Carbonate Reservoir Quality Research Articles

Paleoenvironmental, diagenetic, and eustatic controls on the Permo–Triassic carbonate–evaporite reservoir quality, Upper Dalan and Kangan formations, Lavan Gas Field, Zagros Basin

Permo–Triassic (P–T) successions in Iran are known as one of the most extensive carbonate–evaporite sequences in the world, holding prolific hydrocarbon accumulations, such as the gas fields in the Zagros Basin. This study addresses the impact of paleoenvironmental changes across the P–T extinction boundary, variations in eustatic level and diagenesis on the carbonate reservoir quality of the Permo–Triassic Upper Dalan and Kangan formations in the Lavan Gas Field (offshore Zagros). A total of eight lithofacies have been defined and interpreted, representing the shallower parts (inner ramp to shoal) of a carbonate homoclinal ramp. The diagenetic features show the mixing influence of marine, meteoric and burial processes, with prevalence of multistage dolomitization and late meteoric‐related imprints. The main dolomitization processes are interpreted to be penecontemporaneous and associated with continuous seawater reflux and high evaporation within the intertidal environment. Combined analysis of facies and petrophysical properties has been utilized to define six rock types, including RT4 (grainstones from oolitic shoals) as the best reservoir, whereas RT1 (supratidal anhydrite) is acting as the main cap rock within the studied carbonate–evaporite sequence. Multiscale characterization of lithological and petrophysical properties suggest that the Upper Dalan Formation has a single reservoir unit (D1), whereas the Kangan Formation may be divided into two reservoir units (K1 and K2). The best reservoir quality is promoted by dissolution and dolomitization associated with late Transgressive Sequence Tracts (TST) to early Highstand Sequence Tracts (HST) sequences, while low reservoir quality corresponds to late HST sequences accompanied by pore‐occluded cements. Petrophysical analysis suggest better porosity‐permability for the Upper Dalan than for the Kangan Formation. This observation is closely associated with the different nature of lithofacies, where the Kangan Formation contains more fine‐grained carbonate rocks, and the higher intensity of porosity‐grain dolomitization in the Upper Dalan Formation. This study provides a better understanding on reservoir quality prediction across the P–T boundary and the effect of eustatic fluctuations and diagenesis in controlling porosity‐permeability evolution with similar settings elsewhere.

Carbon dioxide injection in carbonate reservoirs – a review of CO2‐water‐rock interaction studies

AbstractCarbon dioxide injection in geological formations is currently a common procedure in several reservoirs worldwide. More recently, it has been considered a permanent storage solution, avoiding emission to the atmosphere from large industrial sources. Also, it is largely employed in the oil & gas exploration industry, for enhanced oil recovery (EOR) operations. However, it is a known fact that injection of large amounts of CO2 into geological reservoirs may lead to a series of alterations due to chemical and physical interactions with minerals and fluids, especially in carbonate or carbonate‐rich reservoirs. Experimental and numerical models have been employed in many studies in the past, to investigate these effects on the geological environment. So far, most of these studies focused on siliciclastic formations, whereas carbonate reservoirs, which are known to be much more chemically reactive when interacting with CO2, were much less investigated. We present a review of experimental and numerical models that have been employed for studying CO2‐water‐rock interactions, and their application to the investigation of the impact in carbonate reservoir quality and integrity caused by the injection of carbon dioxide. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

Reactive Transport Modelling of Dolomitisation Using the New CSMP++GEM Coupled Code: Governing Equations, Solution Method and Benchmarking Results

