A New Method for Evaluating Layer Productivity Using a Permanent Monitoring System

A new method is presented for layer evaluation in pumping wells based on the inflow-performance relationship (IPR) determination for each layer contributing to the well production Both the theory and field examples of the application are explained The fundamental principle of the method is the IPR determination for each layer that is contributing to the well production. A permanent monitoring system consisting of a permanent gauge and a shut-in valve is installed in the well to discriminate the flow rate from each layer corresponding to a given stabilized formation dynamic pressure. The method is inherently quality controlled: both rate and transient pressure are continuously monitored at the surface during the test to assure stabilized conditions for a valid IPR. The new method is illustrated with field cases of wells located in the Chihuido de la Sierra Negra oil field, Argentina, which is undergoing a secondary recovery project by water injection. Water is injected and produced from two main layers Both lateral and vertical displacement efficiency determination have been evaluated from the beginning of the project. In most of the wells, production from the two main zones is combined A permanent monitoring system was installed in several key wells, and the IPR for each zone was obtained. The rate from each layer was obtained directly using the system. In addition, the reservoir pressure was obtained by direct measurement and an interference test conducted using one of the nearby injectors as the active well A relevant conclusion obtained in one of the evaluated wells was that the production of one of the layer was responsible for most of the total production, contrary to the expected results based on conventional methods of assigning layer production based on total production split according to layer petrophysical properties IPR data fit was done using the Fetckovitch model. It can be concluded that the methodology presented can be considered as a major breakthrough in testing and evaluation of layer productivity applicable to multilayer completions.