Reliability Study of Data Microchips for Downhole Data Acquisition Subjected to Pseudorandom Vibrations

Abstract Downhole data acquisition is a critical aspect of drilling operations for maintaining optimized and safe drilling conditions. However, the real-time downhole data readings while drilling are best captured using affordable drilling data microchips. Typically, microchips include an SoC (System on a chip), secondary memory, sensors, and an on-chip battery. But during drilling and releasing procedures into the well annulus, the data microchips may be subjected to random stresses that cause interconnects and components to fail, which ultimately results in damage, loss of stored data, and a low recovery rate after being released. Since random vibration loads can limit the efficient performance of drilling microchips, it is crucial to study the peak responses of the device when exposed to such stresses or a designed response spectrum. The development and validation of simulation modelling approaches is the initial step in this direction. This paper presents the numerical analyses and stress development mechanisms of the data microchips subjected to pseudorandom acceleration by a specified Power Spectrum Density (PSD). The highest computed RMS acceleration values are estimated to be about 25 g, 16 g and 18 g in the X, Y and Z directions respectively. However, assuming that the allowable peak value is thrice more than the RMS values, the peak acceleration can be evaluated to be 75 g, 48 g and 54 g in the X, Y and Z directions respectively. This indicates that there may be damage and loss of stored data on the memory chip. The permitted accelerations for the impacted components should be examined due to these high peak values which are more than the allowable vibration levels for downhole drilling tools. Hence, this device may require vibration absorber system. It is also necessary to estimate the margin of safety from the projected peak values. The pre-stress on the supporting unit is evaluated to be 60 MPa assuming 1 kN of force, the margin of safety is evaluated to be 7.6, 12.0 and 6.7 for the excitations in X, Y and Z directions respectively. In all excitations, the margin of safety is positive, indicating that the support might not break free from the housing unit and demonstrating how much stronger the support is than what is required to hold the actual vibration.