BowSpring Centraliser

Description

BowSpring Centralizer

Technical Description and Specifications

The Bow Spring Centralizer is a passive mechanical tool crucial for downhole zonal isolation and cement integrity in casing and liner strings. Its primary function is to ensure the casing string is centralized within the wellbore, maintaining a uniform annular gap between the casing OD and the wellbore/formation.² This is essential for achieving complete, concentric placement of the cement sheath.

Key Technical Specifications and Operation

• Function: To provide the necessary radial restoring force to position the casing string concentrically within the wellbore or a larger casing/liner, preventing differential fluid migration and ensuring effective cement bonding (hydraulic seal).

• Design: Consists of upper and lower collars (stop collars) connected by multiple high-strength, flexible steel bow springs. The springs are designed to compress significantly when passing through restrictions and then expand to exert a continuous, radial restoring force against the borehole wall.

• Performance Metrics: Centralizer performance is defined by two key metrics:

  • Restoring Force: The force exerted by the bows to push the casing away from the wellbore wall. Measured in pounds (lbf) at a specific radial offset.

  • Stand-Off: The minimum percentage of the annular space maintained by the centralizer (industry standard often requires $>67\%$).

• Deployment: Installed directly onto the casing joints at calculated intervals (centralizer spacing) determined by the required stand-off percentage and casing stiffness (governed by API Specs 10D).

• Types: Available in both Weld-On (fixed collars) and Slip-On (secured by stop collars) configurations.

• Connection (Customizable):

  • The collars are designed to fit over standard API casing ODs.

  • Custom OD collar sizes are fabricated to fit non-standard liner or specialty tubular ODs, including specialized designs for high-fatigue or rotating liner applications.

• Material (Customizable):

  • Standard construction uses high-yield carbon spring steel alloys (e.g., AISI 4130/4140) for maximum restoring force memory.

  • Custom material options are available, including NACE MR0175 compliant alloys (e.g., specific stainless steels) for the collars in sour service environments where exposure to $\text{H}_2\text{S}$ is anticipated.

• Critical Parameters (Customizable Size & Force):

  • Casing OD and Hole ID: The centralizer must be specified by the Casing OD (inner dimension) and the Open Hole ID (outer dimension) to ensure correct bow sizing.

  • Custom Bow Springs: Fabricated with specified metal thickness and curvature to achieve a specific restoring force for extremely large or highly deviated well sections. Clients must specify the Casing OD, Hole ID, and the minimum required restoring force (lbf) when placing a custom order.

SEO Keywords (Targeted for Slickline Procurement)

Primary: Bow Spring Centralizer,

Secondary: Slip-On Centralizer, Restoring Force Bow, Cement Sheath Integrity Tool.