RU2490443C1 - Procedure for treatment of bottomhole zone of producer with two wellheads - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: in procedure for treatment of bottomhole zone with two wellheads in case of failure of an electric-centrifugal pump (ECP) with no apparent deviation in its operating parameters and in case of alkalinity growth for extracted product up to pH>7 the required volume of hydrogen chloride solution is calculated on the basis of a length and diameter of the well filtering part; the required volume of hydrogen chloride solution is selected to treat the whole volume of the strainer; the required volume of flush fluid is calculated for delivery of compounds into a slope wellhead. ECP is shutdown at the vertical wellhead before pumping of hydrogen chloride solution is started. The required volume of hydrogen chloride solution is carried out into tubular annulus from the side of the vertical wellhead. When pumping of hydrogen chloride solution is over extraction from the slope wellhead is increased and ECP is started from the vertical wellhead. ECP is stopped at the vertical wellhead and hydrogen chloride solution is overflushed by the flush fluid into filtering part of the well. After ECP startup in enlarged extraction rate from the slope wellhead samples are taken periodically in order to check pH value, monitor dynamics in changes of fluid supply from the slope wellhead. When pH value id recovered up to the normal value ECP is started into operation from the vertical wellhead and supply from the slope wellhead is returned back to normal operation mode.

EFFECT: effective treatment of bottomhole and filtering zone of the well, cleaning of the pump operating elements from salts and simultaneous technology simplification due to exclusion of tripping operations.

1 ex, 1 dwg

Description

The invention relates to the oil industry and may find application in the treatment of the bottom-hole zone of a dual-well production well.

There is a method of increasing the overhaul period of the deep pump equipment of a producing well, complicated by scaling, including the injection of a composition containing a corrosion inhibitor and water (USSR Author's Certificate No. 1148977, published. 04/07/1985).

Closest to the proposed invention in technical essence is a method for increasing the overhaul period of the deep pump equipment of a producing well, complicated by scaling, including the injection of a composition containing a corrosion inhibitor and water, periodic implementation: preliminary cleaning of the specified equipment from an oil film and deposits of asphalt-resin-paraffins, injection of organic solvent into the well, then removing deposits of iron salts from the surface of the specified equipment, injection to the composition, additionally containing hydrochloric or acetic acid and a scale inhibitor, into the annulus of the stopped well, pumping to the pump and holding for 1.5-2.0 hours, this composition is taken in a volume of 5.0-5.5% of the liquid volume in well from the dynamic level to the pump intake (RF Patent No. 2375554, publ. 10.12.2009 - prototype).

A common disadvantage of the known technical solutions is the complexity of the work, the need for tripping and involving an underground well repair team.

The proposed invention solves the problem of simplifying the technology by eliminating tripping and eliminating the involvement of an underground well repair team.

The problem is solved by the method of processing the bottom-hole zone of a two-wellhead production well, which consists in the fact that when the supply of the electric centrifugal pump (ESP) is interrupted without visible deviations in the pump operation parameters and when the alkalinity of the produced product increases to a pH of> 7, the required volume of hydrochloric acid solution is calculated based on from the length and diameter of the column of the filter part of the well, choose the volume of hydrochloric acid solution necessary for processing the entire volume of the filter, calculate the necessary volume of sales liquid to bring the reaction composition to an inclined mouth, before pumping the hydrochloric acid solution, the ESP is stopped from the vertical wellhead, the required volume of hydrochloric acid solution is pumped into the annulus of the well from the vertical wellhead, and after the hydrochloric acid solution is injected, increase withdrawal from the inclined mouth and briefly start the ESP from the vertical mouth, after stopping the ESP from the vertical mouth, the hydrochloric acid solution is forced through the squeezing liquid into the filter part of the well, in this case, after starting the ESP with an increased rate of sampling from the inclined mouth, fluid samples are periodically taken for pH, monitor the dynamics of the fluid supply from the inclined mouth, after restoring the pH to a normal level, the ESP is launched from the vertical well and the flow is returned from the inclined mouth in normal operation.

SUMMARY OF THE INVENTION

On some deposits of ultra-high viscosity oils (HHV), the productive horizon is composed of sandstones, where HHH acts as a cementing substance, and for sandstones of the aquifer, the cementing materials are calcite, minerals of the clay group, which are in different ratios. In the pore space, calcite grains or their accumulations have a rather weak adhesion to the pore walls and to each other. Calcite is predominantly fine-grained (0.01-0.1 mm) in weakly cemented differences, and fine-grained (0.1-0.25 mm) in compaction zones. The zones of compaction in the reservoir are its bottom parts and zones of heterogeneity within the horizon.

