By Joanne Liou, editorial coordinator
Two questions need to be asked when considering cement as a primary barrier in a deepwater well: 1) Will the job be successful? 2) What if it isn’t? The two considerations beg to question and validate the prospect of a successful cementing operation. Ragheb Dajani of Hess Corp shared an operational perspective on cementing during a keynote speech at the 2012 OTC on 30 April in Houston. “There is a definite increase in recognition and scrutiny on the profound effects cementing can have on operations – on safety, environment and public opinion,” he said, “but the gap is in installing the cement as the barrier downhole.”
On paper, a lot has been done to support cement designs; however, there is uncertainty in effectively executing the operation.
It is important to understand the risks of a cementing operation and to approach it from a perspective that realizes the consequences of failure, Mr Dajani explained. A key challenge is in the cementing design, and the first step is to determine whether cement can realistically provide a barrier. “We can’t always rely on cementing unless we have a high degree of confidence to execute it and to provide a barrier downhole,” he said. “As we go deeper and deeper into the reservoirs, we’re asking for a small volume of cement to travel four or five miles. Yes, we can do that, but there is a lot of work that needs to be done ahead of time in order to protect that cement slurry to reach 20,000 ft.”
A strong understanding of the wellbore environment and the effects of contaminants on the cement slurry are among considerations that need to be addressed ahead of time. “Do we have adequate compressive strength development? Do we need to wait for the cement for a longer period of time until the contaminant actually sets to have an isolation barrier off the cement?”
As the cement is loaded offshore, it travels through a chain of custody that calls for quality control and brings Mr Dajani to pose more questions. “Are we using the right pressure on the lines? Is there too much moisture?” Quality control is necessary for the cement to maintain its chemical properties and a successful end result, he said.
On the training side, young engineers may have the knowledge but still lack field experience. An understanding of best practices cannot replace experience. “There’s a disconnect between designing on paper and having the experience level to have confidence in executing it in the field,” Mr Dajani stated. The challenge can be met by providing them with additional time and field training offshore.