Risk modelling of shale gas development scenarios in the Central Karoo

Abstract

The scientific assessment of shale gas development was compiled by over 200 authors and peer reviewers from around the world. Novel assessment methods were used based on the concepts of risk, scenarios and predictive landscape modelling. Three development scenarios were assessed against a baseline scenario, across seventeen topic-specific chapters. Risk profiles for spatially explicit impacts in distinctive receiving environments were generated and assessed with and without mitigation. Risk was determined by simultaneously considering the consequence of an impact and its likelihood of occurrence, with topic consequence terms calibrated to ensure a degree of consistency across all topics. A landscape risk model was populated to generate a composite spatial overlay representing the cumulative evolution of the risk profile across the scenarios, representing the full life-cycle of shale gas development activities from initial exploration to final closure and site remediation. For the production-scale scenarios considered, risk ranges from very high and high before mitigation to generally moderate after mitigation, assuming that best-practice mitigation is applied and that adequate governance and institutional capacity exists to enforce it. Given the expanse of the study area (171 811 km2) and the relatively small physical surface footprint of shale gas development activities, mitigation best-practice is led through application of the mitigation hierarchy, prescribing avoidance of impacts first, largely by adjusting the exact location of wellpads, roads and other structures to not coincide with critical resources. Through effective project planning, many sensitive environments of the Central Karoo can be avoided, thus maintaining the social and ecological character and integrity of the region. From a cumulative risk perspective, modelling results suggest that shale gas development activities, at the scale expected in the large-scale gas production scenario may be near to exceeding the developmental threshold of the Central Karoo.