Progressive Cavity Pump with Hydraulic Motor for Drilling Mud Recirculation

Application Background

Drilling fluid, also referred to as drilling mud, is pumped down wellbores during the boring process and has many benefits for both the machinery and the well itself. Improvements in fluid compositions and more efficient designs have led to the creation of deeper and more challenging wells. 

Drilling Mud Use

Drilling mud aids the boring process by cleaning cuttings from drill bits, cooling, lubricating, controlling pressure, delivering buoyancy, and stabilising exposed rock. Cuttings are created during the drilling process; with cuttings not posing a problem until the work stops, typically due to drill bit replacement. 

If such fluid is not pumped during downtime, then cuttings will fill the well again, with the fluid acting to keep parts in suspension preventing this from happening. Another benefit of drilling fluid is the control of pressure in the well, the addition of weighing agents raise its density and lead to an increase in pressure on the well walls. Special additives stop the liquid from being absorbed by the rock in the well, this stabilises the rock by ensuring the pores do not become clogged. 

Drilling Fluid Types

Fluids are either oil, water or synthetic based and each type provides different benefits depending on the type of rock. For example, oil-based fluids are better with saltier rock while water-based fluids have less of an environmental impact, which is particularly important when performing offshore drilling. The engineer must select the best liquid type and carefully balance the additives to either minimise friction, add more buoyancy or account for any other requirement. 

As drilling muds provide so many benefits and are such a necessity for the process, it is vital that the pump be reliable while also being capable of producing the required pressure and handling the concentration of sand and silt. Due to the remote locations for drilling, electrically is quite often not available and therefore it is common for the pump to be fitted with a hydraulic motor that is powered by the drilling rig itself.

Customer Need

A UK based drilling company was in the process of modernising their fleet and needed a new recirculating pump for one of their rigs. They use a water-based drilling mud containing sand and silt, their requirement was for a hydraulic powered progressive cavity pump capable of providing 15m³/hr at 12 bar. 

Our Selection for this Application

After close discussions and ascertaining mud viscosity and total operating hours, we selected our FN 40K2 progressive cavity pump operating at 150RPM. This slow speed will protect the pump from premature wear against the abrasive nature of the fluid. The pump is expected to operate around 8 hours a day so selecting the appropriate speed is extremely important to ensure the maximum lifespan for the pump. 

Eccentric screw pumps are perfect for this application due to their solid handling capabilities, providing a constant volume proportional to speed and being of positive displacement design. This means as the amount of drilling fluid increases, pump speed can be increased. Furthermore, should the system become clogged the unit will generate pressures up to 12 bar to clear blockages. 

Some of the main benefits of our progressive cavity pump range are:

•         Wide range of material options, including cast iron, stainless steel 304, stainless steel 316 and bronze for the casing, stainless steel 304 and 316 for the rotor and finally NBR, EPDM or FPM for the rubber stator. 

•         Modern sealed stator design, no o-ring required.

•         Modern rubber sleeve design to improve resistance to abrasive solids.

•         Numerous sealing options, including gland packing, gland packing with flushing, single mechanical seal, single mechanical seal with quench, double mechanical seal, single or double cartridge seals and API rated sealing systems.

•         Can handle viscous fluids up to 1,000,000cp.

•         Excellent self-priming capability.

•         Reversible flow up to 3 bar as standard, Up to 12 bar with hydraulic balance.

•         Excellent at pumping fluids containing solids in suspension.

•         Excellent for shear sensitive fluids due to low pulsations.

•         Available in different versions including flanged, vertical, hopper, oenological hopper and portable for wine transfer.

•         Various accessories available, including dry running protection, bypass valve, control panel, inverter, heating jacket, grinder, and others on request.

Here are the specifications of the supplied mud pump: