Abstract
The negative side effect of the flooding with CO2 is asphaltene deposition; while little work was reported in the literature on asphaltene precipitation due to CO2 flooding in presence of light components. The main objective in this paper is to address asphaltene precipitation for oil containing methane and propane due to CO2 flooding at different miscibility conditions. Experimental measured asphaltene deposition due to miscible CO2 injection is compared with corresponding values estimated by proposed model. It is shown that there is a critical concentration of CO2, where below it; solubility parameter of the liquid is enhanced, hence preventing asphaltene from depositing. The first objective of the paper is to address an approach which is based on solubility parameters/CO2 fraction in the liquid to qualitatively assess stability/instability region for the asphaltene. The second objective is to quantitatively compare the predicted and experimental results. It is shown that the higher CO2 flooding pressure and temperature, the more deposited asphaltene. It was also shown that a higher risk for asphaltene deposition in case of chalk cores than for sandstone cores.
Highlights
IntroductionCarbone dioxide flooding in Enhanced Oil Recovery (EOR) processes has been encouraging; it may result to asphaltene deposition which it turns affect reservoir rock and fluid properties (Moritis, 2006; Chukwudeme & Hamouda, 2009; Hamouda et al, 2008; Idem & Ibrahim, 2002; Simon et al, 1978; De Boer et al, 1995; Burke et al, 1990; Haskett & Tartera, 1965). Haskett and Tartera (1965) reported that crude oils with low asphaltene percentage could experience asphaltene precipitation/deposition due to pressure reduction in early stage recovery, as well as reservoir fluid composition variations during enhanced recovery by gas/chemical injection.Different models have been reported in the literature to describe the behaviour of asphaltene deposition using different approaches
The main objective in this paper is to address asphaltene precipitation for oil containing methane and propane due to CO2 flooding at different miscibility conditions
Mixture of crude oil and heptane was shaken for at least two times a day and left for two days to reach equilibrium conditions, and the solution was centrifuged and filtered through a 0.22 micrometre filter and dried for 1 day using a vacuum at room temperature. 0.25 g asphaltene was dissolved in toluene (22 ml) and mixed with 0.01 M stearic acid (CH3(CH2)16CO2H) dissolved in n-decane (42 ml) and filtered for chalk cores, and 0.01 M N, N-dimethyldodecylamine (CH3(CH2)11N(CH3)2) dissolved in n-decane (42 ml) and after filtration is used for sandstone cores
Summary
Carbone dioxide flooding in Enhanced Oil Recovery (EOR) processes has been encouraging; it may result to asphaltene deposition which it turns affect reservoir rock and fluid properties (Moritis, 2006; Chukwudeme & Hamouda, 2009; Hamouda et al, 2008; Idem & Ibrahim, 2002; Simon et al, 1978; De Boer et al, 1995; Burke et al, 1990; Haskett & Tartera, 1965). Haskett and Tartera (1965) reported that crude oils with low asphaltene percentage could experience asphaltene precipitation/deposition due to pressure reduction in early stage recovery, as well as reservoir fluid composition variations during enhanced recovery by gas/chemical injection.Different models have been reported in the literature to describe the behaviour of asphaltene deposition using different approaches. Haskett and Tartera (1965) reported that crude oils with low asphaltene percentage could experience asphaltene precipitation/deposition due to pressure reduction in early stage recovery, as well as reservoir fluid composition variations during enhanced recovery by gas/chemical injection. Hirschberg (1984) described a method based on solubility model using the Flory-Huggins theory with thermodynamic model considering temperature and pressure effects on asphaltene precipitation. Nghiem (1999) documented a thermodynamic solid model to see the dynamic description of asphaltene precipitation/deposited using a compositional simulator during miscible CO2 injection. Gonzalez et al (2008) demonstrated that CO2 can be an inhibitor or a promoter of asphaltene precipitation depending on temperature, pressure, and composition studied.
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