Reactive transport modelling (RTM) is a powerful tool for understanding subsurface systems where fluid flow and chemical reactions occur simultaneously. RTM has been widely used to understand the formation of dolomite by replacement of calcite, which can be an important control on carbonate reservoir quality. Dolomitisation is a reactive transport process governed by slow dolomite precipitation and cannot be correctly simulated without a kinetic rate model. The new CSMP++GEM coupled RTM code uses the GEMS3K kernel for solving geochemical equilibria by the Gibbs energy minimisation method with the CSMP++ framework that implements a hybrid finite element–finite volume method to solve partial differential equations. The unique feature of the new coupling is the mineral reaction kinetics, implemented via additional metastability constraints. CSMP++GEM is able to simulate single-phase flow and solute transport in porous media together with chemical reactions at different pressure, temperature, and water salinity conditions. This RTM assures mass conservation which is crucial when simulating transport of solutes with low concentrations over geological time. A full feedback of mineral dissolution/precipitation on the fluid flow is provided via corresponding porosity/permeability evolution and two source terms in the pressure equation. First, the mass source term accounts for the mass of solutes released during mineral dissolution or taken from the solution by mineral precipitation. The second source term attributes to the fact that the solution density is affected by mineral dissolution/precipitation, too. This effect is included through the equivalent water salinity, which is calculated from the total amount of dissolved solutes and is used to update the properties of saline water from the H $$_2$$ O–NaCl equation of state. This paper puts emphasis on the thorough mathematical derivation of the governing equations and a detailed description of the numerical solution procedure. Two sets of benchmarking results are presented. The first benchmark is a well-known 1D model of dolomitisation by MgCl $$_2$$ solution with thermodynamic reactions. In the second benchmark, CSMP++GEM is compared with TOUGHREACT on a 1D model of dolomitisation by sea water taking into account mineral reaction kinetics. The results presented in this paper demonstrate the ability of the CSMP++GEM code to correctly reproduce dolomitisation effects.

Carbonate facies and reservoir quality of the Kujung Formation in Kangean Island, East Java, Indonesia

Carbonate facies and reservoir quality of the Kujung Formation in Kangean Island, East Java, Indonesia

Integration of facies architecture, ooid granulometry and morphology for prediction of reservoir quality, Lower Triassic Khuff Formation, Saudi Arabia

Prediction of the reservoir quality of oolitic carbonates is one of the main challenges for petroleum geology due to the inherited heterogeneity in pore systems. This study investigated and characterized the sedimentological, stratigraphic, morphological and granulometric data of oolitic outcrop strata of the Khartam Member of the Khuff Formation in Saudi Arabia, including the giant hydrocarbon reservoirs (Khuff reservoirs), and the results have implications for exploration and development. Linking ooid morphology to sequence stratigraphy revealed that the distribution of the oolitic beds and their pore systems are mainly controlled by stratigraphic position, morphology (controlled by primary mineralogy) and grain size. The systematic distribution of ooids with distinct original mineral compositions allows for the prediction of the porosity distribution and occurrence within analogous reservoirs. The ooids in the studied interval were aragonitic (lower interval), bimineralic (middle interval) and aragonitic (upper interval). Linking ooid grain size with depositional environments indicated that the ooid grain size increases with water energy and follows the upwards-shallowing pattern of the studied succession. These results can be used to improve the understanding and prediction of the reservoir quality of oolitic carbonates.

Hydraulic properties of fault zones in porous carbonates, examples from central and southern Italy

We present the results of in situ permeability measurements performed, using a portable field permeameter, on normal and strikeslip fault zones that crosscut high-porosity carbonate grainstones. The measurement sites expose in the Cretaceous Orfento Formation of the Majella Mountain (Abruzzo, Italy), and the Lower Pleistocene deposits of the Favignana Island (Sicily, Italy). Nine small-displacement, compactive shear banding-based fault zones have been tested in the field. The fault offset ranges between 10 and 200 centimeters. The acquired permeability data indicate a two orders of magnitude decrease of porosity and permeability from the host rock to the cataclastic fault cores. A clear dependence of the fluid circulation paths through porous carbonates is therefore inferred at depth due to orientation, density and connectivity of the fault zones. Moreover, this study indicates the key role played by the pore network characteristics (pore dimensions above all) of undeformed host rocks on determining extremely different permeability values of the faulted porous carbonate grainstones. Accordingly, the results presented in this study may be helpful in applications such as geofluids management for improving the forecasting of carbonate reservoir quality and understanding the extent of reservoir compartmentalization.

