ABSTRACT
The San Andres dolomite formation of the Level land Field in Hockley County, Texas is typically stimulated by acidizing. The types of treatments include workovers of production and injection wells, and initial stimulations of infill drilled wells. This formation is naturally fractured and normally produces a large quantity of released fines following an acidizing treatment. Gelled acid systems are beneficial in stimulation of these type formations due to decreased fluid leakoff and improved fines suspending ability. Several types of acid gelling systems based on polymers are presently available. The use of residual polymer or degraded polymer residue in the Levelland Field may prevent complete recovery of treating fluids and fines.
A gelling agent based on surfactant rather than polymer chemistry has been found to exhibit some unique foam properties in laboratory experiments. Acid gelled with this novel thickener required no additional foaming surfactants, gave higher quality foams than polymer thickened acids of equal viscosity, and allowed stable foams to be prepared which contained less than 50% nitrogen.
An evaluation of this gelling-foaming system has been done in the Levelland Field. A comparison is made based on field results between regular acid and other gelled acid systems. Wells with similar pay quality were selected using log and other analyses and comparative treatments were performed. Details of these treatments and production results are given in the paper. Cumulative production data one year after treatment revealed foamed surfactant gelled acid to be the most effective treatment for initial stimulations.
Further evaluation of acid gelling systems is presented in the paper through a composite of results from surfactant gelled and conventional acid treatments involving workovers of producing wells.
Although many treating variables were not constant, production results from surfactant gelled acid indicates substantial improvement over more conventional acid systems.
