Abstract Improved seismic data quality in the last 10–15 years, innovative use of seismic attribute combinations, extraction of geomorphological data and new quantitative techniques have significantly enhanced understanding of ancient carbonate platforms and processes. 3D data have become a fundamental toolkit for mapping carbonate depositional and diagenetic facies, and associated flow units and barriers, giving a unique perspective on how their relationships changed through time in response to tectonic, oceanographic and climatic forcing. Sophisticated predictions of lithology and porosity are being made from seismic data in reservoirs with good borehole log and core calibration for detailed integration with structural, palaeoenvironmental and sequence stratigraphic interpretations. Geologists can now characterize entire carbonate platform systems and their large-scale evolution in time and space, including systems with few outcrop analogues such as the Lower Cretaceous Central Atlantic ‘pre-salt’ carbonates. The papers introduced in this review illustrate opportunities, workflows and potential pitfalls of modern carbonate seismic interpretation. They demonstrate advances in knowledge of carbonate systems achieved when geologists and geophysicists collaborate and innovate to maximize the value of seismic data from acquisition, through processing to interpretation. Future trends and developments, including machine learning and the significance of the energy transition, are briefly discussed.

Abstract Prediction of fractures in carbonate reservoirs represents a very significant challenge. We describe the use of a digital outcrop analogue from faulted and jointed Lower Jurassic rocks from Somerset, U.K., that provides exceptional exposure of fractured carbonates. The aims were to gather high-resolution and exact information about the fracture systems and to understand the mechanics of the fracture development. A 2.5 km section of coastline was digitally captured and built into a high-resolution photorealistic model. Faults were hand interpreted in an immersive virtual reality environment. A line sample of the faults in the photorealistic model compares well with a similar line sample taken in the field. The photorealistic data also include large bedding-plane exposures of joint systems. The joints were extracted semi-automatically using a combination of image curvature and ant tracking; ground-truthing of the resulting joint map confirms the validity of the interpretation. By using this semi-automatic technique it is possible to digitize far more joints than would be possible for a human interpreter. The detailed fracture data provide a rich source of data for modelling of fracture systems. However, in order to be predictive in the subsurface, it is not sufficient to have a purely statistical fracture description and so we turn to mechanical modelling. On the assumption that the joint system formed in the perturbed stress system around pre-existing faults, we performed boundary element modelling and were able to match to the joint system in the photorealistic model using an extensional stress regime and fluid-pressure perturbations along the fault plane.

Abstract The Norwegian Barents Sea is used as a subsurface laboratory for improving our workflows to retrieve and quantify geomorphic information from seismic data over ancient carbonate systems. Here, we present a novel volume-based seismic interpretation work flow for improved imaging of carbonate features as, for example, subtle build-up complexes and karst. Frequency decomposition followed by RGB-blending is one of the most powerful tools in this work flow for extracting highly detailed information from seismic. A number of seismic surveys in the Norwegian Barents Sea have been revisited and interpreted with this work flow, revealing information on the Upper Paleozoic carbonate systems that otherwise would have remained hidden from interpreter. The newly retrieved seismic geomorphic data is paramount for suggesting new carbonate build-up growth models for the spectacular polygonal build-ups observed on seismic as widespread build-up complexes expanding over thousands of square kilometers. Systematic quantitative shape analyses provide insights on the geometry and self-organization of the polygonal build-ups. Growth is mainly controlled by the paleo-environmental position on the platform, stable slope, or on active fault blocks, reflecting variations in available accommodation space. Two separate phases of polygonal build-up development having distinct geomorphic expression are recognized through time: (1) Subtle features from the volume-based interpretation reveal low-relief Palaeoaplysina —phylloid algae polygonal-elongated ridge systems formed from the warm-water carbonate factory controlling the deposition during the Gipsdalen Group. These subtle systems compete with deposition of more basinal evaporites for space on low angle ramp systems.(2) A second set of polygonal build-ups are recognized in the cooler water carbonate interval of the Bjarmeland Group. These high relief Bryozoan- Tnbiphytes mound complexes have been recognized in previous studies, but our novel seismic geomorphic analysis allows unraveling the internal growth pattern of these spectacular complexes at a seismic scale. Starting as individual nuclei, these mounds amalgamate quickly into ridges that start to form polygonal networks. Subsequently, different cycles of aggradation followed by progradation are recognized in the buildups. Geomorphic quantification proves that basinal settings are dominated by aggradation, whereas slope and platform settings are prone to more progradational development of these polygons.

