Theoretical Study of Water Blocking in Miscible Flooding

Müller, Thomas; Lake, Larry W.

doi:10.2118/20206-pa

Cited by 21 publications

(13 citation statements)

References 15 publications

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“…In their studies, Warner (1977) and Todd et al (1982) deduced that it is quite unlikely that molecular diffusion will be significant in reducing the adverse effects of large-scale bypassing in the field. Muller and Lake (1991) in their numerical modelling of water blocking effect in miscible flooding also concluded that water blocking (which is related to diffusion of CO 2 through the water barrier) apparently has no significant impact on recovery at the field scale. It seems that diffusion is important if the time scale of the diffusion was comparable with those of macroscopic transport parameters.…”

Section: Discussionmentioning

confidence: 99%

Tertiary Oil Recovery and CO2 Sequestration by Carbonated Water Injection (CWI)

Kechut¹,

Riazi²,

Sohrabi³

et al. 2010

All Days

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The increasing availability of the anthropogenic carbon dioxide (CO 2 ) and the drives to reduce its concentration in the atmosphere has increased the interest in CO 2 injection for improving the oil recovery in maturing oil reservoirs. Many of these reservoirs are being waterflooded to sustain the oil production. Instead of injecting plain water, injecting carbonated (CO 2 -enriched) water could bring additional oil recovery and added benefit of safe storage of CO 2 . In carbonated water injection (CWI), CO 2 is dissolved in the injected brine prior to injection and then transported through the reservoir by the flood water. As a single phase, carbonated water mobility contrast with oil is more favourable than in the CO 2 gas-oil system thus improves sweep efficiency and retards CO 2 breakthrough. The slightly higher density of the carbonated water than the unadulterated water would induce the injected CO 2 to slump towards the bottom of the reservoir, eliminating the risk of buoyancy-driven leakage thus securing storage.This paper presents the results of an integrated experimental and numerical simulation study of tertiary CWI. A series of high pressure flow visualisation and coreflood experiments as well as compositional simulation have been carried out to evaluate the process. A North Sea crude oil and brine were used at a pressure typical of real reservoir conditions.The visualisation experiments in high-pressure glass micromodels reveal that the oil swelling from CO 2 diffusion into the oil and the subsequent oil viscosity reduction, coalescence of the isolated oil ganglia and flow diversion due to flow restriction in some of the pores as a result of oil swelling and the resultant fluid redistribution are the main mechanisms of oil recovery by the tertiary CWI. There was also evidence of micromodel surface becoming more water wet that could also play a role in the oil recovery. The coreflood tests results clearly show that the post waterflood CWI could remobilize the remaining trapped oil in the watered-out core that leads to significant additional oil recovery. A very gradual (dissolved) CO 2 breakthrough exhibited in this process is a significant advantage over the sudden CO 2 breakthrough problem commonly faced in the conventional CO 2 flooding. CWI is also highly potential as CO 2 storage injection strategy as demonstrated by almost 50% of the total volume of CO 2 injected (in carbonated water) was being stored at the end of the test. There is a challenge in simulating the physics of the CWI process using the commercially available reservoir simulators which will also be discussed.

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Section: Discussionmentioning

confidence: 99%

Tertiary Oil Recovery and CO2 Sequestration by Carbonated Water Injection (CWI)

Kechut¹,

Riazi²,

Sohrabi³

et al. 2010

All Days

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“…The trapped oil saturation in solvent processes therefore has to be considered a function not only of the water saturation but also of the solvent contact time or the flooding state. 88 Related to trapping is a phenomenon discussed in the literature as water shielding or water-blocking. The phenomenon is viewed in the reservoir as residual disconnected phase surrounded by water.…”

