Oil Recovery in Fractured Oil Reservoirs by Low IFT Imbibition Process

Al-Lawati, Shabir; Saleh, Saad

doi:10.2523/36688-ms

Cited by 5 publications

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“…They found that depending on the relative contribution of the capillary and gravity forces, the imbibition rate may either increase or decrease which leads to contradiction of the dimensionless time scale developed by Mattax and Kyte (1962). This argument was also supported by the experimental work of Al-Lawati and Saleh (1996) and Li and Horne (2001, 2004, 2006. Ma et al (1997) modified the dimensionless timescale proposed by Mattax and Kyte (1962) by introducing geometric mean of fluid viscosities, .…”

Section: Introductionmentioning

confidence: 95%

“…Cuiec et al (1990) presented analogous results where IFT is inversely proportional to the imbibition time. However, the limitation of their dimensionless time was demonstrated by Schechter et al (1991Schechter et al ( , 1994, Al-Lawati and Saleh (1996) and Li and Horne (2001, 2004, 2006. Schechter et al (1991Schechter et al ( , 1994 performed spontaneous water imbibition experiments for Berea sandstone that involved the effects of capillary and gravity forces by varying interfacial tensions and phase densities in oil-water-alcohol mixtures.…”

Section: Introductionmentioning

confidence: 99%

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Residual Trapping of CO2 in Aquifers During the Counter-Current Flow

Nattwongasem¹

2009

SPE Annual Technical Conference and Exhibition

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The key challenge of CO 2 sequestration projects is to ensure that selected formations will provide for long-term storage of CO 2 without significant leakage. This is also the case for sequestration projects in saline aquifers, where substantial evidence must be provided that injected CO 2 will remain in the target formation. However, the time-scales that characterize the immobilization of CO 2 in aquifers are not yet fully understood. In this paper, we investigate the time scale for post-injection immobilization of CO 2 and proposed a new dimensionless time scale that includes the contributions of both capillary pressure and gravity forces. The Bond number (N B ) is included in the approach to capture the impact of the relevant driving forces. We use numerical calculations to study the interplay between capillary and gravity forces on the predicted evolution of a well-defined CO 2 plume in an aquifer. Scaling analysis for 1D and 2D systems is presented for characterizing the plume behavior in different flow regimes as dictated by the relative magnitude of gravity and capillary forces (Bond numbers). A majority of the previous efforts on scaling analysis has focused on processes that are driven by capillary forces alone. However, for sequestration applications the impact of gravity force may be significant. We demonstrate that plume migration at constant Bond numbers may display very different characteristics as a consequence of phase mobilities. The results of our simulations and scaling analysis apply directly to the planning of CO 2 sequestration projects and provide new guidelines for estimating the immobilization time of supercritical CO 2 as well as the amount of CO 2 that can potentially be trapped in a given aquifer.

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Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Residual Trapping of CO2 in Aquifers During the Counter-Current Flow

Nattwongasem¹

2009

SPE Annual Technical Conference and Exhibition

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“…The other possible way is to combine the scaling groups for different mechanisms as applied by DeFour, 35 Al-Lawati and Saleh, 23 and Babadagli. 12 The first two did not find any applicability for the low-IFT case after combining the gravity and capillary terms (Eqs.…”

Section: Flow Type: Cocurrent Flow (Dashed Lines: Surfactant Solutimentioning

confidence: 99%

“…This observation entails an inclusion of the gravity factor into scaling formulation. Al-Lawati and Saleh 23 proposed an approach to incorporate both the gravity and capillary forces, but they observed a poor correlation with the experimental data. Employing polymer solution as an aqueous phase in capillary imbibition recovery has also been studied.…”

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confidence: 99%

“…3,15,[20][21][22][23] Especially under unfavorable matrix boundary conditions, low IFT can be a remedy for low matrix recovery as shown by Babadagli et al 15 Considering the fact that chemical addition into aqueous phase to reduce IFT or increase its viscosity is a useful technique to increase the recovery rate and amount, scaling these processes up to reservoir conditions is necessary for performance estimation.…”

