Minimizing Dynamic Dysfunctions Sets New Drilling Performance Benchmark in Saudi Gas Application

Abstract

The myriad drilling problems associated with dynamic dysfunctions, including substandard performance and premature bit and downhole tool failure, have been well documented in the literature. Alleviating these problems and potential failures requires a systems approach that brings together improvements in the bit, BHA, and operating practices. This paper describes one such approach where a new-generation 16-in. PDC drill bit was applied in tandem with a newly engineered 12 ¾-in. positive displacement motor (PDM) and hard rock drilling techniques. Further, the high RPM and low weight-on-bit (WOB) recommendations inherent in old-school shale drilling gave way to hard rock parameters that maximized depth of cut. Consequently, impact fractures and abrasive wear were reduced, thereby maintaining the bit in an overall sharper and more efficient condition. Through this systems approach, the operator successfully avoided premature bit and motor damage and achieved record ROP and reduced costs in a Saudi Arabia project. Historically, most sections have required a cleanout run with a roller cone bit, followed by a PDC bit for drilling the first 4,800 ft, and another PDC bit to complete the interval. The combination of the new tools and precise drilling techniques has eliminated the complexity and costliness of such runs. In a rare shoe-to-shoe run, the combination drilled out the 18 5/8-in. casing to TD at a record ROP of 33.8 ft/hr, replacing the three planned bit runs and saving the operator US $249,000. The authors will explain the advances in PDC bit technology that focused on minimizing cutter damage, thus allowing bits to drill further at faster ROP. Further, they will examine ongoing initiatives aimed at improving performance and reliability in demanding drilling conditions that resulted in the development of the new and more robust PDM that provides higher torque output at available flow rates and pressures. They will describe how the new PDC bit technology and higher torque PDMs, combined with a change in operating procedures that focused on minimizing dynamic dysfunctions, resulted in a step change in performance.

Drilling Performance Optimization Based on Mechanical Specific Energy Technologies

“…Conversely, if the problem begins with higher RPM and lower WOB, the answer is to reduce RPM and increase WOB. It may also even be necessary to stop surface rotation and simply drill in slide mode (bit rotation is generated only from the PDM) through the problematic formation [26].…”