In the last decade, our understanding of shale reservoirs has progressed significantly. It is now agreed that a major factor for the productivity of shale reservoirs is the existence of a pervasive reservoir fracture network around the well. Accordingly, a common practice is to use hydraulically fractured horizontal wells to improve the connection with the reservoir fractures. Flow in these unconventional systems is considered linear in the fractured volume around the well and is usually interpreted with conventional reservoir engineering wisdom. The flaw in this interpretation is an inaccurate accounting of the matrix contribution due to the unconventional nature of flow in nano-darcy shale matrix.
This lecture presents a discussion of the characteristics of shale reservoirs and their impact on the performance of fractured horizontal wells. Various flow mechanisms in shale matrix and fluid transfer from matrix to fracture network are explained. Key parameters of productivity are identified and explained. Emphasis is given to the estimation of the extent of reservoir fracture network, prediction of the efficiency of matrix drainage and their impact on the estimation of well's drainage volume. The main idea to take away from this lecture is that some conven-tional reservoir engineering interpretations and practices may not be adequate (or appropriate) for shale reservoirs. For example, hydraulic fracture conductivity is usually not a key para-meter for wells in shale reservoirs. Examples are presented to highlight practices/problems in the interpretation of well performance from fractured horizontal wells in shale reservoirs.