RU2774251C1 - Method for eliminating flows behind the casing in petroleum production boreholes - Google Patents

Abstract

FIELD: petroleum industry.

SUBSTANCE: invention relates to the petroleum industry, namely, to methods for eliminating the circulation reservoir water behind the casing in petroleum boreholes. Proposed method for eliminating flows behind the casing in petroleum production boreholes includes the following stages: plugging the borehole, extracting the downhole equipment, implementing a complex of works in surveying the source of water inflow in the borehole, lowering a tubing string and pumping a pack of high-viscosity mud from the bottomhole to the upper perforations; after raising the tubing string, a packer plug is additionally lowered and installed in the interval of the upper perforations; a slot perforator is then lowered into the borehole on drill pipes, and the casing and cement stone are cut in the aquifier interval, creating slot-like channels; after the perforator is raised, a tubing string is lowered with a packer and a grouting composition is pumped into the slot-like channels, pushing the composition into the aquifer; after repair and insulation works are completed and the tubing string with the packer are raised, the borehole is left for the waiting-on-cement period (WOC); drill pipes are then lowered with a mill and the packer plug is drilled, flushing the metal chips and the viscoelastic composition to the surface; a casing of a smaller diameter is then lowered into the well, cemented and left for WOC.

EFFECT: provided reliable barrier for the ingress of reservoir waters in the behind-casing space between the casing and the rock.

1 cl, 7 dwg

Description

The invention relates to the oil industry, and in particular to methods for eliminating behind-the-casing formation water circulation in oil wells.

The flow of water from other horizons through the leaky annular space leads to a sharp increase in the water cut of the produced product, a decrease in the productivity of the producing well in terms of oil and is reflected in the final oil recovery of the reservoirs due to the possible outflow of oil from the bottomhole zone of the well. Often, the inflow of water is several times greater than the inflow of hydrocarbon fluid from the reservoir.

Currently, there are many ways to carry out work to eliminate behind-the-casing flows of formation waters, which have certain advantages and disadvantages.

A known method of isolating behind-the-casing flows [RF Patent No. 2136878] by injecting a composition containing wt. %: anionic polyacrylamide 0.5-2.0, condensed sulphite-alcohol stillage or lignosulfonate 0.75-1.5, wood flour 1.0-4.0, sodium or potassium dichromate 0.02-0.05, silicate sodium 2.0-8.0, water - the rest (1).

The disadvantage of this method is the temporary nature of the isolation due to the solubility of polyacrylamide in formation waters.

The closest technical solution, selected for the prototype, is a method of isolating the behind-the-casing circulation from the upstream non-perforated aquifer to the downstream perforated oil-bearing layer [RF Patent No. 2584256]. When implementing the method, a section of the production string is cut above the depth of the oil-bearing layer and below the depth of the aquifer, the cutting assembly is raised, the pipe assembly with a jet nozzle is lowered, and the cut section is treated. The oil-bearing layer is blocked by backfilling the perforation interval with sand, a drillable packer is installed above the cut out section and below the level of the aquifer, the injectivity of the cut section of the string and the formed channel connecting the aquifer and oil-bearing layers is determined, the cut out section is plugged using a packer. Then the packer is drilled out, the sand is washed out, the pipe assembly is lowered and the oil-bearing layer is blocked by blocking compound injection, the pipe assembly with the liner is lowered to the bottomhole level, the annular space is cemented, after the cement hardens, re-perforation is performed.

The disadvantage of this method is the complexity of the work associated with cutting a separate section of the production string and its processing.

The objective of the invention is to ensure the high-quality elimination of behind-the-casing flows of formation waters from the upstream aquifers to the downstream perforated productive formation in oil wells.

Achievable technical result, which is obtained as a result of the creation of the invention, is to create a reliable barrier to the flow of formation waters along the annular space between the casing string and rocks.

The task and the technical result are achieved by the fact that the method of eliminating behind-the-casing flows in oil-producing wells includes killing the well, extracting the downhole equipment, carrying out a set of works to study the source of water cut in the well, lowering the string of tubing (tubing) and pumping a pack of high-viscosity solution from the bottom to top perforations. After lifting the tubing, the packer plug is additionally lowered and installed in the interval of the upper perforations. After that, a slotted perforator is lowered into the well on the drill pipes and the casing string and cement stone are cut in the aquifer interval with the creation of slotted channels. After lifting the perforator, the tubing string with the packer is lowered and the cement composition is pumped into the slotted channels with its displacement into the aquifer. After carrying out repair and insulation works and lifting the tubing with a packer, the well is left for a period of waiting for cement hardening (WSC). After that, the drill pipes are lowered with a cutter and the packer plug is drilled out with the washing out of metal chips, as well as the viscoelastic composition to the surface. Further, a casing string of smaller diameter is lowered into the well, cemented and left in the WOC. In conclusion, the well is reperforated in the interval of the productive formation, developed and put into operation.

