Redefining the Offshore ERD Envelope: Techniques and Technologies Necessary for an Expanding Frontier
Authors: Foster Brandon , Krepp Tony 
Published: October 2008

Offshore drilling projects have expanded into ever-more challenging environments in recent years, from remote locations, to ultra-deepwater, to HPHT reservoirs, (and a myriad of combinations therein). Several operators have recently investigated the possibility of expanding their development plans to incorporate Extended Reach wells that would greatly exceed the industry's current experience with long departure wells.

The authors discuss the design, equipment, and technology requirements of three "frontier" offshore projects currently being evaluated. Typical limitations and the solutions necessary to expand beyond the current ERD envelope are discussed. Three core philosophies are highlighted that reinforce the need for a "Systems Approach" for any ER well, but especially these frontier projects:Design Around the IssuesCombine Complementary SolutionsDemand Fit For Purpose Equipment

These philosophies not only enable much further reach than the industry has achieved to date, but also allow improved performance from standard directional and ER wells.

Introduction

In recent years, interest in pushing the envelope of known ER drilling experience has been increasing. Part of the explanation for surging interest lies with the high commodity price environment, which has made small satellite fields significantly more economical. Operators have reported substantial drilling and completion cost savings by exploiting offshore fields from a central drilling site in lieu of a subsea solutions1,2. This general tendency has been strengthened by the current cost environment; day rates for platform rigs tend to be substantially lower than MODU's (Table 1).

Table 1: Average rig dayrate from RigLogix database3 (available in full paper)

With ever-longer reach wells becoming more common, the authors have had the opportunity to evaluate several potential "ultra" ERD projects. Although each project is unique in their own right, all extreme wells have several unifying themes;Standard equipment used for conventional wells is generally inappropriate for extreme ER wells, since standard equipment is (a) usually designed for a different application, and (b) introduces too much compromiseStandard well design methodology used for conventional wells is generally inappropriateIn any given area, the tipping point for radical design solutions tends to occur in a non-linear fashion (for example, solutions that work for 10,000'-20,000' stepout well are vastly different than 25,000' and then again at 30,000' stepout)Alternative materials offer major incentives, as they serve to a.) avoid expensive rig upgrades, and b.) improve operating marginsCombining complementary technologies tends to yield a step-change reduction in well complexity and risk

Much has been discussed in past years regarding the "limit" of ER drilling4,5,6. In the context of the industry's worldwide experience with long reach wells, there is clearly a "sweet spot" where most ER wells are drilled (Figure 1). The ultimate reach achieved to date is ±35,000' (the famous Wytch Farm M16z well7). When only offshore wells are considered (Figure 2), the defining "envelope" of industry experience thins dramatically and the ultimate reach falls to ±27,000'. Several factors undoubtedly influence this phenomenon.