Case Histories: Post-Frac Fluid Recovery Improvements of Appalachian Basin Gas Reservoirs
- Javad Paktinat (Universal Well Services Inc.) | Joseph Allen Pinkhouse (Universal Well Services Inc.) | William P. Stoner (Universal Well Services Inc.) | Curtis Williams (Universal Well Services Inc.) | Gregory Alden Carder (Universal Well Services Inc.) | Glenn S. Penny (CESI Chemical)
- Document ID
- Society of Petroleum Engineers
- SPE Eastern Regional Meeting, 14-16 September, Morgantown, West Virginia
- Publication Date
- Document Type
- Conference Paper
- 2005. Society of Petroleum Engineers
- 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 4.1.2 Separation and Treating, 2.2.2 Perforating, 2.5.2 Fracturing Materials (Fluids, Proppant), 1.6.9 Coring, Fishing, 1.8 Formation Damage, 2.4.3 Sand/Solids Control, 4.6 Natural Gas, 1.6 Drilling Operations, 2 Well Completion, 5.6.4 Drillstem/Well Testing, 3 Production and Well Operations
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The primary purpose of surfactants used in stimulating sandstone reservoirs is to reduce surface tension of the fracturing fluid, decrease interfacial tension between injected fluid and reservoir rock and increase post-fracturing fluid recovery.However, many of these chemicals when injected at high pressures adsorb rapidly into the sandstone formation, reducing their effectiveness in post fracturing fluid recovery.
This study describes simulated laboratory experiments and case histories of various surfactants used in the oilfield. Several different surfactants including ethoxylated linear alcohol, nonyl phenol ethoxylate and a microemulsion system were investigated to determine their adsorption properties when injected into a sand packed column. A laboratory simulated comparison study of these surfactants versus a microemulsion system was used to identify their water recovery properties from gas wells.
Field data collected from Benson, Balltown, Injun, and Speechley Sandstone formations confirm experimental sand packed column and core flow investigations. Reservoirs treated with microemulsion fluids demonstrate exceptional water recoveries when compared with conventional non-emulsifying surfactant treatments.Case histories reported from several gas wells stimulated in the Appalachian Basin illustrate the advantages microemulsions have over conventional surfactant treatments when faster cleanup, increased post fracturing fluid recovery and well productivity are of concern to the operator.
Surfactants or surface active agents are predominately used in hydraulic fracturing fluids to reduce emulsion tendencies between reservoir oil and treatment fluids.This problem is normally addressed by incorporating a non-emulsifier within fracturing fluids.However when gas wells are stimulated with water based fracturing fluids, fluid retention and a reduction in interfacial tension between the rock and the injected fluid are the key driving forces worthy of consideration for well cleanup.One of the continuing challenges in Appalachian Basin gas wells is post fracturing fluid recovery due to low pressure reservoirs.This could be due to the water based fluid creating fluid retention, or interfacial tension between the injected fluid and the reservoir rock, or capillary end effect on and around the vicinity of the face of the fractured rock1.To reduce these problems, commonly available surfactants are incorporated within the fracturing fluid to reduce surface tension.However, surfactants alone do not provide adequate water recovery properties for the reservoirs in the Appalachian Basin.Low temperature, pressure and permeability of these reservoirs may be some of the major reasons that less than 50% of the treatment fluids can be recovered from gas wells through conventional methods1.As illustrated in figure , it is possible that large quantities of injected fracturing fluids could be trapped in the area near the fractured proppant pack.
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