Gas injection techniques, such as WAG, frequently require consideration of co-existing oil, gas and water phases and the impact of saturation cycles as water and gas slugs move through the reservoir. These processes may be assessed using numerical simulations. This paper presents the analysis of a detailed laboratory study, designed to provide data for verifying hysteresis models for such simulations. A number of studies have reported evidence for hysteresis in gas relative permeabilities in WAG flooding, leading to lower gas mobilities than predicted by conventional two-phase models. A reduction in gas mobility tends to improve gas sweep and incremental recovery for WAG based IOR schemes. Three-phase hysteresis models have recently been developed to include these hysteresis effects. The models include trapping of gas and reduction of water relative permeability in the presence of trapped gas. In these models, saturation changes can be irreversible, and relative permeability may decrease with each change in direction in saturation. A carefully planned laboratory study investigated secondary and tertiary immiscible WAG floods in both water-wet and intermediate-wet Berea cores, giving four separate sets of experimental data (a total of over 30 individual floods). For each flood, in-situ saturation profiles, mass balance and pressure drop data were measured. The in-situ saturation data ensures that laboratory artefacts (such as capillary end effects) do not influence conclusions. Analysis of the experimental data shows that hysteresis models should include the following features:Irreversibility of hysteresis cycles;Potential for the reduction in the residual oil saturation with trapping of gas by water;Reduction in both water and gas permeability, with potential for the fractional flow to vary with trapped gas saturation;Variation in Land trapping factor between hysteresis cycles. This study confirms the need for three-phase hysteresis models. Although published models may include some of the observed hysteresis effects, no model includes them all. Introduction Reservoir engineering calculations frequently require consideration of co-existing oil, gas and water phases. In the case of immiscible hydrocarbon gas WAG flooding, these considerations include the displacement of oil by simultaneous gas-water flow. These displacement processes are usually assessed using numerical simulation. Although the permeability of reservoir rock typically depends on the interstitial pore geometry, the relative permeability depends on factors such as wettability, spreading characteristics and the fluid distribution in the pore space. There is usually more than one way a given fraction of the pore space can be occupied by each fluid phase and so it is possible for different relative permeability values to be measured for the same fluid saturation. The sequence of saturation changes will, therefore, affect fluid distribution and the relative permeability. Historically, hysteresis effects have been included in numerical simulations using empirical models based on two-phase flow [1,2]. Recent investigations have considered hysteresis for more complex three-phase processes and a number of new models have been proposed for inclusion in commercial simulation packages [3,4,5].
Copy ri ght 7896 , Stee ri ng Committee of the Euro pean IOR -Symposium. This paper was presented at the 8th . Eu ropean IOR -Symposium in V ierma, Austr ia, May 15 -17, 1995 Thi s paper was eelected for presentation by the Stee ri ng Committee , follow ing review of information contained i n en abstract subm itted by the authorlsl . The paper, as presented hes not been reviewed by the Stee ring Comm itt ee . AbstractThe drainage of oil under gravitational forces has been an important mechanism in the production of many oil fields . In order to extend the economic implementation of gas injection into more marginal fields, a reduction in the uncertainties associated with gravity drainage is required. This paper describes a series of three tertiary, nitrogen experiments which investigated the effect of permeability on gravity drainage . The experiments ware conducted at low pressure using long, vertical, water-wet sandstone sores and decane in the presence of connate brine .The residual oil saturation following 62 days of nitrogen injection in a 0 .37 µmz core was 0 .26. The residual oil saturation following 53 days of nitrogen injection in a 1 . 5 µm2 Gore was 0 . 10.The residual oil saturation following 63 days of nitrogen injection in a 2 .0 µmz Gore was 0 . 13 . The variation of the oil and brine saturations ware determined as a function of space and time for each experiment using a radioactiva tracer technique . This independent measurement of both o il an d brine in-site saturations is a new development for the literature and enables vore a rtefacts to be identified and relativa permeabilities to be derived .Detailel analysis of the 2 µm2 experiment showed that the o il relativa permeability was independent of position and was only a function of oil saturation . The relativa permeabilities are characterised by a zero asymptotic residual oil saturation and a Corey exponent of approximately four , which is higher than the value of three proposed from theoretical models of film drainage . A numerical simulation of this experiment gave a good match to the production and in-site saturation data. This paper presents the determination of oil and brine relativa perineabilities under a flow regime which is representative of gravity drainage during gas injection . The method outlined thus gives added confidence when assessing field development options .
