CASE STUDY Rugged Centek Centralizers enable casing rotation during cementing operations
In a 3 well comparison in Oklahoma, USA, Centek Centralizers are proven to aid rotation, enhancing uniform annular cement placement.
Casing reciprocation in the past has been performed for most cementing cases. Today’s drilling technology with top drive rigs now gives the added opportunity of casing rotation, and with the correct cementing heads, can also include simultaneous reciprocation. Rotation also helps with fewer side effects on ECD’s (Equivalent Circulation Density). With rotation operations being performed, the centralizers on the casing string have to be rugged enough to stand up to these procedures.
Typical standard welded hinged bow spring centralizers are not a first choice for this wellbore environment during primary cementing.
Centek S2 and Centek UROS Centralizers are tough enough and field proven to withstand today’s complicated well designs and provide the performance to achieve cased well integrity. The unique non-welded one piece Centek design has the product characteristics that provide a flexible semi-rigid integral centralizer that can help reduce torque and drag in getting casing to bottom and can also aid in casing rotation. The high performance centralizer design eliminates most issues that deter the use of a standard bow spring centralizer product for casing rotation operations. Making sure the centralizers can withstand internal rotational torque from the casing is crucial to the centralizer’s life cycle.
The 3 well comparison on a North Central Oklahoma customer’s drilling project in the Mississippian Field, yielded field proven results of the enhancement Centek Centralizers could provide in their ability to get casing to TD and aide in rotation during cementing to enhance successful primary cementing from casing shoe to the top of the liner. All three wells were completed at near 90 degrees horizontal.
Project Well 1 - With the use of another manufacturer’s 37 rigid positive stand-off centralizers, the liner got stuck 800-feet off bottom along with higher pump pressure seen during cementing. On the next well (Project Well -2) the customer chose Centek Technology but was hesitant to increase the number of centralizers to be used due to the previous unsuccessful well’s liner casing run with positive centralizers.
Project Well 2 – Customer ran 4 ½-inch 11.6# L80 liner casing with 42 Centek centralizers (spaced every other joint) on 5,062-feet of pipe. When TD was successfully reached the casing was rotated at 14,000 ft-lbs at 25 RPM. The torque dropped to 11,000 ft-lbs by last 20 bbl of displacement. The casing was rotated approximately 445 revolutions during cementing. The liner was cemented successfully.
Project Well 3 – Customer again ran a 4 ½-inch 11.6# L80 liner/casing, but on this well ran 190 Centek centralizers (3 per 2 joints) on 5,538-feet of pipe. After successfully reaching TD, the casing was rotated at 25 RPM with 9,800 ft-lbs torque. Rotation was stopped briefly to drop dart and then rotation was continued achieving 25 RPM and 9,500 ft-lbs torque. Full circulation through job was achieved and cement was circulated to surface after setting the liner. Calculated about 1900 revolutions were made during cementing.
Centek centralizers showed that casing rotation is easily achievable and will help improve the placement of the casing and cement. This type of success promotes improved bond logs and life of the well cementing integrity.