This paper presents a novel method for visualizing injection responses in patterns that include horizontal and/or vertical wells. Horizontal wells can respond to half a dozen or more vertical injectors. Understanding fluid communication between the horizontal well and the surrounding injectors is essential to estimating the effectiveness of the waterflood and helps to predict responses to the waterflood. Armed with the understanding of responses, we can optimize injection patterns, improve production rates, and achieve more efficient oil recovery.
Comparing the produced rates of oil and water to the injected water demonstrates fluid communication through a reservoir. However, typical oilfields can exhibit complex geology in patterns, accidental schedules of wells and/or random changes in the injection and production rates. Together with the shear volume of data, manual analyses may lead to ambiguous and biased associations between producers and injectors. The technique presented in this paper provides a rigorous and unbiased approach. It is based on the Spearman rank correlation between the injected and produced rates over a period of time. The correlation and the time lag between the injection and the associated production rates allow us to compress these two series of rates into a set of two simple parameters.
The advantage of the approach outlined in the paper is the capability to do a quick analysis and interpretation of fields under the waterflood, with a large number of injectors and many years of history. Furthermore, the analysis is based only on the ready available injection and production history. The development of the methodology was originally intended for injection optimization. It may however play an essential role in studies to locate the under-performing fields that may represent the acquisition targets.