Abstract:
In the last two decades, development of directional and horizontal drilling has led to the upcoming of multilateral well technology in the oil and gas industry. This ability to drill multiple laterals from a single bore has enabled new possibilities of development, especially to maximize reservoir exposure in low productivity reservoirs. Heterogeneity and particularly anisotropy of reservoir permeability are critical information that may lead to major uncertainties in well performance. This study focuses on effects of both horizontal anisotropy and vertical anisotropy on performance of multilateral well in bottom water drive reservoirs. Effects of aquifer size, effective well length and oil gravity are also investigated through reservoir simulation. Dual lateral and quadrilateral wells simulations are performed and results are compared to that obtained from horizontal wells in several reservoir models.
Results demonstrate the benefits of multilateral wells to reduce uncertainty of permeability anisotropy in bottom water drive reservoirs. Quadrilateral well geometry enables to average oil production within each lateral and thus, decrease uncertainty of anisotropic reservoirs compared to horizontal wells.
Aquifer size amplifies effects of anisotropy on well performance. Dual-opposed and quadrilateral wells both decrease pressure drop, reducing water influx from bottom aquifer and increasing oil drainage. Benefits of multilateral wells are increased with aquifer strength. An extremely large ratio of aquifer to oil reservoir pore volume would lower its sensitivity due to large water influx in the well. In low anisotropic reservoirs, a minimum effective length of well has to be identified to obtain benefits of quadrilateral wells to decrease lateral interferences which consequently causes pressure drop.
