RU2389866C2 - Bottom-hole cutoff valve - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: bottom-hole cutoff valve is installed in the well together with a packer. It includes housing and movable part with shutoff devices. It operates from resultant force appearing from difference of pressures in the cutoff valve design and from buoyancy force of liquid during the well operation. It cuts out the passage in the well under influence of the force determined by the weight of the valve movable part and buoyancy force of liquid in the well. It allows carrying out the repair of the well without its being plugged with kill liquid and provides the well pressurisation.

EFFECT: increasing efficiency of automatic covering of bottom-hole interval of the well when carrying out repair or lowering-and-uplifting operations.

1 dwg

Description

The invention relates to the field of oil production, namely to killing wells. Currently, the development of oil fields is carried out with the maintenance of reservoir pressure by injecting water or gas into production horizons. In most such fields, as a result of the intensification of reservoir pressure maintenance, reservoir pressure is higher than the initial pressure or higher than the pressure of the hydrostatic column of the reservoir fluid. Despite the fact that most wells are flowing, high-performance sucker-rod or electric submersible pumps are lowered into the wells to increase fluid withdrawal.

For the descent of pumping units into wells that have excess pressure at the wellhead, it is necessary to pre-fill them, that is, replace the column of formation fluid in the well with special solutions (usually saline) with a large specific gravity.

Well filling is a laborious, expensive, lengthy process that leads to large shortages of oil after putting a well into operation. Shortages, as a result of damage to the bottom-hole zone, continue for a long time after the completion of repair work, as well as the need to work out filling fluid from the formation.

In addition, due to the influence of saline, there is intense corrosion of oilfield equipment and well structures.

Various killing methods have been proposed and are being offered. The main disadvantage of these methods is that they are based on the injection of certain chemicals into the well in order to increase the density or specific gravity of the injected solutions, including salt water. There are also designs of downhole shutoff valves operating under the action of return springs, blocking the passage in the well under the action of these springs or springs installed in the design of the shutoff valve. These are the well-known designs of the Guiberson valve and others. The same class includes "Device for blocking the fluid flow in the well" - patent No. 2237152. In this invention, the main element for controlling the shut-off valve is a return spring. The main disadvantage of this invention and other similar designs is the use of springs to control the cutting process. With alternating loads that are unavoidable during operation in the well, these loads violate the adjustment system, the main element of which is return springs or a spring, as a result of which failure in operation. Another disadvantage is the complexity of the design.

The aim of the invention is the automatic shutdown of reservoir pressure during the overhaul and maintenance of wells. The positive effect of the use of the invention is to eliminate the need to use expensive killing fluids to maintain reservoir pressure, to prevent disturbance of reservoir properties in the bottom-hole zone of the formation resulting from the absorption of killing fluid by the reservoir, to avoid additional costs associated with pumping heavy killing fluids after repairs, ensuring reliable killing of wells by using a shut-off valve, the principle of which is based on others, reliable operation of hydraulic and mechanical laws.

The problem is solved by applying one of the basic equations of hydromechanics D. Bernoulli, which with the steady motion of an incompressible ideal fluid in a uniform field of gravity has the form:

gh + p / ρ + v ^2/2 = 0,

where v is the fluid velocity,

ρ is its density,

p is the pressure in it,

h is the height of the liquid particle above a certain horizontal plane,

g is the acceleration of gravity,

C is a value constant on each streamline, but in the general case changes its value when moving from one streamline to another.

The sum of the first two terms on the left side of the equation is equal to the full potential, and the third term is the kinetic energies referred to the unit mass of the liquid;

consequently, the entire equation expresses the law of conservation of mechanical energy for a moving fluid and establishes an important relationship between v, p and h. For example, if with constant h the flow velocity along the streamline increases, then the pressure drops, and vice versa. In accordance with this, the principle of operation of the shutoff valve is based on the effect of the occurrence of a pressure difference during pumping fluid from the well, and during the repair of the well, the shutoff valve is constantly closed. Another physical phenomenon used in the solution is the Archimedean force, that is, the force that pushes the body out of a liquid or gas and is determined by the formula:

F _A = g · ρ _W · V _T ,

where F _A is the Archimedean force, ρ _W is the density of the liquid, V _T is the volume of the body immersed in the liquid,

that is, a body immersed in a liquid can float, swim inside it, or sink.

The invention is illustrated in the drawing, which shows a schematic diagram of the action of the shutoff valve (arrows indicate the movement of oil). The shut-off valve 3 is lowered into the well 2 together with the packer 8 and the coupling 1 to a depth below the production pump. Upon reaching the necessary depth of descent under the action of the buoyancy force of oil, the movable part 4 of the shutoff valve 3 rises and closes the bore hole in the well.

The design and weight of the movable part 4 of the shutoff valve 3 are designed in such a way that it operates at a certain depth in the well for stable operation of the descent pumps, that is, its weight in this case becomes less than the buoyant Archimedean force. After passing a certain volume of oil under the action of the resultant force determined by the weight of the movable part 4 of the shutoff valve 3 and the buoyancy force of the fluid in the well, the movable part 4 of the shutoff valve 3 is lifted and the force is transmitted through the stem 6 to the plate 7, which blocks the flow of oil. The upper plate 5 and the lower plate 7 in the movable part 4 of the shut-off valve 3 are locking devices in the form of valves. During operation of the pump during operation, the oil is sucked into the movable part 4 of the valve of the shut-off valve 3 and flows around with a speed around the lower end of the flange of the movable part 4 of the valve of the shut-off valve 3, thereby creating a zone of reduced pressure. This decrease in pressure depends on the geometric dimensions of the structure and is determined by hydraulic calculations and amounts to 10-15% of the pressure existing in the installation zone of the shutoff valve. (Hydraulics, water supply and sewerage. Textbook for high schools. V.I. Kalitsun, B.C. Kedrov and others. M., 1980, pp. 44-45.) And high pressure remains above the upper part of the flange. The resulting force equal to the pressure difference at the upper and lower ends of the flange of the movable part 4 of the valve of the shut-off valve 3 is transmitted through the stem 6 to the plate 7, opening it and ensuring the flow of oil. The same force provides reliable technology for crimping the tubing string. Plate 5 of the movable part 4 of the shutoff valve 3 provides reliable overlapping of the bottom of the well during pressure testing of the tubing. The stem 6 connecting the upper plate 5 and the lower 7 of the movable part 4 of the shut-off valve 3 is of sufficient length to ensure reliable operation of the shut-off valve.

The advantages of the invention:

1. The simplicity of the design.

2. The valve is a self-contained device that opens when the pump is running and automatically closes when oil withdrawal ceases.

3. A simple and reliable method of regulating the pressure of opening and closing the valve.

4. The valve does not require hydraulic, electrical or any other remote control methods, tubing manipulation or cable operation.

5. An additional advantage of the system is the prevention of flights of dismembered electric submersible and other pumps to the bottom, which is especially important in directional wells and wells with a horizontal bottom hole interval.

Claims (1)

A downhole shut-off valve installed in the well together with a packer, including a housing and a moving part with shut-off devices in the form of valves, operating from the resultant force arising from the pressure difference in the design of the shut-off valve and the buoyancy force of the liquid during well operation, which cuts off the passage in the well under the action of a force determined by the weight of the movable part of the valve and the buoyancy force of the fluid in the well, which allows repairing the well without killing it with the filling fluid and providing vayuschy well molding.