Effects of vertical anisotropy on optimization of multilateral well geometry

Abstract

Multilateral wells have been increasingly used in recent years by different industries such as the oil-and gas industry (incl. coal-bed methane (CBM)) and geothermal energy production. The common purpose of these wells in the oil industry and partially in the geothermal industry is to achieve a higher production rate per well without increasing the hydraulic gradient significantly. In geothermal systems the ultimate objective is to improve heat extraction performance by enhancing productivity but also by increasing the heat transfer area.Optimal design of multilateral wells has been the focus of numerous publications in CBM and unconventional oil-and gas production, but as a result of cross-fertilization and technology-transfer among different sectors in the energy industry in the last few years, the focus of research on multilateral wells has turned to enhanced geothermal systems (EGS).Recently, several papers have been published on the use of multilateral wells in deep geothermal reservoirs. Coaxial closed-loop geothermal systems with multilateral wells utilize only the increased heat transfer area due to the laterals while EGS's with multilateral injection and production wells also benefit from the hydrodynamic advantages of such well configurations. However, substantial emphasis isunderstandablyplaced on the effect of artificial and natural fracture networks of EGS reservoirs and less focus is devoted to the impact of vertical permeability anisotropy which can seriously influence the flow pattern of a given configuration. Similarly, in CBM-related studies, the effect of horizontal permeability anisotropy along the face cleats to the butt cleats on multilateral well-design was investigated and vertical permeability anisotropy was not considered.In the current work we present a generalized approach for evaluating the effects of vertical permeability anisotropy on multilateral well geometry by numerical hydrodynamic modelling in an idealized, homogeneous hydrogeological setting.Current paper proposes an alternative modelling approach for representing the non-horizontal branches of multilateral wells by introducing a thin layer for the laterals with the same inclination as the well branches. This approach is then is used to investigate the effect of anisotropy on the flow pattern and near-wellbore drawdown and hydraulic gradient in the case of different branch deviations. Results suggest that the benefits of highly deviated or horizontal laterals emerge when vertical anisotropy is high. Evaluation of branch deviation vs. anisotropy indicates that above approx. 60 • there is no significant benefit in increasing deviation which implies that very highly deviated or horizontal laterals might not necessarily pay off the associated technical challenges and extra costs.

Increasing the profitability of production of hard-to-recover oil reserves based on the choice of a rational development system

“…At the same time, the massive use of horizontal wells with multi-stage hydraulic fracturing, despite the increase in the previously given parameters, made it possible to reduce the cost of the well by 29%, which, together with an increase in cumulative oil production, made the development of hard-to-recover oil reserves even more economically viable. Under conditions of uncertainty of reservoir properties or their high anisotropy, the risks of not achieving the design flow rates and cumulative oil production increase significantly, which leads to unprofitable production [5][6]. To date, multivariate modeling has become one of the main tools for 1229 (2023) 012022 IOP Publishing doi:10.1088/1755-1315/1229/1/012022 2 predicting and substantiating the optimal parameters of field development [7][8][9].…”

A Comprehensive Review of Fishbone Well Applications in Conventional and Renewable Energy Systems in the Path towards Net Zero

“…Fishbone drilling (FbD), another drilling technique, is distinguished by micro-holes branching from the primary horizontal well, giving an appearance reminiscent of a fish's skeleton [3]. These micro-boreholes operate similarly to multilateral wells.…”