Supersize Hole Creates Drilling Opportunity

Abstract

Traditional well designs for high angle and extended-reach wells often mandate long 12¼" hole sections through the overburden. Effective hole cleaning and wellbore instability management are key technical challenges commonly associated with delivery of this section. However, despite the use of rotary steerable systems, which help promote good hole cleaning and minimise open hole exposure times, problematical trips out of hole are commonplace. The symptoms of tight hole are often associated with significant cuttings bed accumulations, use of packed assemblies or creep arising from swelling formations.In an attempt to improve overall drilling performance, a supersize hole strategy has been implemented to intentionally drill an enlarged hole through the overburden. At face value, this tactic seems to have as many disadvantages as advantages . However, practical experience of simultaneously drilling and underreaming 12¼ "×13½" hole sections over a number of wells has resulted in overall efficiency improvements.The primary benefits associated with drilling an enlarged hole are ease of tripping-out drilling assemblies and more straightforward casing runs. Other advantages relate to lower downhole pressures or equivalent circulation density (ECD), decreased swab and surge pressures , and less string contact area. Disadvantages relate to increased hole cleaning requirements, additional tool failures as a result of higher vibration and a decreased rate of penetration (ROP).The paper discuss es various aspects of drilling and underreaming and contrasts results between enlarged and conventional hole sizes. Results from drilling both 12¼" and 12¼"×13½" hole sections in the Azeri-Chirag-Guneshli (ACG) fields in the Caspian Sea are reported. ROP (Rate of Penetration) and a new metric TTSW ( Time To Secure Wellbore) are used to provide meaningful comparisons.

Digital transformation: a review on artificial intelligence techniques in drilling and production applications

“…Well instability associated with partial or total loss of circulation in the well is pointed out by Beacom et al [31], and including cleaning problems and drill string vibration is related by Veeningen et al [39]. Mason et al [32] study widening of extended reach wells, and Nybø et al [34] describe kick occurrences. Mason et al [38] and Bardasz et al [40] use digital technologies to the monitoring of specific drilling operations in real-time.…”

“…A highlight point was the stimulus for more intense communication between geologists and engineers, which would allow information to be retransferred, avoiding the isolation knowledge. Mason et al [32] studied the widening of wells in the Chirag field, in shallow waters in the Caspian Sea. They are long-reach wells (extended reach wells, with a large horizontal distance between the rig and the well final objective), with a high degree of inclination and a large diameter.…”

“…IA-based tools for avoiding loss of circulation [35,45] use formation parameters and drilling mud properties. Solutions for well instability issues and widening of extended reach wells are based mainly on formation parameters, operational drilling parameters, and mud density data [31,32,39]. Several historical parameters have been monitored by Nybøet et al [34] for kick occurrences detection, including formation parameters (pore pressure, hydrostatic pressure), drilling fluids parameters (mud weight, mud fluid flow), and operational parameters (rate of penetration, internal and external pressure of the casing).…”