The upstream oil business is an important branch to employ people with geo-scientific education. Beyond clear geological HC-schoolbook-traps there is a certain gap between pure geosciences and a final G&G model in hydrocarbon exploration. The absolute knowledge of geosciences about Mother Earth will always remain on an intermediate level somewhere in between zero and hundred percent. Aiming from such trusted intermediate standpoint for a final scientific solution of a given exploratory problem, the number of possible G&G models would increase to infinity then. Geosciences provide the general technical platform for all exploratory tasks, but to achieve the final decision level for a monetary investment in hydrocarbon exploration a human filter must be added to this G&G technology. Such human filter consists of the personal experience of people and the solid technical brain trust of upstream oil companies. Solely this human filter could delimitate the number of possible scientific solutions in hydrocarbon exploration to just one final G&G model which has then to face the economic project hurdles and the exploratory risk. It's a fully normal behaviour when human beings are permanently trying to avoid risks because we all have an immanent adherence to safeness. But in hydrocarbon exploration only those characters will be successful who could accept a failure to be a landmark on their way to success. The discrepancy amongst pure geosciences and the requirements of hydrocarbon exploration may be generally defined to be the gap in experience between a junior and a senior G&G position in the upstream oil business. This book aims to close this gap with a closer look on the basic requirements of hydrocarbon exploration. In addition, this book describes the general economic rules of the upstream oil business and tries to pass some practical information to the next generation of explorationists. At the very end, to become explorationists in the upstream oil branch, people wi