Mark Semmelbeck, Enron Oil & Gas Company; Ron Oden,
Coastal Management Corporation
This paper presents a methodology for evaluating waterflood performance on a pattem-bypattern
basis to identify wells that may benefit from some type of intervention or remediation. We
developed this approach to have a rapid screening method to analyze the commonly available data from
a waterflood and maximize the amount of useful information that can be determined from these data.
We calculate permeability and the variation in skin factor at the injector with time. We also calculate
average reservoir pressure, saturation and net voidage within each pattern as a function of time.
Diagnostic plots and maps show regions of high and low reservoir pressure, areas of poor sweep efficiency and the locations and types of various conformance problems. We have implemented the technique described here in a spreadsheet program on a PC. We also use a mapping software package to visualize and present the results of the analysis. We show how to calculate skin factor at injection wells and average reservoir pressure as a function of time on a pattemby- pattern basis. We also describe several diagnostic plots and maps to visualize and evaluate the waterflood performance. The data required for this analysis consists primarily of data that is gathered during the normal course of water-flood operations. We use the following data in our analysis. 1. Historical monthly production volumes of oil, water and gas. 2. Historical monthly water injection volumes and pressures for each injection well. 3. Average reservoir pressure and water saturation at the beginning of the analysis (either at the start of primary production or at the beginning of the waterflood). 4. Net pay and porosity distribution, preferably on a pattern-by-pattern basis. 5. The x-y location of each well and, preferably, information on how each well is completed including tubulars, perforations and stimulation.