Alternative method to lift cement in Permian basin
Highly depleted wells and naturally fractured formations have
contributed to challenging cementing operations in the Permian basin. Apache
Corporation needed to lift cement in the upper Spraberry Formation of the basin
to the designed target levels. In the Permian basin, it is common to drill and
cement wells without mud returns because the upper and lower Spraberry
Formations are two of the main thief zones in the Permian basin. Conventional
lost circulation control materials (LCM) are added to the drilling fluid with
marginal or no improvements. When cementing across depleted and corrosive
formations in the Permian, specifically designed pills loaded with LCM are
pumped ahead of cement slurries, which exhibit high viscosities. As a result,
displacing the pills to the thief zone without channeling through the formation
is a challenge.
Additionally, low-density fluids typically have a low solid content,
which is detrimental to the performance of LCM. Certain types of LCM in cement
affect the cement mechanical properties.Costly alternatives to cure losses in
the Permian basin did not perform as expected, thus prompting the operator to
seek an alternative, cost-effective method.
Reinforced composite mat pills and placement technique
To address these concerns, Apache Corporation consulted with
Schlumberger, which recommended an engineered combination of a placement
technique and Losseal composite mat pills to lift cement in the basin to the
designed targets when the technique and pills are used in a specific sequence.
Based on the observed lost circulation zones, 67 bbl of the lead cement was
treated with the solids package. The first part of the lead was treated with 30
bbl followed by 30 bbl of the lead cement as a buffer, and then 37 bbl of
cement treated with LCM before switching to tail cement.
Success rate of 90% in loss mitigation during cementing operations
The unprecedented results obtained with the Losseal composite mat pills
enabled lifting cement to the depths specified by regulatory entities (e.g.,
Texas Railroad Commission). The Losseal pills also provided long-term zonal
isolation and casing protection across the corrosive formations in the Permian
basin. These operational optimizations prevented the further need for costly
remedial cement operations.
The Losseal composite mat pills have been implemented in more than 170
wells with more than 90% success rate in mitigating losses while cementing, and
more than 70% of wells achieved the required TOC. This technology has also been
adapted by 10 other operating companies in the Permian basin.