Wellbore Quality (WBQ) is an abstract industry term that can be used to describe nearly any cause of problems that can occur on wells throughout their life cycle. However, it has never been precisely defined nor are there industry-wide standards on how to assess wellbore quality. However, the economic impact of WBQ is not negligible: not only in the early stages, but also towards the end of the well life cycle, quality is the factor that makes a difference. While it may cost more to drill a perfect well, the long-term savings are likely worth making those expenses. This thesis reviews the importance of wellbore quality and existing assessment strategies from the literature. In a second step, new KPIs will be developed that could become a new industry standard for WBQ assessment. Opposed to existing methods, they rely on physical measurements only, thus being more reliable and unbiased. These will be split into three categories: geometrical, operational and wellbore success indicators. In a third step, the proposed KPIs will be tested using real-world data provided by OMV E&P Austria GmbH.