Porosity and permeability of tight carbonate reservoir rocks in the north of Iraq

Abstract The distribution of reservoir quality in tight carbonates depends primarily upon how diagenetic processes have modified the rock microstructure, leading to significant heterogeneity and anisotropy. The size and connectivity of the pore network may be enhanced by dissolution or reduced by cementation and compaction. In this paper we have examined the factors which affect the distribution of porosity, permeability and reservoir quality in the Turonian–Campanian Kometan Formation, which is a prospective low permeability carbonate reservoir rock in northern Iraq. Our data includes regional stratigraphy, outcrop sections, well logs and core material from 8 wells as well as a large suite of laboratory petrophysical measurements. These data have allowed us to classify the Kometan Formation into three lithological units, two microfacies and three petrofacies. Petrofacies A is characterized by dense and compacted and cemented wackstone/packstone with nanometer size intercrystalline pores and stylolites and presents a poor reservoir quality (porosity range 0.005±0.01 to 0.099±0.01, permeability range 65 nD–51 μD). Occasional open fractures in Petrofacies A improve reservoir quality resulting in a 2–3 order of magnitude increase in permeability (up to 9.75 mD). Petrofacies B is a dissolved wackstone/packstone that contains moldic and vuggy pores (porosity range 0.197±0.01 to 0.293±0.01; permeability range 0.087–4.1 mD), with both presenting good reservoir quality, while Petrofacies C is a carbonate mudstone that has undergone dissolution and possibly some dolomitization (porosity range 0.123±0.01 to 0.255±0.01; permeability range 0.065–5 mD). All three petrofacies can be distinguished from wireline log data using porosity and NMR measurements. A poroperm plot of all of the data is fitted by a power law of the form k ( mD ) = a ϕ b with a=28.044 and b=2.6504 with coefficient of determination, R2=0.703. When the permeability is predicted with the RGPZ model of the form k ( mD ) = d 2 ϕ 3 m / 4 a m 2 with mean grain diameter d=10 μm, and mean cementation exponent m=1.5 and a=8/3 a better fit is possible with R2=0.82.

New tools and approaches in carbonate reservoir quality prediction: a case history from the Shu'aiba Formation, Saudi Arabia

Abstract Reservoir quality prediction has historically been the ‘holy grail’ of reservoir geologists, yet few have succeeded at achieving this in a quantitative fashion. This study presents a new approach to pre-drill reservoir quality prediction that involves the integration of a variety of modelling techniques to understand, quantify and predict the geological processes that control reservoir quality. Since the initial reservoir quality framework is established at the time of deposition by a variety of depositional controls, this approach uses numerical process models to predict initial reservoir quality; results from these depositional models are then modified via a series of process modelling technologies to quantify and predict post-depositional modifications that have significantly affected reservoir quality in the interval of interest. This approach is illustrated using an example from the Early Cretaceous Shu'aiba Formation in eastern Saudi Arabia, where depositional facies, diagenesis and resulting reservoir quality are predicted and tested against well and seismic data, with generally positive results. Model-predicted sediment thicknesses match thicknesses measured in wells to within ±0.5%; depositional facies and diagenetic trends seen in key wells from the Shaybah field matched model-predicted facies and diagenesis; and model-predicted porosity matched observed porosity within ±1.8 porosity units.

Geothermal convection in South Atlantic subsalt lacustrine carbonates: Developing diagenesis and reservoir quality predictive concepts with reactive transport models

