Page 204 - A Practical Companion to Reservoir Stimulation

PRACTICAL CONSIDERATIONS FOR FRACTURE TREATMENT DESIGN

able to achieve at a given pressure is best determined on a obtainable for very large treatments where bacteria can often
pump performance curve. Each pump and power system will degrade the gel viscosity of a batch-mixed fluid before
have a unique performance curve. An example is given in pumping can begin. Also, manpower time and costs can be
Fig. P-53. greatly reduced. The continuous mix process eliminates the
need to have gelling crews precede fracturing operations.
P-4.4: Blending and Mixing Considerations This results in a direct saving in time for both personnel and
Material storage and deliverability may also be determining equipment. Finally, viscosities can be easily changed
factors in sizing a fracture treatment. Fluid and proppant throughout the treatment. This allows the polymer loading to
storage must be organized and laid out on location so that the be tapered so that fluid damage to proppant conductivities
pumping procedures of the treatment can be followed can be minimized or net pressure limitation can be met.
smoothly. For the fluid portion, a major consideration is To ensure that a continuous-mix operation goes smoothly
deciding whether the fluids should be batch mixed or con- several.requirements must be observed. The polymers should
tinuously mixed just prior to being pumped. Recent devel- be of a liquid or slurried variety to ensure that they can be
opments in hydration technology as well as new process added at precise concentrations. Liquid or slurried additives
control capabilities have made continuous mix treatments a can be pumped and monitored much more accurately than
viable alternative to batch mix operations (Fig. P-54). There dry, powdered materials. These polymers will show an im-
are several advantages to performing a fracture treatment in a proved and quicker hydration especially when mixed with
continuous mix mode. Environmental concerns are greatly new process controlled equipment (Fig. P-55). These spe-
reduced with only fresh water remaining in the frac tanks cialized mixing and hydration units provide the metering
after a treatment. Besides eliminating the cost of gelled tank capabilities, the proper shear environment and sufficient
bottoms, no tank cleaning or disposal costs are incurred. At residence time for proper hydration. The hydration process
the same time, a more predictable and consistent viscosity is related to time and shear has proved to be extremely impor-

15,000

10,000

5000
4000

3000

2000

1500

1000
1 2 3 4 5 678910 15 20 25 30
Rate (BPM)

Figure P-53-Typical pump performance curve.

P-45