Causes and Types of Water Breakthrough in High Water Cut Wells in Waterflooding Carbonate Reservoirs

Abstract

AbstractCarbonate reservoirs in the Middle East occupy an important position in global oil and gas storage and production, which have the characteristics of high single-well production, good development cost-efficiency, strong heterogeneity, complex distribution of barriers, and high permeability layers. For the thick-bedded massive belt edge-bottom water reservoir represented by Halfaya oilfield in southern Iraq, based on the water injection development experience in recent years, development issues such as unbalanced reservoir production and differential water breakthroughs have gradually become prominent, and the proportion of high water-cut wells has been increasing year by year. This severely restricts the overall production and production capacity of the reservoir. Through the integrated static and dynamic analysis, the study shows that water breakthrough in high water-cut wells is controlled by the intrinsic and extrinsic causes. For innate factors, heterogeneity of the oil reservoir is extremely strong, and the thin interbeds of different development strata are superimposed on each other, and the spatial distribution of barriers separated by physical properties and high permeability strips is complicated. The external reason is caused by the unbalanced and unmatched injection-production relationship. The well patterns of different layers are irregular, and the injection-production parameters are difficult to adjust. At the same time, the lower layers developed strong natural edges and bottoms aquifer. In this research, a comprehensive discrimination method integrating seismic-geology-logging-monitoring-dynamics-simulation is established to reveal the internal and external causes of water breakthrough in high water-cut wells and classify three types of water breakthrough, which are strong bottom water coning at the bottom, rapid breakthrough of injected water, and Layered edge water invasion, and preliminary control strategies are proposed.KeywordsCarbonate reservoirWells with high water cutWater breakthrough (WBT) causes and typesRapid injected WBTStrong edge and bottom aquiferStrategies for WBT wells