Prolific hydrocarbon discoveries in the subsalt, commonly known as the “presalt,” section of Brazil and the conjugate African margin have created a business imperative to predict reservoir quality in lacustrine carbonates. Geothermal convection is a style of groundwater flow known to occur in rift settings, which is capable of diagenetic modification of reservoir quality. We simulated variable density groundwater flow coupled with chemical reactions to evaluate the potential for diagenesis driven by convection in subsalt carbonates. Rates of calcite diagenesis are critically controlled by temperature gradient and fluid flux following the principles of retrograde solubility. Simulations predict that convection could operate in rift carbonates prior to salt deposition, but with rates of dissolution in the reservoir interval only on the order of 0.01 vol. %/m.y., which is too low to significantly modify reservoir quality. The exception is around permeable fault zones and/or unconformities where flow is focused and dissolution rates are amplified to 1 to 10 vol. %/m.y. and could locally modify reservoir quality. After salt deposition, simulations also predict convection with a critical function for salt rugosity. The greatest potential for dissolution at rates of 0.1 to 1 vol. %/m.y. occurs where salt welds, overlying permeable carbonates thin to 500 m (1640 ft) or less. With tens of million years residence times feasible, convection under these conditions could locally result in reservoir sweet spots with porosity modification of 1% to 10% and potentially an order of magnitude or more in reservoir permeability. Integrating quantitative model–derived predictive diagenetic concepts with traditional subsurface data sets refines exploration to production scale risking of carbonate reservoir presence and quality.

Onshore to offshore trends in carbonate sequence development, diagenesis and reservoir quality across a land-attached shelf in SE Asia

Although isolated Miocene buildups in SE Asia commonly form prolific hydrocarbon reservoirs, their equivalents on clastic-dominated land-attached shelves remain poorly known and underexplored. Here, onshore to offshore trends in carbonate development and reservoir quality are assessed across the NW Borneo shelf through study of surface outcrops and subsurface wells. A multidisciplinary programme of fieldwork, petrography and geochemical analyses allowed evaluation of spatio-temporal variations in deposition, diagenesis and pore system development, together with an assessment of controlling influences. In addition to field logging and sample collection >200 samples were studied via transmitted light, cathodoluminescent and scanning electron microscopy together with stable isotopic characterisation (O, C and Sr).Carbonates developed as localised low-, and higher-relief buildups, as well as more continuous sheet-like deposits in near-coast to shelf margin positions. Molluscs, corals, larger benthic foraminifera and coralline algae are common constituents. Most samples show evidence for marine micritisation, and just in shelf margin positions isopachous cements. However, burial diagenesis predominates in the form of compaction, neomorphism, fracturing, late leaching and dolomitisation. Near-coastal carbonates commonly contain siliciclastics, as do some shelf margin deposits that interdigitate with, or are covered in siliciclastics. Some early, probable meteoric leaching affected inner shelf deposits prior to pervasive neomorphic to blocky/poikilotopic calcite cement formation. On the basis of δ18O V-PDB values of −4.5 to −7.9‰ equivalent to δ18O V-SMOW values of 0 to −4‰ at 25–40 °C and δ13C V-PDB values of −0.6 to +1.6‰ cementation probably reflects alteration from terrestrial groundwaters in meteoric aquifers derived from the humid landmass of Borneo. Despite this cementation, moderate energy inner- to mid-shelf grainstones from the core of mounded carbonates still retain, or have enhanced porosity (<8%) over their lower energy counterparts (<4% porosity). Retention of primary porosity and/or late burial dissolution (often associated with saddle dolomite formation) enhancing predominantly primary and minor secondary porosity is key to reservoir quality development in outer-shelf deposits. Best porosity (<20–35%) is in high energy grainstones and rudstones from outer-shelf to shelf-margin positions that experienced minimal clastic influx, most commonly from backstepping to aggradational carbonate sequences. Although stable isotopes for shelf margin calcite cements are consistent with precipitation from marine-derived fluids (δ18O V-PDB values of −3.6 to −5.4‰), those for the late dolomites are suggestive of fluids of meteoric origin (δ18O V-PDB values of −5.2 to −7.4‰ equivalent to values of −0.3 to −6.3‰ V-SMOW at 40–60 °C). Critical factors for reservoir quality development in carbonates from siliciclastic-dominated shelves in the equatorial tropics are: (1) development and preservation of primary porosity, (2) cementation associated with meteoric aquifers draining large humid equatorial landmasses, and (3) burial leaching and fluid pathways.

