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Gary A. Pope - One of the best experts on this subject based on the ideXlab platform.
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New Method To Reduce Residual Oil Saturation by Polymer Flooding
SPE Journal, 2018Co-Authors: Mehmet Z. Erincik, Matthew T Balhoff, Gary A. PopeAbstract:Summary Six coreflood experiments were conducted to investigate the effect of hydrolyzed-polyacrylamide (HPAM) polymer solutions on the Residual Oil Saturation (ROS) in Bentheimer-sandstone cores. All six cores were first saturated with brine and then flooded in the following sequence: Oil to zero water cut, brine to zero Oil cut, glycerin solution to zero Oil cut, polymer in low-salinity brine to zero Oil cut, and finally polymer in high-salinity brine to zero Oil cut. The first polymer solution had approximately the same viscosity as the glycerin solution. The first polymer flood was designed to maximize the effect of viscoelasticity on the ROS by flooding the cores at a high Deborah number (NDe), and, as expected, resulted in a lower ROS. The second polymer flood in high-salinity brine had approximately the same viscosity, but a much lower relaxation time, and the flood had a much lower NDe. Unexpectedly, there was a further substantial reduction in ROS during the second polymer flood. The lowest ROS after the second polymer flood was only 0.07. This is a truly remarkable result, considering that there was no reduction in interfacial tension (IFT), the capillary numbers were maintained below the critical capillary number for Bentheimer sandstone, and the viscosities of both polymer solutions were equal to or less than that of the glycerin solution.
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New Method to Reduce Residual Oil Saturation by Polymer Flooding
Day 2 Tue October 10 2017, 2017Co-Authors: Mehmet Z. Erincik, Matthew T Balhoff, Gary A. PopeAbstract:Abstract Six coreflood experiments were conducted to investigate the effect of hydrolyzed polyacrylamide (HPAM) polymer solutions on the Residual Oil Saturation in Bentheimer sandstone cores. All six cores were first saturated with brine and then flooded in the following sequence: Oil to zero water cut, brine to zero Oil cut, glycerin solution to zero Oil cut, polymer in low-salinity brine to zero Oil cut and finally polymer in high-salinity brine to zero Oil cut. The first polymer solution had about the same viscosity as the glycerin solution. The first polymer flood was designed to maximize the effect of viscoelasticity on the Residual Oil Saturation by flooding the cores at a high Deborah number, and as expected resulted in a lower Residual Oil Saturation. The second polymer flood in high-salinity brine had about the same viscosity, but a much lower relaxation time and the flood had a much lower Deborah number. Unexpectedly, there was a further substantial reduction in Residual Oil Saturation during the second polymer flood. The lowest Residual Oil Saturation after the second polymer flood was only 0.07. This is a truly remarkable result considering there was no reduction in interfacial tension, the capillary numbers were maintained below the critical capillary number for Bentheimer sandstone, and the viscosities of both polymer solutions were equal to or less than the glycerin solution.
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Experimental Investigation of the Effect of Polymers on Residual Oil Saturation
SPE Journal, 2017Co-Authors: Heesong Koh, Vincent B. Lee, Gary A. PopeAbstract:Summary Polymer flooding is a widely used commercial process with a low cost per barrel of produced Oil, and hydrolyzed polyacrylamide (HPAM) polymers are the most widely used type of polymer. The objective of this research was to better understand and predict the behavior of HPAM polymers and their effect on Residual Oil Saturation (ROS), to improve the capability of optimizing field design and performance. The corefloods were performed under typical field conditions of low pressure gradients and low capillary numbers. The polymer floods of the viscous Oils recovered much more Oil than the waterfloods, with up to 24% lower Oil Saturation after the polymer flood than after the waterflood. The experimental data are in good agreement with the fractional-flow analysis by use of the assumptions that the true ROSs and endpoint relative permeabilities are the same for both water and polymer. This suggests that, for more-viscous Oils, the Oil Saturation at the end of a waterflood (i.e., at greater than 99% water cut) is better described as “remaining” Oil Saturation rather than the true “Residual” Oil Saturation. This was true for all the corefloods, regardless of the core permeability and without the need for assuming a permeability-reduction factor in the fractional-flow analysis.
