Enhanced Oil Recovery in Iraqi Limestone Formation by Intermittent Injection of Xanthan.

Abstract

Abstract Enhanced oil recovery consists of three major methods which are miscible Method, thermal method and chemical method. Polymer flooding is considered as one of the chemical method which is economical compared to other methods. The main objective of this project is to determine the optimum polymer concentration that will bring in the most recovery of a large full-field flooding project at Ahdeb oil field. Thus, the (1) polymer concentration, (2) polymer solution viscosity, and (3) polymer injection rate affects towards oil recovery are investigated. This investigation will solely base on the outcome from the Simulator. The main difficulty in the recovery of oil is the viscosity of oil is higher than injection fluid viscosity, which makes displacement by a low-cost fluid, such as water or gas; inefficient on account of the “unfavorable” mobility ratio (i.e. mobility of the injected fluid is greater than the mobility of the oil). Since improvement in the mobility ratio is the ultimate goal, viscosity of the injected fluid is increased by addition of soluble polymer. The polymer concentrations were varied so that different polymer solution viscosity can be injected into the model. Apart from improvement in the mobility ratio, average pressure of the reservoir will also be maintained for as long as possible, which would lead to an improvement in the oil recovery. In accordance to that, the injection rates of displacing fluid play an important role in maintaining Average reservoir pressure and also the period of polymer flooding. The scope of the study will mainly focus on the polymer injection-water cut relationship. The research methodology used in this study is by varying polymer concentration, polymer solution viscosity and the polymer injection rate, the resulting cumulative oil production and average reservoir pressure will be taken into consideration for each case.From the optimized model, it shows that increment in polymer solution viscosity (increment in polymer solution concentration) increases the oil recovery, but when it exceeds its optimum point, oil recovery stabilized. There are a total of six cases run in this study concerning the polymer solution concentration. It proves that the addition of polymer concentration can give additional recovery up to a certain level, before it maintained. Adjusting the injection rate will be constrained by polymer concentration to maintain the injection bottom-hole pressure below formation fracture pressure since higher concentration requires more energy to move the polymer consequently increase the injection bottom hole pressure. In summary, Polymer flooding allows more oil recovered from the mature oil fields to maintain high oil production. If verified by experiment, this model of polymer behavior may have impact on reducing the residual oil saturation and consequently increase the economic life of the fields.