Pore-Scale Investigation of Phase Distribution and Residual-Oil Development During Secondary and Tertiary Solvent Injection

2014 ◽  
Vol 18 (01) ◽  
pp. 39-52 ◽  
Author(s):  
Yousef Hamedi Shokrlu ◽  
Tayfun Babadagli

Summary Flow of three phases, of which one is miscible with another, in porous media may commonly be encountered during enhanced-oil-recovery (EOR) applications in oil reservoirs. Typical examples include solvent (miscible-gas) injection alternated with water and coinjection or alternate injection of steam (or hot water) and solvent in heavy-oil/bitumen reservoirs. Oil, water, and solvent flow together under immiscible (water/oil and water/solvent) and miscible (oil/solvent) conditions at the same time, and the distribution of phases and removal of residual oil in those types of processes depend on many parameters. This paper reports microscale experimental investigations on this complex flow process and provides an extensive parametric analysis on the microscopic displacement efficiency of oil recovery using miscible solvent. For this purpose, micromodels created by use of a replica of sandstones were used. Waterflood residual-oil displacement requires contact of the injected solvent with the blocked oil. The efficiency of this process depends on several parameters, including matrix wettability, oil viscosity, initial water saturation, and reservoir heterogeneity. On the other hand, the sequence of injection of solvent and water is considered as another parameter by which oil recovery can be affected significantly. The results of the micromodel-visualization experiments showed that injection of solvent before the introduction of any water to the reservoir can increase the recovery factor significantly. Existence of the water phase in the reservoir creates capillary barriers that prevent oil/solvent contact. The matrix wettability and oil viscosity were observed to be critically important to the amount of oil recovery.

2021 ◽  
Author(s):  
Randy Agra Pratama ◽  
Tayfun Babadagli

Abstract Our previous research, honoring interfacial properties, revealed that the wettability state is predominantly caused by phase change—transforming liquid phase to steam phase—with the potential to affect the recovery performance of heavy-oil. Mainly, the system was able to maintain its water-wetness in the liquid (hot-water) phase but attained a completely and irrevocably oil-wet state after the steam injection process. Although a more favorable water-wetness was presented at the hot-water condition, the heavy-oil recovery process was challenging due to the mobility contrast between heavy-oil and water. Correspondingly, we substantiated that the use of thermally stable chemicals, including alkalis, ionic liquids, solvents, and nanofluids, could propitiously restore the irreversible wettability. Phase distribution/residual oil behavior in porous media through micromodel study is essential to validate the effect of wettability on heavy-oil recovery. Two types of heavy-oils (450 cP and 111,600 cP at 25oC) were used in glass bead micromodels at steam temperatures up to 200oC. Initially, the glass bead micromodels were saturated with synthesized formation water and then displaced by heavy-oils. This process was done to exemplify the original fluid saturation in the reservoirs. In investigating the phase change effect on residual oil saturation in porous media, hot-water was injected continuously into the micromodel (3 pore volumes injected or PVI). The process was then followed by steam injection generated by escalating the temperature to steam temperature and maintaining a pressure lower than saturation pressure. Subsequently, the previously selected chemical additives were injected into the micromodel as a tertiary recovery application to further evaluate their performance in improving the wettability, residual oil, and heavy-oil recovery at both hot-water and steam conditions. We observed that phase change—in addition to the capillary forces—was substantial in affecting both the phase distribution/residual oil in the porous media and wettability state. A more oil-wet state was evidenced in the steam case rather than in the liquid (hot-water) case. Despite the conditions, auspicious wettability alteration was achievable with thermally stable surfactants, nanofluids, water-soluble solvent (DME), and switchable-hydrophilicity tertiary amines (SHTA)—improving the capillary number. The residual oil in the porous media yielded after injections could be favorably improved post-chemicals injection; for example, in the case of DME. This favorable improvement was also confirmed by the contact angle and surface tension measurements in the heavy-oil/quartz/steam system. Additionally, more than 80% of the remaining oil was recovered after adding this chemical to steam. Analyses of wettability alteration and phase distribution/residual oil in the porous media through micromodel visualization on thermal applications present valuable perspectives in the phase entrapment mechanism and the performance of heavy-oil recovery. This research also provides evidence and validations for tertiary recovery beneficial to mature fields under steam applications.


