RU2379495C1 - Oil field thermal treatment and equipment for its execution - Google Patents

Abstract

FIELD: oil-and gas industry.

SUBSTANCE: method includes descending well electro heater on a tubing string (TS) into reservoir interval with the following heating and heated product exploration. Heated product production execute with the periodical injection of the heated product back to the oil reservoir. Increase the heated product injection volume and pressure every period till it reaches maximum allowable injection pressure. At the every period the volume of the heated product injected back to the reservoir - few times smaller than the volume of produced heated product. Equipment includes the well electro heater with a drive, located on TS. The TS equipped with a parker higher then the well electro heater, but lower than well's dynamic with production level, hermetically separating well's string clearance. Radial holes performed bellow the parker on TS, and over the parker on TS installed a bottom hole pump. TS is sealed at the bottom, which increases heat transfer area at TS's part from the blind valve to the radial holes.

EFFECT: oil reservoir thermal treatment efficiency increase, due to cover radius increase and providing oil supply from a zone remotely located from the well.

2 cl, 2 dwg

Description

The invention relates to the oil industry and is intended for thermal effects on the bottom-hole zone and the oil reservoir, including for the prevention or heating of paraffin-hydrated deposits.

A well-known electric heater (copyright certificate SU No. 1627671, IPC 7 E21B 36/04, E21B 43/24, publ. 02/15/1991), containing a conductor with a tubular body mounted under it with a long heating element arranged in a spiral on its surface, wherein the heating element is placed unevenly along the length of the housing with an increase in the pitch of the spiral from the end of the housing towards the current lead.

Also known is an induction borehole electric heater (patent RU No. 2198284, IPC 7 E21B 36/04, E21B 43/24, published in Bulletin No. 4 of 02/10/2003), including a housing that is simultaneously a magnetic core, a heating element in the form induction coil wound on the outer surface of the housing, the contact node with a current-supply cable, and the housing, which is also a magnetic core, is a tubing equipped with metal rings with cuts through which the wires of the windings of the induction coil are laid ki, while the induction coil is made of two layers and has three windings of wires with heat-resistant insulation.

The disadvantages of both analogues are:

- firstly, a structurally complex device, in addition, most induction-type heaters with high electrical resistance of the heating element emit a large amount of heat per unit length and therefore are short-lived and not sufficiently reliable;

- secondly, they are not effective enough for heat treatment of thick formations, for example, carbonate, as well as for melting or preventing paraffin-hydrate plugs of great length; large-length asphalt-resinous, afaltosoloparaffin deposits in the tubing and on the sucker rods;

- thirdly, the devices are also not applicable for heating and reducing the viscosity of well products at the reception of deep pumps.

The closest in technical essence and the achieved result are a downhole electric heater (patent RU No. 2198284, IPC 7 E21B 36/04, E21B 37/00 publ. In Bulletin No. 9 of 03/27/2005), containing a current lead with a tubular a casing with a long-length heating element placed on its surface in the form of a cable with the possibility of supplying a voltage from a source through it to a current supply, characterized in that it is grounded to the tubular casing and a cable with low electrical resistance installed in a magnetic tube along the tubular body with the possibility of forming a closed loop and feeding from a source of supplying alternating voltage, while a cable with low electrical resistance is installed in the ferromagnetic tube along the tubular housing along its perimeter in the form of a multi-pass sequence of parallel long-length heating elements, the ferromagnetic tube is made divided into sections, the number of which is determined by calculation depending on the intensity of the curvature of the operational columns and overall dimensions, and the method of its application, including the descent of a borehole electric heater on a string of tubing into the interval of the oil reservoir, followed by heating and production of heated products from the well.

