| dc.description.abstract | Systems to increase efficiency during drilling is desirable in order to have more costeffective well operations. This master s thesis studies the possibility to present new information real-time regarding the actual drilling efficiency, based on already existing data commonly available during most operations. Said data should not only help increase efficiency, but also help identify insufficiencies, and be used when evaluating if re-modelling of the drillstring is profitable to improve efficiency.
Based on the concept of Mechanical Specific Energy presented by Teale (1965), an attempt has been made to adjust and improve this method to present the actual drilling efficiency down-hole in a better way. During work with this method, three main insufficiencies were identified. The original method does not include hydraulic energy, does not estimate actual energy loss, and does not account for formation hardness. These three problems were the cause of the largest alterations.
To test the new method, and to make it compatible with the data usually available, a mathematical agent was modelled in Matlab. The method has so far been tested on drilling data from three sections of a well located in the North Sea. Due to a limited amount of available drilling data, no real conclusions could be made. Nevertheless, some patterns were identified.
Results show, that the current method identifies most of the work used for drilling progress as rotational energy. By more accurately evaluating the actual energy reaching the formation, the actual drilling efficiency will be of more use for the driller. Evaluation of hydraulic energy showed that while these extensions make the method more complicated, hydraulic energy contribution is too large to be considered negligible. Data regarding how the formation hardness affects the drilling efficiency was proven difficult to achieve, as the correlation between the method chosen to specify energy input and formation hardness were considered too large to be a reliable source of information. For future work, a method based on the Unconfined Compression Strength would probably prove more beneficial. Further work with this model should also focus on proper identification of sources of inefficiencies, as this was not thoroughly addressed in present thesis. | |
