Techniques for allocating historical production (oil and water) by layer for individual producers and waterflood patterns are presented. Production splits were approximated from offset injection histories (i.e. spinner profiles, hydrocarbon pore volumes injected, proximity to injection, and injection timing). The techniques presented include the following by layer:

  • Production Gross & Oil Bubble Maps

  • Water Cut Maps

  • Injection Streamline Maps

  • Pattern Performance Graphs

The tools are extremely useful and rapid when well counts and production histories are extensive such as in the Long Beach Unit with 1200 wells and 27 years of waterflooding. Reservoir material balance and pressures are not used in the split logic for a well but checked later for each pattern. Predicted splits and water cuts compared favorably with fullfield reservoir simulation results and field production logs.

The allocation logic works in stratified formations where reservoir cross flow is minimal. Shales or other barriers between zones are required. The logic also requires that injection profiles, pressures, and injection-withdrawal ratios remain relatively constant. However, the logic can be applied over incremental time steps to handle dynamic changes in these parameters.

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