POLARIS Case Study - Kansas
The POLARIS BHA was used in a five-well program in the Niobrara formation along the Colorado-Kansas border in the USA.
Objectives & Challenges
The oilfield in question had five potential low-margin well sites but was in a challenging environment with factors such as agricultural land and uneven well sites that made conventional vertical drilling difficult and a formation with lost circulation problems. The objective was to establish whether Coiled Tubing Drilling could make the field financially viable and whether POLARIS™ could effectively survive and function in an air-drilled environment that is traditionally extremely punishing for downhole tools.
Results & Benefits
- Accurate directional drilling with hole sizes ranging sizes from 6.25” to 8.5”.
- Optimised well paths kept build rates to a minimum necessary to achieve the target, making it easier to run casing.
- Demonstrated potential for multiple wells to be drilled from the same pad, safely and accurately, with the use of the gyro.
- Showed that POLARIS™ can effectively survive and function in an air drilled environment.
- Proved that POLARIS™ can be used to drill wells that were not previously considered financially viable.
- 100% clean health and safety record.
- Captured technical learnings and best practices.
Complete Directional Coiled Tubing Drilling Package.
Well path planning and feasibility modelling.
Underbalanced drilling to protect the formation and allow production to continue while drilling.
Figure 1 - The AnTech Mobile Workshop
Figure 2 - Picking up POLARIS
The first well drilled was an S-curve well. Had it been vertical, the surface location would have needed to have been placed in the middle of a cornfield with crops ready for harvest.
The target reservoirs for the second and third wells were below dry river beds, which again made it difficult to site the rig for a vertical well. AnTech proposed deviated wellbores, which prevented a compromise being made in terms of the reservoir exploitation.
The fourth and fifth wells were in a formation that would need to be air drilled because it would not be able to hold the pressure of a liquid column. AnTech proposed horizontal wellbores planned with an intermediate section that could be drilled with mud, using an 8-1/2” bit. The horizontal section could be air drilled with a 6-1/4” bit.
The program was completed successfully with the plans for all five wells followed accurately, resulting in five producing wells. Mud was used for the build section of each of the wells, and air was used for the horizontal sections. No pads or access roads were prepared in accordance with the low margin nature of the wells in the particular field. The drilling program was completed in two phases in combination with a hybrid drilling rig.
It demonstrated that the POLARIS™ tool is suitable for drilling directional, S-curve and horizontal wells in shallow reservoirs. It also demonstrated the potential for multiple wells to be drilled from the same pad, safely and accurately, with the use of the gyro.
The POLARIS™ tool produces real-time readings of downhole vibration. When air drilling, or more accurately, with the bit off bottom, shock spikes of up to 250G were recorded by the accelerometers. The tool demonstrated it was able to withstand these types of forces and this data will be analysed with a view to modifying operational procedures and future tool qualification tests.
Well 1 - Drilling Profile
Well 5 - Drilling Profile
Onshore - Gas
Niobrara Chalk, Colordo-Kansas
POLARIS - Kansas
The Future of Directional CTD Applications
Operators around the world are looking at Directional Coiled Tubing Drilling (DCTD) as a reliable and economically viable technique for unlocking the potential of mature and under-producing oilfields. Both onshore and offshore. It is the safest and best way to drill underbalanced because the well is contained at all times.
DCTD technology and experience have advanced significantly over the past few years and that forms a strong basis for future work.