Carbonate porosity creation by mesogenetic dissolution: Reality or illusion?: Reply

Many authors have proposed that significant volumes of porosity are created by deep-burial dissolution in carbonate reservoirs. We argue, however, that this model is unsupported by empirical data and violates important chemical constraints on mass transport. Because of the ubiquitous presence and rapid kinetics of dissolution of carbonate minerals, the mesogenetic pore waters in sedimentary basins can be expected to be always saturated and buffered by carbonates, providing little opportunity for the preservation of significantly undersaturated water chemistry during upward flow, even if the initial generation of such undersaturated pore water could occur. A review of the literature where this model has been advanced reveals a consistent lack of quantitative treatment. In consequence, the presumption of mesogenetic dissolution producing a net increase in secondary porosity should not be used in the prediction of carbonate reservoir quality.

Spacing and distribution of bed-perpendicular joints throughout layered, shallow-marine carbonates (Granada Basin, southern Spain)

This contribution focuses on the controls exerted by sedimentological, petrographic and mechanical rock properties on the distribution of bed-perpendicular joints throughout layered carbonates. The study was conducted on Tortonian, shallow-marine skeletal grainstones and rudstones cropping out in the Granada Basin, southern Spain. The results of combined field and laboratory analyses are consistent with the rock grain size of the studied carbonates exerting a key control on distribution of the bed-perpendicular joints. A positive correlation between joint spacing and mechanical unit thickness is computed for the grainstones, whereas joints are almost absent in rudstones. The rock grain size affected the diagenetic processes, such as cementation and dissolution, and therefore the resulting porosity and uniaxial compressive strength (UCS) values. Quantitative data show that higher UCS values are commonly associated with greater calcite amounts, lower values of porosity and finer grain sizes and, hence, denser bed-perpendicular joint sets. In conclusion, this study documents that it is possible to infer the density of bed-perpendicular joints in layered carbonates based on the sedimentological, petrographic and mechanical parameters. Considering the impact that this type of joints has on subsurface fluid flow, the acquired knowledge can help the management of geofluids as well as the overall prediction of carbonate reservoir quality.

IMPACT OF DIAGENESIS ON RESERVOIR QUALITY IN RAMP CARBONATES: GIALO FORMATION (MIDDLE EOCENE), SIRT BASIN, LIBYA

The reservoir quality of Middle Eocene carbonates in the intracratonic Sirt Basin is strongly influenced by depositional facies and various diagenetic processes. Based on data from core samples and well logs from five boreholes in the Assumood and Sahl gasfields in the subsurface of the north‐central Sirt Basin, six major carbonate facies (and fourteen microfacies) are distinguished in the Middle Eocene Gialo Formation (thickness ∼1100 ft/335 m). Wackestones‐packstones dominate the Gialo Formation with abundant grains of larger benthic foraminifera, especially nummulites, in a matrix composed mostly of finely comminuted bioclastic material. Sediments were deposited as a mosaic of facies on a broad carbonate ramp in moderate‐energy nummulite‐packstone banks, with locally restricted back‐bank lagoons and fore‐bank areas of foraminiferal debris passing to offshore lime mudstones.Marine diagenesis was minor with micritization of bioclasts and rare vadose marine fibrous cements. Sparry calcite cements are ubiquitous and were precipitated during shallow to moderate burial from seawater and/or meteoric water, the latter largely unaffected by surface‐pedogenic processes. This is indicated by the fabrics and pre‐ and post‐compaction precipitation of drusy spar and echinoderm overgrowths, and supported by their bright‐to‐dull luminescence and low negative δ18O signatures (‐2.68 to ‐4.16%° PDB). Some early neomorphic alteration of calcitic bioclasts is suggested by bright CL and marine to low negative δ18O values (‐1.06 to –3.93%° PDB). Bioclastic grains have δ13C values ranging between 0.76 and 1.19%° PDB, interpreted as marine signatures. Similar low positive δ13C values of the cements (0.9 to 1.05 %°) indicate a source of carbonate from dissolution of grains and/or seawater/meteoric water, but without any near‐surface/soil effects. Dissolution of grains and matrix, notably originally aragonitic grains but also the originally high‐Mg calcite nummulites, was a major porosity‐enhancing process, and took place from shallow to moderate burial depths. Fractures may locally have increased porosity too.Shallow‐water packstones/rudstones containing both primary intergranular and secondary biomouldic porosity have the best reservoir quality and these are concentrated in the upper parts (top ∼100 ft/30 m) of the wells, with porosity‐permeability decreasing downwards. This trend relates to the broad, large‐scale facies pattern of more mud‐dominated facies giving way upwards to more grainy, nummulite‐dominated facies as a result of an overall shallowing of the depositional environment. In addition, the influx of meteoric waters in the upper part of the Gialo platform, before drowning and deposition of the overlying Augila Shale, increased porosity through dissolution. This integrated study has helped in understanding the reservoir heterogeneity and hydrocarbon potential of the Gialo carbonates.

