Hydraulic Fracturing-New Developments

Abstract

Abstract This paper discusses the theory of hydraulic fracturing and the new developments in fracturing fluids and fracturing techniques which are continuing to make fracturing n important production tool. The discussion of hydraulic fracturing theory includes reasons for fracturing, objectives in fracturing and considerations in designing hydraulic fracturing treatments. The considerations in designing hydraulic fracturing treatments include formation characteristics as they control fracture extension, type of fluids used in the treatment, treatment size, proppant type and economics. New developments in the last few years have proven successful in stimulating zones that were previously considered uneconomical or marginal. These new developments, relating to fluids and treating techniques, are being used in the massive hydraulic fracturing treatments now being conducted in the U.S. Rocky Mountain area. Introduction The hydraulic fracturing process, developed on a commercial scale in 1949, has been successfully employed to increase production many formations which could not otherwise have been produced economically. There are many factors which should be considered prior to conducting a stimulation treatment by hydraulic fracturing. These relate to conditions of the wellbore, the reservoir and the economics involved. The two primary objectives in hydraulic fracturing are (1) to bypass formation damage and/or (2) to stimulate the zones of interest. The design of a successful hydraulic fracturing treatment requires that consideration be given to the formation characteristics. These are a function of depositional environment and, therefore, knowledge of the geology of the formation is important. In many cases, the formation characteristics at the extent of induced fractures are different from the formation characteristics at the well bore. The characteristics can be known only from knowledge gained from offset wells and/or the geology of the area. With formation characteristics known, the fracturing fluid type, proppant type and other treatment variables may be evaluated. New developments in the area of hydraulic fracturing relate to fluids with specific characteristics and to techniques for application of these fluids. The recent emphasis in hydraulic fracturing has been on creating extremely long fracture systems in tight gas sands. From this emphasis, the Massive Hydraulic Fracturing concept has emerged. In the text of this paper, the term production increase will relate to the generation of a fracture system with flow capacity greater than the flow capacity of the formation. In this sense, the term production increase will be synonymous with the term injectivity increase. Discussion Hydraulic Fracturing Considerations Prior To Hydraulic Fracturing Several factors should be considered prior to conducting a hydraulic fracturing treatment. Some of these are:the wellbore damage;the formation flow capacity;the existing reserves and/or depletion; andthe economics. The extent of wellbore damage can be determined by production tests, pressure testing and production history. This information is helpful in determining the type of treatment required to remove or bypass the damage. Once it is determined that a fracturing treatment is necessary, the formation flow capacity should be considered. If it is high, only a small-volume treatment may be necessary to bring the well to its expected production.