Bow-spring centralizers help center the casing in the wellbore during cementing operations, allowing the cement to be evenly distributed around the casing string. The degree to which the casing is centered (standoff) depends on the performance of the centralizer and the spacing between the centralizers installed on the casing OD.
Bow-spring centralizers, both welded and non-welded, provide the following advantages:
Welded Bow-Spring Centralizer
- Help center the casing in the wellbore, allowing even distribution of cement around the casing.
- Help reduce casing drag on the wellbore during casing running operations.
- Help prevent differential stroking of the casing.
- Increase fluid turbulence at the tool, helping remove filter cake from the wellbore.
- Can be run through hole restrictions in the wellbore or through smaller casing strings that are cemented in the well, thereby centering the casing below the restriction.
Welded bow-spring centralizers are available in two styles: slip-on and hinged. Slip-on centralizers are manufactured with solid end rings, requiring the centralizer to be slipped on the casing OD during installation. Hinged centralizers are manufactured in segments, allowing the centralizer to be installed easily around the casing OD. Hinge pins hold the segments together during installation. All welded
bow-spring centralizers are manufactured to API Specification 10D. The dual-contact (double bow) welded centralizer is designed for small-clearance casing-to-hole size applications. The centralizer will perform as a standard bow centralizer in holes up to ½" smaller than the centralizer’s nominal OD. When run in holes less than ½" smaller than the OD, the center of the centralizer contacts the casing OD, performing as a rigid centralizer. Because of its high restoring force with very little spring deflection, the dual-contact centralizer is excellent for deviated and horizontal wellbores. The dual-contact centralizer should only be installed between a collar and stop ring—never over a casing collar.
Non-welded Bow-Spring Centralizer
Non-welded bow-spring centralizers are available in the hinged style only. The bow springs of this centralizer are attached to the end rings without welding. The centralizer bow end is connected to the end rings with a locking tab that bears the load force on the centralizer. The centralizers are supplied in hinged segments joined by hinge pins in each segment. All non-welded centralizers meet or exceed the requirements of API Specification 10D, which dictates the minimum restoring and maximum starting forces for centralizers for various casing/hole size combination's. Centralizers with turbo-fins attached to each bow spring are designed to create localized turbulent fluid flow at the centralizer. The turbo-fins divert the fluid flow to more evenly distribute cement around the casing. All welded and non-welded bow spring centralizers are available in the most common hole/casing sizes.