Stratigraphic Forward Modelling Research Articles

A new objective function designed for the calibration of stratigraphic forward models

This paper presents a novel and quantitative method of comparing facies successions of distinct sizes and resolutions, adapted for the automated calibration of stratigraphic forward models (SFM). The method, which corresponds to the calculation of an objective function, consists of correlating time-sampled SFM results with space-sampled well logs using a strategy inspired by methods of automated well log correlation. The method was designed to be generic and to accept multi-variate definition of facies, so that it can be applied in a variety of geological contexts (e.g., mixed carbonate-clastic environments). The method demonstrated properties suitable for automated calibration, such as a smooth and almost convex relationship with individual simulation parameters. The method was applied to a case-study using gradient-based, meta-heuristic, Bayesian, and random optimization strategies in an 8-dimensional uncertain space. The results show that calibrated models can be found, but there are still non-uniqueness issues due to compensation effects between uncertain parameters. Therefore, a calibration strategy capable of identifying these multiple solutions is necessary to propagate geological uncertainties in petroleum system assessments and field production predictions.

Forward stratigraphic modelling to understand sedimentary system evolution

Forward stratigraphic modelling to understand sedimentary system evolution

3D basin and petroleum system modelling of the early cretaceous play in the NW Persian Gulf

Petroleum systems analysis has become a key part of hydrocarbon resource exploration. Early Cretaceous petroleum system in the northwest of the Persian Gulf basin with prolific source rocks and reservoirs, is the main petroleum system in the region. Most Iranian offshore oils have been stored in this geological interval. Recent studies indicate that finding new resources is still possible. Therefore, for the first time, this study applied a 3D petroleum system modeling approach to predict new prospects based on available seismic and well data in ∼30,000 km2 area. Results showed that the Berriasian Garau, Albian Kazhdumi and Barremian upper Gadvan are the dominant source rocks. Most of the hydrocarbons have originated from the two Binak and Northern troughs as oil kitchens in the northern and northwest areas. Most anticlines formed in the Late Cretaceous before the critical moment of the source rocks. At first, traps adjacent to the Binak and Northern troughs oil kitchens were charged. Then, hydrocarbon migrated laterally to the far structures. The activity of normal faults has played an important role in vertical migration and reservoir oil mixing, especially in oilfields located above the Khafji-Norooz Arch. Albian Burgan sandstone distribution map from process-based forward stratigraphic modeling suggests low probability of stratigraphic traps. Nonetheless, the Burgan anticline reservoirs have the highest oil in place because they have broad drainage area. Finally, three new anticlinal traps with significant oil reserves were identified in the Yamama, Burgan, and Khalij formations in the northwest of the study area. Results of this study help to better understand Early Cretaceous petroleum system performance and identify new hydrocarbon prospects in the study area.

Improving off-structure carbonate reservoir characterization using integrated Shared Earth Approach and Forward Stratigraphic Modelling: The Marrat Fm of southern Kuwait

A high-resolution reservoir characterization workflow is applied to assess the off-structure prospectivity of Lower Jurassic complex carbonate reservoirs of the Marrat Formation in the southern part of The State of Kuwait along the Dharif-Abduliyah fields. A detailed sedimentological and petrophysical assessment was integrated with 3D seismic interpretation and delineated vertical and lateral facies changes within the fields, which are affected by sets of complex fault patterns. Carbonate geo-bodies have been mapped using seismic stratigraphy, and 3D multi-seismic attribute and seismic acoustic inversion workflows. The Middle Marrat has been subdivided into 5 units (Middle Marrat 1-MM1 to Middle Marrat 5-MM5) that show vertical and lateral lithological and facies variability. The developed integrated sequence stratigraphic framework permitted to better assess the influence of accommodation variations as well as carbonate ecological settings on sedimentary facies development. This framework pointed to the influence of marine incursions and subsequent flooding surfaces, on the development of wackestone to mudstone textures interbedded within porous grainier inner ramp/shoal reservoir intervals. This integrated Shared Earth Approach that combined the various multi-disciplinary and multi-scale results was supported for the first-time by high resolution Forward Stratigraphic Modelling to provide a mapping and identification of petroleum systems elements including potential reservoir locations and baffles as well as stratigraphic trapping mechanisms. This workflow opens a new perspective to increasing hydrocarbon reserves along the Dharif and Abduliyah Fields as well as many other fields along the State of Kuwait.

