The Spiral Flow Cylindrical Mud Mixer (SFCMM)* is a unique system recently developed for mixing large volumes of mud quickly under controlled conditions. Its streamlined internal shape allows regular flow by minimizing obstructions. A well organized flow pattern from the outside walls of the mixer into the centrally located suction eliminates dead spots and promotes uniform mixing of the contents. Field tests indicate that this system will mix mud approximately four times as fast as other existing systems. The speed of mixing up to this time has been determined by the limitations of adding materials to the mixer, and not the speed of the mixing action of the mixer.
This new system may be applied whenever an operator needs large volumes of mud with carefully controlled properties to solve well control problems. Plant tests have shown that this mixer will produce Plant tests have shown that this mixer will produce 214 bbl. of 17+ lb/gal. mud in a 24 hour period.
The SFCMM* is a unique mixer that provides more uniform mud at higher rates than that provided by other mixers available.
Mud mixing has progressed from the herd of cows run through the mud pit for the Lucas well at Spindletop to modern current systems. In general as the demands made on the systems in use were increased, improvements were developed to meet the new demands.
The early mud systems were simply pits in the ground that provided storage for the drilling mud and a simple management where the heavier drilled solids were permitted to settle to the bottom of the pit. Such pits mere satisfactory as long as the natural clays in the drilled section or cheap sources of clay were relied upon to develop the desired mud properties.
When it became necessary to control the mud properties such as density, viscosity, and water properties such as density, viscosity, and water loss, a new demand was placed on the mud systems. Now instead of simply separating the heavier drilled solids from the returned drilling mud, the weighting materials and other additives were to be blended and mixed into the mud in a controlled manner as well.
As the muds became more expensive, it became more common to use metal tanks instead of earthen pits. Mud guns (high pressure jets) operated from rig main mud pumps were used to mix the mud contained in the mud tanks as shown by Figure 1. Conventional high speed electrically or air driven propeller mixers or stirrers such as those used in the chemical industry were also mounted on the mud tanks as shown by Figure 2. As hydrocyclones and centrifuges were used to supplement the simple settling of the earlier mud separation systems, the use of stirred compartments became more important. Mud powered jet assisted hoppers became the most common method of adding dim or powdered materials to the mud system.
As more mud guns and other mud operated devices were added to the systems, the use of lower pressure, high volume centrifugal pumps rather than the main rig mud pumps became the usual method of supplying mud to such devices. The application of these independent pumps provided greater flexibility and more dependability to the mud systems. By the early 1970's mud tanks with independent, high capacity centrifugal pumps and submerged mud gun manifolds or "roll bars" were enable. These provided a high shear environment within the mud tank and frequent passage of the fluids through the centrifugal pumps. passage of the fluids through the centrifugal pumps. The flow of the mud through the centrifugal pumps and through the jets provided significant mixing action as well. These systems proved to be very helpful when adding polymers and other hard to disperse materials to the mud system.
There were at least four serious problems encountered with mud tanks and mud mixers using conventional fixed mud gun manifolds or stirring motors.
(1) As the fluids moved from the region where the jets or blades were installed into other regions of the tanks, there were large changes in the velocity of the fluids. Typically, solids accumulated behind obstructions or in the square corners of the tanks as shown by Figure 3.