Pressure transient testing has been the standard method used to obtain well information such as reservoir pressure, permeability, and skin in conventional reservoirs. However, with the shift towards unconventional, ultra-low permeability reservoirs, the only type of test that is economically practical for operators to use to determine reservoir and fracture properties is a diagnostic fracture injection test (DFIT). The DFIT provides a simple, cost-effective method for identifying fracture design parameters and essential reservoir properties in a relatively short period of time. Both fracturing and reservoir properties are critical inputs for proper fracture design, optimization, and reservoir characterization.

When performing a DFIT, it is critical to use a high-quality pressure gauge that is thermally compensated, capable of one-second sampling and with a resolution of 0.01 psi. Detection of subtle pressure changes over a short period of time is essential in analyzing the fall-off data to determine reservoir characteristics accurately.

The recently developed Self-Powered Intelligent Data Retriever system (SPIDR®) is an option for capturing accurate pressure data from the surface for use in DFIT analysis. This system provides a lower cost alternative that allows operators to view and download the data periodically during the fall-off without data interruption and without erasing the data. The downloads can then be reviewed to provide near real-time analysis, and also, will help determine when the test has been completed.

A case study will be discussed that will show how data from a high-quality surface gauge mirrors that of bottomhole pressure gauges and can provide accurate DFIT analytical results more economically.

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