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Experimental Investigation of the Effect of Polymers on Residual Oil Saturation
All Days, 2016Co-Authors: Heesong Koh, Vincent Lee, Gary A. PopeAbstract:Abstract Polymer flooding is a widely used commercial process with a low cost per barrel of produced Oil, For this application, hydrolyzed polyacrylamide (HPAM) polymers are the most widely used type of polymer. In an era of low cost Oil, it is becoming even more essential to optimize the polymer flooding design under realistic reservoir conditions. The objective of this research was to better understand and predict the behavior of HPAM polymers and their effect on Residual Oil Saturation, in order to improve the capability of optimizing field design and performance. The corefloods were performed under typical field conditions of low pressure gradients and low capillary numbers. The polymer floods of the viscous Oils recovered much more Oil than the water floods, with up to 24% lower Oil Saturation after the polymer flood than the water flood. The experimental data are in good agreement with the fractional flow analysis using the assumptions that the true Residual Oil Saturations and end point relative permeabilities are the same for both water and polymer. This suggests that for more viscous Oils, the Oil Saturation at the end of water flood (i.e. at greater than 99% water cut) is better described as ‘emaining’ Oil Saturation rather than the true ‘esidual’ Oil Saturation. This was true for all of the corefloods regardless of the core permeability and without the need for assuming a permeability reduction factor in the fractional flow analysis.
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Mechanistic Simulation of Residual Oil Saturation in Viscoelastic Polymer Floods
Day 2 Tue March 22 2016, 2016Co-Authors: Mohammad Lotfollahi, Heesong Koh, Mojdeh Delshad, Gary A. PopeAbstract:Abstract Polymer flooding is one of the most widely used enhanced Oil recovery methods due to its good performance in numerous large commercial field projects and its relative simplicity and low cost compared to most other enhance Oil recovery methods. The main mechanism is considered to be improved sweep efficiency, but numerous studies have also reported lower Residual Oil Saturation to polymer than to water. Because the results depend on many variables such as the initial Oil Saturation, rock characteristics and polymer characteristics, such experiments must be performed at reservoir conditions and at controlled capillary numbers and so forth to measure the reduction that applies to field polymer floods. Furthermore, a mechanistic model is needed to scale up the laboratory coreflood results to the field. We implemented and tested the new model for the Residual Oil Saturation in a mechanistic numerical reservoir simulator. The simulation model was used to match the Oil recovery and pressure drop of both secondary and tertiary polymer flood experiments. The results showed a strong correlation between the remaining Oil Saturation and the Deborah number.
B. Harker - One of the best experts on this subject based on the ideXlab platform.
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Interwell Tracer Test To Determine Residual Oil Saturation In A Gas-Saturated Reservoir. Part II: Field Applications
Journal of Canadian Petroleum Technology, 1991Co-Authors: J.s. Tang, B. HarkerAbstract:Abstract This paper entails the implementation and interpretation of the first successful interwell test ever reported in the industry to determine Residual Oil Saturation in a gas-saturated reservoir. Two interwell tests were conducted in Golden Spike to measure the Residual Oil Saturation to gas-flood at two different depths. This method, which involves the comparison of the whole partitioning and non-partitioning tracer curves to derive Residual Oil Saturation values, is an improvement of the original method that compared only the breakthrough times. A chromatographic transformation technique was developed for curve comparison so as to avoid tedious simulation for data interpretation. For layers with different Residual Oil Saturation, the transformation method works only for a pseudo single porosity reservoir with ordered layers, i.e. low Residual Oil Saturation for a high permeability layer. The first test indicated that there were three layers with Residual Oil Saturations of 7%, 15% and 20%. The results from the second test conducted in a lower production interval were masked by the presence of extensive fractures in the production zone. In spite of the interference from the fracture production, the Residual Oil Saturation in some flow channels could still be estimated to be about 12%. Because it is unlikely that the tracers could enter the matrix during the test, the Residual Oil Saturation measured is probably the Oil Saturation in some secondary channels. Sulphur hexafluoride, F13BI (brome-trifluoro-methane) and F12 (dichloro-difluoro-methane) were selected as the tracers from the previous lab tests. The tracers were pre-mixed and injected as a liquid. A Freon phase behavior program was developed to calculate the exact amount of the Freon's injected. Introduction Upon evaluation of various conventional methods, the interwell tracer test(1) has been identified as the most reliable means to determine Residual Oil Saturation in Golden Spike, a low-pressure, low-porosity, gas-saturated carbonate reservoir. The original interwell method disclosed by Cooke(2) in 1971 involved the comparison of the relative breakthrough times of the partitioning and non-partitioning tracers for Residual Oil Saturation calculation. Breakthrough time is not a well-defined quantity, as it is often obscured by dispersion, the detection limit, and most importantly, by the streamline and layer distributions. As a result, the interpretation technique, certainly inadequate, draws criticism(3,4). Consequently, because of the lack of suitable chemicals and interpretation technique, no single test has been tried in the field or, at least, published in the literature. To circumvent the problems anticipated in Cooke's method, our interwell method employed a whole curve comparison to derive a Residual Oil Saturation value at any location on the curve using a simple "landmark" comparison technique. Under ideal conditions, Residual Oil Saturation can be determined by layers. To demonstrate the feasibility of the method, extensive tests were performed in the lab(5). Slim tube displacement results indicated that Residual Oil Saturation could be measured in an accuracy of± 1 % pore volume from the separation of tracers. This paper entails the design, implementation and interpretation of the two field tests conducted in Golden Spike in 1987.
