Technological improvements of drilling and reaming methods continue to be evaluated and introduced to the drilling industry. This paper describes recent, controlled testing of new expandable concentric stabilizers and reamers, performed on a full-scale, highly instrumented drill rig.

An inherent problem of drilling and reaming concurrently is that conventional fixed stabilizers run above expandable reamers can be no larger than the pass-through diameter of the restriction above it and thus cannot effectively stabilize the upper BHA, which often results in undesirable vibrations. However, recent controlled tests have been conducted in twin wells drilled from the same casing under a full-scale drilling rig, one well with only a concentric expandable reamer and the other with both expandable stabilizer and reamer. The testing has shown that utilization of this novel stabilizer produces significant gains in performance.

BHA modeling predicted lower bending moments above the reamer when a concentric stabilizer was utilized. The well drilled with the stabilizer above the reamer resulted in higher ROP with lower downhole WOB and up to 35% reduction in drilling mechanical specific energy (MSE), as compared to the well drilled without the expandable stabilizer. The stabilized well had significantly better drilling efficiency, which is attributed to reducing buckling and whirl in the drill pipe and upper BHA, and reduced frictional losses against the borehole wall. Additionally, lower levels of whirl, lateral and stick-slip vibrations were recorded with the new expandable stabilizer.

The paper describes the novel design features of this expandable stabilizer, which are credited with the step-change improvement in drilling efficiency. Monetary savings from increased drilling efficiencies and improved reliability are anticipated for operators and will be discussed in this paper.

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