Coil Tubing Jet Cutting-Multiple Stage Fracture Treating in SW Arkansas Lower Cotton Valley Sands is the key to economic development of previously bypassed reserves in layered Cotton Valley reservoir. Changes from previous hydraulic fracture treatments are categorized as follows: (1) focus fracture coverage per stage by sand jet cutting each stage with treatment fluids pumped via coil tubing and using sand plugs or packer assembly for zonal isolation between stages, (2) annular fracture treatments using reduced pump rates to limit fracture height growth, (3) proppant with higher strength and conductivity, and (4) environmental friendly chemicals to enhance flow back and increase oil production.
Bonanza Creek Energy, due to increased environmental considerations, changed to an environmental friendly fluid system. Substitutions which provide improved environmental chemistry, while supporting formation stability of clay, offer reduced environmental risk eliminating conventional polymeric chemistry. Recovery of fracture treatment fluids approach 30% of treatment volumes. The fracture fluid is a cross-linked 30# system, borate guar, loaded with optimized breaker schedule and enhanced surfactants. The high viscosity allows for adequate fracture width generation for placement of preferred 16/30 proppant at low pump rates.
The past hydraulic fracture treatments of the Lower Cotton Valley Sands separated the 500 ft gross Cotton Valley/Haynesville interval into two (2) treatment stages with limited entry perforating of sands in each stage Fracture treatments in 2007 typically used 150,000# of 20/40 Ottawa Sand per stage pumped at 30-50 BPM down the casing. Tracer surveys and production logging have shown that these treatments were not effective in treating all the reservoir layers of sand.
The new method of fracture treatment has unlocked previously bypassed reserves. Credit for the higher initial flow rates and ultimate recoveries are estimated to be 70% due the contributions of coil cutting technology, 20% due the improved proppant strength and conductivity and 10% due the improvements in the fluid system. One hundred six (106) wells have been drilled and stimulated using the new method of fracturing and 100+ wells are in inventory at 10-acre spacing.