Published on 22 August 2020
How to overcome SCP?
The client in the Middle East was seeking to mitigate risks of channeling. Likewise, reinforcing the primary cement with an annular isolation packer was one of the options. The drilling complexity came from a challenging high-pressure formation. This formation caused Sustained Casing Pressure (SCP) in the annulus after cementing operations.
External casing packer in tough secondary cementing conditions?
Schlumberger proposed a mechanical annulus barrier between the 9-5/8in and 13-3/8in casing. This hydraulically expanded barrier would be an external casing packer (ECP). Schlumberger external casing packer uses Saltel Xpandable expandable steel technology. The external casing packers would set in fresh cement, immediately after bumping the plug. This permanent isolation devices would contain the high pressure coming from the troublesome below formation. Then, the ECPs would improve the cement bond, to prevent future sustained casing pressure.
However, among the challenges, there were extreme circulation conditions during operation. It barely allowed effective displacement of the cement. The external casing packer had to withstand:
- An 8 to 10 bbl/min flow rate.
- A 1200-1250psi differential pressure for several hours.
Subsequently, we reviewed the client requirement. As a result, We customized the external casing packer with a thicker metal sleeve. This, to postpone the start of the expansion and keep it above circulation pressure. The robust steel design would provide strong resistance to this high flow rate. The Engineering team managed to design the product on time to meet the operational timeline.
External casing packer (ECP) is a robust expandable stainless steel device. Firstly, the external casing packer is designed to set at low pressures to achieve zonal isolation. Secondly, the ECP serves for any stage cementing operation or to prevent fluid migration in the annulus. For example, in this case, the ECP sets in green cement. Thirldy, The ECP is engineered using Saltel Xpandable expandable steel technology. Then, this external casing packer improves sealing performance. Indeed, the ECP exceeds conventional packers, especially in irregular boreholes.