A new method of completing multiple layer wells has been successfully tested in the Piceance basin for Petrogulf Corporation. This new method placed sliding sleeve valves in the casing string and completed the well with normal cementing operations. The sliding sleeves were opened one at a time to fracture layers independently without perforating.

The valves have a unique design feature which allows an unlimited number of valves to be placed in a single well without incremental reductions to the ID, thus allowing normal cementing operations. A control line is connected to sequential valves. When the bottom valve opens, the control line becomes pressurized and transfers this pressure to a piston in the valve immediately above. This piston squeezes a C-ring and makes the ID smaller. At the end of the fracture treatment to the lower valve, a dart is dropped during the flushing operation. This dart lands on the C-ring and seals the bore inside the sliding sleeve. Pressure is then increased until the next valve is pumped open. When this valve opens, the next control line is pressurized, squeezing the next C-ring.

The main feasibility issue with this cemented sliding sleeve concept was the possibility of high fracture initiation pressure through the cement and into the formation without perforated holes. Significant laboratory testing was conducted that predicted fracture initiation pressure to be near openhole fracture initiation pressure. To confirm the laboratory testing, Petrogulf agreed to place two of these casing valves in a well in the Piceance basin to measure the fracture initiation pressure and test the functionality of the valves.

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