Abstract
Water coning is often a serious operational problem in oil reservoirs producing with strong bottom water drive. In Libya, many of the oil fields have water coning problems. The Production from such fields would normally consider limitation of the production rate to a certain minimum (critical rate) to prevent water coning from happening. However, since such a rate is normally very small (i.e., not economical), the company will be producing at a higher rate, and it becomes essential to estimate the time required for the water cone to reach the lower perforations (i.e., breakthrough time), and to predict the water performance afterwards to make the proper design for the surface facilities.
Some of the published correlations for predicting the critical oil rate, breakthrough time, and water cut performance were applied to actual well data from three Libyan wells. Also, a single well 2D radial model was constructed on selected wells. The model results were compared to the actual field performance as well as to the correlations results.
This study shows clearly that some of the empirical correlations can be considered more reliable than the others. It also shows that even though simulation of water coning is possible and gives more reliable results, the lack of data (i.e., good reservoir description, lack of vertical permeability data on a layer basis, lack of reliable special core analysis, and improper documentation of work-overs) will always limit the validity of the coning results obtained by the numerical models, especially at late times.
Finally, this study is mainly aimed to set up the proper procedure of analyzing the water coning phenomena. Since the study considers the actual field data of only three wells, it should be expanded to a larger number of wells producing from different formations to confirm (or disconfirm) the results and conclusions of this study.