Sustained casing pressure in Romania’s Totea gas field
Operated by OMV Petrom, S.A., the Totea field in Romania is divided into
six assets, which ar split further into field clusters. Cementing operations
for clusters Ticleni, Mamu-Otesti, and Bradesti occurred over 15 years, after
which 49 gas wells were determined to have SCP ranging from 3 to 50 bar. Cement
sheath damage or debonding can allow hydrocarbon gas to migrate to surface,
resulting in SCP. Identifying such damage and its location can be difficult,
and fixing the damage to restore well integrity can be expensive or
impractical.
Combination of technologies
OMV Petrom, S.A., chose to use FUTUR self-healing cement to address SCP
in a Totea well. Optimized for gas composition, this cement technology
self-heals to prevent long-term gas migration and effectively seal the gas
reservoir. Any hydrocarbon that comes into contact with FUTUR cement activates
the self-healing properties of this unique sealant material. Once activation
occurs, cracks, fissures, or microannuli in the cement sheath are healed, and
the hydraulic seal is reestablished, eliminating the need to suspend production
in order to perform remedial operations.
The Totea well was cemented with 1,670 kg/m3 of the FUTUR technology as
the lead slurry. To prevent the short-term gas migration that occurs
immediately after cementing, the company implemented the D600G GASBLOK system
for the tail slurry at 1,900 kg/m3. The D600G GASBLOK cement additive created
an impermeable barrier that prevented gas migration into the slurry during its
hydration phase.
CemNET advanced fiber cement was used in the slurry to cover
low-fracture-gradient zones to minimize the losses. CemNET cement is composed
of an inert, fibrous material capable of forming a network across the loss
zone. Pressure analysis and cement bond logging were performed to measure the
effectiveness of these services.
Well integrity for producing wells
The wells showed good bonding across the gas interval after cementing,
indicating that no gas migration had occurred. The combination of FUTUR, D600G
GASBLOK, and CemNET technologies allowed OMV Petrom, S.A., to prevent SCP. More
than 8 months after implementation, the well showed no signs of pressure
buildup in the annulus or at surface.