In FIG. 1-7 are diagrams of how the method is implemented.

The method is carried out as follows.

The well 1, watered due to behind-the-casing flows from the upstream aquifer 2 relative to the productive formation 3, is stopped, killed with a killing fluid with a certain density to create the necessary back pressure on the productive formation 3 in order to prevent gas, oil and water intrusions in the process of repair and isolation work.

The downhole equipment 4 is removed and a set of works is carried out to study the source of water cut in the well 1 (Fig. 1).

If the formation water comes from the aquifer 2 located above the productive formation 3, the tubing string 5 is lowered into the well 1 and a pack of high-viscosity solution 6 is pumped from the bottom hole 7 to the upper perforations 8 (Fig. 2).

As a viscoelastic composition, a composition for killing oil and gas wells is recommended [RF Patent No. 2601708. Viscoelastic composition for killing oil and gas wells / Leontiev D.S., Kustyshev A.V., Kleshchenko I.I. and others], containing peat, alkaline modifier, inhibitor, defoamer, polymer, weighting agent, flocculant and water in the following ratio of components, %:

Peat 5-7 Potassium-containing alkaline modifier 0.5-1.5 Potassium chloride 1-3 Polymer CMC 0.8-1.5 Defoamer MAS-200M 1-3 Weighting compound 10-50 Water Rest

Raise the tubing string 5 and additionally lower and install the packer plug 9 in the interval of the upper perforations 8 (Fig. 3).

After that, a slotted perforator 11 is lowered on the drill pipes 10 into the well 1 and the casing string and cement stone are cut in the interval of the aquifer 2 with the creation of slotted channels 12 (Fig. 4).

After that, the perforator 11 is raised, the tubing string with the packer is lowered, and the grouting composition is pumped into the slotted channels 12 with the composition being forced into the aquifer 2 (Fig. 5).

As a composition for creating a water-proof screen, a composition is recommended that includes microdur R-U, a polyfunctional modifier PFM-ISO, a superplasticizer F-10 and water at a water-cement ratio of 0.5 in the following ratio, wt. %: microdur R-U 48.75-49.05, polyfunctional modifier PFM-ISO 1.0-1.2%, superplasticizer F-10 0.9-1.3%, water - the rest [RF Patent No. 2613067. Composition for repair and insulation works in wells / Leontiev D.S., Kustyshev A.V., Kleshchenko I.I. and etc.].

The mutual influence of the components on each other, their synergistic action in the proposed composition allows, due to the reaction and curing in reservoir conditions, to form a strong stone-like material.

After carrying out repair and insulation works and lifting the tubing with a packer, well 1 is left at the WOC.

Then the drill pipes are lowered with a cutter 13 and the packer plug 9 is drilled out with the washing out of metal chips, as well as the viscoelastic composition 6 to the surface (Fig. 6).

Further, a casing string of smaller diameter 14 is lowered into the well 1 in the interval from the bottom hole 7 to the roof of the aquifer 2, cemented and left on the WOC (Fig. 7).

In conclusion, well 1 is reperforated in the interval of the productive formation 3, developed and put into operation.

EXPLANATION TO THE FIGURES

1 - Well

2 - Aquifer

3 - Productive layer

4 - Downhole equipment

5 - Tubing string

6 - Pack of VUS

7 - Bottom hole

8 - Perforations

9 - Packer plug

10 - Drill pipes

11 - Perforator

12 - Slotted channels

13 - Cutter

14 - Smaller diameter casing

Claims (1)

A method for eliminating behind-the-casing flows in oil-producing wells, characterized in that it includes killing the well, removing the downhole equipment, carrying out a set of works to study the source of water cut in the well, running a string of tubing (tubing) and pumping a pack of high-viscosity solution from the bottom to the upper perforations; after lifting the tubing, the packer plug is additionally lowered and installed in the interval of the upper perforations; after that, a slotted perforator is lowered into the well on the drill pipes and the casing string and cement stone are cut in the aquifer interval with the creation of slotted channels; after lifting the perforator, the tubing string with the packer is lowered and the cement composition is pumped into the slotted channels with its displacement into the aquifer; after carrying out repair and insulation works and lifting the tubing with a packer, the well is left for a period of waiting for cement hardening (WSC); after that, drill pipes with a cutter are lowered and the packer-plug is drilled with washing out of metal chips, as well as viscoelastic composition to the surface; further, a casing string of smaller diameter is lowered into the well, cemented and left on the WOC.

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