Reducing risk in extended reach drilling
Jon Ruszka • Baker Hughes INTEQ
Technology advances continue to push the boundaries of extended reach drilling (ERD) to access stranded reserves, reduce environmental impact, improve both production and recovery, and lower field development costs. These technical advances include continuous improvements in rotary steerable systems (RSS), development of higher specification drilling rigs, and migration of comprehensive wireline logging to logging-while-drilling (LWD) services.
The value of an ERD project always must be balanced against the operational risk. By definition, these wells push the envelope and require a high degree of personnel competency to quantify and mitigate these risks. Through growing competency and technological advancement the risks continue to reduce, allowing more operators in more diverse locations to realize the value of ERD in their field developments.
Personnel competency
One of the greatest challenges facing the drilling industry is personnel competency. While ERD projects are increasing in number, it is still very much a niche application. It is unlikely that any one E&P company has significant global experience in these operations. Service providers, operating globally on the widest variety of projects, have the greatest exposure to ERD operations and therefore are well placed to help fill the “competency gap”. As an example, INTEQ has a global network of subject matter experts and certified application engineers to connect directly with local operations. By providing a resource of experienced professionals, ERD projects can be planned and supported more effectively.
For example, one challenge associated with ERD operations is that it is not uncommon for there to be little or no drilling experience in the area between the surface location and the target. Information in this area may be restricted to seismic data only. Experience may be limited to vertical wells, which provides only a glimpse of what may be encountered from an operations perspective while drilling a high-angle ERD well. In the early stages of an ERD program it is important to capture as many lessons learned as possible to develop field-specific best practices. This is one core competency of the certified application engineers. It also is critical that unexpected events be diagnosed and resolved as efficiently. This is one area where a network of subject matter experts can provide a valuable contribution.
Drilling, evaluation technology
There is little doubt that the introduction of rotary steerable systems in the mid- to late- 1990s played a large role in advancing ERD capabilities. By eliminating the need to slide drill for 3D directional drilling control and by delivering a smoother, higher quality well trajectory, these systems reduce drilling torque and drag, increase attainable reach, provide continuous hole cleaning, and lower risks associated with target intersection and casing/completion deployment. Based on 20 years experience in the engineering and scientific development of closed-loop directional drilling systems, the industry is using field proven autonomous steering control to enhance overall wellbore quality and accurate target intersection. The ability of the closed-loop system to maintain the desired inclination and, via downlink commands sent from surface while drilling, to make fine adjustments to the required inclination as the well progresses has been achieved.
This enhancement to the already important benefits of rotary steerable drilling is of particular value in ERD applications. As a result, it is estimated that 15 of the world’s 20 record ERD wells (categorized by either lateral departure or measured depth) have used these systems.
More recently a high powered downhole drilling motor has been integrated with the closed-loop steerable system mentioned above. While retaining the benefits of the closed-loop system, these integrated systems simultaneously can increase rate of penetration and further extend the attainable reach in ERD certain applications.
LWD systems
Logging-while-drilling technology has advanced so significantly in recent years that its capabilities are, in many respects, superior to those traditionally provided on wireline. In ERD applications, the ability to eliminate time consuming wireline logging operations is just one benefit. The primary benefit is the delivery of formation evaluation data in real-time while drilling to provide immediate analysis of the downhole environment to improve drilling efficiency and to lower operational risk.
One of the greatest risks in ERD projects is wellbore instability. High definition image logs from LWD systems such as INTEQ’s StarTrak system now provide invaluable information, along with other data sets, to assist in the identification and accurate diagnosis of wellbore stability problems. This can help avoid non-productive-time associated with wellbore instability and, in the worse case where late or misdiagnosis occurs, help prevent loss of the hole section or even the entire well.
Pushing the limits
As a result of improving personnel competency and technology developments, not only are more ERD wells being drilled, these wells are pushing the envelope in terms of lateral reach and geometric complexity in order to access ever more challenging geological targets. The complexity of ERD operations has progressed from 2D to complex 3D trajectories where, for an example, an abandoned 2D ERD well has been sidetracked to tap shallower satellite reserves, requiring a highly complex uphill well profile. In 2007, an ERD world record was set in remote eastern Russia and this was surpassed in January 2008.
Driven by a need to minimize environmental impact and improve recoverable reserves, it is anticipated that ERD activity will continue to increase. Simultaneously, rising competence and drilling technology development will continue to lower the operational risk. As a result, ERD limits will continuously be tested and pushed to new levels as the growing benefits outweigh the diminishing operational risks.