The purpose of this paper is to show the practical usefulness of Ramey et al. type curves in evaluating the results from stimulation treatments. This in turn aids in designing more effective stimulation treatments. Several case histories from different areas are included for illustration.
A large number of wells now being drilled and completed are in reservoirs which would have been classified as uneconomical a few years ago. These low permeability reservoirs (less than 1 md) permeability reservoirs (less than 1 md) normally do not produce hydrocarbons economically without some type of stimulation treatment. Large size stimulation treatments (hydraulic fracturing and/or acidization) are increasingly becoming an integral part of well completion practices. In many cases, the production from these wells is too small to measure prior to the stimulation treatment, however, the same wells produce at economical rates after the stimulation treatment. Therefore, it is important that stimulation treatments for these low permeability reservoirs be carefully designed.
Traditionally, transient pressure tests have been used for determining the condition of a well prior to a stimulation treatment. The same type of tests may be applied in evaluating the effectiveness of a stimulation treatment. The application of such tests is discussed briefly in the SPE Monograph, Vol. 2, on Hydraulic Fracturing by Howard and Fast. Details concerning the different types of tests and analysis techniques are covered in SPE Monograph, Vol. 1, by Matthews and Russell. This monograph (Vol. 1) covers the state of the art as it existed prior to 1967.
Since 1967, considerable progress has been made in the field of transient pressure analysis. Most significant has pressure analysis. Most significant has been the improved understanding, of the early time pressure behavior of transient tests, which were considered too complex for analysis and thus were not utilized in the past. This has led to the analysis of the short-time data by type curve matching techniques. Developments in the field of well testing since 1967 have been summarized from a practical point of view by Ramey.