Abstract
Horizontal Wells are gaining popularity because of the advantages they offer, mainly high productivity and reduced coning. In this paper, the case of a high permeability reservoir producing at high rates is examined. The emphasis is specifically on how the length and selection of perforated intervals affect the production rate. The approach is to combine the inflow performance of the reservoir to the outflow performance of the horizontal section of the well to obtain the overall performance of the horizontal well. This is accomplished using a computer program that couples a theoretical solution of the productivity index to an empirical multiphase model of the flow in the horizontal section of the well. This program has been tested against actual data from some reservoirs in the Middle East. A good match between the measured and simulated pressures and rates is observed. The program has been used to generate inflow performance curves for horizontal wells drilled under different reservoir conditions. The results show that:
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The performance of a horizontal well is directly affected by the length and distribution of the perforated intervals.
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20% of the horizontal section of the well perforated at the heel yields twice the production of the same length perforated at the toe of the horizontal well.
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The same length fraction perforated uniformly across the well yields 3 to 4 times the production of the case where this perforated length fraction is concentrated at the toe of the horizontal well.
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For any given set of reservoir conditions, there is an optimum perforated length that yields maximum production rate.
