Abstract:CO2 and N2 injection is an effective enhanced oil recovery technology in the oilfield especially for low-permeability and extra low-permeability reservoirs. However, these processes can induce an asphaltene deposition during oil production. Asphaltene-deposition-induced formation damage is a fairly severe problem. Therefore, predicting the likelihood of asphaltene deposition in reservoir conditions is crucial. This paper presents the results of flash separation experiments used to investigate the composition o… Show more
“…Because of the impact of asphaltene aggregation during gas injection, several studies have been conducted focusing on cyclic gas injection in conventional reservoir cores. − Others investigated the stability of asphaltene under carbon dioxide (CO 2 ) gas injection and different factors were studied. − CO 2 can evaporate more hydrocarbon components and condensate at a higher concentration into crude oil than N 2 , resulting in more asphaltene depositions . There have been very little studies employing N 2 gas injection to illustrate the severity of asphaltene deposition and precipitation as well as the factors influencing its stability. − Jamaluddin et al examined the asphaltene stability by contacting various molar concentrations of N 2 with the reservoir fluids and the findings revealed that increasing the concentration of N 2 negatively impacted the instability of asphaltene and increased the quantity of bulk precipitated asphaltene.…”
Cyclic gas injection methods have been shown to improve oil recovery in conventional reservoirs. Even though similar technologies have been used in unconventional reservoirs with some success stories in shale resources, cyclic gas injection enhanced oil recovery (EOR) is still a little-understood subject in boosting oil recovery from unconventional reservoirs. During gas injection, asphaltenes start to deposit and precipitate, which causes pore plugging and reduces oil recovery. Studies of asphaltene deposition challenges during cyclic nitrogen (N 2 ) gas injection and oil production in unconventional reservoirs are yet relatively limited. Therefore, a comprehensive experimental study was conducted using 12 Eagle Ford shale cores (dynamic mode), and filter paper membranes (static mode) were used to evaluate whether miscible and immiscible huff-n-puff (cyclic) N 2 injection increases oil recovery and aggravates asphaltene precipitation. To ensure that miscibility can be examined in cyclic experiments, N 2 minimum miscibility pressure (MMP) was determined using a slim tube technique. The factors studied included the injection pressure, number of cycles, production time, and injection cyclic mode, all conducted at 70 °C. The findings showed that a high asphaltene weight percent was calculated during static experiments (i.e., using filter membranes), and this increase was severe on smaller pore size structures. Dynamic tests (i.e., using shale cores) showed that miscibility increased oil recovery, but a stronger intermediate-wet system was observed when measuring the wettability of cores after N 2 cyclic tests. When starting with shorter soaking times, more oil recovery could be achieved. Oil recovery reduction and asphaltene depositions were observed at later cycles. Microscopy and scanning electron microscopy (SEM) imaging of the Eagle Ford cores showed asphaltene clusters inside the cores after cyclic tests. A mercury porosimeter emphasized the degree of pore plugging after cyclic tests, and the findings revealed a smaller pore size distribution after N 2 tests due to the asphaltene deposition process when compared to cores that had not been pressured. This extensive study focuses on the effects of asphaltene deposition on oil recovery under cyclic N 2 -miscible and immiscible conditions in shale resources.
