Importance of drilling-related processes on the origin of borehole breakouts — Insights from LWD observations

Logging while drilling (LWD) images are widely used for the analysis of borehole stability. In this context, borehole breakouts are a crucial indication of rock failure developing when the circumferential stress around the borehole exceeds the yield value of the rock. This study investigates the impact of drilling-related processes (DRPs) on the origin of borehole breakouts. DRPs, for instance, include connections or tripping operations. For this purpose, we analyze data from 12 boreholes in different geological settings throughout the Norwegian and Danish North Sea, containing a total of 208 borehole breakouts. The extensive data acquisition of LWD offers the unique possibility to link the imaging to real-time drilling operations and to monitor anomalies of e.g., bottom hole pressure. These records allow us to connect any thermal, hydraulic, or mechanical interaction next to the borehole wall to perturbations of the stress field. This analysis resulted in an apparent strong coincidence of borehole breakouts, representing major stress perturbations, with DRPs. The causal relationship is highlighted by one order of magnitude higher occurrence of DRPs in depth sections containing breakouts. Major pressure reductions in the annulus of the borehole seem to be the most significant cause of drilling-related wellbore failures. This applies in particular to shutting off the pumps during connections, where pressure reductions of up to 16 % of the annulus pressure led to higher circumferential stresses. This process will increase the likelihood of compressive and shear failure, therefore causing borehole breakouts. These observations further open the perspective of counteracting wellbore instabilities by pressure modification. In addition to the initiation of breakouts, their temporal evolution – as seen in relogs – can also be ascribed to DRPs. This study indicates that not only plasticity but also mechanical interaction from DRPs is a key driver of the temporal growth of borehole breakouts

Automated production of recombinant human proteins as resource for proteome research

<p>Abstract</p> <p>Background</p> <p>An arbitrary set of 96 human proteins was selected and tested to set-up a fully automated protein production strategy, covering all steps from DNA preparation to protein purification and analysis. The target proteins are encoded by functionally uncharacterized open reading frames (ORF) identified by the German cDNA consortium. Fusion proteins were produced in <it>E. coli </it>with four different fusion tags and tested in five different purification strategies depending on the respective fusion tag. The automated strategy relies on standard liquid handling and clone picking equipment.</p> <p>Results</p> <p>A robust automated strategy for the production of recombinant human proteins in <it>E. coli </it>was established based on a set of four different protein expression vectors resulting in NusA/His, MBP/His, GST and His-tagged proteins. The yield of soluble fusion protein was correlated with the induction temperature and the respective fusion tag. NusA/His and MBP/His fusion proteins are best expressed at low temperature (25°C), whereas the yield of soluble GST fusion proteins was higher when protein expression was induced at elevated temperature. In contrast, the induction of soluble His-tagged fusion proteins was independent of the temperature. Amylose was not found useful for affinity-purification of MBP/His fusion proteins in a high-throughput setting, and metal chelating chromatography is recommended instead.</p> <p>Conclusion</p> <p>Soluble fusion proteins can be produced in <it>E. coli </it>in sufficient qualities and μg/ml culture quantities for downstream applications like microarray-based assays, and studies on protein-protein interactions employing a fully automated protein expression and purification strategy. Future applications might include the optimization of experimental conditions for the large-scale production of soluble recombinant proteins from libraries of open reading frames.</p