RU2326229C1 - Method for water isolation in bottom-hole zone of exploitation well - Google Patents

Abstract

FIELD: oil and gas producing industry.

SUBSTANCE: invention is referred to oil and gas producing industry. According to the method in the beginning water-insulating material volume is defined. The water- insulating material is injected in a hole. It is pressed through in a formation. Thus, a water- insulating material is placed in annular space of a bottom-hole zone of the hole, bounded by isopotentials. Pressure on isopotentials makes 0÷1/3 to 1/2 from a total pressure drop between reservoir and bottom-hole magnitudes. Radiuses of isopotentials are counted under the formula.

EFFECT: it provides efficiency upgrading of water inflow isolation.

1 ex

Description

The proposal relates to the oil industry, in particular to methods of limiting water inflow and isolation of produced and injected water in production wells.

The closest in technical essence to the claimed method is a method of isolating water in the bottom-hole zone of a producing well, including pumping a waterproofing material into a well with a preliminary determination of the volume of waterproofing material and pushing it into the formation (Insulation work when completing and operating oil wells / I.I. Kleshenko , A.V. Grigoriev, A.P. Telkov. - M .: Nedra. - 1998, p.143-147).

The effectiveness of the method of isolating water in the bottomhole zone of a producing well depends on the accuracy of creating the interval of the insulating screen, which is selected according to the results of geophysical and hydrodynamic studies. The difficulty in choosing the interval for creating a screen is sometimes due to the inability to unambiguously distinguish oil-saturated and flooded intervals of the reservoir, despite a significant amount of research. The radius of the screen is determined from the condition that the partial derivative of depression along the radius of the depression funnel should not exceed the value:

where ρ _in - the density of formation water.

The partial derivative, after preliminary calculation of the depression value according to the radius of the depression funnel according to the Leibenzon formula and preliminary determination by the Dupuis formula of the established bottomhole depression on the well wall, is determined by graphical differentiation of the depression funnel curve. Then, by interpolation, they select such a length of the screen radius, on the external boundary of which condition (1) will be fulfilled. The effectiveness of this method of water isolation completely depends on the exact preliminary determination of a number of quantities, the calculation error of which is large. Thus, the disadvantages of this method are obvious - a large error in the calculation of determining the volume of injection of waterproofing material, the complexity, cumbersome and subjective calculations, the need for a complex of preliminary laborious downhole research and calculations. As a result: either overspending or insufficient injection of insulating material. In the first case, economic costs increase, in the second, the effectiveness of waterproofing works decreases.

The technical task is to increase the efficiency of isolation of water inflow in the producing well by increasing the reliability of the blocking effect by increasing the accuracy of determining the optimum water-proof screen, as well as expanding the technological capabilities of the method of isolating water in the bottom-hole zone of the producing well, simplifying operations and reducing economic costs.

The problem is solved by the described method, including the injection of waterproofing material into the well with a preliminary determination of the volume of waterproofing material and pushing it into the reservoir. New is that the waterproofing material is placed in the annular space of the bottomhole zone of the well, limited by equipotentials, the pressures of which are from 0 ÷ 1/3 and up to 1/2 of the total pressure drop between the reservoir and bottomhole values, and the radii of the equipotentials are calculated by the formula:

where R _a are the radii of the equipotentials, where 1/2 and 0-1 / 3 of the losses of the input pressure drop to overcome the filtration resistance occur;

R _κ is the radius of the conditional power circuit;

r _c is the radius of the well by bit;

α - coefficient taking into account the pressure distribution in the bottomhole formation zone, equal to 0 ÷ 1/3 and 1/2, respectively.

Comparative analysis with the prototype shows that the inventive method has distinctive features that are absent in the known method of isolation of water inflow. These features ensure that the new technical solution meets the criterion of "novelty." When comparing the method not only with the prototype, but also with other well-known technical solutions in the field of waterproofing works in producing wells, no solutions were found that have the same characteristics as the present invention, performing a similar technical task. This allows us to conclude that the new technical solution meets the criterion of "inventive step".

