Because any increase in hydrocarbon recovery helps the petroleum industry respond to the ever-increasing demand for energy, increasing recovery from both conventional and unconventional reservoirs is the primary goal of developing new completion strategies. This paper introduces a new completion strategy, called Complex Toe-to- Heel Flooding (CTTHF), that increases oil recovery from sandstone formations. It then confirms the viability of CTTHF by using a commercial reservoir simulator to compare CTTHF to conventional waterflooding and Toe-to- Heel waterflooding. Finally, it presents several different methodologies for implementing CTTHF successfully, efficiently, and cheaply.

CTTHF improves reservoir management and enables better oil recovery than do other methods. It begins with the injection of a highly viscous slug near the toe of a horizontal well to form an impermeable barrier. An appropriate plug is then set to separate the perforations used to inject the barrier from the rest of the well. Then, the entire horizontal section of the well is perforated and a suitable packer is set to separate the horizontal section into a flooding zone (the perforations immediately heel-side from the plug) and production zone. The flooding zone is then used to create an injector hydraulic fracture into which water is injected to flood oil towards the production zone. As the flood material to oil ratio increases, the packer can be moved heel-ward. The oil is produced from the annulus through dual tubing completion or by any other convenient method, and the flood material can be either liquid or gas, depending on the application.

Though CTTHF is more complex than conventional strategies, it enables better recovery and can be implemented using a variety of completion techniques and technologies. Because the location of the packer can be changed, moreover, CTTHF minimizes the production of flood material. It is also compatible with dual tubing, coil tubing, and annulus production, and its design can be optimized using a variety of tubes, plugs, and packers.

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