RU2431033C1 - Method to restore tightness of borehole annulus in well of gas field or field that contains natural gas in its produce - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method to restore tightness of borehole annulus in a well of a gas field or a field that contains natural gas in its produce, relates to oil and gas producing industry and may be used in reconstruction, repair, preservation and liquidation of wells with gas-untight borehole annulus at fields and underground gas depots (UGD). The method includes formation of a ring channel in a well to connect borehole annulus and tubing of the well. On completion of the ring channel formation, production tubing is lowered into the well, equipped with a packer and a circulation valve. The ring channel and the joined borehole annulus are filled with liquid via the circulation valve of the production tubing. Variation or maintenance of density and/or height of the pumped liquid column above the formed ring channel are used to provide for permanent exceeding of hydrostatic pressure of the liquid column over the layer pressure of gas.

EFFECT: simplified and more efficient method to restore tightness of borehole annulus.

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Description

The invention relates to the oil and gas industry and can be used in the reconstruction, repair, conservation and liquidation of wells with gas-tight annulus in fields and underground gas storages (UGS) to exclude migration and gas loss from productive formations along the annulus of the wells through the reservoir cover.

After the commissioning of wells of a gas deposit or a reservoir containing gas (natural, associated, etc.), in many cases annular gas shows with interstratal flows and / or griffins at the mouth are detected. One of the reasons for these gas manifestations is the flow of gas along an unpressurized cement ring in an annular space. In some cases, permeable layers are saturated with gas and technogenic accumulations of gas can form in them. All this is the reason for the high rate of decrease in reservoir pressure of the natural reservoir, especially in the initial period of development. When developing oil fields with a gas cap, uncontrolled replacement of gas by oil or water occurs. The size of the gas cap is reduced without gas extraction, as, for example, at the Samotlor field. This leads to serious violations of the design regimes for the development of deposits and irretrievable gas losses.

Uncontrolled and uncontrolled gas manifestations in the form of griffins, especially gas manifestations with hydrogen sulfide, cause irreparable environmental damage.

A known method of restoring the tightness of the annulus of a gas well or reservoir containing gas in its products (patent RU 2272890 C1, IPC EV 33/13, publ. 03/27/2006.), Including window cutting in the casing in the interval of the reservoir layer cover, removal section of the casing string in the range of 20-80% of the thickness of the tire, the removal of grouting material in the interval of the removed casing string, the expansion of the barrel in the casing window to a diameter exceeding the filtration zone of the grouting material in the primary tampo casing string and the zone of residual stresses of the primary and secondary opening of the tire, while the expansion of the wellbore is carried out in stages with an increase in the diameter of drilling at each stage by no more than 10% and ensuring the total diameter of the expansion of the wellbore exceeding the maximum size of the mentioned zones of residual stresses by 10 -40%, after which the extended section of the wellbore is covered with lining, and its holding space is plugged with a non-hardening material, for example, a viscoelastic composition based on polyacrylamide, or hypane, or natural or synthetic latex, and a hardening grouting material with additives of particles from an elastic material, for example, rubber particles or microspheres with gas.

The main disadvantage of this method is that, preventing the flow of gas through the annular space by creating an annular channel and filling it with sealing material, it essentially returns the well to the previous regime of loading annular space with reservoir gas pressure. The pressure drop arising after the well returns to the operating mode, directed from the formation to the wellhead, during operation over time can again destroy the sealed annular channel and again cause gas flows in the annulus. That is, the known method of repairing and restoring the tightness of the annulus of the well does not guarantee efficiency for a long period of operation and is temporary in nature, as is any “patch”, since after the “patching” of the annulus the mode of gas loading is restored again, and therefore destruction and leakage. In addition, in this method, to restore the tightness of the annular space of the well, various solutions are used that are necessary to create a support in an extended section of the wellbore, as well as for subsequent plugging of its fixed space, which greatly complicates the known method.

The technical result of the claimed invention is to simplify and increase the efficiency of the method of restoring the tightness of the annulus of the well. The technical result is achieved by creating a sealing shutter on the path of gas movement through the annulus that is capable of reliably performing and constantly maintaining the function of a sealant during well operation.

The specified technical result is achieved due to the fact that in the method of restoring the tightness of the annulus of the well of a gas deposit or a reservoir containing natural gas, including forming an annular channel in the well by cutting a window in the casing in the interval of occurrence of the overburden of the reservoir, removing the cut section casing string, removing grouting material in the interval of the removed cut section of the casing string and expanding the borehole in the casing window the columns according to the invention, after the formation of the annular channel is completed, the elevator column is equipped with a packer and a circulation valve, after which the annular channel and the annular space of the well associated with it are filled through the circulation valve of the elevator column by changing or maintaining the density and / or column height liquids over the formed annular channel provide a constant excess of the hydrostatic pressure of the liquid column over the reservoir gas pressure.