Competition of deltaic feeder systems reflected by slope progradation: a high-resolution example from the Late Miocene-Pliocene, Drava Basin, Croatia

The thick Lake Pannon sedimentary record provides insights into the downdip and lateral development of stratigraphic surfaces through the analysis of the basin-scale clinoform progradation. The clinoform architecture from the eastern part of the Drava Basin (Pannonian Basin System) was interpreted to reflect the base-level changes. A major downlap surface interpreted as a flooding event followed by rejuvenation of slope progradation was recognized on 2D seismic sections. Detailed 3D seismic interpretation combined with well data revealed that the large sigmoidal and the overlying small oblique clinoform sets that downlap the large one only apparently produce the geometry of a maximum flooding surface. Instead, the 3D mapping revealed the influence of two competing slope systems arriving from the north and northwest. Lateral switching of sediment input, similar to many recent deltaic systems. e.g., Danube and Po rivers led to the variability of stratigraphic surfaces, lithology, and thickness, which resulted in non-uniform shelf-edge migration. These observations were supported by forward stratigraphic modeling simulating different scenarios, which led to the generation of the depositional architecture with an apparent maximum flooding surface. This study also implies the potential pitfalls in basin analysis based only on scarce 2D seismic and emphasizes the role of lateral variations in sediment input controlling the depositional architecture.

Modelling parametric uncertainty in large-scale stratigraphic simulations

We combine forward stratigraphic models with a suite of uncertainty quantification and stochastic model calibration algorithms for the characterization of sedimentary successions in large scale systems. The analysis focuses on the information value provided by a probabilistic approach in the modelling of large-scale sedimentary basins. Stratigraphic forward models (SFMs) require a large number of input parameters usually affected by uncertainty. Thus, model calibration requires considerable time both in terms of human and computational resources, an issue currently limiting the applications of SFMs. Our work tackles this issue through the combination of sensitivity analysis, model reduction techniques and machine learning-based optimization algorithms. We first employ a two-step parameter screening procedure to identify relevant parameters and their assumed probability distributions. After selecting a restricted set of important parameters these are calibrated against available information, i.e., the depth of interpreted stratigraphic surfaces. Because of the large costs associated with SFM simulations, probability distributions of model parameters and outputs are obtained through a data driven reduced complexity model. Our study demonstrates the numerical approaches by considering a portion of the Porcupine Basin, Ireland. Results of the analysis are postprocessed to assess (i) the uncertainty and practical identifiability of model parameters given a set of observations, (ii) spatial distribution of lithologies. We analyse here the occurrences of sand bodies pinching against the continental slope, these systems likely resulting from gravity driven processes in deep sea environment.

Relative sea‐level control on the building of two distinct shelf‐margin clinothems on the late‐Quaternary Pearl River margin: Insights from numerical stratigraphic forward modelling

AbstractAs one of the most important forcing factors, relative sea‐level changes exert a major influence on the building of shelf‐margin clinothems. However, it is still not well understood how these changes control the growth of shelf edges and the condition of sediments transporting into deep water, especially over the individual‐clinothem scale of several 100 ky. On the late‐Quaternary Pearl River margin, there are two distinct shelf‐margin clinothems: SQ3 and SQ4. They have different shelf‐edge trajectories (slight rising vs. steep rising) and different styles of deep‐water deposition (fan lobes consisting mainly of MTDs vs. fan lobes consisting mainly of turbidites). This work takes those SQ3 and SQ4 as study objects and runs a total of 136 experiments from the Dionisos stratigraphic forward model to investigate how relative sea‐level changes control the trajectories of shelf edges and the volumes of MTDs in deep water over the individual‐clinothem scale. Our quantitative results suggest that under the geological background of high sediment supply on the late‐Quaternary Pearl River margin, the duration of highstand systems tracts (HST) relative to lowstand systems tracts (LST) or forced regressive systems tracts (FST) has a significant influence on the building of individual shelf‐margin clinothems. If the relative duration of HST is either very short or very long, slight‐rising shelf‐edge trajectories and large‐volume MTDs would be formed, whereas if the relative duration of HST is comparable with LST or FST, steep‐rising shelf‐edge trajectories and limited MTDs would be formed. Through the constrains of the model set to the real geological condition of the SQ3 and SQ4 clinothems, it is found that SQ3 was caused by the quite long relative duration of HST, which made highstand deltaic systems advance over the pre‐existing shelf‐slope break, leading to significant accretion and instability of the shelf edge and thus, giving rise to the formation of slight‐rising shelf‐edge trajectories and fan lobes with high MTDs contents. SQ4, however, formed as a result of the comparable durations of HST, LST, and FST, which made highstand deltaic systems advance to but not beyond the previous shelf‐slope break allowing the subsequent FST to be directly perched on the clinoform slope. Such building processes did not drive pronounced accretion and instability of the shelf edge and thus, caused the formation of steep‐rising shelf‐edge trajectories and fan lobes with low MTDs contents.

