(729b) Effect of Drill Pipe Whirling on Cementing Integrity in Horizontal Shale Gas Wells: A Simulation Study

Shale gas production from horizontal wells faces potential problems related to gas leakage from various zones of a well into the air and water reserves. Avoiding such leaks, and thus achieving better environmental friendliness as well as well productivity, is one of the biggest challenges for shale gas production.  To avoid gas communication between well zones in a rock formation penetrated by a well (i.e. to achieve zonal isolation) the integrity of the cement placed in the annulus between the metal casing and the borehole wall must be ensured at all times.  While the cement may be placed and set properly in the annulus, subsequent drilling operations that extend the well depth, may affect the strength of the cemented annulus.

            During drilling of subsequent well sections, the drill pipe often experiences a whirling motion and impacts on the casing of already cemented sections.  As a result of this impact, excessive stresses are generated in the casing and cemented annulus, which compromises the strength of the cement sheath.  While this hypothesis is reasonable, it is difficult to confirm it through direct measurement of stresses developed as a result of whirling-induced impact forces.  Therefore, we undertook a simulation study, to estimate such stresses.  This exercise will help in assessing the need for better control of drill pipe whirling and in designing cement slurries that can sustain impact forces of such magnitude.  Comparisons with experimental observations will be discussed.