As a fluid for a water trap (over-packer fluid), for example, salt water, diesel fuel, gas condensate can be used. The circulation valve is used to pump fluid, create a water seal and replace fluid if necessary. The packer separates the reservoir from the annulus of the well, and also holds the above-packer fluid in the annulus.

The effectiveness of the proposed method is achieved not only by restoring the tightness of the annulus of the well, but also by constantly maintaining the specified tightness during operation for a long time. The creation of the described hydraulic lock and the provision of a reliable and constant excess of the hydrostatic pressure created by the liquid column both in the annulus and in the annular channel communicating with it, over the reservoir pressure changes the action vector of the indicated excess of the hydrostatic fluid pressure over the reservoir gas pressure to the opposite, i.e., side of the reservoir, and thus without “patching” the cement lining eliminates the flow (migration) of gas through the annular space.

The invention is illustrated in the drawing, which, as one of the possible options, shows a diagram for implementing the proposed method.

The diagram shows a well containing a casing 1, a pipe casing 2, an annulus 3 behind the casing 1 filled with grouting material, an annulus 4 between the casing 1 and the pipe 2 equipped with a circulation valve 5 and a packer 7, a producing formation 9 s located above it is an impermeable tire 8, the perforation interval 10 and the annular channel 6.

The method is as follows.

Known methods are used to investigate a borehole having a casing pressure, after which the cause of gas development, parameters, migration paths and source of supply are determined, for example, by constructing a pressure recovery curve or by a geophysical method. They plug the well with a working fluid, after which, in the interval of the casing 1 in dense impermeable rocks, which serve as a cover 8 of the productive formation 9, a cutting device, for example, UVU (universal cutting device) or a sandblasting hammer, is lowered on the drill pipes opposite to the specified impermeable rocks. A window in the casing 1 is cut out with a cutting device to remove part of the casing with a height of at least 5 centimeters, after which the grouting material is completely removed from the annulus 3 in the casing 1 removal interval, destroying the migration channels. In the cut-out window, the borehole is expanded to the maximum possible diameter by removing the rock, then the well is washed and cleaned from the products of the destruction of metal, grouting material and rock, thereby forming an annular channel 6, with the help of which hydraulic communication between the annular and the annular well space. Then drill pipes with a cutting device are removed from the well and a pipe string 2 equipped with a packer 7 and a circulation valve 5 is lowered into the well formation 9 of the well so that the packer 7 and the circulation valve 5 are located between the reservoir 9 and the formed annular channel 6. Further, after the elevator column 2 is lowered into the well, through the circulation valve 5, the annular space 4 above the packer 7, including the annular channel 6 connected with the annular space 4, injects the selected Shutter liquid whose density is calculated by the formula:

,

,

Where

ρ is the density of the liquid column above (above) the formed annular channel, kg / m ³ ;

k is the coefficient of excess of the hydrostatic pressure of the liquid column over the reservoir pressure, according to the "Safety Rules in the Oil and Gas Industry" (PB 08-624-03, clause 2.7.3.2);

p _max - the maximum reservoir gas pressure in the reservoir, MPa;

g is the acceleration of gravity, m / s ² ;

h - the height of the liquid column (water seal) above the annular channel, m,

after which the well is put into operation.

To create a water trap in the well, fluids are used that contain electrolyte-based brines, polymers and corrosion inhibitors.

The fluid selected for the hydraulic seal is pumped in a volume corresponding to the volume of the annular channel 6 with a margin of 0.5 m ³ for leaving to create excess pressure, after which the tightness of the annular channel 6 is checked by gradually increasing the pressure to the value of the possible difference between the hydrostatic pressure of the column pumped as a hydraulic seal fluid and reservoir gas pressure, which may occur due to a decrease in reservoir pressure during the operation of the well or the operation of the underground gas storage.

The use of the invention allows to ensure the tightness of the annulus, to eliminate the inter-reservoir flow from the productive to the overlying reservoir, and also to eliminate gas losses during the life of the well, which improves the environmental conditions of operation of the wells.

This method is implemented in wells in which the source of gas development is the reservoir, and migration occurs in the annulus to the overlying permeable layer or to the mouth.

Claims (1)

A method of restoring the tightness of the annulus of a well of a gas deposit or a reservoir containing natural gas, comprising forming an annular channel in the well by cutting a window in the casing in the interval of the productive formation cover, removing the cut section of the casing, removing the grouting material in the interval of the removed cut section casing strings and extensions in the casing window, characterized in that after completion of the formation of the annular channel into the well, the descent an elevator column is equipped with a packer and a circulation valve, after which the annular channel and the annular space of the well associated with it are filled with liquid through the circulation valve of the elevator column, and by changing or maintaining the density and / or height of the liquid column above the formed annular channel, the column hydrostatic pressure is constantly exceeded fluid over reservoir gas pressure.

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