Open hole multistage fracturing is a technique used to improve the productivity of a gas producing well. When applying this method, one key factor is reliable zonal isolation, and this is achieved by placing packers between zones to be stimulated.

In this case, a Middle East client was experiencing difficulty in isolating zones during high pressure fracturing operations. It was suspected that the issue stemmed from a loss of differential pressure rating across a single element packer in washouts and because of the short seal length of the packer.

A longer sealing element would be required as well as the ability to provide isolation in a washed-out hole – the client contacted Welltec®.

The WAB for Zonal Isolation was custom designed to provide high expansion in potentially washed out wellbores, and included a long multi-element sealing system with built-in redundancy to account for fracturing fluid chemical reaction with the rock behind the seals. The system is just under 4 meters, complemented with multi-elastomer seals, each delivering full Delta P capability within a washed-out hole up to 6.5”. The unique design allows full rotational capabilities during deployment minimizing the risk of operations.

534WAB10:10 frac packer.
Welltec designed and qualified the 534WAB specifically to meet the client’s high-pressure zonal fracturing requirements. The unique design combined two WAB sleeves into a four-meter assembly, providing a longer than usual sealing element.

It was considered imperative that the packers anchor reliably to prevent movement of the seals against the rock during fracturing, also ensuring Life of Well (LoW) sealing. Pre-job, Welltec calculated the maximum loads generated by thermal and hydraulic forces during the HP acid frac, removing the need for an anchor.

A 4 ½” liner assembly was deployed with four sets of 534WAB installed. A 1.5” ball was dropped in order to isolate the toe and set the liner hanger – and the running tool was released. With the Upper completion installed and production packer set, all WABs were fully expanded at 5,500 psi.

Approximately one month later, a frac unit arrived on site and completed a ball drop zonal acid frac. Furthermore, the pressures from the frac operation confirmed zonal isolation had been achieved. The WABs were run in combination with NOV’s Multi Open Close (MOC) hydraulic fracturing sleeves with a pressure activated BPS Toe Initiation Sub.

Welltec provided an effective and reliable zonal isolation, achieving the requirement to isolate the different pressure zones for frac operations.

This case represents a 10,000 psi zonal isolation with the 534WAB, for conventional gas carbonate development. The WAB is designed to carry an industry leading, calculated max hydraulic and thermal anchor load of 480k lbs.