Application of Fuzzy Logic for Determining Production Allocation in Commingle Production Wells

Abstract

Abstract For oil or gas fields with stratified reservoir layers, detailed production contribution for individual layer is always desired. Unfortunately, in some particular cases, production wells are completed following commingled scheme. This is worsened further if only very few production tests are run for the field. This is the case for the Central Sumatera field with its 95 commingled production wells, among which only a few had undergone production tests and none of them have ever undergone production logging. Problems rise when the occassion came in which detailed production contribution from individual reservoir layer is required for the field's reservoir simulation modeling and production evaluation/prediction. This paper presents an approach to solve the problem. The approach is basically based on the application of soft computing (Fuzzy Logic) to investigate pattern of relationships between production contribution of layers in commingle wells and rock petrophysical data as well as other relevant geological/engineering data. For the purpose, thirteen wells (key wells) that have production tests are assigned, among which three wells are assigned for checking the validity of the recognised pattern. Using the validated most valid pattern, individual layer's production allocation for other wells are determined with well-log analysis data as the major input. Result estimates for the candidate wells are better compared to results produced by the conventional method of productivity index (PI) analogy. The resulted variation in water cut and separate oil and water split factors appear to be more realistic from any point of view.