A case study has been conducted on over 90 gas wells in West Texas to optimize fracture conductivity and well profitability. This study provides direct comparisons evaluating the effectiveness of treatments incorporating various designs and breaker systems. The wells stimulated with new designs focusing on methods to improve fracture conductivity have shown significant increases in production rates. These same wells have also shown improved clean-up properties, as compared to surrounding wells, by eliminating swabbing time and returning higher volumes of fracturing fluid. Recent laboratory studies have demonstrated that realistic in-situ fracture conductivity values are significantly lower than previously thought. New testing procedures have concluded that proppant permeability values are greatly reduced when exposed to long term tests. Additionally, fluid damage and polymer concentration further impair these permeability numbers. When breaker concentrations are increased to a level to effectively degrade the concentrated polymer the rheology of the fluid will be adversely affected, thus sacrificing the execution of the treatment. New designs have evolved placing emphasis on proper fluid selection, increasing proppant volumes and concentrations, and improved breaker scheduling. Encapsulation techniques have been developed allowing a controlled delay of breaker activation until after the proppant is placed. Extremely high breaker concentrations are now obtainable without adversely effecting the rheological properties of the fracturing fluids.

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As North American oilfield operations mature, there is a perceptible loosening of the autocratic ties between oil companies and contractors. They are being replaced by alliances or partnerships designed to minimize cost while improving profitability of the companies involved. This paper evaluates a mature alliance, its implementation, structure, and results.

SPE Members Abstract Foam cement is a low density cement system prepared by mixing nitrogen gas and surfactants with API portland cement. The lower density limit for conventionally extended slurries is between 11.0 and 12.0 lb/gal. Foaming permits cement slurry densities lower than water (8.33 lb/gal) while maintaining relatively high compressive strengths. These advantages and others have been well documented. Actual field mixing procedures and additive rates are critical and must be monitored to assure a competent foam cement. Slight variations in base slurry density, base slurry rate, foamer and stabilizer rate, or nitrogen rate can significantly alter the final foam density. Formerly, foam density was measured by a radioactive densitometer. This allowed for significant error when densities were less than 8.33 lb/gal. There was no physical means to collect and weigh an actual foam cement sample. This paper explains methods to improve the accuracy of the additive rates. It also defines a method for real-time measurement of foam cement density. The paper describes the use of a high pressure device downstream of the nitrogen addition that can weigh a pressurized foam cement sample during the job. Introduction Foam cement is used extensively on wells where weak formations or lost circulation zones, depleted zones, or other formation problems are encountered which require the use of a low-density cement system. The two basic methods of performing foam cement jobs are: the constant nitrogen rate method and the constant cement density method. The constant nitrogen rate method is the easiest to perform in the field. It simply involves maintaining a constant rate of nitrogen throughout the cement job. The resulting in situ foam cement column varies in density, compressive strengths, and permeability from top to bottom of the wellbore. Under some well conditions these variations can be tolerated because the only concern is the hydrostatic pressure exerted by the cement column on the weak formation. P. 639^

A case study has been conducted on over 90 gas wells in West Texas to optimize fracture conductivity and well profitability. This study provides direct comparisons evaluating the effectiveness of treatments incorporating various designs and breaker systems. The wells stimulated with new designs focusing on methods to improve fracture conductivity have shown significant increases in production rates. These same wells have also shown improved clean-up properties, as compared to surrounding wells, by eliminating swabbing time and returning higher volumes of fracturing fluid.Recent laboratory studies have demonstrated that realistic in-situ fracture conductivity values are significantly lower than previously thought. New testing procedures have concluded that proppant permeability values are greatly reduced when exposed to long term tests. Additionally, fluid damage and polymer concentration further impair these permeability numbers. When breaker concentrations are increased to a level to effectively degrade the concentrated polymer the rheology of the fluid will be adversely affected, thus sacrificing the execution of the treatment.References and illustrations at end of paper.New designs have evolved placing emphasis on proper fluid selection, increasing proppant volumes and concentrations, and improved breaker scheduling. Encapsulation techniques have been developed allowing a controlled delay of breaker activation until after the proppant is placed. Extremely high breaker concentrations are now obtainable without adversely effecting the rheological properties of the fracturing fluids.