The claimed method solves the problem of increasing the efficiency of water isolation in the bottom-hole zone of production wells. The problem is solved by non-standard interconnected operations of calculating the placement of the displacement material in a strictly defined annular space around the wellbore, which is a coaxial cylinder in geometry, the height of which is equal to the thickness of the flooded formation, and the outer and inner radii of the cylinder are equal to the radial distances from the axis of the well, where respectively 0 ÷ 1/3 and 1/2 of the losses of the supplied differential pressure to overcome the filtration resistance, while the calculation of these calculations Thawings (radii are equipotential) are carried out according to the proposed formula. Equipotential is a conditional contour around a well, in which the pressure drop between reservoir and bottomhole values is one value. The outer radius of the coaxial cylinder corresponds to the equipotential with a value of 1/2 of the total differential pressure, and the inner radius of the cylinder can vary (correspond to equipotentials) from 0 to 1/3 of the total differential pressure.

The proposed method allows to achieve a new technical effect due to the installation in the bottomhole formation zone of the optimal size of the waterproofing screen, which provides isolation of water inflow according to the criterion of formation energy efficiency - pressure drop; the screen provides neutralization from 1/6 (1 / 2-1 / 3) to 1/2 (1 / 2-0) of the fraction of the total pressure drop. There are no similar solutions (at the same time simple, universal and effective) in the field of optimization of water insulation works in wells in the world.

The method in practice is implemented as follows.

The volume of the waterproofing composition and the displacement fluid are determined based on the current values of the well injectivity and the following parameters:

- conditional radius of the power circuit - R _K , m (determined by the grid of wells and taken as the average distance between the wells);

- well radius by bit - r _C , m;

- thickness of the oil-saturated part of the reservoir - h _HH , m;

- porosity - m, fractions of a unit;

- viscosity of oil and water in reservoir conditions - μ _n and μ _in , MPa · s;

- water cut - In, the share of units.

As a waterproofing material, for example, gypsum, water glass, mixtures thereof, phenol-formaldehyde resins, oil-cement mixtures and other known materials are used. The procedure for calculating the volume of insulating material is based on the idea of the geometric shape of the insulating screen in the form of a coaxial cylinder, the overall dimensions of which determine such parameters as the height of the cylinder h _IZ , m; outer radius R _N , m; inner radius R _Â , m

The volume of insulating material V _of , m ³ is calculated by the formula:

where π = 3.14; m - porosity, fractions of units

The insulating material is placed in an annular zone with an outer radius R _H = R _1/2 , and an inner radius R _B = R ₀ ... R _1/3 , where R _1/2 and R _1/3 are the distances in the radial direction from the axis wells, where half and one third of the losses of the input pressure drop occur (the difference between the reservoir and bottomhole pressure) to overcome the filtration resistance. The inner radius can be from R ₀ (the inner radius of the coaxial cylinder is equal in this case to the radius of the well bit) to R _1/3 . The volume of waterproofing material, ensuring an outer radius of more than R _1/2 (equipotentials with more than 1/2 of the total pressure drop), is energetically and economically impractical.

The calculation of the radius R _α that determines the size of the zone of the given losses of the total pressure drop is determined by the formula:

The value of the parameter h _FR is determined by the formula:

where δ = -0.4 ... 0.6 is the correction factor for the productive part of the formation with a thickness of h _NN , fractions of units

The correction factor δ determines the proportion of the oil-saturated part of the formation along the section, which effectively manifests oil when a well is put into operation;

ξ _max - correction factor that determines the proportion of the flooded part of the reservoir, the share of units

The value of the correction coefficient ξ is determined by the formula:

The volume of the squeezing liquid is calculated by the formula:

V _RV = V _MB + V _tubing

where V _MV - the volume of the displacement fluid, m ³ ;

V _tubing - the volume of the squeezing fluid based on the killing fluid (internal volume of the tubing string), m ³ .

An example of a specific implementation (design) of the method.

The proposed method was tested at well No. 1544 of the Romashkinskoye field.

