Oil recovery performance and permeability reduction mechanisms in miscible CO2 water-alternative-gas (WAG) injection after continuous CO2 injection: An experimental investigation and modeling approach

Wang, Zhilin; Yang, Shenglai; Lu, Hao; Yang, Mengshi; Li, Lvwei; Song, Yang

doi:10.1016/j.petrol.2016.11.003

Cited by 35 publications

(48 citation statements)

References 38 publications

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“…After the core flooding experiment was completed, the cores were cleaned twice by using n-heptane and toluene plus methanol, respectively. Asphaltene is soluble in solvents but not in alkanes (Wang et al, 2017). Consequently, the cores were first cleaned by using n-heptane.…”

Section: Methodsmentioning

confidence: 99%

“…Precipitation of insoluble metal carbonates and the release of clay particles caused by CO2-brine-rock interactions are also nonnegligible factors, which may lead to changes in the petrophysical properties of the reservoir rocks, and which are exhibited as formation damage . In addition, changes in the rocks' petrophysical properties due to asphaltene precipitation and CO2-brine-rock interaction are exacerbated by heterogeneity, the choice of the CO2 injection schemes, as well as the pore-throat microstructure (Wang et al, 2017;Zou et al, 2018). .…”

Section: Introductionmentioning

confidence: 99%

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Oil production and reservoir damage during miscible CO₂ injection

2020

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The blockage and alteration of wettability in reservoirs caused by asphaltene deposits are problems that contribute to poor oil recovery performance during carbon dioxide (CO2) injection. Oil production and reservoir damage are both controlled by macroscopic interlayer heterogeneity and microscopic pore-throat structure and may be optimized by the choice of flooding method. In this work, the residual oil distribution and the permeability decline caused by organic and inorganic precipitation after miscible CO2 flooding and water-alternating-CO2 (CO2-WAG) flooding have been studied by carrying out core-flooding experiments on a model heterogeneous three-layer reservoir. For CO2, flooding experimental results indicate that the low-permeability layers retain a large oil production potential even in the late stages of production, while the permeability decline due to formation damage is larger in the high-permeability layer. We found that CO2-WAG can reduce the influence of heterogeneity on the oil production, but it results in more serious reservoir damage, with permeability decline caused by CO2–brine–rock interactions becoming significant. In addition, miscible CO2 flooding has been carried out for rocks with similar permeabilities but different wettabilities and different pore-throat microstructures in order to study the effects of wettability and pore-throat microstructure on formation damage. Reservoir rocks with smaller pore-throat sizes and more heterogeneous pore-throat microstructures were found to be more sensitive to asphaltene precipitation, with corresponding lower oil recovery and greater decreases in permeability. However, it was found that the degree of water wetness for cores with larger, more connected pore-throat microstructures became weaker due to asphaltene precipitation to pore surfaces. Decreasing the degree of water wetness was found to be exacerbated by increases in the sweep volume of injected CO2 that arise from cores with larger and better connected pore throats. Erosion of water wetness is a disadvantage for enhanced oil recovery operations as asphaltene precipitation prevention and control measures become more necessary.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Oil production and reservoir damage during miscible CO₂ injection

2020

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“…It could be seen from Figure 9 that the T 2 spectrum measured for the water-saturated core after CO 2 flooding moved a slightly lower position compared to that measured for the initial watersaturated core. Because the petroleum ether was used to clean the cores after CO 2 flooding and asphaltene cannot dissolve in the petroleum ether [12]. The reduced amplitude of the T 2 spectrum indicated the pores were clogged due to the asphaltene precipitation and deposition, which could not be saturated with water.…”

Section: The Effect Of Asphaltene Precipitation On Pore Structurementioning

confidence: 99%

“…Cao and Gu [11] demonstrated that less amount of asphaltene remained in the cores in immiscible conditions while more asphaltene precipitation is observed under miscible conditions. Wang et al [12] found that permeability reduction due to asphaltene precipitation mainly occurs in the middle and tail end of the reservoir in the miscible CO 2 Water-Alternating-Gas (WAG) injection after the continuous CO 2 injection through long coreflood experiments. Moreover, the wettability alteration also occurs due to asphaltene precipitation, which has negative influence on the formation.…”

Section: Introductionmentioning

confidence: 99%

Formation damage due to asphaltene precipitation during CO₂ flooding processes with NMR technique