Effects of depositional and diagenetic characteristics on carbonate reservoir quality: a case study from the South Pars gas field in the Persian Gulf

ABSTRACT The largest non-associated gas reserve of the world is hosted by the Upper Dalan–Kangan (Upper Khuff equivalent) Permo-Triassic carbonate–evaporite successions. Detailed characterization of these strata in the South Pars field has shown that the reservoir properties are a function of both sedimentary and diagenetic processes at the field scale. Facies analysis of the studied units indicates that the sediments were deposited in the inner regions of a homoclinal carbonate ramp and were subsequently subjected to shallow diagenesis and minor burial. The vertical distribution of the facies shows cyclic patterns that impact reservoir quality. The rock type classes have been grouped on the basis of the dominant pore spaces, and have enabled distinct fields to be identified. This approach has demonstrated a relationship between poroperm values and rock type groups. Diagenetic overprinting has significantly affected the reservoir properties. Although the original poroperm heterogeneities in the studied reservoir are inherited from the Upper Dalan–Kangan palaeoplatform, they have been modified strongly by diagenetic overprinting. Consequently, tentative correlation may be possible between facies types and reservoir properties based on diagenetic effects. Therefore, for precise characterization of the Upper Dalan–Kangan reservoir properties it has been necessary to integrate both the depositional history and diagenetic features.

The relationship between petroleum, exotic cements and reservoir quality in carbonates – A review

Exotic minerals, i.e. those that do not have an obvious source of components within the host rocks, can be major porosity occluding cement and replacement phases in subsurface carbonate reservoirs. Here we present and discuss petrographic and fluid inclusion data from a number of petroleum systems. These have had different geological histories but a common factor is the presence of exotic mineral cements and late stage dissolution. The effect of these cements and late stage dissolution on reservoir quality is also considered. Petroleum filling does not appear to inhibit the precipitation of exotic cements in the way that it appears to inhibit the precipitation of calcite. Burial dolomite and anhydrite are the most important of these volumetrically but they are often accompanied by other late stage cements such as fluorite, kaolin, quartz, barite, celestite, sphalerite and galena, generally in much smaller quantities. In accounting for the concentration of the material contained in these cements compared with the host rocks, stylolitisation is a possible mechanism in some cases, but, in many others, import from sources external to the reservoir is required.

