Step-rate injectivity test (SRT) is a widely accepted method for determining the formation fracture pressure (or formation parting pressure, FPP). The FPP defines the maximum safe injection pressure without fracturing the formation rock for a disposal or storage well. The purpose of a step-rate injection is to incrementally increase the injection rate in steps of equal time. By doing so, a fracture will initiate at a point when the pressure reaches the FPP. Subsequent injection will cause the fracture to grow, thereby producing smaller increases in the pressure although the rate increments remain the same.
An adequate initial injection rate, as well as appropriate time steps and rate increments are critical to the success of an SRT. Formation fracture should occur during one of the time steps, and it is desirable to have a number of steps below and above the FPP. For this reason, BGES collects historical well data and uses a test simulator to carefully design the injection schedule.
As an alternative to SRT, a DFIT (or Diagnostic Fracture Injection Test) can also be conducted to obtain information about the formation’s fracture pressure.
From test design and field execution to the final regulatory reporting, BGES is well experienced in developing successful and seamless injection/disposal well applications.