Modified starches used as additives in Enhanced Oil Recovery (EOR)

Abstract

Nowadays, conventional oil recovery involves mainly three phases named primary, secondary, and tertiary, respectively. In the primary phase, the natural pressure of the reservoir is employed to push crude oil to the surface, allowing a yield up to 10 %. In the secondary one, pressurized gas and water are injected to recover part of the remnant oil (~ 30 %). Secondary extraction, which involves mainly the injection of water into oil wells, is the most used methodology due to its low complexity and cost, recovering less than 50 % of the original oil. However, several difficulties are found along its application related to the water-cut (or water channeling) phenomena and the consequently low oil recovery yield, making this process non-economically attractive. Within this context, even if the oil recovery is improved in 1 %, this increment represents hundreds of millions of tons without any exploration and development investment. However, heterogeneous nature of the reservoirs hinders the complete oil phase extraction by water flooding.Oil field applications of starch and their derivatives include filtrate-loss control, mud-rheology modification, shale stabilization, drag reduction, water shutoff and EOR. For such a purpose, some characteristics of starch such as molar mass, chemical structure and solubility, as well as, reservoirs´ salinity and temperature influence on the oil recovery efficiency. In this chapter, we will discuss the state of the art related to the use of different starch derivatives in EOR. Besides, diverse methodologies developed to synthesize modified starches are also presented, by analyzing the optimal conditions of each reaction. The degree of modification and the physicochemical properties of the derivatives are also included and discussed along the chapter, hoping that this interchange of ideas and methodologies will contribute to a better understanding of the use of modified starches for EOR.