A study has been made and a series of charts are provided so that one may estimate the swept areas after breakthrough in flooding or cycling heterogeneous reservoirs. It is well known that reservoirs are not uniform and homogeneous, nor do they exist in uniform layers without crossflow, yet, the working charts and figures available to the engineer assume uniformity of the rock from an input well to an output well.
A series of charts has been developed various flooding patterns to show the swept areas after breakthrough for the case in which the rock is heterogeneous in nature, and the heterogeneity is distributed at random within the rock matrix. To use the charts one makes a plot of the permeability distribution data for the field and then refers to a figure in the paper to find a permeability distribution data paper to find a permeability distribution data nearest that of the real reservoir from this figure one then refers to the proper pattern such as five-spot or direct line-drive to find the expected areal sweep at breakthrough and performance afterward to depletion.
Commencing about thirty years ago a number of methods have been presented in the literature for estimating the performance, area swept at breakthrough and after breakthrough for waterflooding and pressure maintenance programs.
In the early analytical work Muskat reported on the calculated sweep efficiency. His work showed the sweep efficiency for the five-spot and direct line-drive, square pattern, to be of the order of 72 percent and 56 percent, respectively. Muskat's calculated percent, respectively. Muskat's calculated results were based on a uniform homogeneous rock, fluid mobility ratio of one, gravity effects were neglected and capillary effects were neglected. His work has served as the basis for many computations.
An unusually fine paper on engineering waterfloods was presented by Herman Dykstra and R. L. Parsons at the May 1948 API Meeting in Los Angeles. In the Dykstra Parsons method it was suggested that a straight line may result when the cumulative percentages of samples were plotted against the logarithm of the permeability.