Rate Transient Analysis (RTA) has become very popular over the past decade as a theoretically robust, yet very practical tool for well performance evaluation, making use of continuously measured production rates and flowing pressures which are collected as part of good production practices. With the advent of unconventional resource plays (particularly shale gas and liquids-rich shale plays), these RTA techniques have evolved significantly, adapting to much greater reservoir and completion complexity and accommodating the availability of much richer and varied datasets.
In light of these recent developments, it is easy to become lost in the details when trying to analyze unconventional reservoirs, particularly when one considers the complexities of flow behavior, pressure-dependent reservoir properties, HP/HT phase behavior, and the challenges of the well completion geometry. This presentation describes how and why RTA techniques evolved as they have over the years, starting with relatively simple conventional (high permeability) reservoir systems and progressing to the complexity of fractured, ultra-low permeability systems. Techniques specific to unconventional reservoirs are presented — and their strengths, limitations, and applications are discussed. These techniques are demonstrated using real field production data.