The drainage of oil under gravitational forces has been an important mechanism in the production of many oil fields. In order to extend the economic implementation of gas injection into more marginal fields, a reduction in the uncertainties associated with gravity drainage is required. This paper describes a series of three tertiary, nitrogen experiments which investigated the effect of permeability on gravity drainage. The experiments were conducted at low pressure using long, vertical, water-wet sandstone cores and decane in the presence of connate brine. The residual oil saturation following 62 days of nitrogen injection in a 0.37 mu m 2 core was 0.26, following 53 days of nitrogen injection in a 1.5 /mu m 2 core was 0.10 and following 63 days of nitrogen injection in a 2.0 /mu m 2 core was 0.10. The variation of the oil and brine saturations were determined as a function of space and time for each experiment using a radioactive tracer technique. This independent measurement of both oil and brine in situ saturations is a new development and enables core artefacts to be identified and relative permeabilities to be derived. Detailed analysis of the 2 mu m 2 experiment showed that the oil relative permeability was independent of position and was only a function of oil saturation. The relative permeabilities are characterized by a zero asymptotic residual oil saturation and a Corey exponent of approximately four, which is higher than the value of three proposed from theoretical models of film drainage. A numerical simulation of this experiment gave a good match to the production and in situ saturation data. Determination of oil and brine relative permeabilities under a flow regime are presented which are representative of gravity drainage during gas injection. The method outlined gives added confidence when assessing field development options.
A determination of oil relative permeability data during secondary and tertiary, gravity stable, nitrogen injection experiments is described. Four experiments were conducted at high and low pressure using vertical Clashach sandstone cores and a dead oil in the presence of connate brine. The spatial distributions of oil throughout the cores were determined using a radioactive tracer technique and these in-situ saturation measurements were used to determine the oil relative permeability. The results of two new experiments are presented. A high pressure, secondary, gravity stable, nitrogen injection was conducted in a 1790 mm core with a connate water saturation of 0.25. The residual oil saturation following 12 days of gas flooding was 0.19. A low pressure, tertiary, gravity stable, nitrogen injection was conducted in a 841 mm core with a connate water saturation of 0.19. A residual oil saturation to water flooding of 0.51 was reduced to 0.09 after 37 days of drainage. The rate of change of oil relative permeabilities with respect to oil saturation was larger in the secondary, gravity stable, nitrogen injection than in the tertiary injection. The predicted residual oil saturation to gas corresponding to an infinite drainage time appears to be finite for secondary gas injection and zero for tertiary gas injection. The permeability data is consistent with a theoretical model of film drainage which predicts a Corey Exponent of three.
The institutional frameworks within which we conceive, design, construct, inhabit and manage our built environments are widely acknowledged to be key factors contributing to converging ecological crises: climate change, biodiversity loss, environmental degradation, and social inequity at a global scale. Yet, our ability to respond to these emergencies remains largely circumscribed by educational and professional agendas inherited from 20th-century Western paradigms. As the crises intensify, there is a compelling case for radical change in the educational and professional structures of the built environment disciplines. This paper presents a work-in-progress examination of an emergent architecture programme at Te Wānanga Aronui O Tāmaki Makau Rau/Auckland University of Technology (AUT), Aotearoa New Zealand. The program is within Huri Te Ao/the School of Future Environments, a transdisciplinary entity formed in 2020 to integrate research and teaching across Architecture, Built Environment Engineering, and Creative Technologies. The school itself is conceived as a collaborative project to co-create an outward-facing civic research platform for sharing ecologically positive design thinking across diverse communities of practice. The programme foregrounds mātauranga Māori (Indigenous ways of knowing), transdisciplinary systems, and regenerative design as regional place-oriented contributions to planetary-scaled transformation. We illustrate and evaluate a specific curriculum change tool, the Living Systems Wellbeing (LSW) Compass. Grounded in Te Ao Māori (Māori cosmology and context), the Compass offers a graphic means for students to navigate and integrate ecological relationships at different scales and levels of complexity, as well as affords insights into alternative foundational narratives, positive values, design strategies, and professional practices. This paper identifies four foundational factors for transformative pedagogies. The first factor is the value of a collectively held and clearly articulated vision and focus. The second factor is the capacity and commitment of an academic team that supports and values the vision. Thirdly, the vision needs to meet and acknowledge place-specific knowledges and values. Finally, the pedagogy should have an action research component founded in real-world interactions. While this research-based pedagogy is place-based and specific, we argue that these four factors are transferable to other learning institutions and can support critical pedagogies for social, cultural, and ecological wellbeing.
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