Effectively reduce clearance between the guide and the conductor
When the maximum allowable clearance is a value below that achievable by a fixed blade design, an adjustable mechanism is required to reduce the clearance after installation.
Adjustable conductor guide centralizers are typically fitted at the splash zone level where lateral loads are higher and tighter tolerances are required. The adjustable blades open and retract to minimise the clearance between the guide and the conductor.
There are two main types of adjustable centralizers:
- Shim type adjustable centralizer – Hinged designs which are constructed in two halves with two bolting flanges, containing two sets of adjustable blades per half. The blades on the design are adjustable and are kept to the required extension with the installation of nylon shims behind the blades. The adjustment is carried out by rope access personnel.
- Remotely adjustable centralizer – In the same manner as shim type adjustable design, remotely adjustable centralizers are of a hinged design constructed from two halves with bolting flanges for easy installation around the casing. The blades are activated by a deployment ring which uses hydraulic cylinders to activate the adjusting mechanism. The adjustment is carried out remotely, enhancing operational safety.
When using these types of centralizers, to allow space for the adjusting mechanism, a minimum radial clearance of 5″ and 6” respectively is required between the conductor and the guide.
- Application loading – Loads vary depending on conditions but typically range from medium to high lateral loads (40-60 tonnes).
- Failsafe assurance – To provide additional assurance and failure protection, adjustable conductor guide centralizers are normally supplied with thrust collars. This is a clamp that is installed directly under the centralizer as a special contingency in the unlikely event that the fasteners on the centralizer were to fatigue. The thrust collar, with a smaller diameter than the centralizer and located below the guide, is not subjected to environmental loading and can take the weight of the centralizer so that it remains within the guide providing lateral support throughout the life of the well.
By working together with clients and really understanding their requirements, we can simplify the designs and methodologies of installation to provide a solution that is fit for purpose, safe but also cost-efficient.