Chemical precipitation of calcite occurs according to the following scheme:

$$C{a}^{2+}+2HC{O}_3{}^{-}=CaC{O}_3+H_{2}C{O}_3(\mathrm{one})$$

The formation of the NSO ₃ anion ^is described by the schematic equation:

$$C{H}_n+O_2=C{O}_2+H_{2}O+tePl\mathrm{about}t\mathrm{but}\text{reactions (2)}$$

where CH _n are hydrocarbons,

СО ₂ + Н ₂ О = НСО,

H ₂ CO ₃ = H ⁺ + HCO ^- ,

$$H^{+}+C{O}_3{}^{2-}=HC{O}^{3-}(3)$$

The deposit is underlain by waters of sodium bicarbonate composition, therefore formation water is a source of calcium cation. The newly formed calcite envelops the grains and forms a network of thin channels and films penetrating the rock in all directions. IOS is the central part of the pore space. The main source of CO ₂ is the oxidation of hydrocarbons (reaction 2). The HCO ^3- ion is formed during the hydrolytic decomposition of feldspars due to the absorption of CO _{2 by the} resulting hydroxyl ions:

$$2KaA{l}_{2}S{i}_2{O}_8+H_{2}O+2C{O}_2=K^{+}+A{l}_2{O}_3{}^{x}2Si{O}_2+\mathrm{four}Si{O}_2+2HC{O}_3{}^{-}(\mathrm{four})$$

Reaction 3 and 4 lead to an increase in the alkalinity of the solution, i.e. ion OH ^- . This growth, as well as exothermic reaction 2 favors the precipitation of calcite. Thus, we can conclude that the gradual weathering of oils, and then the IOS, led to a gradual increase in the content of authigenic calcite in productive sandstones. This process is most developed near water-bitumen contact and to a lesser extent in zones of heterogeneity of the reservoir. At the same time, less bitumen is oxidized in the middle part of the formation and, as a result, the medium becomes less alkaline, which prevents calcite from precipitating.

An SVN deposit is developed by the method of steam gravity drainage, which implies the presence of two horizontal wells at a distance of 5 m vertically. In this case, steam is injected into the upper injection well, and liquids are taken from the lower producing well. Fresh steam when mixed with formation water contributes to the deposition of salts of carbonate composition within the productive horizon. Also, the deposition of salts is favored by the active selection of liquid, in which partial breakthrough of bottom water to the faces of production wells is also not ruled out.

All this leads to the fact that during steam injection and production, intense deposition of calcium carbonate occurs both in the near-well part of the wells and directly in the slit filter of production wells and at the working nodes of deep ESPs. All this creates additional obstacles in the production of liquids, as a result, the supply of production wells is interrupted, with the subsequent failure of the deep ESPs.

Existing materials and technologies for the control of scaling in the well are mainly ineffective, difficult to implement, expensive. So, for the treatment it is necessary to involve a team of overhaul of the well, apply the appropriate equipment, carry out the hoisting operations, perform work with the interval processing interval slot filter. Especially these works are complicated when they are carried out in a double-well well.

The proposed invention solves the problem of simplifying the technology by eliminating tripping and eliminating the involvement of an underground well repair team. The problem is solved as follows.

During the operation of a double-well well producing IOS, the operation of pumping equipment and the parameters of the produced products are analyzed. If the ESP supply is interrupted without visible deviations in the pump operation parameters and when the alkalinity of the produced products increases to a pH value of pH> 7, a conclusion is drawn about salt deposits on the equipment and in the bottomhole zone of the well. The required volume of hydrochloric acid solution is calculated based on the length and diameter of the column of the filter portion of the well. The volume of the hydrochloric acid solution necessary to process the entire volume of the filter is selected. Calculate the required volume of displacement fluid to refine the reaction composition to an inclined mouth. As a solution of hydrochloric acid, a solution of 6-10% concentration is used, which has sufficient reactivity, but does not cause active corrosion of underground equipment.