“…Because of the impact of asphaltene aggregation during gas injection, several studies have been conducted focusing on cyclic gas injection in conventional reservoir cores. − Others investigated the stability of asphaltene under carbon dioxide (CO 2 ) gas injection and different factors were studied. − CO 2 can evaporate more hydrocarbon components and condensate at a higher concentration into crude oil than N 2 , resulting in more asphaltene depositions . There have been very little studies employing N 2 gas injection to illustrate the severity of asphaltene deposition and precipitation as well as the factors influencing its stability. − Jamaluddin et al examined the asphaltene stability by contacting various molar concentrations of N 2 with the reservoir fluids and the findings revealed that increasing the concentration of N 2 negatively impacted the instability of asphaltene and increased the quantity of bulk precipitated asphaltene.…”
Cyclic gas injection methods have been shown to improve oil recovery in conventional reservoirs. Even though similar technologies have been used in unconventional reservoirs with some success stories in shale resources, cyclic gas injection enhanced oil recovery (EOR) is still a little-understood subject in boosting oil recovery from unconventional reservoirs. During gas injection, asphaltenes start to deposit and precipitate, which causes pore plugging and reduces oil recovery. Studies of asphaltene deposition challenges during cyclic nitrogen (N 2 ) gas injection and oil production in unconventional reservoirs are yet relatively limited. Therefore, a comprehensive experimental study was conducted using 12 Eagle Ford shale cores (dynamic mode), and filter paper membranes (static mode) were used to evaluate whether miscible and immiscible huff-n-puff (cyclic) N 2 injection increases oil recovery and aggravates asphaltene precipitation. To ensure that miscibility can be examined in cyclic experiments, N 2 minimum miscibility pressure (MMP) was determined using a slim tube technique. The factors studied included the injection pressure, number of cycles, production time, and injection cyclic mode, all conducted at 70 °C. The findings showed that a high asphaltene weight percent was calculated during static experiments (i.e., using filter membranes), and this increase was severe on smaller pore size structures. Dynamic tests (i.e., using shale cores) showed that miscibility increased oil recovery, but a stronger intermediate-wet system was observed when measuring the wettability of cores after N 2 cyclic tests. When starting with shorter soaking times, more oil recovery could be achieved. Oil recovery reduction and asphaltene depositions were observed at later cycles. Microscopy and scanning electron microscopy (SEM) imaging of the Eagle Ford cores showed asphaltene clusters inside the cores after cyclic tests. A mercury porosimeter emphasized the degree of pore plugging after cyclic tests, and the findings revealed a smaller pore size distribution after N 2 tests due to the asphaltene deposition process when compared to cores that had not been pressured. This extensive study focuses on the effects of asphaltene deposition on oil recovery under cyclic N 2 -miscible and immiscible conditions in shale resources.
“…It indicates that the extraction caused by methane contact is not strong. Compared to CO 2 injection-caused composition change, , the composition change-related asphaltene precipitation is not the primary mechanism of the crude oil used in this work. Moradi et al proved that methane shows stronger ability to induce asphaltene precipitation in crude oil than N 2 at the same mole fraction.…”
A unique experiment design is proposed to study the asphaltene
precipitation caused by multiple contact processes during gas injection.
The newly proposed experiment quantified the asphaltene precipitation
at different methane contact steps. Twenty times methane contacts
and corresponding asphaltene precipitation states are measured using
a light scattering setup under reservoir condition. The amount of
the asphaltene precipitation, the composition changes, and the physical
properties changes are measured for the 20 times methane contacts.
After verifying the asphaltene precipitation in the static experiments,
the formation damage caused by the asphaltene precipitation is studied
by core flooding tests for three different permeability cases. We
found that the primary asphaltene precipitation mechanism in the multiple
contact process during methane injection is not the composition change
caused by methane extraction. The methane-induced asphaltene stability
loss during the multiple contact process is vital. The size and the
structure of asphaltene precipitation particles in the crude oil change
with the methane contacts. We found that the mechanism of permeability
reduction caused by asphaltene precipitation is different depending
on the porous media pore throat size and the asphaltene precipitation
particle size. Under our experimental condition, the asphaltene precipitation
acts as a conformance control method, leading to well-distance optimization
considerations in field applications.
“…It is corresponded to the weak solubility of N 2 in crude oil due to the weak mass transfer capacity. It is caused to decrease the oil recovery factor which was discussed in previous literature 15 . Figure 4 Comparison of foams injection with CO 2 and N 2 .…”
Development of tight formations would be one of the main priority for petroleum industries due to the enormous demand to the fossil fuels in various industries. In this paper, we provided a set of experiments on the generated foams by carbon dioxide (CO2) and nitrogen (N2), cyclic CO2 injection, water alternating gas injection (WAG), active carbonated water injection (coupling surfactant effects and carbonated water (CW)), and introducing the impact of active carbonated water alternating gas injection (combination of WAG and CW injection) after waterflooding. Carbon dioxide is more feasible than nitrogen, it can be mobilize more in the pore throats and provided higher oil recovery factor. Generated foam with CO2 has increased oil recovery factor about 32% while it’s about 28% for generated foam by N2. Moreover, according to the results of this study, the maximum oil recovery factor for active carbonated water alternating gas injection, active carbonated water injection, and water alternating gas injection measured 74%, 65%, and 48% respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
