Analysis of Water/Oil Ratio in Complex Carbonate Reservoirs Under Water-Flood

Abstract

Abstract Knowing the source of excessive produced water from oil wells in complex carbonate reservoirs under water-flooding sheds light for engineers to optimize development plans and better design remedial actions for enhanced water management. Although oil-well water production has been studied extensively, and hence different techniques have been introduced, only a few have addressed the source of produced water. Chan (1995) was among first to develop diagnostic plots to analyze the water-oil ratio (WOR). Chan plots (double-logarithms of WOR & its time derivative WOR’ vs. time) can, for example, indicate whether produced water comes through water coning or water channeling. Yet, these plots were obtained from conceptualized black-oil simulations which should be validated by more diverse field data. In this paper, Chan diagnostic plots were scrutinized using a suite of diverse field data that include permeability, production logs (PLT) and pressure transient analysis (PTA) from many vertical and horizontal wells with different completions. In this study, we demonstrated that more benefit of using Chan plots to diagnose water source can be gained through incorporating other field data into the analysis such as core data, PLT, and PTA. The diverse examples presented in this study revealed that near-well reservoir characteristics play a major role in shaping WOR & WOR’ plots rather than the well being whether vertical or horizontal. We suggest that, for a more accurate Chan analysis, only the production data at constant total liquid rate should be used. The second derivative of WOR may be utilized to identify the concavity of the WOR curve or the slope of the WOR’ curve.