IMPACT ASSESSMENT AND INPUT PARAMETERS SELECTION FOR STRATIGRAPHIC FORWARD MODELLING (SFM)

In deep-water reservoirs, predicting geometry of sedimentary bodies and distribution of facies become inefficient due to data limitations. Stratigraphic forward modelling (SFM) appears as an alternate geological modelling method. High uncertainty is related to definition of input parameters and calibration of the SFM models. This study assesses responses and respective sensitivities of models from the Morro do Chaves Formation (Sergipe/Alagoas Basin) by carrying out SFM multi-realizations. These assessments allow the evaluation and reduction of uncertainties to define input parameters capable of generating models more suitable to the data observed.

Stratigraphic analysis of XES02: Implications for the sequence stratigraphic paradigm

ABSTRACT Sequence stratigraphy has the potential to provide a consistent method for integrating data, correlating strata, defining stratigraphic evolution, and generating quantifiable predictions. However, the consistent application requires a precise definition of concepts, stratigraphic units, bounding surfaces, and workflow. Currently no single generally accepted approach to sequence stratigraphic analysis exists, nor are there any robust tests of models and methods. Applying conventional sequence stratigraphic analysis to strata from an analog laboratory experiment (eXperimental EarthScape02, XES02) with known boundary conditions and chronology provides some initial robust testing of the models and methods. Despite stratigraphic architectures apparently consistent with those expected within the sequence stratigraphic paradigm, blind-test applications yield: 1) deducted erroneous base-level curves, 2) systems-tract classification mismatches, 3) disconnected systems-tracts type and actual base level, 4) time-transgressive basin-floor fans, and 5) missing systems tracts. Stratigraphic forward models using base-level curves derived from Wheeler diagrams cannot match the timing, redeposited-sediment volume, and depositional environments observed in the XES02 experiment. These mismatches result from common Wheeler diagram construction practice, producing poorly resolved base-level minima timing and base-level fall durations, hence inaccurate fall rates. Consequently, reconstructions of controlling factors based on stratal architectures remain uncertain, making predictions similarly uncertain. A reasonable path forward is to properly acknowledge these uncertainties while performing stratigraphic analysis and to address them through multiple scenario analysis and modeling.

Testing sea-level and carbonate production effects on stratal architecture of a distally steepened carbonate ramp (Upper Miocene, Menorca): A 3D forward modelling approach

Although distally steepened carbonate ramps have been studied by numerous researchers, the processes that control the development of these carbonate systems, including tectonics, differential carbonate production along the ramp profile, or antecedent physiography of the slopes, are an ongoing discussion. We use a stratigraphic forward model to test different hypotheses to unravel controls over distally steepened ramp development, referenced to the well-known Upper Miocene Menorca carbonate ramp (Spain). Sensitivity tests show that distally steepened ramps develop under complex interaction among accommodation, carbonate production and sediment transport parameters. Ramp slope initiation is favoured by still stands and falls of sea-level, in a setting with high-frequency sea-level fluctuations with amplitude between 20 m and 40 m. Low-frequency and higher amplitude sea-level fluctuations of about 115 m tend to form models with no significant slope development. The impact of antecedent slope on the geometry of ramps is determined by the paleoslope inclination, with flat to subhorizontal paleosurfaces resulting in ramps that mirror the antecedent slope. In contrast, steeper paleosurfaces tend to result in ramps with well-defined slopes. Our models, therefore, show that the ramp profile becomes more influenced by the depth constraints on the carbonate sediment producers than by the geometry of the underlying topography as the inclination of the paleosurface increases. The presented models also show that seagrass-dominated shallow carbonate production tends to result in steep slopes due to the low-transport characteristic imposed by seagrass trapping. This steepness can, however, be altered by the introduction of high transport sediment grains from deeper carbonate producers, which fill the slopes and more distal sections of the ramp profile.

