Abstract
K reservoir is a highly heterogeneous pore carbonate reservoir with thin layer and high permeability zone at the top. It adopted the overall horizontal well pattern, the water cut rose rapidly and "double-inverse" water flow dominant channel formed subsequently after water injection. The water cut of most producers rose rapidly to more than 85%, resulting in a large decline of oil production and poor sweep efficiency.
In the paper, a novel methodology and data-driven analytics workflow was established for detecting the characteristics of watered-out horizontal wells, revealing the highly watered-out mechanism, describing the residual oil mode on different main factors and proposing the solution for highly watered-out horizontal wells. The paper analyzed the rules and characteristics of water cut change after water injection and clarified the effect of the matching relationship of horizontal well trajectory and the main factors on the rapid rise of water cut. To diagnose the mechanism and reasons for the rapid rise of water cut, the watered-out conditions have been described for producers, injectors and inter-wells in longitudinal direction at different times through passing wells from lower formation based on logging data. The paper put forward the theoretical calculation formula for liquid effusion of horizontal well bore and the prediction formula of liquid discharge time. By discharging the accumulated liquid from the well trajectory at the high permeability zone, the residual oil with the well trajectory in other layers could be used to expand flooding volume, reduce the water cut of the producer, and restore the normal production for these high water cut wells. It was indicated that the actual incremental oil result for these wells were decided by the relationship of well trajectory and the main controlling factors and the remaining oil distribution.
This workflow has successfully been applied to a giant heterogeneous carbonate reservoir. The water cut of most wells was significantly reduced, with an efficiency of more than 90.0%. The time of liquid discharging and water cut controlling was 1 and a half months to 4 months, and the water cut decreased between 8% and 24%, and the total incremental oil of 2 million barrels has been achieved.
Strong heterogeneity in carbonate reservoirs of Middle East generally develops and easily causes high water cut for producers, the innovative strategies in the paper has good adaptability and reference for these reservoirs.
