Stimulation of weakly cemented formations is not the same fracturing process that occurs in hard rocks because the weak formations have minimal strength and basically zero fracture toughness. It has been demonstrated conclusively that vertical planes can be injected in weakly cemented formations with control of the plane's azimuth, and multiple planes can be injected at differing azimuths, both sequentially and simultaneously in a single well. Laboratory and near-surface experiments involving injection from a perforated casing have yielded random injected geometries that are not repeatable and do not develop a planar-injected feature. On the other hand, if the casing is dilated during the injection process, repeatable consistent vertical planar-injected geometries are formed with control of the azimuth of the injected planes. These experiments have been conducted in laboratories at numerous shallow-field sites involving excavation of the injections and at deeper field sites with the injected geometry determined by real-time imaging using the active resistivity method. The specialized casing system is conventionally drilled and cemented in place, sub-surface resistivity receivers installed, the casing dilated during injection, and the subsequent injected geometry imaged in real-time during the injection process. The application has field demonstrated both simultaneous and sequential multi-azimuth, vertical planar injections from a single casing horizon. The method has significant potential in soft rock formations for production enhancement in both shallow gas and shallow heavy oil reservoirs. This paper presents field injection experiments of multi-azimuth, injected, vertical planar geometries in a variety of weakly cemented formations and describes the application of the method to shallow petroleum soft rock reservoirs, especially for thermal and solvent recovery of heavy oil.

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