Drilling program for Middle-European Volcanoclastic rock: Design/evaluate and optimize
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The reason for the implementation of the project was that one wanted to optimize a drilling program. The drilling program should be used in the geothermal project to CEE energy in Slovakia. The research area is important to develop a broad understanding of drilling in its entirety, and also the possibility to combine air-hammer drilling with conventional rotary drilling. More equipment and planning are required, but better optimization can be obtained. It is also introduced an innovative drilling method called electromagnetic pulse drilling. This is not done calculations for, but it is discussed in theory as an alternative method.The problem of the project related to the thesis is to drill down to the reservoir with as large diameter as possible. This is necessary financially to meet the production target without pressure loss to become too large. This presents challenges particularly with air-hammer when you get large annulus with a lot of cuttings to be lifted.It has been working extensively with model building in this master. This is done as a result of that there is little knowledge of the formation. Moreover, it helps to create a theoretical basis that can serve as framework for the different drilling methods. For the hammer, the model was built with respect to lift cuttings and hammer effect associated with ROP. The model is limited to the settling velocity of spherical particle in the annulus. It also takes into account that the air can be compressed when pressure drop is calculated. For rotary drilling it was focused more on the calculation of the ROP against mechanical refractive energy. PDC and roller-cone drill bit was considered, the models takes parameters such as RPM, formation strength, number of teeth or cutters in contact with the formation, etc. Estimated ROP are compared to resulting MSE to check reality against other values from the reference. For PDC it is assumed that MSE is equal to formation strength when the bit is running smoothly. If not energy is lost.For air-hammer there are clear indications that the inflow of water aggravates the situation considerably. It is difficult to relate the estimated depth to reality especially in terms of complexity when the flow of water occurs. Theoretically the model varies the critical depth with both particle size and water in the annulus. Depth Interval with 22 inch hammer is 350-700 meters. It is believed that pressure, water and fractured formation falling from the well wall can quickly worsen this. For rotary drilling after the air-hammer stops one assumes that PDC bits has problems drilling this formation. This is especially due to the formation hardness and content of abrasive minerals. Broken cutters in the shape of grinding or bending are problematic and can quickly become expensive. Here roller-con bits are advantageous since they are better suited to hard formation. For roller-cone it was estimated an interval for ROP which is 1.0 to 1.5 [m / h]. This is not particularly fast, but in reality this may be bigger since uncertainty exists with respect to formation test. Another argument is that this is estimated on the basis of a solid and strong matrix. From the microscopy it can be seen that the matrix is fractured and oxidized, this can quickly lead to a significant increase of ROP which is very positive from an economic point of view.Based on the results, it is assumed that the roller-cone bit is more effective than PDC after you stop using the air hammer. If you do not meet high pore pressure at shallow depths it may also be desirable to decrease the diameter of the hammer. This can increase ROP and also the maximum attainable depth with the hammer. However, if the hammer meets high pressure one may get into trouble since air is to light to counter the pore pressure. This can result in a blowout.