The disadvantage of this method is its low efficiency due to a slight increase in oil recovery of the oil reservoir, since the radius of heating is small, and this does not ensure the flow of oil to the well from a zone remote from the well. Moreover, as a result of the practical application of this method, it was found that the largest increase in oil production was achieved in low-production (up to 2.0 tons / day) production wells. In production wells with an initial flow rate of 3-5 tons / day, the relative increase in flow rate due to the use of this electric heater is significantly lower. It follows that the use of an electric heater in order to intensify oil production is advisable only in low-rate producing wells (with a flow rate of up to 2.0 tons / day).

The disadvantages of this device are large heat losses, since the heating of the well’s products occurs only in the interval of placement of the downhole electric heater and the main part of the heat generated by the electric heater is taken along with the products that are extracted from the well and a small area coverage (practically this section is limited by the geometric dimensions of the electric heater ) on which the product is heated.

The objective of the invention is to create an effective method of thermal impact on the oil reservoir, allowing for extensive heating of the oil reservoir, increasing the radius of coverage and ensuring the flow of oil to the well from a zone remote from the well, as well as allowing to intensify oil production from low production wells with flow rates up to 2 tons / day, and from wells with higher flow rates, and a device for its implementation, which allows to reduce heat loss and direct a significant part of the heat to heat the oil field one hundred by increasing the coverage area heated by the borehole.

The problem is solved by the method of thermal action on the oil reservoir, including the descent of the borehole electric heater on the string of tubing into the interval of the oil reservoir with subsequent heating and production of heated products from the well.

The new fact is that the production of heated well products is carried out with periodic injection of the heated well products back into the oil reservoir, while the volume and pressure of the heated products are injected and, accordingly, the depth of penetration of the heated products into the oil reservoir is increased with each period until the maximum allowable injection pressure is reached products in the oil reservoir, and in each of the periods the volume of injection of heated products back into the oil reservoir is several times less than the volume of extracted heated product ns from a well.

The problem is also solved by a device for thermal impact on the oil reservoir, including a downhole electric heater with a current lead, placed on a string of tubing.

New is that the tubing string is above the borehole electric heater, but below the dynamic level of production in the well, is equipped with a packer hermetically separating the annulus of the well, while below the packer radial holes are made in the tubing string, and an inserted sucker rod pump is installed above the packer in the tubing string, moreover, the tubing string is plugged from below, which increases the heat transfer area on the tubing string portion from the plug to the radial holes.

Figure 1 shows the proposed method of thermal effects on the oil reservoir and a device for its implementation at the time of selection of heated production wells.

Figure 2 shows the proposed method of thermal exposure to the oil reservoir and a device for its implementation at the time of injection into the oil reservoir of heated well products.

The proposed method is as follows.

First determine the dynamic level of production in the well. Then downhole electric heater 3 is lowered into the well 1 on the tubing string 2 (for example, the electric heater described in patent RU No. 2198284, IPC 7 E21B 36/04, E21B 37/00, published in Bulletin No. 9 dated March 27, 2005) with a current lead 4 and a packer 5 placed on a tubing string 2 above the electric heater 3, while the electric heater 3 is installed in the interval of the oil reservoir 6, and the packer 5 is planted in the well 1 below the dynamic level, for example, 100 meters (not shown in FIGS. 1 and 2). Then the plug-in deep sucker-rod pump 7 is lowered into the well, the downhole electric heater 3 is turned on, which heats the products of the well 1 in the interval of the oil reservoir 6. The drive (for example, a rocking machine) (not shown in FIGS. 1 and 2) of the deep-well rod pump 7 and produce heated products along the tubing string 2 from the well 1 in the volume of V _d

After a certain period of time, which is determined by calculation, depending on the power of the electric heater, the physicochemical properties of the produced products (viscosity, density, etc.), the drive of the plug-in deep-well pump 7 is turned off and the plunger 8 is lifted (see figure 2) from the cylindrical body 9 of the deep-well rod pump 7.

After that, from the wellhead 1 through the tubing string 2, any known pump injects in a volume of V _s , several times smaller than the volume of produced products V _d , which is determined by calculation.

