Linear boundary detection using pressure buildup tests

Linear boundary detection has received considerable attention in the past. Although linear boundaries are frequently suspected and observed in well tests, conventional interpretation methods rely upon the development of two straight lines, which may not occur in practice. This report introduces two new semilog type curve matching methods for finding the distance to linear boundaries using buildup tests. Idealized curves are plotted from analytical solutions generated using the image well concept. These curves are then collapsed mathematically to a single type curve. By matching field data to the semilog type curve, the distance to a linear boundary may be estimated. The new methods have distinct advantages. The transition zone is the most important feature of the pressure response for type curve matching. Since development of the second straight line is not required, the range of interpretable tests is greatly extended. No estimates of reservoir characteristics are required to calculate the distance to the boundary because dimensionless parameters are used.