D5.2 - Jet drilling at simulated reservoir conditions

• Main Authors: Hahn, Simon, Wittig, Volker, Jasper, Sarah, Schwarz, Dennis, Albadroui, Dhafir, Hoogland, Koos, Bakker, Richard
• Format: Report
• Language: English
• Published: GFZ German Research Centre for Geosciences 2019
• Subjects: Nozzle; Iceland
• Online Access: https://dx.doi.org/10.2312/gfz.4.8.2019.002; https://gfzpublic.gfz-potsdam.de/pubman/item/item_5002026

Deliverable D5.2 presents the experimental outcome of jetting experiments at simulated reservoir conditions. Different rock types are tested under various conditions with the use of three different types of test bench. At first jetting experiments are conducted under submerged conditions in order to derive a better understanding of the governing erosion mechanism. Therefore pitting tests are combined with PIV measurements in order to derive and explain the erosion pattern of the occurring cavitation erosion and why the rock is more like to be eroded by the stagnation pressure of the impinging jet. Second, jetting experiments under pressure controlled conditions are performed. Rate of penetrations (ROP) of up to 100 m/h can be achieved which proofs the successful application of RJD technology especially in sand stone reservoir rock types. Especially the rotating nozzle design bears the highest potential for jetting operations where the static nozzle designs tend to fail, especially when pore pressure increases. The third experimental series under application of a bi- axial stress field show that the current RJD technology, as being used by project partner WSG, is not able to penetrate harder sandstone rock types (e.g. Dortmund sandstone) when field operating conditions are applied. The induced stress in the specimen does not initiate or enhance ROP. A second experiment thereby shows that higher nozzle exit speeds can lead to massive breakouts. Fourth, experiments are performed under a tri-axial stress field in collaboration with TU DELFT. Rock cubes are tested under different and very severely stress regimes while jetting into them. Compared to tests at atmospheric conditions it can be stated that the application of a stress field does not enhance the erosion of rock. At last experiments are conducted with the project partner WSG in order to determine the jetability of the Icelandic Basalt rock type and Icelandic inter basalt sediment layer. The experiments show that already higher pump pressures result in higher jetting performance, hence making them jetable as previously not expected. Furthermore the experiments approved the feasibility of the planned field test in Iceland when the soft sediment layer is the target zone. All in all the experiments conducted with the RJD technology show different results at simulated reservoir conditions compared to those at atmospheric which are described in deliverable D5.1 (Hahn & Wittig, 2017). Therefor, further testing at conditions representing the reservoir conditions more closer are needed in order to better understand and analyze the jetting process downhole.