39% Increase in Footage and 50% Decrease in Drilling Dysfunctions Achieved via Implementation of Shaped and Multidimensional Inserts in the Slimhole Lateral Section through Hard Carbonates

Abstract

Drilling operations in the Middle East contain many applications where extended reach laterals target hard and interbedded carbonate reservoirs. Such applications are associated with elevated levels of drilling dysfunctions resulting in tool reliability and bit durability issues. These challenges include lateral and torsional vibrations that impact the drilling system longevity and premature cutting structure damage resulting in multiple drilling trips and an increase of nonproductive time (NPT). To address the lateral stability and loss of drilling efficiency challenges of drilling hard carbonates, this paper explores three new concepts applied to drill polycrystalline diamond compact (PDC) bit design. The 5.875′ Slimhole section through hard carbonate of the Middle East was identified as the target application. A study of existing PDC drill bit performance in this section was conducted to determine current design limitations and set objectives. After optimizing the cutting structure and overall PDC bit frame, three new design concepts were also incorporated. Targeting lateral stability, a "chisel" shaped diamond element (SDE) was placed trailing the cutting structure to provide a stable drilling response. Multiple iterations were studied to optimize the bit lateral stability without compromising bit efficiency. The iterations included changing the radial position, the count and orientation angle of these elements. Non-planar faced PDC inserts were strategically placed on the bit cutting structure to reduce the cutting temperatures during rock cutting, and increase the drilling efficiency. Depth of cut control (DOCC) rubbing elements are commonly used to mitigate stick-slip dysfunctions, but standard DOCC elements wore down too quickly to maintain their function. An impregnated blade based DOCC rubbing element was implemented to maintain the stick-slip protection throughout the length of the run. The new PDC bit design completed six successful field trials in the target section and achieved an average increase of 39% in footage and 11% in rate of penetration. Validation of the design concepts via comparing surface data, downhole vibrations data and the bit dull condition showed marked improvements in the desired metrics. A step change improvement of 50% in the level of lateral vibrations and torsional stability was achieved due to the combination of the SDE and the impregnated DOCC elements. The bit drilled consistently smoother protecting the bit & BHA. Final dull conditions also improved with a reduction in broken or chipped cutters across the cutting structure due to MCE inserts. Combination of innovative geometries and materials targeting stability and efficiency significantly increased performance, reduced NPT and lowered tool maintenance costs in one iteration.