1971 ◽  
Vol 11 (04) ◽  
pp. 342-350 ◽  
Author(s):  
Abbas A. Alikhan ◽  
S.M. Farouq Ali

Abstract An experimented study was conducted of the recovery of oil from as porous medium overlain and underlain by heat-conducting formations and containing a residual oil or connate water saturation by injection of a small slug of a light hydrocarbon followed by 1/2 PV of hot water driven by a conventional waterflood. The fluid production histories and the temperature distribution obtained showed that a light hydrocarbon sag injected ahead of a hot water slug leads to a considerable increase in oil recovery. The net oil recovery was found to depend on the original oil viscosity, hydrocarbon slug viscosity, and the injection rate. The process was more effective in a previously waterflooded core rather than in one containing connate water. The over-all ratio of the total hydrocarbon produced to the hydrocarbon injected ranged from 1.10 to 3.96, the variation corresponding to the viscosity of the hydrocarbon slug employed. Introduction Numerous methods have been proposed for recovering oil from previously waterflooded porous media. Some methods involve the application of heat in one form or another, while others utilize miscible displacement processes. The proposed method involves a combination of the two, employing a small hydrocarbon slug followed by a slug of hot water, which is driven by a conventional waterflood. An attempt was made to investigate the conditions (residual oil saturation, viscosity, etc.) under which such a method would yield a sizable oil recovery. Use of a solvent dug followed by at heat-carrying agent was earlier considered by Pirela and Farouq Ali. The process was designed to take advantage of the improved ternary-phase equilibrium behavior at elevated temperatures in the alcohol slug process. The experimental runs were conducted under isothermal conditions. In another study, Avendano found that injection of a light crude oil into a core containing a highly viscous oil prior to steam injection led to a large improvement in oil recovery. A number of investigators have studied the effect of water-driven hydrocarbon slugs on oil recovery from waterflooded porous media. Csaszar and Holm employed slugs of propane in waterflood cores containing oils with viscosities ranging from 3 to 9 cp. The volume of the oil recovered was 2 to 3 times the propane injected, the efficiency of the process depending on the amount of mobile oil process depending on the amount of mobile oil near the point of injection and the viscosity of the in-place oil. Wiesenthal used gasoline as an intermediate slug when waterflooding cores containing oils having viscosities of 1.28 to 324 cp. He found that the process was effective in waterflooded porous media, especially in the case of viscous oils. Fitzgerald conducted similar experiments using gasoline and arrived at more or less the same conclusions. The process under consideration involves a combination of miscible displacement and hot waterflooding, both of which have been amply discussed in the literature. A comprehensive survey of miscible displacement has been presented by Perkins and Johnston, while a description of hot Perkins and Johnston, while a description of hot waterflooding may be found elsewhere. In the following, only the most important features of the two processes operating in the combination process will be considered. EXPERIMENTAL APPARATUS AND PROCEDURE PROCEDURE APPARATUS The porous medium used in the present investigation consisted of a steel cube 4 ft in length with a rectangular cross-section and inside dimensions of 1.5 × 3.5 in., packed with 130-mesh glass beads. The resulting core had a porosity of 39.95 percent (PV = 1,690 cc) and permeability of 7 darcies. The core was provided with 15 connections on one side for thermocouples and 5 connections on the other side for transducers. SPEJ P. 342


2021 ◽  
Author(s):  
Songyan Li ◽  
Rui Han ◽  
Qun Wang ◽  
Xuemei Wei

Abstract Steam-assisted gravity drainage (SAGD) is an important method of heavy oil production, and the solvent vapor extraction (VAPEX) process is also an economically feasible, technically reliable, and environmentally friendly in situ heavy oil recovery method. In this paper, a microscopic visual flooding device was used to conduct seven groups of visual flooding experiments, including hot water, steam, liquid solvent and vapor solvent, at different temperatures. It can be directly observed that the residual oil in the hot water swept area is generally distributed in “spots”, “strips” and “clusters” of varying sizes. The residual oil after steam flooding generally has a “cluster” distribution, the residual oil after liquid solvent flooding has a “film” distribution, and there is only a little “spot” residual oil distributed after solvent vapor flooding. Additionally, we found that the sweep efficiency and displacement efficiency of hot water, steam and solvent increase with increasing temperature, and the sweep efficiency of hot water is higher than that of steam and liquid solvent. Vapor solvent has the greatest recovery factor, reaching approximately 90%. The experimental results hint at the future development trend of solvent injection and support the foundation of more general applications pertaining to the sustainable production of unconventional petroleum resources.


