Water coning management for oil reservoir with bottom aquifer by downhole water loop

Abstract

Water coning is a common problem encountered in oil field operation especially for those exploited in reservoir with strong water aquifer beneath hydrocarbon bearing zone. Water moves upward in conical shape into productive oil zone, accelerating termination of well and resulting in cost of water treatment as well as disposal. Delaying of water coning is investigated in this study by the use of Downhole Water Loop (DWL). DWL is a technique producing water-free hydrocarbon in water sink zone and produced is re-injected back into discharge zone. From this method, oil-water contact is stabilized. The results show that, perforation location of oil bearing zone should be located far from oil-water contact, whereas water sink section should be located just beneath oil-water contact. Water discharge zone has to be located as far as possible from water sink zone in order to avoid inference of oil-water contact stabilization. From a study of reservoir parameters it is found that small ratio of vertical to horizontal permeability shows good results for DWL implementation. Big aquifer size assists DWL function in maintaining oil-water contact level through pressure support and thus oil can be produced for longer period. Thick oil bearing zone results in less effect from water coning problem since perforation interval can be located distance away from oil water contact. Implementing DWL in reservoir containing light oil is favorable since water coning problem that eventually occurs is compensated by favorability of mobility ratio.