A new interpretation approach to detect induced fracture opening with pressure transient analysis of step-rate tests

Step-Rate Test (SRT) is a way to monitor induced fracturing and fracture opening after it was created. Nowadays, many modern wells are equipped with permanent downhole gauges (PDG) that provide real-time measurements such as pressure and temperature that has revolutionized well testing and monitoring. Permanent pressure monitoring and flow-metering enable interpretation of flowing periods in combination with shut-ins, providing insights from the start of operations and widely used for monitoring of induced fracturing and fracture opening through time-lapse SRTs during injection operations. This paper proposes a new interpretation approach for early detection of induced fracturing by developing further existing SRT analysis practices using the advantage of permanent pressure measurements available now in many wells. This paper proposes a new SRT interpretation approach for early detection of induced fracturing or fracture opening using Pressure Transient Analysis (PTA). Proposed PTA-SRT approach is based on step-by-step technique introduced previously for reservoir flow evaluations and is developed further and tested in this study for induced fracture monitoring using a combination of existing analytical and numerical flow simulations. The flow simulations have revealed a new specific signature of induced fracture creation or opening in the Bourdet derivative of flowing transients, which is further used as theoretical basis of the PTA-SRT approach. This study suggests the concept of uncertainty envelope for practical applications of PTA-SRT for on-the-fly fracture monitoring separating the signature of induced fracture from measurement noise. The PTA-SRT approach has been tested and verified on a real SRT data from a vertical well injecting water in a sandstone reservoir confirming the capabilities of the PTA-SRT approach for early detection of induced fracture opening. The paper concludes with potential application areas of the interpretation approach for well and reservoir containment monitoring in different industries including automated workflows. • Capabilities and limitations of SRT interpretation using p-Q plot and PTA have been critically reviewed. • New signature of induced fracture opening has been revealed in the Bourdet derivative of pressure transients. • New approach for SRT interpretation for early detection of fracture opening using PTA has been developed. • Uncertainty envelope concept has been developed for practical applications of this approach. • Capability of this approach to detect induced fracture opening has been confirmed via testing on real well data.