| dc.description.abstract | Foam cementing the reservoir liner has proven to be a good solution for achieving zonal
isolation due to its low permeability and high compressive strength. However, out of the
32 reservoir liners cemented on the Ekofisk M platform only 16 were defined as 100 %
successful.
In this thesis foam cement and liner string components are introduced before evaluating
the outcome of the different jobs. A success criterion for the outcome is established,
incorporating liner centralization, zonal isolation and liner movement. The criterion
regards the outcome a success if liner manipulation is maintained throughout the job and
no remedial job is needed, a semi-success if manipulation is maintained for most of the
job and no remedial job is needed, and a failure if none of the previously mentioned.
Data from all the reservoir liner cementing operations are gathered and the outcome of
each is evaluated based on the above criterion. 16 of the liners were cemented
successfully, 6 were semi-successfully, and the last 10 were failures. Failing to
reestablish rotation after setting the liner hanger is the most common reason for failure, 7
out of 10 failures can be related to this.
Wellbore inclination and liner length are both parameters which seems to contribute to
the outcome of foam cementing the reservoir liner. 13 of the 32 wells have an inclination
above 80 º at the liner shoe. Out of these 13 wells only 4 are regarded as successful, the
rest are either semi-successful, 4, or failures, 5. Even though failures are observed for all
inclinations, this happens more frequently at higher inclination.
The success rate also seems to be influenced be the length of the liner. For shorter liners,
i.e. with a length below 2000 ft, nearly 78 % of the cement jobs were successful, whereas
the same percentage for liners with a length between 5000 ft and 6000 ft is 25 %. In fact,
a near linear trend is observed for the success rate as the length increases. | no_NO |