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confidence: 99%

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Scaling of Cocurrent and Countercurrent Capillary Imbibition for Surfactant and Polymer Injection in Naturally Fractured Reservoirs

Babadagli

2001

SPE Journal

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Summary This study tests the existing capillary imbibition scaling formulations in literature and proposes modifications to them for surfactant- and polymer-injection applications. Laboratory tests were performed using Berea Sandstone cores with different shapes, sizes, and boundary conditions. Kerosene, engine oil, mineral oil, and crude oil were selected as the oleic phase. Brine and two different concentrations of surfactant and polymer solutions were the aqueous phases. The capillary imbibition recovery curves were then used to test the existing scaling formulations. It was observed that the scaling groups were applicable with certain modifications to the cocurrent flow of surfactant and polymer solution-oil pairs as well as the brine-oil cases. In case of cocurrent flow, the gravity forces dominate recovery for low-interfacial tension (IFT) experiments, and modification to the gravity-scaling group for the boundary conditions is required. For countercurrent flow, however, the scaling groups were observed to be inapplicable even after the modifications. Introduction When the matrix part of a naturally fractured reservoir (NFR) contains great amounts of oil, enhanced oil recovery methods are aimed to recover this oil effectively. Matrix-fracture interaction is required for matrix oil recovery, and capillary imbibition is the underlying mechanism if the matrix is water-wet and enough water is supplied in the fracture network. The capillary suction of water by matrix, and expelling the oil simultaneously, is a phenomenon governed by numerous parameters. Matrix permeability,1–4 size and shape,1,3-5,7 wettability,8–12 heterogeneity,2,8,13 and boundary conditions3,5-7,14,15 determine the rate of the oil recovery. The properties of imbibing water,16 viscosities of the phases,11,12,17-19 and IFT3,15,20-23 also play a role on the capillary imbibition recovery rate. Mattax and Kyte1 first proposed a scaling equation for capillary imbibition based on the Rapoport's24 scaling laws. Later, modifications to Mattax and Kyte's scaling group were proposed.3,5,6,11,12,23,25-27 Scaling equations for gravity-dominated imbibition recovery were also provided for different purposes.21,26-28 On the other hand, under unfavorable conditions such as high oil viscosity, low matrix permeability, high IFT, and unfavorable matrix boundary conditions, capillary imbibition recovery may be very slow and may also yield high residual oil. Different methods can be applied to overcome these difficulties. Heat injection resulting in the reduction of oil viscosity and IFT,11,12,29,30 injection of surfactant,15,20-23 and polymer solutions18 have been tested in laboratory conditions previously for this purpose. Laboratory-scale experiments showed that these methods yield an increase in ultimate recovery. Heat injection also gives rise to an increase in the production rate. Therefore, the applicability of these methods is proven, but the existing scaling groups should be tested and modified, if necessary, for the field-scale applications of chemical injection into NFRs. Under the tertiary recovery applications, matrix fracture transfer due to capillary imbibition is more complicated than it is with the brine-oil pair. Additionally, the gravity forces could be effective depending on the boundary conditions and the type of injected fluid. Some attempts have been made to scale the capillary imbibition experiments for low IFT, polymer, and heat injection. The scaling of capillary imbibition under thermal effect has been examined in a few studies. Reis29 reviewed the matrix recovery mechanisms for nonisothermal conditions and provided the characteristic recovery times for them. Babadagli12 proposed an approach for scaling the capillary imbibition under temperature effect. However, due to the number of mechanisms involved, there still exist certain difficulties in the scaling associated with the thermal effects, as also pointed out by Briggs et al.30 Difficulties arise due to thermal expansion of oil, change in oil viscosity, IFT, and, therefore, relative permeabilities under temperature. Scaling the capillary imbibition for a low-IFT case is also challenging. Schechter et al.21 studied low-IFT capillary imbibition and observed that gravity may dominate the matrix recovery at low values of IFT. This observation entails an inclusion of the gravity factor into scaling formulation. Al-Lawati and Saleh23 proposed an approach to incorporate both the gravity and capillary forces, but they observed a poor correlation with the experimental data. Employing polymer solution as an aqueous phase in capillary imbibition recovery has also been studied. Ghedan and Poettmann18 observed changes in recovery curves when the polymer solutions were used instead of brine, but they did not study the scaling of the phenomenon. Note that low-IFT solutions as an aqueous phase can be useful for accelerating the capillary imbibition recovery as well as reducing the residual oil in matrix.3,15,20-23 Especially under unfavorable matrix boundary conditions, low IFT can be a remedy for low matrix recovery as shown by Babadagli et al.15 Considering the fact that chemical addition into aqueous phase to reduce IFT or increase its viscosity is a useful technique to increase the recovery rate and amount, scaling these processes up to reservoir conditions is necessary for performance estimation. This study aims to test the validity of available scaling groups for static imbibition when low-IFT and polymer solutions are used as the aqueous phase. Capillary imbibition experiments were conducted for different rock and fluid properties. After testing the scaling groups for different cases, the conditions for which the existing scaling group applies were identified. For other cases, modifications to scaling groups were proposed. Experiments All the experiments were conducted on the same type of rock (unfired Berea sandstone), but different types of oil, aqueous phases, and matrix boundary conditions were used. The sample preparation and experimental procedure are explained below.

