API cement difficult to obtain

American Petroleum Institute (API) standard well cements are often difficult to obtain in many parts of the world. Schlumberger Well Services’ cementing operations in the Castilla Field in Colombia had been seeing erratic cementing results due to a shortage of API standard cements.

Manufacturers have begun moving to non-API cements, causing a shortage of API Class G and H cements. The API manufacturing cost is quite high when compared with regular construction cement. A big reason for this is that production requirements are becoming more stringent. This has resulted in single suppliers of API cement in some countries, and, therefore, a big cost increase in API Class G and H cement.

The challenge was how to make construction cement behave the same way as API cement, and how to make its chemical and mechanical properties predictable in the same way that can be done with API cements. The operator had previously used conventional Class G slurries. This produced acceptable results, but was expensive.

Additive provides predictable chemical, mechanical properties

In order to improve the predictability of cementing systems, Schlumberger developed CORRECT basic cements enabler. The CORRECT enabler allows the utilization of construction cement at temperatures below 275 degF, resulting in slurries with the same and, in some cases, superior properties to those of API cement. The mixture has chemical and mechanical properties that are predictable in the same way as API cements.

The success of the application of CORRECT slurries in surface strings in Castilla Field led to a local project of expanding its application for other well sections. Extensive laboratory testing was conducted in order to evaluate compatibility and performance with extenders, retarders, dispersants, and gas migration control additives. This resulted in a positive outcome.

Because of the use of the CORRECT enabler, Schlumberger was able to offer a lower slurry cost for the surface casing in Colombia.

For the production casing, the local blends that were developed using Type III cement and the CORRECT additive package resulted in a slurry with early compressive strength development. This allowed the client to run the cement evaluation logs a full 12 hours earlier than before. The CORRECT enabler also translated into potential savings of 17.4% in the operational cost of each well.

Savings of nearly 20% per well

Having better availability of a product gives Schlumberger the ability to optimize product cost, thus offering the customer a more competitive price. Full deployment of the CORRECT systems in Castilla Field for surface and production casings yielded potential savings in the operative cost per well by an average of nearly 20%.