Controls on large-scale architecture and facies distribution of an oolitic-microbial carbonate shelf margin, Nanpanjiang Basin, south China

Carbonate factory types and facies architecture of carbonate depositional systems result from complex interactions among several space- and time-dependent variables, including paleobathymetry, tectonic setting, water chemistry and oceanographic setting, clastic sediment influx, and accommodation. Whereas tropical factories that dominate modern settings have been documented and modelled extensively, microbial-oolitic systems, which are very common throughout the Paleozoic and Mesozoic, have received less attention.Continuous exposures along a platform-to-basin transect of an Early Triassic (Induan) microbial-oolitic carbonate ramp to shelf system in the Nanpanjiang Basin, South China, serves as a viable analogue to similar systems, including the Jurassic Smackover Formation of the Gulf of Mexico, and provide a natural laboratory to test these variables. Carbonate deposition following end-Permian regional drowning and retreat of the Yangtze Platform resulted in low-angle margin-slope systems during the Early Triassic. Lower Triassic carbonate systems display shifts in carbonate factory types, including skeletal, microbial, and abiotic factories, and lateral and vertical architectural variability.We applied stratigraphic forward modelling using DIONISOSFLOW, calibrated with detailed stratigraphic sections and facies mapping, to assess the impact of carbonate factory type, antecedent topography, and variations in accommodation on facies distribution and large-scale geometries of the carbonate shelf margin. Results from model simulations suggest that in the absence of skeletal carbonates in the Lower Triassic, the architecture of the carbonate margin is mainly controlled by rate of microbial growth along the slope.

A biotic perspective on the Oligo-Miocene evolution of the Maldives carbonate platform from forward stratigraphic modelling (Indian Ocean)

Forward stratigraphic modelling is a fast-developing modelling approach, used to test conceptual models, and predict stratigraphic architecture and depositional facies from basin to reservoir scales. Published subsurface applications demonstrate its added value by integrating multidisciplinary data as well as geological concepts into its constraints. When applied to carbonate depositional systems, composed of multiple sediment factories, the co-operating and interdependent production mechanisms remain poorly studied. By applying the technique to a well-studied section of the Maldives carbonate platform, a specific model design—adapted to the geological age and setting, and constrained by available data—sheds light on the interaction of its carbonate producers. The results yield a naturalistic depositional facies distribution and offer insight in the changing relationship between biotic communities during the platform evolution. After calibration, the reference model unequivocally links the formerly proposed genetic model to the seismostratigraphic architecture. Furthermore, the results show how environmental changes (seemingly of secondary impact compared to changes in physical accommodation in the stratigraphic record) can induce substantial fluctuations in carbonate production rates of biotic communities, affect the ecological accommodation, and thus impact the platform architecture. Therefore, it is crucial to treat carbonate production rates during periods of environmental change as variables with associated uncertainties in a forward stratigraphic model setup.

Stratigraphic Forward Modeling Assists Carbonate-Reservoir Characterization

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202775, “Application of Stratigraphic Forward Modeling to Carbonate-Reservoir Characterization: A New Paradigm From the Albion Research and Development Project,” by Jean Borgomano, Aix-Marseille University, and Gérard Massonnat and Cyprien Lanteaume, TotalEnergies, et al. The paper has not been peer reviewed. _ Improving carbonate-reservoir prediction, field development, and production forecasts, especially in zones lacking data, requires novel reservoir-modeling approaches, including process-based methods. Classical geostatistic modeling methods alone cannot match this challenge, particularly if subtle stratigraphic architectures or sedimentary and diagenetic geometries not directly identified as properties with well data control the reservoir heterogeneity. Stratigraphic forward-modeling approaches can provide pertinent information to carbonate-reservoir characterization. The complete paper describes a modeling package tested and calibrated with high-resolution stratigraphic outcrop models. It allows valid prediction of carbonate facies associations mimicking the spatial distribution mapped along the Urgonian platform transects. Background Classical carbonate-reservoir characterization protocols rely mainly on 3D geostatistical models based on well data, allowing the realization of 3D numerical grids of reservoir properties. These geostatistic property models are supported by deterministic geological interpretations such as stratigraphic well correlations that are commonly based on sequenced stratigraphic concepts and carbonate sedimentological interpretations. The stratigraphic framework obtained from these deterministic interpretations has a critical effect on further static and dynamic reservoir models because it constrains the spatial stationarity of the geostatistic property simulations or imposes discrete flow units or barriers. These deterministic carbonate sequence stratigraphic and associated sedimentological interpretations, however, introduce significant biases, uncertainties, and imprecisions in reservoir models and furthermore are not validated by process-based modeling approaches as one should expect from any scientific protocol. This lack of validation represents a fundamental scientific gap in classical reservoir-characterization work flows that is generally avoided in other scientific domains such as physics by iterations combining experimentation and process-based models to verify deterministic interpretations and hypothesis. The paradox is that this virtuous scientific method is applied at the ultimate stage of the reservoir flow modeling with the classical “flow history matching,” implying the following strong hypothesis (Fig. 1a): If the dynamic model obtained from the upscaled static model matches the dynamic history and the flow records of the studied field and carbonate reservoir, then the geological model, including the deterministic stratigraphic and sedimentary interpretations, is validated. Reservoir flow and dynamic behavior certainly are controlled by initial geological conditions, but those are not dependent on flow processes. According to fundamental scientific principles, geological interpretations and deterministic models must be validated by geological process-based models. To fill this scientific gap in the presented carbonate-reservoir characterization approach, the authors introduce process-based stratigraphical and sedimentological models that are calibrated on pertinent, well-studied outcrop analogs.

