Novel Concentric Expandable Stabilizer Results in Increased Penetration Rates and Drilling Efficiency with Reduced Vibration

Abstract

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. Introduction The following three passages from previously written technical papers introduce the subject of this paper and the inherent problem of stabilizing the BHA and collars above the reamer in the enlarged borehole. "Historically, concentric underreaming has been plagued by several challenges. Some reamers, especially earlier models used after drilling a hole, were not rugged and failed downhole, leaving parts behind to fish out. Some current industry concentric reamers have complex functionality, requiring a fine balance of WOB, flow, and pressure drops in order to activate and operate properly. Some have multiple sliding mandrels with close tolerances that have problems closing after use due to accumulation of solids. Some reamers require lower flow rates while drilling out the casing plug and then a higher flow rate to activate the reamer, sometimes failing to open and remaining closed the entire run. Some reamers utilize hydraulic pistons for cutter blades that are difficult to close and pull into casing after drilling with water-based mud. These hydraulic reamers had problems with blades closing under reaming of high-angle holes due to weight of the BHA. Some of the reamers in the market have had small and less-effective cutter blocks that only allowed a few PDC cutters, reducing their life and cutting efficiency." (Radford et al. 2008)

A Review of the Evaluation, Control, and Application Technologies for Drill String Vibrations and Shocks in Oil and Gas Well

“…The advantage of roller reamer is not only suppressing the lateral vibration and torsional vibration at the same time but also reducing the friction between the drill string and borehole wall. The fixed stabilizer installed on the reamer could not stabilize the upper drill string, which aggravated the drill string V&S [112]. A new expandable reamer to mitigate drill string V&S was developed by Schlumberger and Baker Hughes [59] and its configuration is depicted in Figure 12(b).…”

Fit-for-Purpose Under-reaming Blades Design and Total System Approach Helped Drill a Challenging 18 1/8-in. × 22-in. Section 20 Days Ahead of AFE in Deepwater Exploration Well Offshore Brazil

“…Unfortunately, this stabilizer size is limited by the previous casing size. These undersized stabilizers do not provide good stabilization affecting by this way the drilling dynamics (S. Radford et al, 2009). In order to mitigate lateral vibration problems in upper BHA section, the service company and operator deployed an expandable stabilizer.…”

Efficiently Delivering Difficult Tortuous Well Profile Deepwater Brazil Ream-on-Demand System Saves Operator Trip for Tool Change-Out

“…1 The new design was in response to the requests from several operators for greater control of the underreamer while downhole. [2][3][4] The new technology uses a sophisticated activation and deactivation mechanism.…”