Radial and Huff-n-Puff Gas Injection on Microfluidic Chips

Abstract

AbstractMost of the reservoirs today are mature, and traditional waterflooding is not enough for the effective development of oil formations. One of the ways to significantly increase production efficiency for deep, low permeable reservoirs is gas EOR (enhanced oil recovery) methods. This paper presents a method for screening and increasing efficiency of gas EOR methods based on microfluidic studies and for studying the influence of various factors on the oil displacement process. Such technology can be used on par with traditional core flooding tests, reducing time, cost, and the amount of needed fluid. The porous structure was realized as a silicon-glass microchip that can withstand high pressure and temperature close to the reservoir conditions. For the tests, n-decane was chosen as a model oil phase, while nitrogen was used along with carbon dioxide for screening. On the microchips, several tests were done that proved the approach's effectiveness for screening gases before field application. The most effective for carbon dioxide occurred miscible displacement, resulting in the almost complete displacement of n-decane. Additionally, when comparing tests with the same system pressure but a different pressure drop, a more considerable drop led to a higher oil recovery coefficient. Since the conventional nitrogen injection resulted in an insignificant displacement coefficient even after an increase in differential pressure, it was decided to use this agent for the huff-n-puff injection experiment. The test led to the raising of the sweep efficiency coefficient by two times. Thus, an experimental procedure and a unique microchip geometry with the radial homogenous porous structure were developed, allowing tests to be performed for both conventional gas flooding imitating a five-spot pattern and huff-n-puff gas injection.