This paper focuses on the operational and financial benefits of using Hex Mud Pumps compared to traditional Triplex Pumps. The Hex Pump has a significantly smaller footprint and reduced weight, that allows for increased variable deck load capacity on floating drilling rigs. Also, the Hex Pump's improved pumping performance leads to safer and more accurate drilling in extended reach and complex directional wells.
The Hex Pump is an axial piston mud pump with six vertical pistons driven by two AC motors via a gear and a specially profiled cam. In contrast to crankshaft-driven triplex pumps, the Hex pump delivers a nearly pulsation free flow. Consequently, there is no need for pulsation dampeners on either the suction or discharge side when running this pump. Other major advantages are compactness (reduced weight and footprint) and no need for replacing liner sizes to achieve high pressure or flow. The Hex 240 version with 4 1/2" liners has a rated capacity of 2540 HP, a maximum rated pressure of 7500 PSI and a maximum flow capacity of 1034 GPM.
The Hex Pump has substantially less weight than a comparable Triplex pump, and this results in increased variable deck load capacity on drilling units. The potential cost savings related to increased variable deck load capacity both on new builds and on existing rigs will be discussed in this paper. Also, the potential steel weight reduction in the substructure on drilling units will be discussed.
The Hex Pump creates a clean standpipe pressure with much lower pressure fluctuation levels than triplex pumps. Due to this, there are no need for pulsation dampeners when running the Hex Pump. This additionally leads to much better and cleaner MWD-signals for the directional driller. As a consequence, this will contribute to faster and more accurate drilling in long and complicated directional wells.
The design and development of the Hex Pump is described in SPE paper 79831, ref /1/; "Development and Performance Testing of the Hex Mud Pump", but for the understanding of this paper it is important to understand the functionality of the Hex Pump design. Some of the main items are therefore repeated in this paper. SPE paper 92507, ref. /2/, "Operational experience with use of a Hex Pump on a land rig" focuses on the improved MWD-measurements related to use of Hex Pump compared to triplex pumps. Some of the main items discussed there will also be repeated in this paper.
SPM = Strokes Per Minute
GPM = Gallons Per minute
HP = Horsepower
AC = Alternating Current
VDLC = Variable Deck Load Capacity
MWD = Measurement While Drilling
PSI = Pounds Per Square Inch
The Hex Pump design, for which several patents have been awarded, is shown in figure 1.
Figure 1. Hex Pump (patented) (Available in full paper)
The Hex Pump's minimal-pulsation performance is due to the special cam design. The cam is made with a special asymmetric profile responsible for specific timing between the suction and discharge phases when it rotates from cylinder to cylinder.