Advances in drilling and completion technologies create new opportunities for well structure selection design, especially for fields that are sensitive to environmental conservation, cost-effectiveness, safety control, and well management. Horizontal, multibranching, and multilateral technologies are used to enhance hydrocarbon recovery. Producing from complex well structures can be difficult and, sometimes, detrimental to overall recovery. A mathematical model was developed to predict well performance for horizontal and multilateral wells using coupled multiphase models of wellbore/reservoir flow.