Simplified Solution for Managed Pressure Drilling - System that Drillers Can Operate

Until recently many of the wells on US land that were drilled using Managed Pressure Drilling (MPD) technology utilized one size fits all equipment designed for the offshore market. Since the cost and personnel requirements needed to run the offshore manifolds became a challenge due to market conditions and Covid-19 restrictions, the drillers sought a cost effective and simpler system to conduct their day-to- day operations. The challenge was to drill long laterals in Permian and Haynesville without losing the necessary MPD functionality that proved beneficial to reduce the risks associated with safety and to enhance drilling efficiency. For the MPD control system experts, the task was to correctly identify and automate MPD system’s functionality that would be of greatest use to the drillers to sustain their drilling performance. The concept of developing an easier to operate control system was undertaken wherein system accuracy and precision was maintained at the forefront of the development process. Electric motors/actuators and necessary drivers that could work directly on rig power were selected and tested. Control system logic that operates the chokes was modified to quickly adapt to the changes in drilling conditions, maintaining the necessary accuracy. This was done by studying and understanding drillers activities and behaviors like automated pump ramp down speed during connections, pipe movement during tripping etc. Specific MPD engineering charts, simple to decipher graphs, and necessary calculation tables were developed for the drillers to use for managing bottomhole pressures. Calculations which included specific schedules for spotting weighted pills were provided to maintain simplicity of the operations and something the drillers could easily execute. Today, many drillers are using this MPD solution to drill long laterals (Hovland et.al 2020). This trend is slowly leading to reduction of rig MPD personnel, especially during Covid-19, while the drillers are getting familiar with and operating MPD systems. A few of the crucial items that have allowed the drillers to run MPD on their own include MPD controls connected to drilling automation systems and the subsequent continuous revision of these controls based on understanding drillers tasks and needs. The use of electric motors enabled quick adoption to the changing drilling conditions while making connections, tripping etc. The furnished MPD calculations and graphs that drillers could follow for applying required MPD choke pressures kept MPD adaption simpler. The modifications made to the MPD choke controls geared towards facilitating necessary automation enabled the drillers to get trained in few days and operate the MPD systems while maintaining the same level of speed and performance.

On Determination of the Effective Thermal Conductivity of a Bundle of Steel Bars Using the Krischer Model and Considering Thermal Radiation

Cellular solid materials are commonly found in industrial applications. By definition, cellular solids are porous materials that are built of distinct cells. One of the groups of such materials contains metal foams. Another group of cellular metals contains bundles of steel bars, which create charges during the heat treatment of the bars. A granular structure connected by the lack of continuity of the solid phase is the main feature that distinguishes bundles from metal foams. The boundaries of the bundle cells are made of adjacent bars, with the internal region taking the form of an air cavity. In this paper, we discuss the possibility of using the Krischer model to determine the effective thermal conductivity of heat-treated bundles of steel bars based on the results of experimental tests and calculations. The model allows the kef coefficient to be precisely determined, although it requires the weighting parameter f to be carefully matched. It is shown that the value of f depends on the bar diameter, while its changes within the examined temperature range (25–800 °C) can be described using a third-degree polynomial. Determining the coefficients of such a polynomial is possible only when the effective thermal conductivity of the considered charge is known. Moreover, we analyze a simplified solution, whereby a constant value of the f coefficient is used for a given bar diameter; however, the kef values obtained thanks to this approach are encumbered with inaccuracy amounting to several dozen percentage points. The obtained results lead to the conclusion that the Krischer model cannot be used for the discussed case.

Analysis of vibration characteristics of elastic metamaterial sandwich beam

Elastic metamaterials (EMs) are a new kind of artificial composite medium composed of complex micro-structural elements, which have unique dynamic properties and elastic wave regulation ability that their constituent materials do not possess. The existing researches on EMs mainly focus on wave characteristics in two-dimensional and three-dimensional infinite domains. However, actual EM structures are always in the form of finite structures such as rods, beams and plates, so it is more important for engineering applications to understand and master their natural and forced vibration characteristics. Therefore, it is necessary to establish an effective simplified solution method and framework with certain accuracy for the vibration analysis of such structures. In the early stage, we have studied the natural and forced vibration characteristics of EM beams from this point of view, and presented a simplified solution process. In this paper, a kind of sandwich beam structure with EMs as the core is further constructed, the simplified solution process is extended to such more practical model analysis, and the free and steady forced vibration analysis processes of the finite-size sandwich beam are given. The vibration characteristics different from the traditional sandwich beam are investigated, and some interesting and useful phenomena are revealed, including the absence of natural frequencies within bandgap (BG), the gathering of natural frequencies in the vicinity of band edges, and the particular modal correspondence before and after BG. Then, the corresponding formation mechanisms are explained from the perspective of wave propagation.

Dynamic driving formulas and static loadings in the light of wave equation solutions

The advances in pile monitoring have motivated attempts to support dynamic formulas to estimate pile bearing capacity. Based on numerical analysis of the wave equation and the results of dynamic loading tests in three piles the paper deals with the investigation of the soundness of some of the most used in Brazil, namely, the so called Chellis-Velloso Formula, the Energy Approach Equation and Uto’s Formula. The former gained strength through a misinterpretation of Casagrande (1942) statement that the elastic compression of a pile during driving is a measure of the dynamic force with which the soil is tested, and not of its static resistance. Therefore, the elastic compression and rebound, measured during driving, are generally smaller than the corresponding static values. The second is based on an elasto-plastic load-displacement relationship without physical meaning, besides the fact that the effective energy in driving a pile is related to the work of dynamic forces and has nothing to do with the static resistances. The third was derived from a simplified solution of the wave equation, assuming among other hypothesis that there is no friction along pile shaft. The paper shows the ineffectiveness of attempts to universally validate these formulas with dynamic pile monitoring and the implications in the simulation of static loadings.

The effect of flexural–torsional buckling on the stability of timber members: a case study

This study investigates the stability of timber members subjected to simultaneously acting axial compression and bending moment, with possible risk for torsional and flexural–torsional buckling. This situation can occur in laterally supported members where one side of the member is braced but the other side is unbraced. In this case, the free side will buckle out of plane while the braced side will be prevented from torsional and flexural–torsional buckling. This problem can be evident for long members in timber-frame structures, which are subjected to high axial compression combined with bending moments in which the member is not sufficiently braced at both sides. This study is based on the design requirement stated in Eurocode 5. Solution methods discussed in this paper can be of interest within the framework of structural and building Engineering practices and education in which the stability of structural elements is investigated. Article Highlights This case study investigates some design situations where the timber member is not sufficiently braced. In this case, a stability problem associated with combined torsional buckling and flexural buckling can arise. The study shows that the torsional and/or flexural–torsional buckling of timber members can be important to control in order to fulfil the criteria of the stability of the member according to Eurocode 5 and help the structural engineer to achieve safer designs. The study investigates also a simplified solution to check the effect of flexural torsional buckling of laterally braced timber members.

Solution Proposal for Utilization of the Waste Heat in Refrigeration Systems

The possibility for utilization of waste heat from processes in the food industry is presented in this paper. The need for reuse of waste heat comes from the fact that energy consumption in industrial companies is uneconomical and that environmental pollution has increased. Therefore, one of the method of reuse of waste heat that is applicable in industrial processes is presented in the paper. Potential primary energy savings is presented by implementing the waste heat recovery in the food factory. The paper presents a simplified solution proposal for installation of heat exchangers with the aim of utilizing the waste heat of the refrigerant. The results showed that by the implementation of simple heat recovery significant annual fuel energy savings can be achieved as well as fuel cost savings.