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Interwell Tracer Test To Determine Residual Oil Saturation In A Gas-Saturated Reservoir. Part I: Theory And Design
Journal of Canadian Petroleum Technology, 1991Co-Authors: J.s. Tang, B. HarkerAbstract:Abstract The Residual Oil Saturation to gas-flood is an important parameter to evaluate the potential of the Golden Spike D3 ‘A’ pool as a candidate for enhanced Oil recovery and gas storage. Conventional methods, including logging, sponge coring and single well tracer testing, are not applicable to this low-pressure, low-porosity, gas filled carbonate reservoir. An interwell tracer method which works on the chromatographic separation of tracers with different Henry's law constants was therefore proposed and tested in the lab. Stringent selection criteria based on the detection limit and Henrys law constant were established to screen chemicals for application. According to the criteria, sulphur hexafluoride and halocarbons (Freon), which can be detected in the sub ppm range using a gas chromatograph equipped with an electron capture detector, were selected for this study. Henry's law constants were determined experimentally using a static equilibrium method and a dynamic slim tube displacement method. In the preliminary screening of chemicals for lab testing, the Henry's law constant could be estimated from vapor pressure after correcting for the non-ideal behavior using the regular solution theory. It was demonstrated in the slim tube tests that Residual Oil Saturation could be determined within I pore volume % accuracy from tracer separation using the simple chromagraphic theory. A mixing cell model was also developed to simulate the slim tube test results. This model was also capable of handling dual porosities that are common to carbonates. Introduction The Golden Spike D3 ‘A’ pool(1,2), located 29 km southwest of Edmonton in central Alberta, is a carbonate reservoir. With the on-coming of the Beaufort Sea gas development, Golden Spike is being considered as a candidate for Beaufort gas storage and enhanced Oil recovery. In as much as both projects have substantial economic incentive and are somewhat adversely affected by each other, the two projects need to be carefully evaluated using the best possible data. Residual Oil Saturation to gas-flood is the key parameter for the evaluation of either process. Various conventional methods for Sor determination, such as production history, sponge coring, laboratory gas floods, logging and single-well tracer testing, have been extensively reported and compared in the literature(3,4). Unfortunately, these methods are not satisfactory for low-pressure, low-porosity, gas-filled carbonate reservoirs such as Golden Spike. Therefore, an interwell method(5,6) using Freon's with different vapor pressures was proposed and studied in the lab. The interwell method works on the chromatographic separation of Freon in the reservoir. According to the chromatographic theory, the Freon with the highest Henry's law constant (or K value) or the lowest solubility in Oil is produced first. Thus, by comparing the production profiles of various Freon's, the average Residual Oil Saturation between wells can be determined. Although the principle of the interwell method was disclosed by Cooke(6) in 1971, not a single test has been reported in the literature due to a lack of suitable chemicals and the potential interpretation problems(3). The Golden Spike test is the first attempt ever in the industry to apply the theory to the field.
Rui Feng - One of the best experts on this subject based on the ideXlab platform.
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resistivity tomography with a vertical line current source and its applications to the evaluation of Residual Oil Saturation
Journal of Applied Geophysics, 2011Co-Authors: Rui FengAbstract:The forward and inversion methods of resistivity tomography with a vertical line current source (RTVLCS) were introduced in this paper. The technique was applied to the evaluation of Residual Oil Saturation of the reservoir studied in an old Oil region. The observed water Saturation during the course of the measurement of RTVLCS and subsequent drilling records proved the reliability of our result. However, our model has not included the influence of all factors such as electrical contact resistance between the metal casing and surrounding rocks and of the size of the metal cased well taken as a vertical line current source (VLCS). In addition, RTVLCS was carried out after the well had been in use for many years, while the initial resistivity values used in the inversion were obtained from the resistivity curve logged upon the completion of the well. Therefore, the Residual Oil Saturation obtained by RTVLCS is relative and has not complete consistency with real situations, and can only be used as reference for adjusting a plan for Oil production in the mid- or post-phase of an Oilfield.