Technology Focus: Reservoir Surveillance (September 2022)

When it comes to reservoir surveillance, subsurface professionals have a broad array of tools and techniques to understand what is happening in the reservoir. To ensure valuable information is gathered with surveillance, it’s important to first ask “what problem are we trying to solve?” Depending on the problem’s definition and scale, the appropriate surveillance technology will change significantly. Zooming far out, particularly if little data is available for a reservoir, we may be interested in tools and techniques to validate and refine the geological concept for a basin, along with the most likely deposition patterns for sediments. Zooming in to the level of interactions between wells, we need to use a different toolbox that often includes finer-resolution geoscience mapping and engineering methods such as analyzing production, pressure, and fluid-property trends from individual wells. But what’s really exciting is that many new approaches are being developed to understand reservoir behavior and well performance at incredibly high resolution—at the fracture scale or even the pore scale. In this feature, we will examine surveillance technologies that can be applied at the broad scale, midscale, and fine scale. The papers highlighted in this month’s feature apply forward stratigraphic modeling to improve geological models, classical reservoir engineering techniques to understand interwell connectivity in order to optimize waterflooding operations, and exciting new fiber-optic technology to characterize the performance of individual hydraulic fractures in unconventionals. I hope these articles help you to think about “framing” the problem you are trying to solve, like a photographer carefully selecting the right camera settings and lens for a specific shot, in order to select the right tools and methods to add value through surveillance. Recommended additional reading at OnePetro: www.onepetro.org. SPE 202319 - Utilizing Surface Microseismic Monitoring To Improve Understanding of Natural Fractures in Sichuan Shale Gas Play by Cui Jing, Sichuan Changning Natural Gas Development Company, et al. SPE 202837 - Modified Technique To Model Volatile Oil Reservoirs: Implications for Modern Software Programs by Mohamed Ibrahim, Shell Egypt, et al. SPE 201543 - Production Optimization Using a 24/7 Distributed Fiber-Optic DFO Sensing-Based Multiphase Inflow Profiling Capability by Teymur Sadigov, BP, et al.

3D forward stratigraphic modeling of the Albian succession in a part of the northeastern margin of the Arabian Plate and its implications for exploration of subtle traps

During the Albian age, siliciclastic input in the Arabian carbonate-dominated shelf formed important petroleum system elements. Hence, the Albian Burgan-Kazhdumi succession hosts world-class sandstone reservoirs in some Middle East oil fields. Moreover, stratigraphic traps are possible due to changes in facies and structural dips. Accordingly, we used process-based forward stratigraphy modeling as a powerful tool to predict Burgan-Kazhdumi units and de-risking new exploration prospects. A 3D stratigraphic model was constructed in this study for the first time by integrating multi-disciplines and multi-scales of seismic and well data from several countries. The model (324 km × 264 km, 4 km × 4 km grid size) encompasses NW of the Persian Gulf, Kuwait, south Iraq and SW of Iran and is vertically divided into three units based on Albian regional third-order sequences.Results indicated that the lower unit, unit-1, contains onlapping aggradational-retrogradational stacking compounds, high sand bodies thickness and distribution as well as good reservoir quality. This unit was deposited on a tide-dominated delta system. Gradually, with rising sea level, progradational fine-grain marine sedimentation dominated in units 2 and 3. Hence, intra-formational seal facies formed in the proximal and organic-rich facies in the distal intra-shelf areas. The gentle topography of the basin floor seems responsible for the lack of turbidity lobes. The sand bodies of up-dip arches such as Khafji-Norooz and Kharg-Mish highs and pinched out in fine-grained facies provide a significant potential for stratigraphic traps.The model sensitivity analysis showed eustasy, and water-driven diffusion coefficient (Kw) has the most critical impact on the clastic sedimentation of unit-1 and unit-3. Furthermore, tectonic events have the most significant sedimentation effect in unit-2 sedimentation.The findings of this study can help for better understanding of a more precise regional sequence stratigraphic and stratigraphic architecture of the Albian succession of the study area. This study also helps identify elements of petroleum plays as well as stratigraphic trap potential between mixed siliciclastic-carbonate depositional systems.