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Selection of Proper EOR Method for Efficient Matrix Recovery in Naturally Fractured Reservoirs

Babadagli

2001

SPE Latin American and Caribbean Petroleum Engineering Conference

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractAs most of the oil is stored in matrix due to its higher storage capacity than fracture network of naturally fractured reservoirs (NFR), reservoir development plans will aim at maximizing the matrix oil recovery. An enhanced oil recovery (EOR) application principally targets (a) to minimize the residual oil in matrix depleting the matrix as effective as possible and/or (b) to accelerate the recovery rate for rapid production of oil cost efficiently. For reservoirs with high recovery factor, minimizing matrix residual oil saturation is a critical issue to extend the life of the reservoir. For reservoirs with low recovery factor, accelerating the production rate is more vital. For each of these reservoir types, different EOR methods should be considered and implemented accordingly. This paper addresses and discusses these two issues and identifies selection criteria for different EOR methods in NFR, namely chemical (surfactant and polymer) and hot water injection.The focus is specifically on matrix type (permeability and wettability), oil and water viscosities, matrix boundary conditions, transfer type (co-or counter-current imbibition), and IFT. For the different values of these properties, the most proper injection fluid type to be used as an EOR fluid is identified to obtain an effective matrix recovery. Co-current and counter-current capillary imbibition experiments at static conditions are conducted to show how effective and how useful these applications are for different rock and fluid types and matrix boundary conditions. For experimentation, strongly water wet Berea Sandstones and oil-wet carbonates (cores from an oil formation) are used. Light crude oil, kerosene and engine oil are selected as the oleic phase.Proper project implementation (adjustment of injection rate and/or concentrations) and selection of the injection fluid for a cost efficient management are also discussed for different conditions outlined above. Finally, the selection criteria of EOR methods based on the rock and fluid properties are defined. This will provide an insight into an effective management of NFRs and reservoir depletion strategies, if the matrix oil recovery is the main target.

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Oil Recovery in Fractured Oil Reservoirs by Low IFT Imbibition Process

Cited by 5 publications

References 0 publications

Residual Trapping of CO2 in Aquifers During the Counter-Current Flow

Residual Trapping of CO2 in Aquifers During the Counter-Current Flow

Scaling of Cocurrent and Countercurrent Capillary Imbibition for Surfactant and Polymer Injection in Naturally Fractured Reservoirs

Selection of Proper EOR Method for Efficient Matrix Recovery in Naturally Fractured Reservoirs

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