SPE Journal ◽  
2018 ◽  
Vol 24 (01) ◽  
pp. 129-139 ◽  
Author(s):  
J. L. Juárez-Morejón ◽  
H.. Bertin ◽  
A.. Omari ◽  
G.. Hamon ◽  
C.. Cottin ◽  
...  

Summary An experimental study of polymer flooding is presented here, focusing on the influence of initial core wettability and flood maturity (volume of water injected before polymer injection) on final oil recovery. Experiments were performed using homogeneous Bentheimer Sandstone samples of similar properties. The cores were oilflooded using mineral oil for water-wet conditions and crude oil (after an aging period) for intermediate-wet conditions; the viscosity ratio between oil and polymer was kept constant in all experiments. Polymer, which is a partially hydrolyzed polyacrylamide (HPAM), was used at a concentration of 2,500 ppm in a moderate-salinity brine. The polymer solution was injected in the core at different waterflood-maturity times [breakthrough (BT) and 0, 1, 1.75, 2.5, 4, and 6.5 pore volumes (PV)]. Coreflood results show that the maturity of polymer injection plays an important role in final oil recovery, regardless of wettability. The waterflood-maturity time 0 PV (polymer injection without initial waterflooding) leads to the best sweep efficiency, whereas final oil production decreases when the polymer-flood maturity is high (late polymer injection after waterflooding). A difference of 15% in recovery is observed between early polymer flooding (0 PV) and late maturity (6.5 PV). Concerning the effect of wettability, the recovery factor obtained with water-wet cores is always lower (from 10 to 20%, depending on maturity) than the values obtained with intermediate-wet cores, raising the importance of correctly restoring core wettability to obtain representative values of polymer incremental recovery. The influence of wettability can be explained by the oil-phase distribution at the pore scale. Considering that the waterflooding period leads to different values of the oil saturation at which polymer flooding starts, we measured the core dispersivity using a tracer method at different states. The two-phase dispersivity decreases when water saturation increases, which is favorable for polymer sweep. This study shows that in addition to wettability, the maturity of polymer flooding plays a dominant role in oil-displacement efficiency. Final recovery is correlated to the dispersion value at which polymer flooding starts. The highest oil recovery is obtained when the polymer is injected early.


1982 ◽  
Vol 22 (05) ◽  
pp. 647-657 ◽  
Author(s):  
J.P. Batycky ◽  
B.B. Maini ◽  
D.B. Fisher

Abstract Miscible gas displacement data obtained from full-diameter carbonate reservoir cores have been fitted to a modified miscible flow dispersion-capacitance model. Starting with earlier approaches, we have synthesized an algorithm that provides rapid and accurate determination of the three parameters included in the model: the dispersion coefficient, the flowing fraction of displaceable volume, and the rate constant for mass transfer between flowing and stagnant volumes. Quality of fit is verified with a finite-difference simulation. The dependencies of the three parameters have been evaluated as functions of the displacement velocity and of the water saturation within four carbonate cores composed of various amounts of matrix, vug, and fracture porosity. Numerical simulation of a composite core made by stacking three of the individual cores has been compared with the experimental data. For comparison, an analysis of Berea sandstone gas displacement also has been provided. Although the sandstone displays a minor dependence of gas recovery on water saturation, we found that the carbonate cores are strongly affected by water content. Such behavior would not be measurable if small carbonate samples that can reflect only matrix properties were used. This study therefore represents a significant assessment of the dispersion-capacitance model for carbonate cores and its ability to reflect changes in pore interconnectivity that accompany water saturation alteration. Introduction Miscible displacement processes are used widely in various aspects of oil recovery. A solvent slug injected into a reservoir can be used to displace miscibly either oil or gas. The necessary slug size is determined by the rate at which deterioration can occur as the slug is Another commonly used miscible process involves addition of a small slug within the injected fluids or gases to determine the nature and extent of inter well communication. The quantity of tracer material used is dictated by analytical detection capabilities and by an understanding of the miscible displacement properties of the reservoir. We can develop such understanding by performing one-dimensional (1D) step-change miscible displacement experiments within the laboratory with selected reservoir core material. The effluent profiles derived from the experiments then are fitted to a suitable mathematical model to express the behavior of each rock type through the use of a relatively small number of parameters. This paper illustrates the efficient application of the three-parameter, dispersion-capacitance model. Its application previously has been limited to use with small homogeneous plugs normally composed of intergranular and intencrystalline porosity, and its suitability for use with cores displaying macroscopic heterogeneity has been questioned. Consequently, in addition to illustrating its use with a homogeneous sandstone, we fit data derived from previously reported full-diameter carbonate cores. As noted earlier, these cores were heterogeneous, and each of them displayed different dual or multiple types of porosity characteristic of vugular and fractured carbonate rocks. Dispersion-Capacitance Model The displacement efficiency of one fluid by a second immiscible fluid within a porous medium depends on the complexity of rock and fluid properties. SPEJ P. 647^


