| In the past decade the use of horizontal wells increased rapidly due to improved drilling techniques e.g., coil tubing drilling, as well as high motivation by the industry to find efficient method of depleting oil reservoirs where vertical wells proved to be uneconomical. Reservoirs with natural vertical fractures, huge gas caps and/or underlying aquifers or heavy oil and tar sands reservoirs were the major reservoir candidates. Horizontal wells are currently being drilled in reservoirs that are assumed to be well understood. The need to identify pay is not a primary goal of an evaluation process, as the horizontal project is predicated on exploiting an already-identified commercial reservoir.; Initially horizontal wells were modelled by a simple sink/source approach. In this method frictional pressure drop effects are neglected. Several approaches were tried by different authors to include the hydraulics in the modelling of wellbore flow; industry tools providing the ability to more accurately predict performance and to better design a horizontal well are in demand. The primary purpose of this work is to address the need for a comprehensive, accurate, flexible tool for predicting the performance of horizontal wells completed in any arbitrary manner.; In this work a finite conductivity horizontal well model has been developed utilizing a discrete wellbore, where the frictional pressure losses in the wellbore are accounted for. The present model incorporates a variety of wellbore conditions and frictional pressure drop correlations to enable greater flexibility in the choice of correlation. The capability of adding skin arbitrarily along the horizontal section in the model not only enables us to simulate non-uniform skin damage along the well, but also to simulate selectively-perforated intervals. This is important for designing a horizontal well completion program.; The model rigorously incorporates variable rate production, so that it handles situations as complex as simulating pressure buildup following an arbitrary rate production period. The model has been verified using several published works. It is flexible enough to incorporate horizontal wells that are converted from producers to injectors, a common practice in today's industry. |
