Oil Recovery Performance of Immiscible and Miscible CO₂ Huff-and-Puff Processes

Abstract

The recovery performance of immiscible and miscible CO2 huff-and-puff processes for enhanced oil recovery (EOR) in a light crude oil sample was experimentally investigated. The minimum miscibility pressure (MMP) of the original light crude oil–CO2 system was determined by means of the vanishing interfacial tension technique and found to be MMP = 9.18 MPa. Then, the solubility of the CO2 in the light crude oil and oil swelling factor due to the CO2 dissolution in the oil phase were determined at T = 30 °C and various equilibrium pressures ranging from atmospheric pressure to P eq = 12.55 MPa. Later, series of immiscible and miscible CO2 huff-and-puff tests were designed and carried out at various operating pressures (i.e., P op = 5.38–10.34 MPa). The results of the experiments showed that for secondary CO2 huff-and-puff tests performed at the operating pressures below the MMP, the ultimate oil recovery factor is quite low. It was also found that in immiscible CO2 huff-and-puff (i.e., P op < MMP) scenarios, the oil recovery factor substantially increased as the operating pressure approached near-miscible conditions. The oil recovery factor almost reached its maximum value at operating pressure near MMP (i.e., miscible condition), and further increase of operating pressure beyond MMP did not improve the recovery factor at all. The tertiary mode of miscible CO2 huff-and-puff was also examined, and it was revealed that the oil recovery is significantly improved after a waterflooding process. The oil recovery mechanisms during the CO2 huff-and-puff were mainly recognized to be interfacial tension reduction, oil swelling, and extraction of lighter components by CO2, especially during miscible CO2 injections. In addition, the average asphaltene content of produced oil and the permeability reduction of the porous medium as a result of asphaltene precipitation were measured in each test. It was found that the amount of precipitated asphaltene in the porous medium as well as permeability reduction are considerably higher in near-miscible and miscible CO2 huff-and-puff tests compared to those in immiscible cases. The compositional analysis of remaining oil from CO2 huff-and-puff tests at immiscible and miscible conditions also showed that lighter components of oil are extracted by CO2, leading the remaining oil to become heavier with greater amounts of heavy hydrocarbons (i.e., C30+). However, it was observed that the extraction of lighter components during miscible injection processes is more predominant than that during immiscible injections, resulting in the production of higher quality oil.

Laboratory measurements of solubility and swelling factor for CO2/Brine and CO2/heavy oil binary systems under low‐medium pressure and temperature

“…Afterward, CO 2 solubility in terms of grams of CO 2 in 100 g of crude oil was determined at various temperatures and saturation pressures using Equations (3)- (7): [1,12] m dis ¼ m co2;i À m co2;f ð3Þ…”

“…Several researchers have investigated the solubility of CO 2 in water and brines as well as CO 2 solubility in oil and the oil swelling factor to understand the key parameters required to design and simulate oil recovery. [1,[7][8][9][10][11][12][13][14] The solubility of CO 2 in the crude oil was calculated for a wide range of pressures and temperatures by Dodds et al [15] and are reconstructed and presented in Figure 1. Other studies showed that CO 2 solubility in crude oil is a function of several thermodynamic parameters, mainly saturation pressure, temperature, and crude oil properties such as viscosity and density.…”

Fast Fluorescence-Based Microfluidic Method for Measuring Minimum Miscibility Pressure of CO2 in Crude Oils

“…Injecting CO 2 at or above MMP increases both the uptake of CO 2 in the reservoir and oil production as interfacial force barriers are eliminated and the oil is displaced as a single phase liquid. 13,[15][16][17] Current methods used to measure the MMP of gas and oil include the rising bubble apparatus (RBA), 18 slim-tube test, 19 and vanishing interfacial tension method. 20,21 The RBA method is illustrated in Figure 1e.…”

Experimental investigation on influencing factors of CO2huff and puff under fractured low‐permeability conditions

“…As a consequence, more oil can be produced and oil recovery can be enhanced by reducing oil viscosity, expanding oil volume, and extracting the light components of crude oil. [18][19][20][21][22][23] Mohammed-Singh et al 24 summarized the cases of CO 2 huff and puff in oil fields over the past two decades. Among above methods, CO 2 huff and puff has attracted more attention as an efficient and important technique.…”

“…[13][14][15][16][17] Both soaking time and CO 2 injection volume are important operation parameters to improve the performance of CO 2 huff and puff. [18][19][20][21][22][23] Mohammed-Singh et al 24 summarized the cases of CO 2 huff and puff in oil fields over the past two decades. They found that the best soaking time was 2-4 weeks and massive CO 2 injection enhanced the oil recovery of CO 2 huff and puff.…”