RU2339809C1 - Method for construction and operation of steam well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to extraction of oil by means of heat methods and can be implemented for injecting of heat carrier into payout bed. Method includes construction of well with cased borehole, the lowering of pump-compressor tube column (PCT) with packer into it and sealing of well head. At construction of the well it is cased with additional upper column of casing tubes, wherein column of casing tubes of a smaller diameter is lowered; at that, tubing centralisers are secured to sections conjugated with the upper column of casing tubes. A back valve is arranged on the lower centralizer, while a connecting pipe for connection of a gas source and a compensator of heat extensions of the column of casing tubes are arranged at the well head; then the column of PCT with the centralisers is lowered. At the lower centralizer there is arranged the back valve and the packer in form of an anchor-compactor, expanded with a mandrel, which together with the mandrel seals the annular space of the well and creates a sturdy mechanical connection. A connecting pipe for connection to a gas source and a compensator of heat expansions of the case tubes column PCT are arranged on the well head. The well head is thermo-insulated with a split thermo-insulating material and is equipped with a compensator of heat expansions of PCT.

EFFECT: upgraded reliability of steam well and reduction of heat losses at ejecting of heat carrier to payout bed via well.

6 cl, 4 dwg

Description

The invention relates to the oil industry, in particular to the field of oil production by thermal methods, and can be used to pump the coolant into the reservoir.

A known method of construction and method of operating a horizontal well (RF patent No. 2159317, ЕВВ 7/04, 43/20, published in Bull. No. 32 of 11/20/2000), including the construction of a two-well well, cased with casing and equipped with an annular packer . A liquid or gaseous agent is pumped from a wellhead to the well in order to maintain reservoir pressure, and hydrocarbons are extracted from another wellhead.

The disadvantage of this method is that the wellhead is not thermally insulated and when the coolant is pumped through the pipe string into the formation, the entire well warms up and heat losses will be significant. In addition, the device does not provide devices for compensating for thermal expansion of pipes, which can lead to emergency situations.

There is also known a method of thermal insulation of an injection well (RF patent No. 2120540, ЕВВ 36/00, published in Bull. No. 29 of 10/20/1998), including the descent of a tubing string with a packer into a cased pipe casing, installation concentric tubing above the packer of the additional separation pipe with the formation of annular cavities in communication with the surface, and sealing the wellhead. When the coolant is pumped through the tubing into the reservoir along the annular cavities, a heat-insulating agent (gas) is simultaneously pumped, which constantly removes heat from the heat insulation zone.

The disadvantage of this method is that the wellhead is not thermally insulated and there are no expansion joints for the temperature expansion of the pipes, which can lead to emergency situations. In addition, instead of thermal insulation of the wellhead, tubing and temperature control of the coolant, the steam generator constantly removes heat from this zone, which leads to additional costs.

The objective of the proposed technical solution is to increase the reliability of the steam injection well and reduce heat loss during injection through it of the coolant into the reservoir.

The problem is solved by the described method, including the construction of a well cased with casing pipes, lowering into it tubing string with a packer and sealing the wellhead.

What is new is that during the construction of a well, it is cased with an additional upper casing string, into which a smaller casing string is lowered, centralizers are attached to it in sections mating with the upper casing string, and a check valve is placed on the lower centralizer, and the wellhead is equipped a fitting for supplying gas to the annulus and a compensator for thermal expansion of the casing string, lower the tubing string with centralizers, moreover, on the lower centralizer a check valve is installed, and a packer in the form of an anchor-seal expanded by the mandrel, which together with the mandrel seals the annular space of the well and forms a strong mechanical connection with the casing, the wellhead is equipped with a fitting for supplying gas to the annular space, a compensator for thermal expansion of the tubing string pipes and isolate a collapsible heat-insulating material, providing a compensator for thermal expansions and protecting against atmospheric influences. The new fact is that the annular spaces of the casing and tubing strings are freed from the accumulated fluid, as necessary, successively squeezing out the gas pressure supplied through the fittings through the check valves, expansion joints of expansion joints are used, the housings of which are attached to the upper casing couplings . In addition, a heat-reflecting coating is applied to the inner surfaces of the casing, air is used as a heat insulator, and measured rolls of mineral (stone) wool are used to insulate the wellhead, protecting them from atmospheric influences, graphite-containing material is used as stuffing box packing, and mating with the outer surfaces of the casing and tubing are subjected to finishing and isolation from corrosion.

Figure 1 shows a diagram of the proposed steam injection wells (surface pipeline shown conditionally).

Figure 2 - thermal insulation of the wellhead, section AA in figure 1.

In Fig.3 - the lower centralizer with a check valve on the tubing string, section BB in Fig.1.

Figure 4 - check valve on the lower centralizer of the casing string, callout In figure 1.