Figure 1 shows a two-wellhead production well, the well has a vertical wellhead 1, an inclined wellhead 2, an ESP of a vertical wellhead 3, an ESP of an inclined wellhead 4, a slit filter 5. Both ESPs are suspended on tubing strings 6 and 7. The well is cased with a casing string 8.

Before the injection of the hydrochloric acid solution, the ESP 3 of the vertical wellhead 1 is stopped. From the vertical wellhead 1, the required volume of the hydrochloric acid solution is pumped into the annulus of the well, i.e. the space between the tubing string 6 and the casing 8. After injecting the hydrochloric acid solution, increase the withdrawal from the inclined wellhead 2 and start the ESP 3 briefly for 3-5 minutes from the vertical well 1. After stopping the ESP 3 from the vertical well 1, the solution is forced through hydrochloric acid with a squeezing liquid (water) into the filter part of the well into the zone of the slit filter 5. After starting the ESP 4 with an increased sampling rate from the inclined wellhead 2, fluid samples are periodically taken for pH, the dynamics are monitored changing the fluid supply from the inclined mouth 2, after restoring the pH to a normal level, start the ESP 3 from the vertical mouth 1 and return the flow from the inclined mouth 2 to normal operation.

Concrete example

On the double-well well producing the IOS, there is a disruption and a decrease in supply from both the vertical and inclined wellhead. Also in the sample of the selected fluid, the pH was 8.12. Oil production rate decreased from 31 to 25 tons / day. Based on this, it was decided to conduct treatment of the bottom-hole zone. The filter part of the well has a diameter D = 168 mm and a length of 415 m. Based on this, the acid volume in the volume of 3.5 m ^{3 was} calculated. To sell acid to an inclined mouth, 7.5 m ^{3 of} water is needed. As a solution of hydrochloric acid, a solution of 8% concentration is used.

Before the injection of the hydrochloric acid solution, the ESP 3 of the vertical wellhead 1 is stopped. From the vertical wellhead 1, the required volume of the hydrochloric acid solution is pumped into the annulus of the well. After injection of the hydrochloric acid solution, the extraction is increased from the inclined wellhead 2 and the ESP 3 is started for 4 minutes from the vertical well 1. After stopping the ESP 3 from the vertical well 1, the hydrochloric acid solution is pushed with the squeezing liquid (water) into the filter part of the well into the zone of the slotted filter 5 After starting ESP 4 with an increased sampling rate from the inclined mouth 2, fluid samples are periodically taken for pH, the dynamics of the fluid supply from the inclined mouth 2 is monitored. The pH shows that the acid composition went to the inclined mouth in 45 minutes and in 1 hour the pH was restored to normal. After restoring the pH to a normal level, the ESP 3 is launched from the vertical wellhead 1 and the feed from the inclined wellhead 2 is returned to normal operation.

As a result of acid treatment using the described technology, it was possible to treat the bottom-hole zone and the filter part of the well, the working parts of the pump were cleaned of salts, which can be seen by the absence of a further stall or decrease in supply both in the vertical and inclined mouth, and oil production was restored from 25 to 35 tons / day., which indicates the effective treatment of the bottom of the well.

The application of the proposed method will allow to clean the well and equipment from salts and restore the well without the use of tripping and underground repair crews.

Claims (1)

A method of processing the bottom-hole zone of a two-wellhead production well, which consists in the fact that when the supply of an electric centrifugal pump ESP is interrupted without visible deviations in the pump operation parameters and when the alkalinity of the produced products increases to a pH of pH> 7, the required volume of hydrochloric acid solution is calculated based on the length and diameter the columns of the filter part of the well, select the volume of hydrochloric acid solution necessary for processing the entire volume of the filter, calculate the necessary volume of displacement fluid for the flow of the reaction composition to the inclined mouth, before the injection of the hydrochloric acid solution, the ESP is stopped from the vertical well, the required volume of the hydrochloric acid solution is pumped into the annulus of the well from the vertical well, after injection of the hydrochloric acid solution, the extraction from the inclined mouth is increased and the ESP is briefly started with the vertical wellhead, after stopping the ESP from the vertical wellhead, hydrochloric acid solution is pushed with the squeezing liquid into the filter part of the well, In this case, after starting the ESP with an increased rate of sampling from the inclined mouth, fluid samples are periodically taken for pH, the dynamics of the fluid supply from the inclined mouth are monitored, after the pH is restored to the normal level, the ESP is launched from the vertical mouth and the flow from the inclined mouth is returned to normal mode work.