HYDROTHERMALLY FLUORITIZED ORDOVICIAN CARBONATES AS RESERVOIR ROCKS IN THE TAZHONG AREA, CENTRALTARIM BASIN, NW CHINA

Reservoir rocks at the Tazhong 45 oil pool, central Tarim Basin, consist of fluoritized carbonate strata of Middle - Late Ordovician age. Petrological observations indicate that the fluorite replaces calcite. Several other hydrothermal minerals including pyrite, quartz, sphalerite and chlorite accompany the fluorite. Two generations of fluid inclusions are present in the fluorite. Homogenization temperatures (Th) for primary inclusions are mostly between 260°C and 310°C and represent the temperature of the hydrothermal fluid responsible for fluorite precipitation. Th for secondary inclusions range from 100°C to 130°C, and represent the hydrocarbon charging temperature as shown by the presence of hydrocarbons trapped in some secondary inclusions. The mineral assemblage and the homogenization temperatures of the primary fluid inclusions indicate that the precipitation of fluorite is related to hydrothermal activity in the Tazhong area. Strontium isotope analyses imply that the hydrothermal fluids responsible for fluorite precipitation are related to late-stage magmatic activity, and felsic magmas were generated by mixing of mafic magma and crustal materials during the Permian. Theoretical calculations show that the molecular volume of a carbonate rock decreases by 33.5% when calcite is replaced by fluorite, and the volume shrinkage can greatly enhance reservoir porosity by the formation of abundant intercrystalline pores. Fluoritization has thus greatly enhanced the reservoir quality of Ordovician carbonates in the Tazhong 45 area, so that the fluorite and limestone host rocks have become an efficient hydrocarbon reservoir. According to the modelled burial and thermal history of the Tazhong 45 well, and the homogenization temperatures of secondary fluid inclusions in the fluorite, hydrocarbon charging at the Tazhong 45 reservoir took place in the Tertiary.

Automated mapping of carbonate build-ups and palaeokarst from the Norwegian Barents Sea using 3D seismic texture attributes

Geological heterogeneity in hydrocarbon reservoirs is normally related to variability in depositional facies, diagenesis and structure. On the Loppa High, Norwegian Barents Sea, reservoir quality in prospective Upper Palaeozoic carbonates is considered to be controlled mainly by primary depositional facies variability linked to active faulting, with a secondary overprint of palaeokarst. The best quality reservoirs are anticipated in build-up facies. Although high-quality 3Dseismic data exist over the prospect, it is a challenge to map the buildups and palaeokarst in three-dimensional space using conventional 3Dseismic interpretation tools. This is mainly due to the internal heterogeneity of the build-ups and palaeokarst, which are characterized by a range of seismic reflection/attribute patterns. A procedure for multi-attribute mapping of seismic facies is described and utilized to provide a truly threedimensional interpretation of build-up and palaeokarst geobodies. A neural network classifier is used to analyse a set of 3D attributes that capture the seismic stratigraphical and structural patterns inherent in the data. These attributes are referred to as 3D texture attributes since they describe the reflector-geometry in a small 3D neighbourhood. Pattern recognition is interpreter-guided, with the desired seismic facies to be mapped input as ‘training data’ and analysed prior to their presentation to the 3D-classification system. Once the classification is made, the interpreter is presented with a 3D classified volume and an uncertainty analysis of each of the mapped facies/classes. This is used to evaluate the results prior to their visualization in 3D space. The method allows the interpreter to identify quickly a volume where the features of interest occur and to focus the interpretation work directly on them. In addition, the 3D visualization of the mapped geobodies brings important new information that might be overlooked when inspecting data in vertical or horizontal data windows. In the Norwegian Barents Sea case study, 3Dseismic facies mapping provides the first truly three-dimensional interpretation of the build-ups and palaeokarst, where their external form, juxtaposition, cross-cutting relationships and structural information are preserved. These data give new insights as to the stratigraphic distribution and internal variability of the build-ups and palaeokarst system; this information is important to estimation of reservoir volume, connectivity and variability.

ABSTRACT: Assessing the Reservoir Quality of Burrow-Mottled Carbonates in the Devonian Wabamun Group, Pine Creek Area, Northwest Alberta, Canada

ABSTRACT: Assessing the Reservoir Quality of Burrow-Mottled Carbonates in the Devonian Wabamun Group, Pine Creek Area, Northwest Alberta, Canada

ABSTRACT: Prediction Of Reservoir Quality (Porosity/Permeability) In Frontier Basin Carbonates

ABSTRACT: Prediction Of Reservoir Quality (Porosity/Permeability) In Frontier Basin Carbonates

Abstract: Distribution and Controls on Carbonate Reservoir Quality in the Mississippian Mission Canyon Formation, Carter Creek Field, Uinta County, Wyoming

Abstract: Distribution and Controls on Carbonate Reservoir Quality in the Mississippian Mission Canyon Formation, Carter Creek Field, Uinta County, Wyoming