Qian

Yang

Dou

et al. 2019

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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In order to quantitatively evaluate the pore-scale formation damage of tight sandstones caused by asphaltene precipitation during CO2 flooding, the coreflood tests and Nuclear Magnetic Resonance (NMR) relaxometry measurements have been designed and applied. Five CO2 coreflood tests at immiscible, near-miscible and miscible conditions were conducted and the characteristics of the produced oil and gas were analyzed. For each coreflood test, the T2 spectrum of the core sample was measured and compared before and after CO2 flooding to determine the asphaltene precipitation distribution in pores. It is found that, the solubility and extraction effect of the CO2 plays a more dominant role in the CO2-EOR (Enhanced Oil Recovery) process with higher injection pressure. And, more light components are extracted and recovered by the CO2 and more heavy components including asphaltene are left in the core sample. Thus, the severity of formation damage influenced by asphaltene precipitation increases as the injection pressure increases. In comparison to micro and small pores (0.1–10 ms), the asphaltene precipitation has a greater influence on the medium and large pores (10–1000 ms) due to the sufficient interaction between the CO2 and crude oil in the medium and large pores. Furthermore, the asphaltene precipitation not only causes pore clogging, but also induces rock wettability to alter towards oil-wet direction.

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“…Physical property changes in rocks caused by above factors damage the injection capacity of CO 2 and brine, changing the concentrations and types of ions contained in fluids. Due to these interactions, the released fines migrate to the distant reservoir with the flow of fluid, which will cause serious damage to the reservoir and ultimately affect the efficiency of EOR and CO 2 storage [16][17][18][19][20]. On the other hand, the in-situ multiphase flow characteristics in rocks under different CO 2 displacement methods are different, and these also have different effects on physical properties changes.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation on the Effects of CO2 Displacement Methods on Petrophysical Property Changes of Ultra-Low Permeability Sandstone Reservoirs Near Injection Wells

Wang

Yang

Han³

et al. 2019

Energies

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The petrophysical properties of ultra-low permeability sandstone reservoirs near the injection wells change significantly after CO2 injection for enhanced oil recovery (EOR) and CO2 storage, and different CO2 displacement methods have different effects on these changes. In order to provide the basis for selecting a reasonable displacement method to reduce the damage to these high water cut reservoirs near the injection wells during CO2 injection, CO2-formation water alternate (CO2-WAG) flooding and CO2 flooding experiments were carried out on the fully saturated formation water cores of reservoirs with similar physical properties at in-situ reservoir conditions (78 °, 18 MPa), the similarities and differences of the changes in physical properties of the cores before and after flooding were compared and analyzed. The measurement results of the permeability, porosity, nuclear magnetic resonance (NMR) transversal relaxation time (T2) spectrum and scanning electron microscopy (SEM) of the cores show that the decrease of core permeability after CO2 flooding is smaller than that after CO2-WAG flooding, with almost unchanged porosity in both cores. The proportion of large pores decreases while the proportion of medium pores increases, the proportion of small pores remains almost unchanged, the distribution of pore size of the cores concentrates in the middle. The changes in range and amplitude of the pore size distribution in the core after CO2 flooding are less than those after CO2-WAG flooding. After flooding experiments, clay mineral, clastic fines and salt crystals adhere to some large pores or accumulate at throats, blocking the pores. The changes in core physical properties are the results of mineral dissolution and fines migration, and the differences in these changes under the two displacement methods are caused by the differences in three aspects: the degree of CO2-brine-rock interaction, the radius range of pores where fine migration occurs, the power of fine migration.

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Oil recovery performance and permeability reduction mechanisms in miscible CO2 water-alternative-gas (WAG) injection after continuous CO2 injection: An experimental investigation and modeling approach

Cited by 35 publications

References 38 publications

Oil production and reservoir damage during miscible CO₂ injection

Oil production and reservoir damage during miscible CO₂ injection

Formation damage due to asphaltene precipitation during CO₂ flooding processes with NMR technique

Experimental Investigation on the Effects of CO2 Displacement Methods on Petrophysical Property Changes of Ultra-Low Permeability Sandstone Reservoirs Near Injection Wells

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Oil recovery performance and permeability reduction mechanisms in miscible CO2 water-alternative-gas (WAG) injection after continuous CO2 injection: An experimental investigation and modeling approach

Cited by 35 publications

References 38 publications

Oil production and reservoir damage during miscible CO2 injection

Oil production and reservoir damage during miscible CO2 injection

Formation damage due to asphaltene precipitation during CO2 flooding processes with NMR technique

Experimental Investigation on the Effects of CO2 Displacement Methods on Petrophysical Property Changes of Ultra-Low Permeability Sandstone Reservoirs Near Injection Wells

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Oil production and reservoir damage during miscible CO₂ injection

Oil production and reservoir damage during miscible CO₂ injection

Formation damage due to asphaltene precipitation during CO₂ flooding processes with NMR technique