Non-stationary Flooding Research Articles

LRFD methodology for river embankments against non-stationary flooding under climate change

Riverine floods have become increasingly prevalent on a global scale, posing significant risks to infrastructure systems and communities. The escalating impacts of climate change associated with the increase in rainfall intensities and frequencies necessitate the improvement of the existing design methodologies to account for the non-stationary climate change effects to ensure that the reliability is above the target level and mitigate future flood disasters. This paper presents a novel LRFD approach for river embankments subjected to extreme rainfall under non-stationary climate change effects. This approach introduces an additional partial factor to account for the effects of climate change. Precipitation and temperature projections are collected from various climate models considering several cases of emission scenarios. An integrated hydrological and hydraulic modeling of the analyzed river is carried out to estimate the associated time-variant river discharge and water surface elevation. The non-stationary extreme value associated with the maximum flood level is leveraged using the peak-over-threshold approach. The embankment reliability and the corresponding most probable points are evaluated using limit states associated with overtopping and slope failures. Based on the estimated and target reliability indexes, the design point for each random variable is assessed considering the cases with and without climate change effects. Finally, the partial factors associated with climate change effects are determined. As an illustrative example, the proposed framework is applied to the Ashida River in Fukuyama city of Japan.

Применение внутритрубного электроцентробежного насоса для повышения нефтедобычи на месторождении имени Ю. Корчагина

Offshore field development projects are significantly different from onshore projects. Offshore operations include many difficulties, such as the specific technology for the operation and construction of wells, and the high cost of technical means. One of the most popular offshore field development projects is the Yu. Korchagin field. Various types of non-stationary flooding are actively and effectively used in this project, which are equipped with inflow control devices, among which passive and autonomous inflow control devices are distinguished. In the early 2010s, during the first drilling of the Neokomsko-Volzhskaya deposit, slit filters were used on wells, and later they began to use counter-pressure filters with the installation of sliding couplings. In multi-barrel wells, multi-position couplings are used to regulate the operation of each barrel. The introduction of some technologies in the conditions of extended horizontal boreholes of the Yu. Korchagin field had limited possibilities for launching equipment due to the complex trajectory of the well. The most urgent problems of modern oil and gas production are the completeness and efficiency of fluid extraction, achieving a uniform inflow profile, limiting and isolating gas and water breakthroughs. Inflow control systems, including and "intelligent" ones allow to minimize the flooding of wells, and the descent into the pumping and compressor pipes of the in-line electric centrifugal pump in case of failure of the standard pump will avoid the suspension of drilling operations. The purpose of the work is to analyze the application of the latest technological solutions at the Yu. Korchagin field in the waters of the Northern Caspian Sea.

ABOUT SOME PROBLEMS OF WATERFLOODING IN CARBONATE RESERVOIRS

The features of waterflooding of carbonate (fractured-porous) rocks, caused by the interaction of the system of fractures with the matrix (blocks) of the rock, are considered. It is shown that the slower propagation of the pressure pulse in the rock matrix in comparison with the propagation of this pulse along the fracture system of the formation leads to compression of the rock blocks in the near-wellbore zone of the injection well, as a result of which stress concentration occurs at the ends of vertical fractures, which increases the likelihood of these fractures growing into the roof of the productive formation. It is shown that in order to prevent the development of this process, the growth rate of water injection pressure should be limited in accordance with the time of liquid pressure equalization in the pore space of the rock matrix and in the fracture system. When developing production wells drilled in fractured porous media, in order to prevent the development of the process of closing fractures in the bottomhole zones of these wells, the drawdown reduction rate must also be limited in a similar way. It is noted that when applying technologies for non-stationary flooding of productive reservoirs, the main factor determining their effectiveness is the change in the direction of filtration flows in the reservoir. This leads to the activation of filtration processes in the stagnant zones of the formation and the intensification of the processes of capillary impregnation of low-permeability interlayers with water from more flooded highpermeability interlayers.At the same time, it is important to take into account that when changing the direction of filtration flows at a late stage of development of carbonate reservoirs, in order to prevent reimpregnation of hydrophobic rock blocks with oil, it is more expedient to change the operating modes of production rather than injection wells. It is shown that water flooding of hydrophobic carbonate reservoirs results in incomplete water displacement of oil as a wetting phase from rock blocks. To reduce the residual oil saturation of rock blocks, it is advisable to increase the displacement pressure gradient in the reservoir in combination with a change in the direction of filtration flows in it.

The method of non-stationary flooding and the conditions for its effective use in the operation of an oil field

The article describes the essence of unsteady waterflooding, which is one of the most effective methods of increasing the oil recovery factor, used to change the direction of filtration flows, which makes it possible to engage in the development of undeveloped oil reserves and reduce the rate of watering of the deposit in productive reservoirs. A common technological method of unsteady water flooding is the use of cyclic modes of operation of injection wells. The essence of this method is that at an unsteady state in the oil deposit, there are conditions for the continuous manifestation of elastic forces of the reservoir system. In a heterogeneous reservoir between different zones, channels, and fluid flows there are gradients of hydrodynamic pressures, due to which there can be fluid flows from one layer to another, from fractures to blocks, as well as changes in flow directions. During unsteady flooding of heterogeneous formations, a part of oil reserves in low-permeability layers or zones remains uncovered by injected water. The waterflooded reservoir appears as an unsystematic alternation of watered and oil-saturated microflows. While creating in such reservoirs alternately changing in value and direction of pressure gradients, conditions for injection water penetration into stagnant oil-saturated low-permeable zones and channels appear in the oil reservoir and oil movement from them to active drainage zones. As a result of the analysis, the positive effect of the implementation of unsteady waterflooding technology was revealed, and recommendations for improving its application at other operational facilities of oil fields were given.