Inverting passive margin stratigraphy for marine sediment transport dynamics over geologic time

AbstractPassive margin stratigraphy contains time‐integrated records of landscapes that have long since vanished. Quantitatively reading the stratigraphic record using coupled landscape evolution and stratigraphic forward models (SFMs) is a promising approach to extracting information about landscape history. However, there is no consensus about the optimal form of simple SFMs because there has been a lack of direct tests against observed stratigraphy in well‐constrained test cases. Specifically, the extent to which SFM behaviour over geologic space and timescales should be governed by local (downslope sediment flux depends only on local slope) versus nonlocal (sediment flux depends on factors other than local slope, such as the history of slopes experienced along a transport pathway) processes is currently unclear. Here, we develop a nonlocal, nonlinear SFM that incorporates slope bypass and long‐distance sediment transport, both of which have been previously identified as important model components but not thoroughly tested. Our model collapses to the local, linear model under certain parameterizations such that best‐fit parameter values can indicate optimal model structure. Comparing 2‐D implementations of both models against seven detailed seismic sections from the Southeast Atlantic Margin, we invert the stratigraphic data for best‐fit model parameter values and demonstrate that best‐fit parameterizations are not compatible with the local, linear diffusion model. Fitting observed stratigraphy requires parameter values consistent with important contributions from slope bypass and long‐distance transport processes. The nonlocal, nonlinear model yields improved fits to the data regardless of whether the model is compared against only the modern bathymetric surface or the full set of seismic reflectors identified in the data. Results suggest that processes of sediment bypass and long‐distance transport are required to model realistic passive margin stratigraphy and are therefore important to consider when inverting the stratigraphic record to infer past perturbations to source regions.

The roles and seismic expressions of turbidites and mass transport deposits using stratigraphic forward modeling and seismic forward modeling

• Mass transport is more efficient than turbidity current in forming submarine canyons . • Turbidites are inside the river-fed systems as jigsaw puzzle geometries vertically. • MTDs are not constrained by river-fed systems and tend to occur in the bottom. • MTDs have chaotic or transparent seismic facies with irregular, massive thick shapes. • Turbidites have high amplitude seismic facies with sheet, mound or channel shapes. Turbidity currents and mass transport are two principal processes in deepwater settings. However, their roles in shaping deepwater depositional systems and interpreting their deposits in seismic profiles have not been fully settled due to the lack of extensive well data and high-quality seismic data in comparison with onshore oil fields. Therefore, this study integrated stratigraphic forward modeling (SFM) and seismic forward modeling to differentiate between the contributions of turbidity currents and mass transport as well as their seismic expressions. The workflow firstly compared three single-scenario SFM models, Model A (mass transport active), Model B (turbidity currents active), Model C (both active) to explore their contributions and interplay. Secondly, a multi-process and multi-scenario SFM model, Model D, is discussed with special emphasis on canyons. Thirdly, synthetic seismic profiles are generated via seismic forward modeling using the outcomes of the second step, then compared with actual seismic facies to verify the reliability. Through the abovementioned three steps, this study reveals that mass transport plays a major role in initiating canyons whereas turbidity currents act mainly as the reworking process. Turbidites are usually confined to shelf-incised canyons and adjacent canyons fed by terrestrial systems. Mass transport deposits (MTDs) are mainly distributed on the bottom of canyons and deep basins, forming the base boundary of each depositional cycle. A total of 14 synthetic seismic facies are identified. The comparison with actual seismic data shows that modeling results are similar to equivalent actual seismic features. This study helps to predict the spatial emplacement of MTDs and turbidites and interpret deepwater seismic data.