The method is carried out in the following sequence. During the construction of the well, it is cased with an additional upper casing string 1 (Fig. 1), into which a lower casing string 2 of a smaller diameter with a slotted filter (not shown in Fig.) Is lowered for the zone of the reservoir, attaching centralizers 3 to it interfaced to the upper casing string 1 sections, with a check valve 4 being placed on the lower centralizer (Fig. 4), and the wellhead is equipped with a fitting 5 (Fig. 1) for supplying gas to the annular space 6 and a compensator of thermal expansions 7 (compensator) of the casing string 1 . In to the casing pipe 2 is lowered by the tubing 8 with centralizers 9, and the check valve 10 (Fig. 3) and the packer 11 (Fig. 1) in the form of an anchor-seal 12 expanded by the mandrel 13 are also placed on the lower centralizer which together with the mandrel 13 seals the annular space 14 of the well and forms a strong mechanical connection with the casing 2, and the wellhead is equipped with a fitting 15 (Fig. 1) for supplying gas to the annular space 14 and the compensator 16 of the tubing string 8. In this case, the annular spaces formed 6 and 14 between complement Flax upper string of casing 1 and the pipe string 2 of smaller diameter, smaller diameter pipe columns 2 and 8 of tubing, filled with air. Air is a good heat insulator (thermal conductivity - 0.03 W / m · K). The wellhead is isolated with a collapsible heat-insulating material 17, on which a cover 18 is put on having a corrugated portion 19, and is fastened with belts 20, 21 and provided with a compensator 22 of the ground pipes 23, which are also insulated. It is recommended that a heat-reflecting coating (e.g. zinc) be applied to the inner surfaces of the casing. Gland type expansion joints are used, including housings 24 and 25, respectively attached to the upper couplings 26 and 27 of the casing pipes 1 and 2. Gland packing 28 is pressed, whenever necessary, with packing followers 29 and 30 using nuts 31. As an stuffing box, 28 graphite-containing material, and the external surfaces of the casing and tubing mating with it are subjected to finishing treatment and corrosion protection (for example, by spraying an anticorrosive material).

When producing highly viscous oils and bitumen by thermal methods, it is necessary to supply a coolant (superheated steam) with a temperature of up to 350 ° C to the reservoir. The materials of all structural elements of the well must be operational under these conditions. Known materials - mineral (stone) - wool can be used for thermal insulation of surfaces with a working temperature of up to 700 ° C. They have good thermal insulation properties (thermal conductivity at a temperature of 300 ° C - 0.09-0.16 W / m · K), fibrous structure, fireproof, compressible, environmentally friendly, can be delivered in the form of stitched rolls of a given thickness and in the form of stitched rolls reinforced with steel mesh and aluminum foil. However, when using these materials in practice, it is necessary to reliably protect them from atmospheric influences. This provides a protective cover 18 made of reinforced plastic film. Corrugated section 19 of the protective cover 18 protects it from destruction during operation. As a stuffing box material for 28 expansion joints 7 and 16, we propose using a material of the "Graflex" type, which consists of 99% graphite and a binder, can operate at temperatures above 700 ° C, is molded, pressed and has lubricating properties.

Steam is injected into the reservoir through a ground insulated pipe 23 and tubing 8 (figure 1). In this case, the annular cavities 6 and 14 are filled with air and together with the heat-insulating material 17 reduce the heat loss of steam. The resulting thermal expansion of the casing string 2, tubing 8 and pipe 23 compensate for the corresponding compensators 7, 16 and 22. If the annular cavities 6 and 14 are filled with borehole fluid (water) that increases the heat loss of the steam, first connect the gas source to the nozzle 5 and water is pressed by pressure through the check valve 4 into the cavity 14, then the gas source is connected to the nozzle 15 and water is squeezed out through the check valve 10 into the tubing. These operations are performed as necessary. Dry gas can be used as gas.

The presence of insulating cavities 6 and 14 also allows you to protect the cement stone of the casing string of the well from exposure to high temperatures.

The technical and economic advantage of the proposed method for the construction and operation of a steam injection well is as follows. Equipping the tubing with a packer, and the wells with compensators located on the surface and convenient for maintenance, increases the reliability of the well. Thermal insulation of the wellhead with a collapsible heat-insulating material protected from atmospheric influences, and the presence of several heat-insulating cavities filled with air, as well as coating the inner surfaces of the casing with heat-reflecting material will reduce heat loss during injection of the coolant into the reservoir. Periodic extrusion of fluid accumulated in the cavities does not cause technical difficulties. The use of mineral (stone) wool as a heat-insulating material, and graphite-containing material as an stuffing box will increase the temperature of the pumped coolant. The use of simple stuffing box expansion joints, their placement on the upper casing couplings, as well as the finishing and isolation of the surfaces of the casing and tubing mating with them from corrosion also increase the reliability of the well. To seal the wellhead does not require the use of expensive valves. The method is applicable in deviated and horizontal wells.

Claims (6)

1. A method of constructing and operating a steam injection well, including constructing a well with a cased casing string, lowering tubing string with a packer into it and sealing the wellhead, characterized in that during construction of the well, it is cased with an additional upper casing string into which it is lowered a smaller diameter casing string, attaching centralizers to it in sections mating with the upper casing string, and a check valve is placed on the lower centralizer, and the mouth e wells are equipped with a fitting for supplying gas to the annulus and a compensator for thermal expansions of the casing string, lower tubing with centralizers, and a check valve is placed on the lower centralizer, and with a packer in the form of an anchor-seal, expandable by a mandrel, which together with the mandrel seals annular space of the well and forms a strong mechanical connection with the casing, the wellhead is equipped with a fitting for supplying gas to the annular space, a compensator of thermal expansion column tubing and isolate collapsible teploizolizoliruyuschim pictures by providing expansion joints and protection against atmospheric influences. 2. The method according to claim 1, characterized in that the annular spaces of the casing and tubing strings are freed from the accumulated fluid as necessary, successively squeezing out the gas pressure supplied through the fittings through the check valves. 3. The method according to claim 1, characterized in that compensators for thermal expansion of the stuffing box type are used, the housings of which are attached to the upper couplings of the casing. 4. The method according to claim 1, characterized in that a heat-reflecting coating is applied to the inner surfaces of the casing, and air is a heat insulator. 5. The method according to claim 1, characterized in that for the thermal insulation of the wellhead, measured rolls of mineral (stone) wool are used, protecting them from atmospheric influences. 6. The method according to claim 1, characterized in that graphite-containing material is used as the stuffing box packing of the compensators, and the external surfaces of the casing and tubing mating with it are subjected to finishing treatment and insulation from corrosion.

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