Abstract
In the first part of this study, we scrutinize the equivalent skin concept used to emulate the influence of uneven formation damage on the performance of horizontal wells. Rigorous 3D multisegment well models are used to simulate the local changes due to nonuniform formation damage around wellbore accurately. We show that the simple models, presented in the literature, to compute equivalent skin factors are quite limited in their accuracy.
Equivalent skin factor resulting from nonuniform formation damage around a horizontal well, in general, is influenced not only by the static damage distribution itself but also by many reservoir and wellbore variables. A convoluted interaction of well location, distance to reservoir boundaries, reservoir boundary type, formation thickness, well length, extent and nature of static formation damage itself, production time, and the contrast between the flux distributions around damaged and undamaged wells affects and controls the equivalent skin factor around horizontal wells.
In the second part of the study, we investigate the uneven formation damage around multilateral wells. Our investigation concludes that, as far as the equivalent skin factor values are concerned, the multilateral cannot be represented as an extension of horizontal wells. The interaction between the laterals affects the flux distribution around the laterals which in turn influences equivalent skin factors. Commingled production from duallateral systems changes the nature and size of equivalent skin in comparison with equivalent skin factors resulting from individual and separate productions from each lateral. In a duallateral system, the contrast in the individual lateral lengths may have a strong impact on the equivalent skin factors for both laterals.
