Quality Assurance (QA), a critical component of a hydraulic fracturing treatment, must be performed prior to and during the job. Failure to follow QA procedures may result in added well costs and poor production. It begins during the design and ends after the completion of the job. The importance of Quality Assurance has been magnified in recent years due to the increased size and complexity of fracturing treatments. It is a tool used to ensure that fluids, proppants and equipment meet the increased demands placed upon them.
This paper discusses several steps taken in order to provide Quality Assurance. An explanation of procedures used during the job design and prior to the job is given. A discussion of procedures and troubleshooting prior to the job is given. A discussion of procedures and troubleshooting techniques used prior to and during the job is also presented. The sensors and computer system used in order to monitor QA data are also discussed.
The advent of crosslinked gels and massive hydraulic fracturing (MHF) has made treatments more complex. Previously, fluids exhibited poor proppant transport characteristics and fluid loss was anybody's guess. In short, fracturing was as much "art" as "science." Most fracturing design was a trial-and-error process where a slight viscosity increase would generally offset gross inefficiencies in fluid-formation unknowns and allow transport of two to three pounds of sand per gallon. However, fracture technology has been advanced within the last 10 yr by the following major developments that require engineering support for proper utilization:
crosslinked polymer gels with ultra-high viscosities;
fracturing micro, now nano, Darcy formations with design penetration of 2,000 ft at 300F;
better proppants (resin-coated sand and sintered bauxite);
clean, less damaging gelling agents (PSD or HPG);
high-pressure (over 10,000 psi) pumps (Pressure Multipliers/Intensifiers);
better reservoir/fracture models for design based on advances in rheology of gels and rock mechanics data;
N2 or CO2 energized fluids;
additives to reduce fluid loss into secondary, natural fractures; and
fluid stability for 18-hr pump times.
These developments also led to new problems. With efficient, high-viscosity crosslinked gels, it became possible to carry more proppant for more reservoir penetration but it now became possible to over gel and produce a fluid so viscous it would "gel out" (pressure out) in the produce a fluid so viscous it would "gel out" (pressure out) in the formation as cool-down occurred in the fracture. Thus, for each advantage in improved efficiency came an accompanying problem which must be minimized by proper fracturing design. Once maximum proppant concentrations tripled to eight to nine pounds per gallon, blenders and additive control systems reached the limits in human ability to respond before design limits were exceeded. The era of fully automated control will become a part of fracturing technology in the 1980's.