As a result of pumping heated oil into the oil reservoir 6, the radius of heating by the electric heater 3 of the oil reservoir 6 increases, which ensures the flow of oil to the well 1 from the zone remote from the well. After pumping the calculated volume V _s , the plunger 8 is installed back into the cylindrical body 9 and the drive of the deep-well sucker-rod pump 7 is put into operation and the heated product is again extracted from the tubing string 2 from the well 1.

After a certain period of time, when the plug-in deep well pump 7 will be extracted from the well 1 to the surface of the heated product

V _d1 more than the pumped V _s , turn off the drive of the deep-well pump 7 and lift the plunger 8 (see figure 2) from the cylindrical body 9 of the deep-well pump 7.

After that, from the wellhead 1, the heated product extracted from the well 1 is pumped through the tubing string 2 back into the oil reservoir 6 in the estimated volume V _s1 , while the heated product penetrates even deeper into the oil reservoir 6 compared to the originally injected volume V _s .

Injection pressure P _{P1 P1} volume V in the oil reservoir 6 exceeds the injection pressure P _of the volume V _s, i.e. (F _P1> P _s) that is caused by deeper penetration (pushing through) the heated products in an oil reservoir 6.

As a result, the radius of heating by the electric heater 3 of the oil reservoir 6 is further increased, which ensures the flow of oil to the well from a zone farther from the well. After the calculated volume of preheated products is pumped into the oil reservoir 6 (see FIG. 1), the plunger 8 is installed back into the cylindrical body 9 and the drive of the deep-well sucker rod pump 7 is started up and the production of preheated products through the tubing string 2 from the well 1 begins.

Further, the above cycle is repeated. As a result, with each cycle of production and injection of heated products, the radius of heating of the oil reservoir 5 increases with the electric heater 3 of the oil reservoir 6 and the flow of oil to the well 1 with the zone farther from the well 1 is provided, while the electric heater 3 is constantly working. At the same time, with each subsequent injection of heated products into the oil reservoir 6, the penetration depth (coverage radius) of the heated products into more distant zones of the oil reservoir 6 increases, and, accordingly, with each subsequent injection, the injection pressure increases.

Thus, the injection volumes V _dn and V _{sn are} gradually and proportionally increased until the maximum allowable injection pressure P _{s max} is reached into the oil reservoir 6, which limits the depth of penetration of the heated product into the oil reservoir 6.

In the future, periodically combining the production and injection of heated products, not exceeding the maximum allowable injection pressure P _{s max} , continue to develop the oil reservoir 6.

The proposed method of thermal treatment of the oil reservoir allows for extensive heating of the oil reservoir by gradually increasing the volume of heated products back into the oil reservoir with each cycle of injection, thereby increasing the coverage radius, which ensures the flow of oil to the well from a zone remote from the well and makes it possible to intensify oil production both from low-production wells with a production rate of up to 2 tons / day, and from wells with higher production rates.

A device for implementing the above method includes a downhole electric heater 3 with a conductor 4 lowered into a well 1 on a tubing string (tubing) 2, located on a tubing string (tubing) 2. A packer 5 is installed in the tubing string 2 above the electric heater 3 located in the interval of the oil reservoir 6 and planted in the well 1 below the dynamic level of production in the well 1. In the tubing string 2 above the packer 5 there is an inserted sucker-rod deep pump 7 consisting of a plunger 8 and a cylindrical body whisker 9. The tubing string 2 from the bottom is plugged with a plug 10, which allows the heat generated by the electric heater 3 to be accumulated at a distance S, that is, in the section of the tubing string 2 from the plug to the radial holes 11, a stagnant zone of the well production heated by the electric heater 3 is formed. Below the packer 5, the tubing string 2 is equipped with radial holes 11. The packer 5 hermetically separates the annular spaces 12 and 13 of the well 1 among themselves.

Device for thermal effects on the oil reservoir works as follows.

