ABSTRACT
The most valuable diagnostic tool available to the frac engineer is pressure. The interpretation or the pressure response during a treatment and the pressure decline following a diagnostic fracture injection test as a diagnostic tool are described in Chapter 8. The pressure signature is an indirect measurement meaning that the pressure change as a function of time is used as the tool. There are a number of additional direct measurement diagnostic tools that measure either a feature being caused by the fracture or that resulted from the injection of the µuid or some active material during the treatment. Direct nearwellbore diagnostics such as temperature logs and radioactive tracers provide information about fracture height at the wellbore and proppant placement effectiveness. The effectiveness of these tools will vary with different in situ environments. Direct far-želd diagnostics such as microseismic and tiltmeter mapping are used to determine hydraulic fracture dimensions and orientation away from the borehole. When using any diagnostic tool, it is important to recognize that there are many interpretations that can be made. There is an anonymous quote that says, “Here you have my story. I will tell you some valuable truth, some half-truth and some bold-faced lies! It will be your job to žgure out which-is-which.” This is the essence of all of these techniques. They are, for the most part, subjective, and all have limitations that the engineer has to evaluate to determine the uncertainty. It should also be understood that without this information, it is usually impossible to determine why a fracture treatment is unsuccessful or if all the productive zones were treated.
