Appraisal follows a discovery. Although a discovery well can provide a considerable amount of vital information about the basement reservoir, it is in effect just a single data point so we need to do more to get closer to development.
The appraisal process therefore sets out to drill a number of appraisal wells across the mapped area of the discovery in order constrain the distribution of the reservoir properties in the basement reservoir and also the extent and volumes of hydrocarbon present. The results of the appraisal drilling programme will be fundamental in deciding whether the discovery is taken forward to development and production.
For any oil discovery, numerous key technical questions have to be answered during appraisal drilling and so considerable thought needs to go into the design and location of the wells. This is no different for basement reservoirs. For instance, some wells may be designed to penetrate deeply into the basement in order to evaluate how far down the hydrocarbon column goes, whilst others may be designed to assess the productivity of the reservoir or target potentially more fractured parts of the basement so that future production rates can be predicted and incorporated into the development plan. In particular, drilling high angle or horizontal well paths through the basement is considered to be highly beneficial as it allows a greater number of potential productive fractures to be intersected. The first appraisal well that Hurricane plans to drill is a 1 km long horizontal well designed to test the production potential of a series of seismic scale faults and well connected fractures. The well will penetrate a crestal volume of the field, which geological modeling predicts to be be oil rich. An artist’s impression of the well path is shown below.
The horizontal well that will not only evaluate the productivity of the basement towards the crest of the reservoir but determine whether further horizontal wells will be the optimum way to develop the field in the future.
Hurricane's appraisal programme also enables various well technologies, particularly those that can increase well productivity such as the incorporation of downhole pumps, to be evaluated in advance of development.