Multistage propped hydraulic fracturing is applied to horizontal wells in tight sand reservoirs to increase the productivity and ultimate recovery per well. This technique is credited with the increased contribution of tight gas portfolio as part of the unconventional gas revolution in the United States. Horizontal wells and hydraulic fractured wells alter the flow geometry around the wellbore, and their expected flow regimes are well documented in the pressure transient analysis literature. The two geometries have some common characteristics such as linear flow behavior. The combined effect of horizontal wells and multistage fractures adds to the degree of freedom in test interpretation and makes more difficult to get a unique interpretation. Therefore it is critical to get a pre stimulation flow capacity from pre frac test on vertical pilot hole or a post frac test of the same.
In this paper we compare and contrast the pressure transient response of the multistage fractured horizontal well to that of vertical fractured and un-fractured horizontal well. We show that multistage fractured horizontal well response can often be matched with either vertically fractured well or with fractured horizontal well. Our simulation show that the long term response of the different interpretation are similar as long as we use drainage area with the same gas in place.
The above discussion will be presented in light of our expereicne with several case histories from tight gas wells. In particular, an example depicted in the paper where three buildup tests are available: pre-frac and post-frac tests on the vertical hole and post multistage frac test on its horizontal side track shows the flow behavior, reservoir and fracture properties, long-term flow response and performance, and the importance and impact of correct modeling of the well configuration.
The paper contributes to a better understanding of the pressure transient behavior of the complex multistage fracture system and provides practical guidelines for the correct analysis and interpretation of its well test data.