EVALUATING THE EFFECT WELL INCLINATION AND FORMATION ANISOTROPY ON CONING RATE IN DEVIATED WELLS

Abstract

In oil reservoirs with bottom water drive, coning is a fundamental problem during oil production. Horizontal and deviated wells are often used to reduce the effect of water coning on total oil production. To avoid the premature breakthrough of water, the production of oil should be maximised through effective monitoring of the critical coning rate, and many researchers have developed models to determine the critical coning rate. However, very few studies have been conducted to evaluate the effect of good inclination and formation anisotropy on the critical coning rate. Therefore, we have incorporated well deviation and formation anisotropy into a water coning model to investigate their effects on the critical coning rate. Previous researches have been limited mainly to the calculation of water critical coning rate in the vertical well. In this study, a combination of radial and spherical flows in deviated wells has been adopted to develop a new model for analysing coning in non-vertical wells. The well inclination considered ranged from 20o to 80o, horizontal permeability (kh ) from 100 mD to 200 mD and the vertical permeability (kv ) was varied from 2 mD to 10 mD. Results showed that highly-deviated wells and formations with a high degree of reservoir heterogeneity (kv/kh) result in high critical coning rate and therefore less susceptible to early water breakthrough. This shows that more allowance to increase the production rate is possible for horizontal wells and anisotropic formations than in vertical and homogeneous reservoirs.
 Keywords: Water coning, deviated wells, reservoir heterogeneity, anisotropy permeability, critical coning rate, critical parameters.