Initial data: density of wells grid - 600 × 600 m, well radius by bit - 0.11 m, perforation interval 1700-1705 m, effective formation thickness - 5 m, porosity - 20%, water content in the well production - 90%, viscosity of oil and water in reservoir conditions - 4.0 and 1.0 MPa · s, respectively, length 2.5 ^// tubing string - 1706 m

Calculation algorithm

R _1/3 = 300 ^1/3 · 0.11 ^{1-1 / 3} = 1.54 m

R _1/2 = 300 ^1/2 · 0.11 ^{1-1 / 2} = 5.74 m

h _FR = 0.6 × 0.692 × 5 = 2.1

The volume of insulating material, m ³ :

V _out = 3.14 × 0.2 × (5.74 ² 1.54 ² ) × 2.1 = 40.3

Volume of squeezing liquid, m ³ :

V _MV = 3.14 × 0.2 × (1.54 ² -0.11 ² ) × 2.1 + 3.14 × 0.11 ² × 5 = 3.3

V _tubing = 3.14 × 0.031 ² × 1706 = 5.5

V _pancreas = 3.3 + 5.5 = 8.8.

Through the lowering of the lower perforation holes, the tubing string (tubing) was pumped with a water-insulating material, gypsum-liquid glass with an open valve on the annulus. Water-insulating material was injected into the well until the liquid level (water-insulating material) was raised in the annulus to the interval of the formation roof. They closed the valve on the annulus. They sold waterproofing material in the estimated volume of 40.3 m ³ in the interval of water inflow. The estimated volume of the squeezing fluid of 8.8 m ³ provided the rim of the waterproofing material to be offset by a predetermined distance from the well wall, in this case by 1.54 m. Next, the well was left under pressure for the time of structuring and setting the waterproofing material. It should be noted that the entire calculation of the required volumes of process fluids took only 15 minutes. A waterproofing screen was formed in the annular space of the bottomhole zone of the well, limited by equipotentials, the pressures of which amounted to 1/3 and 1/2 of the total pressure drop between the reservoir and bottomhole values.

After well No. 1544 entered the regime, the following results were obtained: water cut decreased 3 times, from 95-97% to 33-35%; oil production rate increased by 5 times, from 0.9-1.2 tons / day to 4.5-5.5 tons / day. The effect stably lasts for 9 months.

In the neighboring well No. 1542 (similar to well No. 1544 of the design), a known prototype method was tested. The calculation of the required volume of waterproofing material was performed within 7 days (according to the results of hydrodynamic studies, the following initial data were clarified: permeability, hydraulic conductivity, flow rates for liquid and oil, elasticity of injection fluid, piezoelectric conductivity, well injectivity was determined, reservoir elasticity, and others). The length of the screen radius (with a density of produced water of 1170 kg / m ³ ) turned out to be 120 cm with a partial derivative of 0.02. The required volume of insulating material was 20 m ³ .

20 m ^{3 of} insulating material Hypan + liquid glass was pumped into the well, 5 m ^{3 of} squeezing liquid was pushed into the formation. Left to react (setting) solutions. After insulation work, the well was put into operation.

After the well entered continuous operation, the following results were obtained: there was a decrease in water cut from 93% to 78%, an increase in oil production from 1.1 tons / day to 2.0-2.3 tons / day. The effect lasted for 3 months. Then, repeated water isolation operations were required.

A comparative analysis of the effectiveness of the proposed method for isolating water showed that the new method is 2.5-3 times more effective than the known method for isolating water in the bottomhole zone of a producing well.

Thus, field tests of the proposed new method for isolating water in the bottomhole zone of a producing well have shown its high technological and economic efficiency. A wide industrial introduction of this method of water isolation in the fields of OAO TATNEFT is planned, which will reduce water cut, increase oil production by increasing the reliability of the blocking effect by increasing the accuracy of determining the optimum size of the water barrier, as well as expanding the technological capabilities of the method of water isolation in the bottom-hole zone of the producing well, simplifying operations and reducing economic costs.

Claims (1)

A method of isolating water in the bottom-hole zone of a producing well, which includes injecting water-insulating material into the well with preliminary determination of the volume of water-insulating material and pushing it into the formation, characterized in that the water-insulating material is placed in the annular space of the bottom-hole zone of the well, limited by equipotentials, the pressures of which are from 0 ÷ 1/3 and up to _^1/2 of the total pressure differential between the reservoir and downhole quantities and equipotentials radii calculated by the formula

where R _α are the radii of the equipotentials, where 1/2 and 0 ÷ 1/3 of the losses of the input pressure drop to overcome the filtration resistance occur; R _κ is the radius of the conditional power circuit; r _s - well radius by bit; α - coefficient taking into account the pressure distribution in the bottomhole formation zone, equal to 0 ÷ 1/3 and 1/2, respectively.