The Vienna Basin is a sedimentary basin more than 10 km in thickness and composed of more than a dozen hydrocarbon layers. Since the area has been intensively explored in the past 50 years, future exploration can expect to find only small reservoirs or compartments of already existing reservoirs. However, the existing infrastructure, such as pipelines, facilities and a nearby refinery, would make even small finds attractive. In this light it is of vital importance to reduce risk and costs in hydrocarbon exploration and production.
Multi-target wells were found to be an adequate answer to these problems: the chance of discovery increases more or less directly with the number of targets included in the well trajectory; and several small reservoirs can, in total, provide positive well economics. Moreover, by including exploration, appraisal and production targets into one well path a substantial contribution to improve economic hydrocarbon recovery from existing fields can be made. To further reduce drilling costs a new casing philosophy was established. By skipping the intermediate casing across the build-up section substantial savings could be made.
To plan and execute these challenging projects efficiently a multidisciplinary team has to be set up at an early stage of the drilling project. In this way the number of targets, the actual well path and well construction with respect to production requirements can be optimized. An example of a recently drilled multi-target horizontal well, including one primary and five secondary targets, is given. By applying this new concept drilling costs could be reduced by more than 30%.