Underreamers / Anchors


This multifaceted tool has the capability of cleaning tubing, casing, drill pipe, liners or even open hole. Hydraulically actuated blades allow the capability of running through small diameter restrictions and cleaning out larger inside diameters. Tools range in size form 1.7” OD with a capability of full wall cleaning to 3.5” ID, to the 5.25” OD tool capable of a full wall clean up to an 11” ID. Self centralizing by 90 degree offset blades eliminates the need for a centralizer.

The milling blades can be dressed with any variety of cutting matrixes, from the industry standard Cuttrite for cement and moderate scale, to diamonds of various configurations for the hardest of scales such as Barium and Strontium. A mill or bit of a similar configuration is run on the tool, and circulation is established completely through the bit, effectively cleaning and cooling both the bit and the blades. Blade configurations vary from the standard “bottom cut” to the back reaming capabilities of banana blades. In extreme horizontal situations where centralization is a problem additional sections can be added to the tool with wear pads in place of the blades to centralize.

The Hailey Underreamer can be run in a standard rotary operation, power swivel, or in conjunction with a high torque downhole motor.


Underreamer Operation Prior to shipment, the Hailey Underreamer Tool has been carefully examined to assure that it is properly assembled and tested for proper action. The tool should be inspected on location to determine if any damage has incurred in shipment. Check all threaded connections to assure that they are made up to Hailey Specialty Tools specifications. Do not tong on the threaded connections; tong at least 4″ from the joint. Assemble the Underreamer in the string below the mud motor and tighten to specs. Pump pressure will extend blades so use caution not to pressure up inside BOP or other obstructions. Proper orifice size must be used to maintain 500-1000psi on tool. This can be found from your rate and fluid type and orfice drilled out to proper size. Torque must be used to drill not weight on bit, but care must be given not to overtorque Underreamer. Overtorque on the Underreamer can cause blades to become bent and not be able to fully retract. If this is encountered a jar must be used to knock the blades back inside the Underreamer and allow it to fit through a restriction.

To start initial operation, slowly increase pump rate above desired operation depth and slowly set down weight to start milling operation at desired depth.Slow and steady operation will result in the most successfull job completion. Milling rate is dependent on down hole conditions and operation variables. The variables that can affect Underreamer operation are amount of weight able to set down, down hole temperature, mechanical condition of the hole, motor speed and pump pressure. Weight measurement at surface is not necessarily what is being exerted on the Underreamer. The operator should use caution in applying set down load and not exceed recommended HST Underreamer specifications.Especially on the set down, the tendency is to speed the action by applying additional load. Determine the maximum safe working load for the Underreamer , and never exceed this load during operation.

The torque, and the relative speed of rotation is controlled by the rate pumped, fluid type and mud motor type. It is recommended to work the Underreamer in 10-20 ft. sections. Once you have milled 10-20 ft. pick up and mill same section until all material is removed. This will also reduce the chances of packing the Underreamer off with milled up debris.