Abstract
To determine formation properties surrounding the wellbore, it is necessary to identify the hydrocarbon-producing zones and to obtain an improved understanding of the subsurface before initiating production. Logging while drilling is an effective modern technique in which the physical formation properties are recorded during drilling operations. Timely logging-while-drilling (LWD) data are generally transmitted to the surface through mud pulses. These data can also be used to guide well placement so that the wellbore remains within the zone of interest or in the most productive portion of a reservoir. In practice, the LWD tools are often placed in the bottomhole assembly at the lowest portion of the drillstring.
LWD tools can operate in harsh environments during drilling operations. The increasingly aggressive drilling conditions subject the tools to varying degrees of shock and vibration, which have become the leading cause of mechanical failures for drilling and measurement tools. Furthermore, the aggressive shock and vibration loads can be transmitted from the drill collar to the internal components, which frequently results in premature failures of the expensive electronics or other measurement devices. These failures can have a major impact on operators and service companies, costing millions of dollars in repairs and nonproductive hours of rig time.
In this paper, a high-fidelity 3D finite element analysis (FEA) model that can describe contact interactions between the collar, the chassis, and the mounted electronic board is developed for an LWD mockup assembly. A shock test system of the same (i.e., device under test held by shock arms) instrumented with multiple accelerometers is also presented to mimic such dynamics that the tool could experience while drilling in a controlled laboratory environment. Favorable agreement is observed between experimental measurements and the FEA model predictions, which validates the developed FEA model. The validated numerical model can be employed for virtual qualification of newly developed drilling and measurement tools and for post-job root cause analysis of tool failures.
