Among the important issues concerning formation damage assessment and control studies are to understand and describe effectively the physicochemical and hydrodynamic factors controlling near wellbore damage during well development and reservoir exploitation. The problem is twofold. First, the mechanisms responsible for formation damage require complicated mathematical models. Second, it is difficult to simulate near wellbore flow conditions in a laboratory core flow test.
In a paper presented previously, effort has been made by the authors to solve the first problem. The present work is aimed at providing solutions to the second problem. Laboratory core data and the Ohen and civan model have been employed to determine the parameters that control formation damage for given rock / fluids systems and operating conditions. A mathematical technique has been developed to scale the laboratory response to near wellbore conditions-thereby simulating the actual radial flow conditions that exist in the near wellbore region. The radius and permeability of the damaged zone are computed as functions of exposure time of the zone of interest to the damaging fluids. A factor, herein referred to as the skin factor, is computed as a measure of the overall effect of formation damage on productivity or injectivity.
The major benefit of this work is the ability to design drilling and completion operations to optimize the time the pay zone is exposed to the damaging fluid. The validity of the model has been demonstrated in an earlier publication. A typical example is presented in this study to demonstrate the capability of the radial flow simulator to assess formation damage in the near wellbore region. The simulator presented in this study can be used in the design of well development and reservoir exploitation programs with reduced formation damage as well as cleanup operations.