Successful stimulation in the Cotton Valley sandstone: a low permeability reservoir

The Cotton Valley Sandstone, located in N.-central Louisiana and E. Texas, is an extensive coastal strand plain sandstone deposition. Formation permeability and porosity are very low and stimulation is necessary in most Cotton Valley wells to obtain economic production. Due to the depth of the formation (8,000 to 12,000 ft) and the reservoir temperature encountered (230/sup 0/ to 280/sup 0/F), the choice of fracturing procedures is somewhat limited. During the past 2 yr, much success has been obtained with hydraulic fracturing using moderately viscous, temperature stable aqueous gel systems. Recently, in wells where fracturing fluid retention has been a problem, the use of low surface tension surfactants and carbon dioxide with the fracturing fluid has helped improve fracturing fluid recovery after treatment and has provided encouraging stimulation results.