The given diploma thesis was intended to provide OMV E&P GmbH with a clear understanding on how to address the issue of accumulator volumetric sizing within their new standard for Well Control. The first question that had to be answered was if the provisions made in API standards are sufficient. The thesis discusses the fundamental basics required to understand the calculations made in API and consequently looks at other international standards and their provisions. By defining standard cases for workover and drilling Blow Out Preventer (BOP) stacks it could be shown that API requirements leave room for improvement as they may lead to the inability of closing the BOPs in a worst case scenario. With this gap identified, the thesis describes a recommended practice on how to size accumulators in regard to their volumetric capacities.