Pei-xin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Determination of Residual Oil Saturation in A Carbonate Reservoir
All Days, 2001Co-Authors: Joseph Tang, Pei-xin ZhangAbstract:Abstract Single-well tracer testing has been widely accepted as a standard method for measuring Residual Oil Saturation to waterflood. Residual Oil Saturation is an important parameter in the evaluation of tertiary Oil recovery potential for depleted reservoirs. At an advanced stage of depletion, Leduc, a Canadian carbonate reservoir, has been considered as a candidate for enhanced Oil recovery. As part of the evaluation process, single-well tracer tests were conducted at two watered-out producers to determine Residual Oil Saturation to waterflood. The tracer production profiles were found to be highly skewed with long tails and early arrival times, which are typical for carbonate reservoirs. Two different models, namely a double-porosity model where tracer could distribute between the flowing and non-flowing pores through mass transfer and a single-porosity model where a fictitious water drift rate was assumed in the test zone, were used to interpret the data. It was found that either model could match the data to the same degree of accuracy regardless of the flow mechanisms assumed and the Residual Oil Saturation derived from these two models were 35% and 38% respectively. This demonstrates the robust nature of the test that the non-uniqueness of the match does not affect Residual Oil Saturation determination. The Residual Oil Saturation determined by simple analytical models including mass balance method, peak method and mean retention volume method were all in the range of 34% to 38%, in excellent agreement with the simulation results. As well, the Sorw obtained by the SWTT method compared favorably with those determined by interwell tracing (35%) and sponge coring (33%). Introduction The amount of Oil left in a reservoir after secondary operations is needed to evaluate the potential of enhanced Oil recovery processes. Various conventional methods for Sorw determination, such as production history, laboratory waterflood tests, core analyses, logging, log-injection-log, interwell and single-well tracing tests (SWTT) have been extensively reported and compared1–3 in the literature; each technique offers certain advantages, limitations and different depths of investigation. Of all the methods available to date1,2, SWTT is unique in its large and variable depth of investigation, and relatively free of the near-well bore effect. SWTT is still the most widely accepted method in the industry for measuring Residual Oil Saturation, though an increasing number of interwell tracer testing has been reported recently4,5. Since its invention in 1971, more than 200 SWTT have been run both in sandstone and carbonate reservoirs to determine Residual Oil Saturation to waterflood Sorw.
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Effect of Mobile Oil on Residual Oil Saturation Measurement by Interwell Tracing Method
All Days, 2000Co-Authors: Joseph S. Tang, Pei-xin ZhangAbstract:Abstract Interwell tracing has been recognized as a reliable method for determining Residual Oil Saturation between wells. Sponsored by the United Nations International Atomic Energy Agency, China Institute of Atomic Energy is currently conducting several tests in various China Oil fields to determine Residual Oil Saturation and to delineate reservoir problems. Interwell method assumes tracers contacting immobile Oil in the watered-out zone and the Oil Saturation is calculated from the partitioning tracer propagation rate. In the presence of mobile Oil, the partitioning tracer velocity would increase as it can contact, partition into and move with the flowing Oil. As a result, assuming zero Oil rate would lead to underestimate of Oil Saturation. In an unsteady state displacement where tracers are injected with water into a virgin reservoir, the partitioning tracer will move with Oil at a constant characteristic velocity governed by the partition coefficient. Since tracers are normally injected after the start of waterflood, the injected tracers will lag behind their respective characteristic fronts. The time required for the partitioning tracer to catch up with its characteristic front and the breakthrough time of the tracer in a pseudo 1-D system were theoretically analyzed in this paper. The produced Oil cut, which is dominated by streamline distribution, sweep and layering, is not a definite indicator of mobile Oil in the water zone. The presence of moving Oil and its effect on Oil Saturation measurement can be inferred from the responses of two tracers with different partition coefficients. Introduction Interwell tracer test has been recognized as a reliable method for determining Residual Oil Saturation between wells. The concept of interwell tracer test was first disclosed by Cooke1 in 1970. In this method, a slug of partitioning and non-partitioning tracers is injected into an injector and produced from nearby producers. Partitioning between phases slows down the partitioning tracers in a phenomenon known as chromatographic retardation from which the Residual Oil Saturation can be determined. Oil distribution between wells is derived by matching the tracer production profiles using a 3D finite difference simulator such as UTCHEM8,9 or by a streamline model12,13. Some streamline models have incorporated an automatic matching mechanism to facilitate fast data analysis. To circumvent the technical problems in simulation, a chromatographic transformation method was proposed by Tang2-6 and a moment analysis method by Pope et al.12 to calculate Sor directly by comparing the relative separation of tracers.
