We invite you to SPE young professionals meeting on "Improving WAG efficiency for heterogeneous and low-permeability reservoirs.". by Kirill Viktorovich Kazakov, LLC «LUKOIL-Engineering».
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Meeting will take place on 21 April, Thursday, at 19-00 hours at Sushchevskiy val, 2, Moscow.
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More details about the topic
WAG (SWAG) involves alternating (simultaneous) water and gas injection into the reservoir through the injection well and can achieve a higher oil recovery than injection of only water or only gas. One of the most important tasks in design and implementation of WAG is to define slug volumes and water : gas ratio. This task can be solved by a series of physical experiments on core models and by multivariate calculations on 3D simulation models, but these methods have drawbacks. Core experiments do not take into account the real heterogeneity of the reservoir. As the volume of slugs and the water : gas ratio may be variable over time (from cycle to cycle), then the field of solutions can be so large that it is difficult to cover it by series of variants calculated on the simulation model.
Several algorithms for the management of WAG based on the reaction of production wells were proposed in the work. The idea of the algorithm is to ensure uniform moving of injected water and gas towards production wells. Technological parameters of WAG are adjusted depending on the values of gas-oil and water-oil ratios of production wells which quantitatively characterize moving of injected agents in the reservoir.
Efficiency of the proposed algorithms for WAG was assessed by their simulation compared to waterflooding, gas injection, WAG and SWAG with a constant values of technological parameters in time. Calculations were carried out for hypothetical reservoirs with different heterogeneity and for the sector of real reservoir.
A decreasing of water injectivity after gas injection was noted at the many fields which was developing with WAG. This makes it difficult to maintain reservoir pressure and leads to a decrease in oil production levels. The cause for decreasing of water injectivity after gas injection, in many cases, is the formation of the residual gas saturation in the reservoir near-well zone.
A technology to avoid reducing water injectivity with WAG was proposed in the work. The technology uses effects of high compressibility of gas, and can significantly reduce the amount of residual gas saturation in the near-well zone for the period of water injection. Its effectiveness was evaluated by 3D simulation.
Moving of injected water and gas in the reservoir may be different depending on the distribution of properties of the reservoir and its geometry, accordingly, oil recovery and coverage factor will be different too. Gas resource is often limited and it is not possible to implement WAG on the all area of field. So it is necessary to have criteria for determining the priority locations for the implementation of WAG and for selection of the optimal advancement direction of the front of the injected agents that would ensure the most effectiveness of technology.
Dependence efficiency of WAG on values of major geological parameters of the reservoir and their distribution along the displacement front was studied in the work using 3D simulation. Composite simulation was used for calculation WAG in the work. Simulation model parameters affecting the calculations of relative permeabilities of oil, water and gas were adapted during simulating of experiments of the displacement of oil from the core samples. It was necessary to reproduce experimental values of displacement coefficients in the simulation.
About author
Kirill Viktorovich Kazakov, LLC «LUKOIL-Engineering»
Kirill got Master's degree in Gubkin Russian State Oil and Gas University in 2011 (direction "Petroleum Engineering", specialization "Simulation of oil fields", Department of the development and exploitation of oil fields). Since 2011 he has been working in LLC "LUKOIL-Engineering", now as lead engineer.
During the work activity he engaged in design of field development, creation of simulation models of reservoirs, summarising of experience of oil field development, analysis of the efficiency of enhanced oil recovery methods, summarising of field application and laboratory experience of WAG and Gas EOR, technical and economic evaluation of the development of new fields. He is a SPE member since 2015.