Channel trajectories control deep‐water stratigraphic architecture

AbstractInterpretation of deep‐water channel deposits is challenging because the spatial arrangement of their constituent lithologies is highly variable. This variability is often thought to be a signature of complex interactions between controlling boundary conditions and processes. A three‐dimensional forward stratigraphic model of a sinuous meandering channel is used to explore the production of channelised deep‐water stratigraphy. This model highlights three stages of stratigraphic evolution for channel belts: (1) an initial phase of rapid growth in mean belt width and variability in belt width driven by increasing channel sinuosity; (2) a subsequent phase of reduced belt‐width growth rate because of cutoff processes; and (3) a mature phase during which repeated bend lifecycles act to produce a statistically stable channel‐belt width. When a trajectory defining the vertical movement of a channel over time is added to the model, commonly recognised patterns of deep‐water channel‐belt stratigraphy are produced. These results demonstrate how forward stratigraphic models provide insights into processes governing the evolution of deep‐water stratigraphy that elude interpretations of static outcrops and seismic images of subsurface examples.

Investigating the role of differential biotic production on carbonate geometries through stratigraphic forward modelling and sensitivity analysis: the Llucmajor example

The geometry of carbonate platforms reflects the interaction of several factors. However, the impact of carbonate-producing organisms has been poorly investigated so far. This study applies stratigraphic forward modelling (SFM) and sensitivity analysis to examine, referenced to the Miocene Llucmajor Platform, the effect of changes of dominant biotic production in the oligophotic and euphotic zones on platform geometry. Our results show that the complex interplay of carbonate production rates, bathymetry and variations in accommodation space control the platform geometry. The main driver of progradation is the oligophotic production of rhodalgal sediments during the lowstands. This study demonstrates that platform geometry and internal architecture varies significantly according to the interaction of the predominant carbonate-producing biotas. The input parameters for this study are based on well-understood Miocene carbonate biotas with characteristic euphotic, oligophotic and photo-independent carbonate production in which it is crucial that each carbonate-producing class is modelled explicitly within the simulation run and not averaged with a single carbonate production–depth profile. This is important in subsurface exploration studies based on stratigraphic forward models where the overall platform geometry may be approximated through calibration runs, and constrained by seismic surveys and wellbores. However, the internal architecture is likely to be oversimplified without an in-depth understanding of the target carbonate system and a transfer to forward modelling parameters.

Predicting marine organic-rich deposits using forward stratigraphic modelling: The Jurassic Najmah source rock – Case study

Predicting the distribution and heterogeneity of marine Mesozoic organic-rich rocks is a challenging task that requires multi-disciplinary data integration supported by innovative numerical modelling. This study aims at investigating the factors controlling marine organic matter production, accumulation, and preservation along the eastern Arabian intrashelf basins. Such types of basins exhibit an enhanced lateral and vertical facies variability caused by the interplay between shallow and deeper water sedimentation. The work focuses on characterizing the Mid-Upper Jurassic Najmah Formation that presents source rock, reservoir, as well as seal characteristics along Kuwait. It comprises high maturity levels (>0.6% Ro) and TOC values ranging between 2 and 30%. Forward stratigraphic modelling that includes organic matter production, transport, and preservation (i.e., degradation and dilution) was utilized. Models corresponding to two end-member basin types (restricted and fully open marine) have been simulated to mimic the organic matter deposition within a 3rd-order sequence stratigraphic framework. Simulation outputs provide a qualitative and quantitative assessment of organic matter characteristics (TOC, HI, and OI) at the time of deposition. Results show that (1) a combined variable eustatic sea level change and tectonic subsidence are the main driving mechanisms for sediment accommodation during the Mid-Upper Jurassic time, (2) strong anoxic conditions in the restricted basin simulations promote the preservation of organic-rich deposits in the distal northern sectors while (3) the influence of open marine bottom current oxygenation is not expected to impact the relatively shallower conditions affecting the intrashelf basin (<200 m depth), (4) organic matter dilution can be observed along the southernmost sectors of Kuwait due to high sedimentation rates related to the development of gravity driven deposits. Sensitivity analysis on input parameters (i.e., primary productivity vs water depth) supports the partially restricted basin conditions with occasional connection to the open ocean during eustatic sea level rise. This study contributes to the improvement of basin models in conventional as well as unconventional petroleum system exploration.