Materials in drilling muds are known to sometimes distort the geomagnetic field at the location of the Measurement While Drilling (MWD) tool magnetometers that are used to measure the azimuth of well path. This distortion or shielding effect can contribute to substantial errors in determination of azimuth while drilling deviated wells and with significant well displacements, these errors may result in missing the target of a long deviated section in the range of 1–200m; and thus impact on the overall productivity expectation of the well. The article describes significant shielding effects observed while drilling long wells. The criteria for acceptance of the surveys were not met and resultantly, an alternative survey source had to be obtained with resulted in increased cost and time to the client. A number of measures were implemented to eliminate this shielding effect. The effects of drilling fluid contamination by magnetic materials are calculated, and a method to evaluate the magnetic properties of the drilling fluid is proposed. The effect of taking measurements with the pumps on versus off is quantified.

No abstract

Drilling fluids contain magnetic contaminations that negatively affect Measurement While Drilling directional tools and causes damage to the equipment in contact with the fluid. The effect is relevant while drilling long deviated wells. Ditch magnets are routinely installed in the fluid system to remove magnetic particles while drilling, with the purpose of protecting the Shale Shaker screens from large metallic debris, serve as monitoring tool to detect troubles in the drilling operations and clean the fluid from magnetic particles. In this paper we describe field data for the operation and efficiency of the ditch magnets. An extensive set of samples of drilling fluid and of ditch magnets debris have been taken during offshore operations and have been brought onshore for detailed investigations. The material extracted has been assessed as constituted mainly by steel swarfs and steel fines. The magnetic materials still present in the used drilling fluid have been extracted and quantified by a novel method that provide higher extraction rates and better accuracy than the methods currently employed in the industry, allowing to assess the actual content of magnetic contaminant. The magnetic susceptibility of the fluid has been measured and compared with values predicted for a known concentration of magnetic contaminants, allowing for the evaluation of the bias induced by them on the magnetometers of the MWD tools employed. The capability of ditch magnets to remove the magnetic contaminants from fluid is quantified and compared with other available methods, like gravity separation, with special focus on the removal of magnetic particles in the range of few microns. Operational details and current issues in the deployment of ditch magnets are reviewed, and the most viable directions for improvement are briefly discussed.

Flowers have many traits to appeal to pollinators, including ultraviolet (UV) absorbing markings, which are well‐known for attracting bees at close proximity (e.g., <1 m). While striking UV signals have been thought to attract pollinators also from far away, if these signals impact the plant pollinia removal over distance remains unknown. Here, we report the case of the Australian orchid Diuris brumalis , a nonrewarding species, pollinated by bees via mimicry of the rewarding pea plant Daviesia decurrens . When distant from the pea plant, Diuris was hypothesized to enhance pollinator attraction by exaggeratedly mimicking the floral ultraviolet (UV) reflecting patterns of its model. By experimentally modulating floral UV reflectance with a UV screening solution, we quantified the orchid pollinia removal at a variable distance from the model pea plants. We demonstrate that the deceptive orchid Diuris attracts bee pollinators by emphasizing the visual stimuli, which mimic the floral UV signaling of the rewarding model Daviesia . Moreover, the exaggerated UV reflectance of Diuris flowers impacted pollinators' visitation at an optimal distance from Da. decurrens , and the effect decreased when orchids were too close or too far away from the model. Our findings support the hypothesis that salient UV flower signaling plays a functional role in visual floral mimicry, likely exploiting perceptual gaps in bee neural coding, and mediates the plant pollinia removal at much greater spatial scales than previously expected. The ruse works most effectively at an optimal distance of several meters revealing the importance of salient visual stimuli when mimicry is imperfect.

Flowers have many sensory traits to appeal to pollinators, including ultraviolet (UV) absorbing markings, which are well known for attracting bees at close proximity (e.g. < 1 m). While striking UV signals have been thought to attract pollinators also at greater distances of meters, how the signals impact the plant pollination success over distance remains unknown. Here we report the case of the Australian orchid Diuris brumalis, a non-rewarding species, pollinated by bees via mimicry of rewarding pea plant Daviesia decurrens. When distant from the pea plant, Diuris brumalis was hypothesized to enhance pollinator attraction by exaggerately mimicking the floral ultraviolet (UV) reflecting patterns of its model. By experimentally modulating floral UV reflectance with a UV screening solution, we quantified the orchid pollination success at variable distance from the model plants. We demonstrate that the deceptive orchid Diuris brumalis attracts bee pollinators by emphasizing the visual stimuli, which mimic the floral UV signalling of the rewarding model D. decurrens. Moreover, the exaggerated UV reflectance of D. brumalis flowers impacted pollinators visitation at an optimal distance from D. decurrens, and the effect decreased when orchids were too close or too far away from the model. Our findings show that salient UV flower signalling plays a functional role in visual floral mimicry, likely exploiting perceptual gaps in bee neural coding, and mediates the plant pollination success at much greater spatial scales than previously expected.