Section: Reservoir Heterogeneity 4 Capillary Forces 5 Dynamics Of Wmentioning

confidence: 99%

A Literature Analysis of the WAG Injectivity Abnormalities in the CO2 Process

Grigg

2000

SPE/DOE Improved Oil Recovery Symposium

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TX 75083-3836, U.S.A., fax 01-972-952-9435. 3. 3 nitrogen-miscible projects 4. 1 hydrocarbon-immiscible 5. 1 nitrogen-and hydrocarbon-immiscible 6. 6 nitrogen-immiscible CO 2 projects continue to grow in numbers. Immiscible CO 2 projects have dropped to zero while ten new miscible CO 2 projects were planned as of January 1998. Brock and Bryan 2 presented a summary of CO 2 EOR projects and reviewed the performance of 30 full-scale field projects and field pilots up to 1987. In 1992 there were 45 active CO 2 projects in the U.S. 3 Initially the industry outlook was pessimistic; however, by 1992 most projects had been shown to be technically and economically successful. In a number of projects, the production performance has been better than was anticipated. 3 At the beginning of 1998 and based on 1997 production figures, the U.S. production from gas injected EOR was estimated at 307,544 b/d or approximately 4.7% of the total oil production in the US. Oil production from CO 2 activity alone contributed nearly 179,000 b/d, which is an increase of 4.9% over 1996 production attributable to CO 2 production and represents 2.8% of the 1997 US oil production of 6.4 MM bopd. 1 The Permian Basin of west Texas and southeastern New Mexico remains a very active area for CO 2 projects. Eight of the ten planned projects are in the Permian Basin. 1 However, new CO 2 EOR projects are possible for areas of California,

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“…Figure 3 shows how a significant improvement in history match was achieved for a naturally fractured reservoir, by enabling diffusion with coefficients taken from the literature. Diffusion of the CO 2 through the water film rather then directly into the oil phase, might significantly affect the performance of the process (Muller, 1991).…”

Section: Diffusive Forcesmentioning

confidence: 99%

Modelling CO2 Injection: IOR Potential after Waterflooding

Berenblyum

Calderon

Kollbotn

et al. 2008

SPE Symposium on Improved Oil Recovery

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This paper combines the knowledge and experience accumulated at the International Research Institute of Stavanger (IRIS) over a number of years, based on several case studies involving the Tjelbergodden CO 2 value chain, modelling of CO 2 injection at the Ekofisk field (fractured chalk reservoir) and Gullfaks CO 2 injection compositional study.The paper discusses the importance of correctly representing the physical effects when modelling miscible or immiscible CO 2 injection in sandstone and carbonate reservoirs. The following aspects were evaluated:• Transfer of CO 2 from fractures to matrix involving diffusive, gravitational and capillary forces;• Viscous effects;• Formation of low and high concentration liquid hydrocarbon phases;• Compositional effects such as miscible displacement and oil swelling;• Chemical interaction between CO 2 , formation or injection water and reservoir rock. The sensitivity and importance of these effects were studied on several simplified mechanistic models and later applied to actual field cases.An overview of viscous fingering effects is presented. Results from mechanistic studies of the CO 2 matrix-fracture transfer are shown and physical effects are discussed. The paper also presenets critical aspects of Equation-Of-State (EOS) modelling and PVT experiments necessary for a CO 2 flood simulation study. From our experience we suggest a "cooking recipe" for building reservoir simulation models for CO 2 based IOR process evaluations. Case studies of the CO 2 and CO 2 -WAG IOR methods for reservoirs on the Norwegian Continental Shelf (NCS) are presented and oil recovery potentials of these IOR processes are discussed. Physical effects during CO 2 floodingThis chapter presents a short review of important physical effects acting during CO 2 injection process and the simulation aspects associated with them. Viscous FingeringDuring miscible CO 2 flooding, displacement instabilities are functions of rock-fluid properties, fluid saturation distribution, viscous forces, and other parameters such as rock wettability, interfacial tension and miscibility. In cases where a miscible slug is injected, followed by chase gas, fluid cross flow and mixing of the slug with the chase gas may result in front instabilities which reduce the displacement efficiency.Fingering of an interface is a hydrodynamic instability that occurs when a more mobile fluid displaces less mobile one. Mobility variations are usually related to differences in viscosity or density of the two fluids considered. The onset of viscous instability and the subsequent fingering has mostly been studied using a Hele-Shaw cell under conditions of a sharp mobility contrast for both miscible and immiscible conditions (Homsy et al, 1987). Such experiments do not account for the CO 2 mass transfer mechanisms. Nevertheless, the Hele-Shaw cell experiments allow identifying and visualizing the fingering pattern mechanisms, see Figure 1.For both miscible and immiscible conditions, propagation of viscous fingering is governed by different mechan...

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Theoretical Study of Water Blocking in Miscible Flooding

Cited by 21 publications

References 15 publications

Tertiary Oil Recovery and CO2 Sequestration by Carbonated Water Injection (CWI)

Tertiary Oil Recovery and CO2 Sequestration by Carbonated Water Injection (CWI)

A Literature Analysis of the WAG Injectivity Abnormalities in the CO2 Process

Modelling CO2 Injection: IOR Potential after Waterflooding

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