This type of test is difficult to execute successfully in low-permeability, high-compressibility reservoirs with wide well spacing. Instead of simply changing the rate at the active well, a series of pressure pulses are created by alternatively flowing and shutting in the active well. Pressure is monitored at one or several observation wells. Pulse tests – An alternative to interference tests in situations where the physical separation between wells is small, such as in pattern floods.The time required for the pressure transient to reach the observation well and the associated pressure change can be measured to characterize the degree of communication between the two wells. Interference test – The flow rate of a production or injection well is changed abruptly and the pressure response of a static observation well is monitored.There are two types of multiple-well tests: Interference and pulse. Multiple-well tests are more sensitive to reservoir heterogeneity than single-well tests ( SPE-10042-PA). Tests that are run between various sets of perforations in the same wellbore usually determine the vertical reservoir permeability. Multiple-well tests between offsetting wells determine the reservoir properties areally. The principle of multiple-well testing can also be applied between various sets of perforations in the same wellbore. Multiple-well Tests – These are used to establish communication between wells and determine the inter-well reservoir properties. The shut-in periods should equal or exceed the length of the flow periods. The modified isochronal test is conducted like an isochronal test, except the shut-in periods are of equal duration. The isochronal test is conducted by alternately producing the well then shutting it in and allowing it to build to the average reservoir pressure before the beginning of the next production period. Flow after flow, isochronal, and modified isochronal are different versions of multi-rate tests. This test is usually considered for a gas well to characterize the degree of turbulence and to measure the parameters associated with deliverability. In gas wells in which it takes a long time to achieve stabilized rates, wells are shut in and produced for a fixed time interval at several different rates. In such cases, the additional pressure drop measured by the skin can be confused with the pressure drop caused by non-Darcy or inertial flow. In gas wells flow rates are sufficiently high that turbulent or inertial pressure drops near the wellbore can be significant. In these tests, several stabilized flow rates are achieved at corresponding stabilized flowing bottom-hole pressures. Multi-Rate Test – These tests can be conducted on both oil and gas wells.
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