Interference and Pulse Testing-A Review

Abstract

Summary Multiple-well tests (interference and pulse tests) are used to establish communication between wells and determine the inter well reservoir properties. This paper reviews the development of multiple-well tests and describes the state of the art for their design and analysis. Interference testing is the oldest form of multiple-well tests. Analysis methods for interference-test data have been reported in the literature as far back as 1935. A review of these analysis methods is presented. Pulse testing was introduced in 1966 and analysis methods for homogeneous reservoirs were shown to be similar to those of interference tests. Pulse testing has one additional advantage it is not sensitive to unknown pressure trends in the reservoir. pressure trends in the reservoir. The principle of multiple-well testing can be applied not only between offsetting wells but also between various sets of perforations in the same wellbore. Multiple-well tests between offsetting wells determine the reservoir properties areally and are sometimes called "horizontal" or "areal" tests. Tests that are run between various sets of perforations in the same wellbore usually determine the vertical permeability and are called "vertical" tests. Multiple-well tests are more sensitive to reservoir heterogeneity than single-well tests. Therefore, attempts have been made to use interference and pulse tests to obtain reservoir descriptions. These attempts demonstrate the need to test the field data to determine the applicability of the different analysis methods before they can be used to obtain a reservoir description. Several studies of the effects of wellbore conditions on multiple-well test data have been reported in the literature during the last 5 years. This paper summarizes the different analysis techniques for both horizontal and vertical testing, delineates the advantages and limitations of the various analysis methods, and points out areas where further research is needed. Introduction Reservoir properties are usually determined in situ by indirect measurements of two variables, well flow rate and well pressure. A disturbance is introduced into the reservoir by changing one of the two variables (usually flow rate), and its effect on the other variable (usually pressure) is monitored. The characteristics of the pressure) is monitored. The characteristics of the pressure behavior vs. time, obtained as a result of pressure behavior vs. time, obtained as a result of changes in the flow rate, reflect reservoir properties. Creating such a disturbance in the reservoir, measuring the reaction, and analyzing the data constitute the area of pressure transient testing. pressure transient testing. When the flow rate is changed and the pressure response is measured in the same well, the test is called a "single-well" test. Examples of single-well tests are drawdown, buildup, injectivity, falloff, and step rate tests. When the flow rate is changed in one well and the pressure response is measured in another well, the test is pressure response is measured in another well, the test is called a "multiple-well test." Examples of multiple-well tests are interference and pulse tests. Tests run between two sets of perforations or test intervals in the same well to determine the properties in the vertical direction are also referred to as "multiple-well tests." Vertical permeability testing is an example of such tests. permeability testing is an example of such tests. Multiple-well tests are run to determine the presence or lack of communication between two points in the reservoir. In homogeneous isotropic reservoirs, multiple-well tests are conducted to determine the values of mobility-thickness product, kh/mu, and porosity-compressibility-thickness product, phi cth. JPT p. 2257