The assembled device, as shown in Fig. 1, is put into operation, while the electric heater 3 simultaneously with the heating of the products in the interval of the oil reservoir 6 transfers heat to the inner walls of the tubing string 2. As a result, the production of the well inside the tubing string 2 from the plug is heated 10 to the radial holes 11 in section S, so the heat transfer area of the electric heater 3 increases several times, that is, inside the tubing string 2 in section S, a stagnant zone of the heated product is formed. The heat from the walls of the tubing string 2 in section S is aimed at heating the well products in the annulus 13, and this allows you to expand the coverage of the heated section to a distance S in comparison with the prototype, where the products are heated only within the electric heater, and keep as much warm as possible products (liquids) both during production from well 1, and when injected into the oil reservoir 6, since the products heated up in the annular space 13 enter the oil reservoir 6.

At the same time, the plunger 8 of the plug-in deep sucker-rod pump 7, by means of the rod string 14 and the drive (not shown in FIGS. 1 and 2), makes reciprocating movements relative to the cylindrical plunger 9, lifting products heated up by the electric heater 3 from the annular space to the surface along the tubing string 2 13 of the well 1, the heated oil being received by the insertion of the deep sucker rod pump 7 from the annular space 13 through the radial holes 11, since the lower end of the tubing string 2 is plugged Coy 10.

Before the heated products are pumped into the oil reservoir 6, the plunger 8 is lifted (see FIG. 2) from the cylindrical body 9 of the plug-in deep-well sucker-rod pump 7. After that, the heated products extracted from the well 1 are pumped from the well 1 through the tubing string 2 through the radial holes 11 , since the bottom of the tubing string 2 is plugged with a plug 10 back into the oil reservoir 6.

After the heated products are pumped into the oil reservoir 6 (see FIG. 1), the plunger 8 is installed back into the cylindrical body 9 and the drive of the deep-well sucker pump 7 is put into operation and the production of heated products from the tubing string 2 from the well 1 starts again. After that, the operation cycle device repeats.

The proposed method of thermal treatment of the oil reservoir allows for extensive heating of the oil reservoir by gradually increasing the volume of heated products back into the oil reservoir with each cycle of injection, thereby increasing the coverage radius, which ensures the flow of oil to the well from a zone remote from the well and makes it possible to intensify oil production both from low-production wells with a production rate of up to 2 tons / day, and from wells with higher production rates.

This device for thermal impact on the oil reservoir allows you to reduce heat loss and direct a significant part of the heat to warm the oil reservoir, due to the fact that the tubing string is plugged from below, and the electric heater simultaneously with the heating of the products in the interval of the oil reservoir transfers heat to the inner walls of the tubing string, and this allows you to accumulate heat in the area of the tubing string from the plug to the packer, thereby significantly increasing the coverage of the heated section of the well.

Claims (2)

1. The method of thermal impact on the oil reservoir, including the descent of the borehole electric heater on the tubing string — tubing into the interval of the oil reservoir with subsequent heating and production of heated products from the well, characterized in that the production of heated products from the well is carried out with periodic injection of heated products from the well back into the oil reservoir, with the volume and pressure of the injection of the heated product and, accordingly, the depth of penetration of the heated product into the oil reservoir with each period increase until the maximum allowable pressure of product injection into the oil reservoir is achieved, and in each of the periods, the volume of injection of the heated product back into the oil reservoir is several times less than the volume of the extracted heated product from the well. 2. A device for thermal treatment of an oil reservoir, including a borehole electric heater with a current lead, located on a tubing string — tubing, characterized in that the tubing string is higher than the borehole electric heater but below the dynamic level of production in the well with a packer that hermetically separates the annular spaces wells, while below the packer in the tubing string radial holes are made, and above the packer in the tubing string there is an inserted sucker-rod deep pump, and the tubing string is below the bottom flush, which increases the heat transfer area on the tubing string section from the plug to the radial holes.

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