“Dry holes” is the term used by experts to describe unsuccessful wells drilled in search of oil and gas fields. Before decisions can be made to spend millions on drilling down to depths of several kilometres, it is important to determine the likely conditions that will be encountered below ground. To carry out this kind of assessment, which also includes taking stock of any potential risks, the scientists at RWE Dea constantly develop new and better three-dimensional computer models of subsurface structures on the basis of a range of different geoscientific measurements. Factors taken into account for the purpose of the evaluation go beyond establishing the presence or absence of the hydrocarbons being searched for; they also include the likely volumes to be encountered, and the fluid flow conditions within the reservoir structure.
In addition to the three-dimensional models mentioned above, there are numerous recent developments in the field of geostatistics that allow a more detailed analysis of potential reservoirs to be carried out. Petrophysical data used to generate a so-called “geostatistical model population” is acquired through extensive geophysical downhole measurements shortly after a borehole has been completed. These data sets, commonly referred to as “logs”, allow conclusions to be drawn regarding the pore content in a reservoir, and this in turn makes the evaluation of a strike much more accurate. The same data also helps in the evaluation and subsequent production of difficult-to-extract hydrocarbon reservoirs, for example in thin-layer sedimentary sequences.
Flow characteristics within porous structures
Whether an exploration well can be considered successful depends largely on the petrophysical properties of the reservoir encountered. For this reason, RWE Dea systematically collects data about subsurface reservoirs in order to determine vital reservoir characteristics such as density, porosity, oil and water saturation and permeability. These findings are a direct input to production planning and enhance the efficiency of sinking a well. In doing so, reservoir simulations – where past and future flow characteristics within a reservoir are simulated using computer modelling for a range of different production strategies – also contribute significantly towards optimising the yield of reservoirs.
In an effort to maintain the level of professional competence going forward, RWE Dea specialists closely collaborate in partnerships with the Centre of Computational Geostatistics at the University of Alberta and the Formation Evaluation Research Consortium at the University of Texas, to mention but a few.