2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Zhanxi Pang ◽  
Peng Qi ◽  
Fengyi Zhang ◽  
Taotao Ge ◽  
Huiqing Liu

Heavy oil is an important hydrocarbon resource that plays a great role in petroleum supply for the world. Co-injection of steam and flue gas can be used to develop deep heavy oil reservoirs. In this paper, a series of gas dissolution experiments were implemented to analyze the properties variation of heavy oil. Then, sand-pack flooding experiments were carried out to optimize injection temperature and injection volume of this mixture. Finally, three-dimensional (3D) flooding experiments were completed to analyze the sweep efficiency and the oil recovery factor of flue gas + steam flooding. The role in enhanced oil recovery (EOR) mechanisms was summarized according to the experimental results. The results show that the dissolution of flue gas in heavy oil can largely reduce oil viscosity and its displacement efficiency is obviously higher than conventional steam injection. Flue gas gradually gathers at the top to displace remaining oil and to decrease heat loss of the reservoir top. The ultimate recovery is 49.49% that is 7.95% higher than steam flooding.


2012 ◽  
Vol 594-597 ◽  
pp. 2451-2454
Author(s):  
Feng Lan Zhao ◽  
Ji Rui Hou ◽  
Shi Jun Huang

CO2is inclined to dissolve in crude oil in the reservoir condition and accordingly bring the changes in the crude oil composition, which will induce asphaltene deposition and following formation damage. In this paper, core flooding device is applied to study the effect of asphaltene deposition on flooding efficiency. From the flooding results, dissolution of CO2into oil leads to recovery increase because of crude oil viscosity reduction. But precipitated asphaltene particles may plug the pores and throats, which will make the flooding effects worse. Under the same experimental condition and with equivalent crude oil viscosity, the recovery of oil with higher proportion of precipitated asphaltene was relatively lower during the CO2flooding, so the asphltene precipitation would affect CO2displacement efficiSubscript textency and total oil recovery to some extent. Combination of static diffusion and dynamic oil flooding would provide basic parameters for further study of the CO2flooding mechanism and theoretical evidence for design of CO2flooding programs and forecasting of asphaltene deposition.


Author(s):  
Fengqi Tan ◽  
Changfu Xu ◽  
Yuliang Zhang ◽  
Gang Luo ◽  
Yukun Chen ◽  
...  