Abstract Paleokarst networks are complex, multi-scale, heterogeneous features that are commonly modified by gravitational, structural and diagenetic processes during burial. In subsurface carbonate reservoirs, paleokarst systems can be a source of significant heterogeneity and complexity. Although 3D seismic data commonly can reveal exquisite details of paleokarst systems at the level of the ‘top reservoir’, the beauty and use of such images is normally superficial. This is because horizon-based interpretations reveal little of the three-dimensional paleokarst network within the reservoir. In order to extract a more complete 3D representation of paleokarst systems, we have focused on the utilisation of volume-based methods of seismic data analysis. Specifically, a concerted effort to develop reliable methods and work flows for paleokarst detection has been made through the analysis and comparison of 6 different 3D seismic datasets imaging carbonate reservoirs. The results of one of these studies are presented here. The work flow is illustrated using an example of extensively karst-modified Upper Paleozoic (Moscovian-Asselian age) carbonates preserved on the eastern flank of the Loppa high, Norwegian Barents Sea. Here it is estimated that some 300-500 m of uplift, erosion, and karstification of a mixed carbonate-evaporite succession occurred during circa 20 million years of subaerial exposure ( i.e. , Roadian-Induan times). Major drainage systems can be traced across basement rocks and into and through the karstified carbonate succession. The carbonates are cut by steep km-scale canyons and penetrative sinkholes. The dataset shows a range of contrasting paleokarst features, so that some of the key seismic attributes and spectral decomposition methods used to delimit contrasting genetic elements of paleokarst systems can be illustrated. Results from the seismic data analysis have been quality-controlled against well data and horizon-based interpretations. The study reveals: (1) how horizon-based interpretations can potentially be misleading; (2) that different seismic properties/attributes are required to recognise and extract paleokarst features formed by different processes; (3) the important controls of bedrock geology and faulting/fracturing on paleokarst development; and (4) new insights as to heterogeneity within paleokarst networks.

Abstract This study evaluates the role of compaction-induced differential subsidence as a control on carbonate-platform architecture, sequence development, and early diagenesis in Permian strata of the Delaware and Midland basins, west Texas and southeast New Mexico. The geometry and stratal patterns of compaction-modified sequences identified from outcrops in the Sierra Diablo, Guadalupe, and Brokeoff Mountains are comparable to those observed in seismic lines from the Northwest and Eastern shelf areas. The modification of platform geometries by differential compaction varies spatially and temporally in the studied area and is most important where Leonardian and Guadalupian highstand strata (sequences and sequence sets) have prograded over antecedent aggradational and/or erosional platform margins and wedge-shaped packages of compactible basin facies. A "compaction hinge" delineates two mechanically distinct parts of a carbonate platform with contrasting stratal patterns, facies, and accommodation histories. The hinge normally develops in highstand strata deformed by compaction-induced differential subsidence over a preexisting platform margin. Updip of the compaction hinge, platform topsets are generally parallel and of constant thickness, whereas downdip, the same topsets thicken, dip, and diverge basinward toward a downward-deflected depositional platform margin. The alteration of platform architecture by differential compaction during a sea-level lowstand forms a compaction-modified sequence boundary. During a lowstand, flexural deformation driven by compaction-induced differential subsidence (at an outcrop-constrained average rate of 0.19 m/k.y.) modifies platform-top physiography and can generate relief and fractures to control facies patterns, stacking patterns, and the distribution of penetrative paleokarst. The resulting compaction-modified platform architectures and sequence boundaries show a characteristic suite of features that allows their identification using the criteria presented herein. The progressive further steepening of the dips formed across compaction-modified sequence boundaries during burial aids their recognition in outcrops and especially on regional seismic lines. The control of compaction-induced differential subsidence on carbonate-platform development has previously been underestimated. Differential compaction can significantly modify the development and dynamics of carbonate platforms and holds important implications for the interpretation of stacking patterns, platform architecture, paleoecology, diagenesis, and accommodation history.