Evaluation of the primary cement operation on the production casing in the Ekofisk field and the Eldfisk field
Abstract
The foremost goal of primary cementing is to provide zonal isolation in a well. Cementing of
the casing/liner set right above the reservoir on the Ekofisk and Eldfisk fields are associated
with a lot of challenges. Depletion and water flooding of a reservoir makes drilling and
cementing increasingly difficult. At the Ekofisk and Eldfisk fields, the operational window
above the reservoir is very narrow and difficult to predict due to the regression of fracture
pressure the last 200 ft above the reservoir. This coupled with the natural faults and fractures
in this area makes lost circulation a hindrance to provide zonal isolation. Cement history on
the two fields shows that there is a very low chance of achieving required casing cement
isolation.
Historical practices within the last two years have been analysed trying to find the root causes
of any failure to meet the company requirements. A review of potential solutions to solve the
issue has been presented. Different studies have been made, including hydraulic simulations,
to come up with suggestions on how to reach the cement target for the two fields. In addition,
simulations on how to cement the entire Miocene section were performed.
A study performed in WellPlanTM-Opticem revealed that there still exist some challenges
before the cement design and real time jobs can be properly imported and analysed in the
software. During the work lack of cement job data storage system was discovered. A new way
of cement data storage was suggested and established.
Collection and analyses of cement jobs during the last two years on the M-wells was
performed in order to investigate if there was a trend between lost circulation and different
parameters. No clear trend was found.
Hydraulic simulations were performed to investigate how different parameters impact the
equivalent circulating density. A colloidal light weight cement was utilized in the simulations.
The main results from the simulations showed that; Warp OBM is superior to Versatec OBM
system from a well cementing perspective, the expandable liner hanger imposed a very high
ECD and the liner hanger dimensions needs to be taken into account in hydraulic simulations.
The overall outcome of the simulations indicates a possible solution on how to cement back to
the previous casing shoe.
Description
Master's thesis in Petroleum engineering