The special sedimentary environments of conglomerate reservoir lead to pore structure characteristics of complex modal, and the reservoir seepage system is mainly in the “sparse reticular-non reticular” flow pattern. As a result, the study on microscopic seepage mechanism of water flooding and polymer flooding and their differences becomes the complex part and key to enhance oil recovery. In this paper, the actual core samples from conglomerate reservoir in Karamay oilfield are selected as research objects to explore microscopic seepage mechanisms of water flooding and polymer flooding for hydrophilic rock as well as lipophilic rock by applying the Computed Tomography (CT) scanning technology. After that, the final oil recovery models of conglomerate reservoir are established in two displacement methods based on the influence analysis of oil displacement efficiency. Experimental results show that the seepage mechanisms of water flooding and polymer flooding for hydrophilic rock are all mainly “crawling” displacement along the rock surface while the weak lipophilic rocks are all mainly “inrushing” displacement along pore central. Due to the different seepage mechanisms among the water flooding and the polymer flooding, the residual oil remains in hydrophilic rock after water flooding process is mainly distributed in fine throats and pore interchange. These residual oil are cut into small droplets under the influence of polymer solution with stronger shearing drag effect. Then, those small droplets pass well through narrow throats and move forward along with the polymer solution flow, which makes enhancing oil recovery to be possible. The residual oil in weak lipophilic rock after water flooding mainly distributed on the rock particle surface and formed oil film and fine pore-throat. The polymer solution with stronger shear stress makes these oil films to carry away from particle surface in two ways such as bridge connection and forming oil silk. Because of the essential attributes differences between polymer solution and injection water solution, the impact of Complex Modal Pore Structure (CMPS) on the polymer solution displacement and seepage is much smaller than on water flooding solution. Therefore, for the two types of conglomerate rocks with different wettability, the pore structure is the main controlling factor of water flooding efficiency, while reservoir properties oil saturation, and other factors have smaller influence on flooding efficiency although the polymer flooding efficiency has a good correlation with remaining oil saturation after water flooding. Based on the analysis on oil displacement efficiency factors, the parameters of water flooding index and remaining oil saturation after water flooding are used to establish respectively calculation models of oil recovery in water flooding stage and polymer flooding stage for conglomerate reservoir. These models are able to calculate the oil recovery values of this area controlled by single well control, and further to determine the oil recovery of whole reservoir in different displacement stages by leveraging interpolation simulation methods, thereby providing more accurate geological parameters for the fine design of displacement oil program.


2018 ◽  
Vol 38 ◽  
pp. 01054
Author(s):  
Guan Wang ◽  
Rui Wang ◽  
Yaxiu Fu ◽  
Lisha Duan ◽  
Xizhi Yuan ◽  
...  

Mengulin sandstone reservoir in Huabei oilfield is low- temperature heavy oil reservoir. Recently, it is at later stage of waterflooding development. The producing degree of water flooding is poor, and it is difficult to keep yield stable. To improve oilfield development effect, according to the characteristics of reservoir geology, microbial enhanced oil recovery to improve oil displacement efficiency is researched. 2 microbial strains suitable for the reservoir conditions were screened indoor. The growth characteristics of strains, compatibility and function mechanism with crude oil were studied. Results show that the screened strains have very strong ability to utilize petroleum hydrocarbon to grow and metabolize, can achieve the purpose of reducing oil viscosity, and can also produce biological molecules with high surface activity to reduce the oil-water interfacial tension. 9 oil wells had been chosen to carry on the pilot test of microbial stimulation, of which 7 wells became effective with better experiment results. The measures effective rate is 77.8%, the increased oil is 1,093.5 tons and the valid is up to 190 days.


Open Physics ◽  
2016 ◽  
Vol 14 (1) ◽  
pp. 703-713 ◽  
Author(s):  
Hao Yongmao ◽  
Lu Mingjing ◽  
Dong Chengshun ◽  
Jia Jianpeng ◽  
Su Yuliang ◽  
...  

AbstractAimed at enhancing the oil recovery of tight reservoirs, the mechanism of hot water flooding was studied in this paper. Experiments were conducted to investigate the influence of hot water injection on oil properties, and the interaction between rock and fluid, petrophysical property of the reservoirs. Results show that with the injected water temperature increasing, the oil/water viscosity ratio falls slightly in a tight reservoir which has little effect on oil recovery. Further it shows that the volume factor of oil increases significantly which can increase the formation energy and thus raise the formation pressure. At the same time, oil/water interfacial tension decreases slightly which has a positive effect on production though the reduction is not obvious. Meanwhile, the irreducible water saturation and the residual oil saturation are both reduced, the common percolation area of two phases is widened and the general shape of the curve improves. The threshold pressure gradient that crude oil starts to flow also decreases. It relates the power function to the temperature, which means it will be easier for oil production and water injection. Further the pore characteristics of reservoir rocks improves which leads to better water displacement. Based on the experimental results and influence of temperature on different aspects of hot water injection, the flow velocity expression of two-phase of oil and water after hot water injection in tight reservoirs is obtained.


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