Massive Hydraulic Fracturing Of High-Temperature Wells With Stable Frac Foams
- C.L. Wendorff (Dowell Division of Dow Chemical U.S.A.) | B.R. Ainley (Dowell Division of Dow Chemical U.S.A.)
- Document ID
- Society of Petroleum Engineers
- SPE Annual Technical Conference and Exhibition, 4-7 October, San Antonio, Texas
- Publication Date
- Document Type
- Conference Paper
- 1981. Society of Petroleum Engineers
- 2.7.1 Completion Fluids, 5.3.3 Particle Transportation, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 2.4.3 Sand/Solids Control, 1.11 Drilling Fluids and Materials, 2 Well Completion, 4.1.6 Compressors, Engines and Turbines, 2.5.2 Fracturing Materials (Fluids, Proppant), 1.8 Formation Damage, 1.6.9 Coring, Fishing, 1.6 Drilling Operations, 4.1.2 Separation and Treating
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Recent studies under downhole conditions show the relationship between foam texture, i.e., bubble size and foam rheology. They also show that under the low shear conditions that exist in a fracture during treatment, foams behave as power law fluids. Dynamic fluid-loss testing indicates stabilized foams are some of the more efficient fracturing fluids available. Formation damage results help explain why foam-fractured wells clean up so well.
As a result of our better understanding-of the properties of foam under downhole conditions, we properties of foam under downhole conditions, we have developed new, highly stable foam systems. These systems are 100 to 1000 times more stable than conventional foams and, therefore, greatly broaden the downhole conditions under which foams can be used.
Field results demonstrate the successful placement of large amounts of proppants with stable foams in both oil and gas wells at temperatures up to 300 degrees F. In addition, foam-fractured wells clean up better and, therefore, pay out. faster than wells fraced with conventional fluids.
The history of the use of foams in the production of oil and gas shows that foams are very versatile fluids with special properties, making them outstanding candidates for some applications. In 1966, Anderson, Harrison and Hutchison reported the development of foams for drilling and wellbore cleanout. They found the following features particularly interesting in well completion fluids. particularly interesting in well completion fluids. Low Hydrostatic Head Excellent Transport of Particles and Liquids Low Fluid Loss
These features were very helpful when drilling and completing wells in low-pressure zones, particularly in low-pressure gas formations. Low-density particularly in low-pressure gas formations. Low-density foams supply much less hydrostatic head than conventional drilling fluids, thus differential pressure into the producing interval is lower. Lower pressure into the producing interval is lower. Lower differential pressure causes less fluid loss and less formation damage due to fluid invasion. Foamed fluids also supplemented air drilling in shallow wells because solids and fluids could be brought to the surface with much lower annular velocities. Lower air velocities resulted in smaller compressors and less downhole erosion. These advantages account for the continued use of foams as drilling and completion fluids.
In 1974, Blauer and Kohlhaas published a paper giving the results of foam fracturing treatments in low-permeability gas wells. The same year, Blauer and Duborrow filed for a patent on the use of foams as fracturing fluids. In both cases, foams were thought to be good potential fracturing fluids because of their ability to transport particles and their low fluid loss.
These authors, and subsequent authors , found that foams had the following additional properties which made them prime candidates for fracturing fluids.
Low Liquid Content Good Rheology Properties High Energy Potential
The small amount of liquid phase present in foams, i.e., 15 to 45 per cent of the volume, coupled with the high energy potential of foams are responsible for the good cleanup characteristic and low formation damage of foam. Lower liquid volumes reduce filter cake buildup and cause less invasion of fracturing fluid. This in turn reduces the change in oil-water saturation in the matrix adjacent to the fracture face and the amount of formation particle movement. Less liquid leakoff also reduces particle movement. Less liquid leakoff also reduces the chances for fluid incompatibilities that lead to precipitates and/or emulsions.
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