K. Kisman - One of the best experts on this subject based on the ideXlab platform.
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Residual Oil Saturation Inside the Steam Chamber During SAGD
Journal of Canadian Petroleum Technology, 2003Co-Authors: E. Walls, C. Palmgren, K. KismanAbstract:Abstract The Oil Saturation inside the steam chamber during steamassisted gravity drainage (SAGD) has an important impact on economics and conservation. However, the SAGD Residual Oil Saturation is difficult to determine and model because it involves long-term thermal effects and three-phase flow. SAGD has been widely studied and piloted, but improved understanding of longterm drainage effects represents a fundamental issue that requires improved understanding. In the first part of the paper, we represent a sensitivity test done on the shapes and the endpoints of the two-phase relative permeability curves. We find that the water relative permeability and Oil relative permeability in the gas-Oil system are the main factors that determine the magnitude and shape of the Oil Saturation curve as a function of time. Secondly, we demonstrate how to adjust the krog relative permeability curve to match a theoretically determined Residual Oil Saturation, which is supported by laboratory data. We propose that, during SAGD, the flow of Oil can be split into two regimes. In the first regime, close to the edge of the steam chamber, Oil drains quickly in a short period of time. In the second regime, Oil drains slowly within the steam chamber for a longer period of time, as it is produced by "film drainage." To capture these flow regimes, the Oil relative permeability curve in the gas-Oil system, krog, is split into two. At higher liquid Saturations, the first flow regime is represented and, at lower liquid Saturations, the second regime is modelled. Thirdly, the krog curve was adjusted so that the decrease in Oil Saturation with respect to time closely matched the theoretical curve while maintaining Oil production rates expected for SAGD. Using this new curve at different pressures, we show that the Residual Oil Saturation increases at lower SAGD operating pressures. Introduction In a steam-assisted gravity drainage (SAGD) process, bitumen drainage occurs mainly along the transition zone, which is the mobile liquid region at the boundary of the steam chamber. Bitumen drainage also continues to occur within the body of the steam chamber over a long period of time, such that the Residual Oil Saturation gradually falls. In this paper, the term Residual Oil Saturation refers to the average remaining Oil Saturation within the steam chamber where the steam chamber includes all grid blocks in a numerical model containing any amount of steam. It is difficult to obtain Residual Oil Saturation data as a function of time in the field so, in this study, we relied on theoretical and laboratory data. We calibrated reservoir simulation results to the theoretical and laboratory data, and then used the simulator to investigate the effects of SAGD operating pressures on the Residual Oil Saturation. Relative Permeability Formulation Multiphase flow in a porous medium can be described using Darcy's Law as follows:
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Residual Oil Saturation Inside the Steam Chamber During SAGD
Canadian International Petroleum Conference, 2001Co-Authors: E. Walls, C. Palmgren, K. KismanAbstract:The Oil Saturation inside the steam chamber during steam-assisted gravity drainage (SAGD) has an important impact on economics and conservation. However, the SAGD Residual Oil Saturation is difficult to determine and model because it involves long-term thermal effects and three-phase flow. SAGD has been widely studied and piloted, but improved understanding of long-term drainage effects represents a fundamental issue that requires improved understanding. In the first part of the paper, we represent a sensitivity test done on the shapes and the endpoints of the two-phase relative permeability curves. We find that the water relative permeability and Oil relative permeability in the gas-Oil system are the main factors that determine the magnitude and shape of the Oil Saturation curve as a function of time. Secondly, we demonstrate how to adjust the k rog relative permeability curve to match a theoretically determined Residual Oil Saturation, which is supported by laboratory data. We propose that, during SAGD, the flow of Oil can be split into two regimes. In the first regime, close to the edge of the steam chamber, Oil drains quickly in a short period of time. In the second regime, Oil drains slowly within the steam chamber for a longer period of time, as it is produced by film drainage. To capture these flow regimes, the Oil relative permeability curve in the gas-Oil system, k rog , is split into two. At higher liquid Saturations, the first flow regime is represented and, at lower liquid Saturations, the second regime is modelled. Thirdly, the k rog curve was adjusted so that the decrease in Oil Saturation with respect to time closely matched the theoretical curve while maintaining Oil production rates expected for SAGD. Using this new curve at different pressures, we show that the Residual Oil Saturation increases at lower SAGD operating pressures.