example.
This also have an impact on the fractionation or segregation on hydrocarbon fluids. Spill points, fault seal, top seal failures, fault rock characterization and variations of fluid contacts are all outputs that allows to risk or de risk the targeted areas and enables reducing uncertainties. Tools such as seismic, basinal model, burial history, diagenesis, fault seal analysis, juxtapositions, etc. are there to provide methods and concepts to strength between the hydrocarbon seals and its association with structural geology and geomechanics. Nevertheless, the role of dynamic aspect of traps while production and its impact, such as on fault stability are crucial to address as well as the controls on column and flow of hydrocarbon like the effect of overpressure on fault seal capacity, lateral water pressure changes, and combined hydrodynamic-membrane seal.
Geomechanics is fundamental in understanding the controls on rock fracture and fault development and fault activity. It assists in estimating fault conductivity and critical to determine reservoir behavior during production. It assists to reproduce subsurface stress state using lab methods and principles for rock failure and fault behavior to relate the rock mechanics. Applications like top sealing effectiveness and capacity and Hydrocarbon retention/column as well as critically stressed faults that can be conductive or reactivation for a fault flow.
This session will emphasize on the use of structural geology and geomechanics linked with exploration and development, with examples from the Middle East. Additionally, will express the tools and concepts utilized along with uncertainties accompanied with calibration and iterative nature of validation.