Delaying Water Breakthrough Using Horizontal Wells in Khurmala Oilfield

Abstract

Water coning presents a serious problem in many oil fields, in terms of reducing oil production rate and increasing production costs. As breakthrough time represents the time until coning occurs, it should be increased by studying the significant affecting parameters and proposing a method to control them. Since horizontal wells are known to have higher potentials than vertical wells, they are used worldwide to delay water coning among other purposes. In this study, four designed horizontal wells are proposed to replace a drilled vertical well in Khurmala oilfield in northern Iraq, and the effect of each on water breakthrough time is studied with four different production rates and six different permeability ratios. PERFORM software is used to model the wells, and calculate the expected breakthrough time for each well. It was found that the 1000-ft horizontal well, and longer wells, will delay water breakthrough time, in all cases. Also, higher permeability ratios increase the breakthrough time for longer wells, by up to 15.69 folds, except with the optimum production rate, and increasing production rate results in decreasing breakthrough time (tBT) in all cases, where doubling the production rate may decrease tBT by more than 73.5%. It is essential to determine the minimum horizontal well length required to delay water breakthrough time, compared to the vertical well, by considering both production rate and permeability ratio. The breakthrough time ratio, depending on the proposed to optimum production rate ratio, can be calculated using the developed correlation with an average error of 1.73%.