Development of Early Water Breakthrough and Effectiveness of Water Shut off Treatments in Layered and Heterogeneous Reservoirs

Abstract

Progressive percentage of total fluid produced in the oil industry is formation brine. Ever, increasing water cut will reduce oil recovery, diminish wells’ productivity and increase cost of eventual artificial lift and produced water handling. This paper investigated the problem of early water development in layered and heterogeneous reservoirs and determined the effect of different reservoir parameters on the development of water front movement in the presence of what is considered as a thief zone. A water injection in a line-staggered pattern was simulated to analyze the effect of various reservoir parameters on the water breakthrough time, WBTT, and the evolution of water front in the thief zone as well as other reservoir layers. Sensitivity analysis was conducted to investigate and determine the effect of most reservoir parameters that would cause and aggravate irregular advancement of injected water resulting in early water breakthrough and high water cut wells. These reservoir parameters included layers’ horizontal permeability, Kv/Kh ratio, and thickness of high permeability layers. Threshold of these parameters beyond which its effect would be constant was determined to help operators to predict the possibility of early water breakthrough through thief zones for better waterflood performance and hence better decision making process. From the first part of the study, a range of extreme cases was then selected to test the effectiveness of the currently available water shut off, WSO, methods of Cement squeeze, polymer-gel, as well as mechanical isolation. This paper simulated these WSO treatments to investigate its effectiveness in delaying the water breakthrough time, reducing high water cuts, and reducing the water handling problem. The paper summarizes the applicability of these WSO treatment methods and the condition under which they are effective and when they are not so.