Tag Archives: фильтрация
At present time the interest to the quantitative interpretation of temperature surveys is growing. Individual flow rate and reservoir pressure of each layer, behind-casing flow rate, hydrodynamic layer parameters, characterization of permeability changing at near-wellbore zone become the purposes of quantitative interpretation. Non-stationary temperature and pressure in the well are used as input data for transient processes analysis, and temperature logs are used for quasi-stationary analysis. Particular interest is in determination of the individual layer flow rates and near-wellbore zone parameters.
The paper studies the problem of unsteady temperature field in heterogeneous reservoir during fluid filtration. The aim of this work was to develop and provide rationale for simplified analytical model of non-isothermal single-phase fluid filtration in heterogeneous reservoir. Analytical solution for the temperature field in the formation after flow rate changeis obtained by the method of characteristics. Two assumptions were made in solving the problem: radial thermal conduction and compressibility of saturated porous medium are ignored. Analytical models are compared with the numerical solution of the problem. Radial heat conduction and compressibility of oil- or water-saturated reservoirs influence insignificantly on the unsteady temperature field after the flow rate changes.
It is possible to solve the inverse problem on the evaluation of the damage zone radius of the permeability in the reservoir basing on the model curves of the temperature change after flow rate change. The possibility of that method realization is demonstrated on model curves of the temperature change.
In recent years, around the world there is deterioration in the structure of hydrocarbon reserves. Many oil companies are forced to take measures to increase the flow of oil to the producing wells. The most popular method is the method of hydraulic fracturing. One of the key characteristics of the effectiveness of hydraulic fracturing is the conductivity of the resulting fracture.
Practice has shown that there are a number of factors negatively influencing the fracture conductivity, one of which is the formation of a filter cake on the fracture surface, which can lead to a significant reduction in well production rates. In this connection it is necessary to conduct laboratory studies to assess the impact of the magnitude of the filter cake on the conductivity of the fracture.
During fracturing operations fracturing fluid in the fracture is under much greater pressure than in the reservoir, so it leaks and breaks the seam. However, since the cross linked guar molecules are too large and can not enter into the pore matrix, the polymer forms a dense cake on the fracture surface. Furthermore, when after the fracturing operation the pressure is reduced, the crack closes creating a tight proppant packing. When cracks close additional displacement of water from the formation of the polymer network occurs, resulting in even more increased concentration of the polymer. If the polymer remains undisturbed, the super viscous gelatinous mass is formed blocking the pore space of the fracture.
This article discusses a negative influence factor on fracture conductivity – the formation of a filter cake on the surface of the crack, which can lead to a significant decrease in well production rates. Also, the technique of calculating the coefficient of instantaneous loss and wall-building coefficient. Were obtained according to changes in recovery coefficient, coefficient of instantaneous loss and wall-building coefficient from permeability of a core.
Solved the problem of the quasi-steady pressure fields in layered orthotropic porous medium in the mode of constant depression. Statement of the problem carried out on the basis of the diffusion equation for the three layers with a plane interface perpendicular to the vertical axis, the different physical characteristics and the equality of pressures and flows at the interface between layers. The original problem is parameterized by adding a factor ε-1 before the first and second derivatives of the function of the pressure in the middle of crosspieces along the vertical coordinate. In this administration, the formal parameter ε, aspiration it to zero corresponds to an increase of the vertical component of permeability average interlayer indefinitely. This tends to equalize the pressure in the middle of the front vertical coordinate inter layers. Using the asymptotic formula of the parameterized problem highlighted mathematical formulation of the problem of the pressure field in a layered – inhomogeneous porous medium to zero coefficient of the asymptotic expansion. It is shown that the formulation of the problem for zero expansion coefficient up to notation coincides with the integral averaged over the thickness of the core layer of the original formulation of the parameterized problem that causes the physical meaning of zero-order approximation. By using the asymptotic method of analytical expressions, allowing to build a spatial – temporal dependence with the physical properties of the porous medium and a fluid filling. An exact solution of the original problem parameterized using the Laplace transform – Carson and sine Fourier transform. The validity of the asymptotic solutions checked by comparing them with the Maclaurin expansion of the exact solution of the problem. Constructed spatial – temporal distribution of pressure perturbations in the three-layer formation.
SUBSTANTIATION OF SELECTIVITY OF GEL-FORMING COMPOSITION DURING WATER-SHUT TREATMENT IN RESERVOIR OF FRACTURED-POROUS TYPE
The article is devoted to one of the main problems of oil production industry – high level of watering. Several methods of water control are investigated, but the accent is made on selective methods and materials, that increase filtration resistance in water-saturated part of a layer. Water shutoff agent based on sodium silicate is developed for selective restraining of water inflow in fractured-porous reservoir. Laboratory research of the developed gelling agent helped to establish interdependence of gel strength and period of gellation between agent concentration and temperature. It is revealed, that addition of polyatomic spirit in water shutoff agent leads to the increase of hydrophilicity if related to water-saturated rock and decrease of hydrophilicity if related to oil-saturated rock. Furthermore, high wettability of the waterproof agent in relation to water-saturated rock in comparison with oil-saturated rock proves the selective characteristic of the developed agent – when the plugging material gets to the water-saturated part it makes firm insulating barrier due to better contact with rock. Besides the change of wettability the addition of polyatomic spirit in water shutoff agent improves operational characteristic of developed plugging material in account of increasing of interionic forces and expands the exploitation temperature range.
The filtration tests proved the effective influence of inorganic gel on core sample of fractured porous reservoir from the eastern part of Orenburg oil-gas-condensate field. Also, permeability of water-saturated core samples decreases better than of oil-saturated ones. This fact proves the selectivity of the developed agent.
SUBSTANTIATION USE OF INORGANIC WATER SHUTOFF COMPOSITION FOR INCREASING OF DISPLACEMENT EFFICIENCY IN RESERVOIR OF FRACTURED-POROUS TYPE
The workis devoted to issuesof development of fractured-porousoil reservoirs. Discrete systems(caverns andfissures) have a significant impact onfiltering in them due to increased filtration characteristics in comparison with the matrix of the rock, so the process of displacing of oil by oil field or injected water is carried out faster. As a result, the water begins to enter the hole through fractures without performing useful work. In these conditions, technical and economic efficiency of development largely determines the timely and proper conduction of operations connected with the restriction of water flow to wells.
For water suppression in fractured-porous reservoirs we have designed gell-forming water shut-off composition based on sodium silicate, as the initiator of gelation we used inorganic chromium salt (III). The mechanism of gelation of the composition is following: due to the process of polymerization of silicate anions through the reaction with cations of chromium a three-dimensional atomic chain are formed in the whole volume of the initial composition.
The water shut-off composition has a wide range of adjustable time of gelling and strength (due to addition of different amount of cross-linking agent).There is dependences of the strength and time of gelling of water shut-off composition by the temperature that helps to quickly determine the optimal concentration of reagents for specific geological conditions.
The effectiveness of the composition is confirmed by results of filtration experiments conducted on samples of natural core with modeling of thermobaric conditions. Proposedwater shut-off composition reduces the water cut of the displaced liquid by 24% and increase the rate of displacement of oil by water in fractured porous reservoir from 0.07 to 0.3.