STEP-RATE TEST (SRT) / DFIT

BGES is capable of conducting mini-fracs/DFITs in both open-hole and cased-hole environments.

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.

Applications

In Alberta, the AER has adopted SRT as the primary way to determine the maximum wellhead injection pressure in an injection / disposal well application (Directive 51). As an alternative, D51 also allows DFIT to be done in lieu of SRT to obtain the formation fracture pressure. BGES can also provide a full suite of cased-hole logging to satisfy all D51 requirements.

Features & Benefits

BGES is equipped to provide an end-to-end D51 application, encompassing casing inspection log, temperature survey, radial cement bond log and the step-rate test, depending on the classification of the injection/disposal well. A detailed engineering analysis with all applicable log interpretations are included in a comprehensive regulatory report for a seamless submission.

Operations

BGES’ SRTs have 3 distinct parts: leak off, step-rate injection and falloff. The leak off test is conducted to confirm the injection rate steps. Pressure falloff is recorded after the pumps have been shut-in. This information may be further analyzed to obtain more information about the injection zone. Downhole measurements are recommended so that data is not affected by pipe friction.

Integration of Services

From core preservation, geotechnical lab testing, cased-hole logging, reservoir and caprock injection testing, data analyses, project management, regulatory reporting, to computer simulation and numerical modelling, our comprehensive and customizable service model offers maximum flexibility for our clients.