Well Structure Optimization in Complex Wells for High Permeability Reservoirs

Abstract

The objective of drilling long horizontal wells and maximum number of laterals is to achieve maximum production rate. Reservoir contact of more than 5 km was drilled successfully through intelligent laterals (up to 5 laterals) that can be controlled from the surface. Currently there is a growing tendency of drilling higher number of laterals in the industry to maximize the production rate. The objective of this study is to evaluate the possibility of achieving this growing multilateral completion through two milestones. The first milestone of this study is the effectiveness and well designoptimization for several cases with critical parameters such as reservoir permeability, wellbore diameter, skin factor, reservoir drawdown, and well tubular roughness. The second milestone is to address the optimal maximum reservoir exposure in high permeability reservoirs (200-800 md) for high lateral-number in multilateral wells. The methodology conducted in this study consists of two main parts, reservoir/wellbore coupling model for production rate calculation from individual lateral and then pressure drop in building sections. Singlephase flow was used to investigate different parameters affecting lateral flow rate. Two-phase flow was used in pipe flow to investigate the possibility of drilling more than 10 laterals. The study shows how pressure at the junction can be used to determine the optimum lateral length as a starting point when designing multilateral wells. The parameters analyzed include viscosity of reservoir fluids, well diameters and number of laterals. The pressure drop due to friction lead to different flow rates at the surface regardless how strong the inflow performance is. The effect of roughness on pressure drop is minimal and only becomes significant at lateral length more than 20000 ft. The characteristics of flow in building section and junction are the key for a well having high number of laterals.