Abstract

Chemical gas tracers have been used in gas flood projects to evaluate interwell communications, formation heterogeneity, channeling, and to calculate volumetric sweep efficiency. For the first time, these tracers are used to evaluate the extent of fracture communication with offset wells and also to evaluate zonal communication between four hydraulically fractured reservoirs. The four horizontal wells are drilled and completed in Berea, Chagrin, Lower Huron Siltstone, and Lower Huron reservoirs. Each well was individually fractured with nitrogen gas in nine stages. A different chemical gas tracer was injected in each of the horizontal wells during the fracture stages with the carrier gas. Upon the completion of each fracture treatment, the well was shut-in to frac the next well. Upon the completion of the last fracture treatment, the well was shut-in for the reservoir pressure to stabilize before all four wells were put back on production. Flowback gas samples were collected at the wellhead for tracer detection analysis and hence flowback analysis. In addition, produced gas samples were collected at the offset wells for gas tracer detection to evaluate the extent of the fractures, interwell communication and formation heterogeneity. The results of flowback, zonal communication and extent of fracturing are presented in detail.

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