Automation of works on a bench to choose the optimal parameters of devices in case of pulsed non-stationary flooding of hydrocarbon reservoirs

The bench was developed in the Laboratory of Hydraulic Devices at the Department of Oil Field Machines and Equipment, which allows creating conditions close to the bottomhole conditions of any well. Laboratory-experimental studies conducted at the bench included two stages: a) study of output parameters and the corresponding selection of optimal design parameters of the developed devices; b) study of the influence of pressure and frequency of fluid pulses on the penetration of working fluid in sand samples.

Development of devices for implementation pulse nonstationary waterflooding

To further improve the efficiency of the non-stationary flooding (acceleration of capillary impregnation oil closed pores) at the bottom of injection wells installed devices, creating pulses in the pumped liquid, with a packer. The article deals with a device designed for this purpose. A mathematical model of the device and output expressions to define the basic operating parameters of output. For comparison of theoretical calculations show the results of bench testing device. In view of previous research, the authors of substantiated the effectiveness of such devices for the nonstationary flooding in the system to maintain reservoir pressure. The preliminary positive data on fishing the use of these devices in the fields of NC «Rosneft» in 2015-2016.

Managing the reliability of the tubing string in impulse non-stationary flooding

Impulse non-stationary flooding requires managing the processes influencing reliability and durability of the tubing string. In this case, it is necessary to determine the medium displacement for known dimensional parameters and stress fields, while taking into account the dynamic solution for the low-frequency limit. The results obtained from the analysis are compared against the measurements performed by various authors. Assuming there is a certain frequency of injected fluid oscillation or pressure pulses, one could expect that the radial movement is in equilibrium with the pressure existing at any given period of time. As a result, expressions describing the behavior of impulse waves propagating along the pipe wall were obtained. The reflected waves appear in all cases: whether the change in speed is caused by a change in the pipe wall thickness, Young modulus or shear rigidity of the environment. Changes in density or bulk modulus of the injected fluid or in the radius of the wellbore also cause reflected waves; all the waves may be described by a single equation.

Адаптивная идентификация циклического режима закачки для оперативного управления нестационарным заводнением

Адаптивная идентификация циклического режима закачки для оперативного управления нестационарным заводнением

Forecasting the parameters of non-stationary water flooding of oil deposits

Non-stationary flooding and water withdrawal with changing the direction of filtration flow as a secondary advanced recovery method allow enhancing oil deposit coverage by filtration processes, reducing or eliminating the amount of bypassed oil in productive formations. Process modelling should be provided for correct forecast about the efficiency of non-stationary formation stimulation. A formation model was designed for modelling cyclic water flooding. There are cross-flows between interlayers of reservoir robbing which have different porosity and permeability properties and unbalanced thrust in pore space. It is noted that when applying ordinary water flooding, high formation heterogeneity, higher than average oil viscosity and low permeability make it impossible to reach even average efficiency of oil pool development. The choice of a stimulation technique and its justification is an important step of planning in order to apply non-stationary stimulation. A possibility to apply non-stationary flooding efficiently for the analysed object has been established.

Selection of Optimal Design of a Universal Device for Nonstationary Pulse Pumping of Liquid in a Reservoir Pressure Maintenance System

A universal downhole device for continuous pulsed pumping of liquid in a reservoir pressure maintenance system is developed. A mathematical model of the device and a derivation of expressions for determining the main basic working output parameters are given. The results of theoretical studies are compared with bench tests of the device. The effectiveness of the device in non-stationary flooding in the pressure maintenance system is demonstrated based on previously conducted scientific studies. Preliminary positive data on commercial use of the device at Rosneft oil fields in 2015–2016 are given.

STAGES OF NONSTATIONARY FLOODING TECHNOLOGY DEVELOPMENT

Background In the article possibilities of nonstationary flooding technology are considered. The basic physical principles of technology are stated. The reasons for low popularity of nonstationary flooding technology for oil production enterprises are revealed. Aims and Objectives To substantiate the urgency of using and improving nonstationary flooding technologies impact, conducting pilot industrial works for adaptation and creation of new nonstationary flooding technologies, and also to determine the conditions for their application effectiveness. Results The results are as follows: 1. in the 1990s, the decisive influence in the oil-producing industry was made by experts oriented to Western technologies. Nonstationary flooding was not included in the list of these technologies; 2. despite its relative simplicity, practical implementation of nonstationary flooding technology requires considerable preliminary preparation. Nonstationary flooding is one of the most knowledge-intensive methods of increasing oil recovery; 3. nonstationary flooding technology, imple-mented on an oil deposit, tends to «aging», i.e. its effectiveness decreases over time. It requires a constant change in technology, its integration with other methods.

OPTIONS OF PULSE NON-STATIONARY WATER FLOODING IN BLOCK SYSTEMS OF DEVELOPMENT

In the block systems of water flooding the features of relative location of injection and production wells allow for the variety of options for changing the mode of operation (single, group, block, etc.). The greatest overall effect of the change in filtration velocity at the cutting line, and hence also the effect of pulsed non-stationary flooding, is achieved by alternate stopping of wells. The maximum distance between the injection wells, the mode of operation of which can be changed at the same time, is limited by the duration of the stop and subsequent water injection. Thus, if the duration of half cycles is the same, then this ratio is equal to two, that is the wells in a row should be stopped through one row.