RU2848537C1 - Method of acid treatment of prizaboynaya zone and development of production well with side shaft - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: in a method for acid treatment of the bottomhole zone and development of a production well with a lateral wellbore, a main production string (2) and an additional production string (3) of the lateral wellbore, including lowering a string of pump-compressor pipes (4) with a lock support (5), pumping an acid solution into the bottomhole zone of the formation (1), lowering an insertable deep well pump (6) on a column of sucker rods (7) with landing in the lock support (5), sampling of well fluid with reaction products into a trough container and subsequent connection of the discharge line to the oil pipeline, the following assembly is installed on the tubing string (4) below the lock support (5) from top to bottom: a pump-compressor pipe (8), a metal pipe (9) with two metal discs (10), between which a rubber disc (11) is placed, a transfer pipe (12), a tailpiece (13) made of fibreglass pipes with upper (14) and lower (15) fibreglass pipes with rubber centring devices at the ends of the tailpiece (13). The diameter of the rubber disc (11) of the assembly is selected to be smaller than the inner diameter of the main production column (2), but larger than the inner diameter of the additional production column (3) of the side shaft. The tubing string (4) is lowered into the well so that the rubber disc (11) is positioned 1-2 m above the head of the additional production column (3) of the side wellbore. The acid solution is brought up the tubing string (4) with the selling fluid to the formation (1). After that, the tubing string (4) with the assembly to a depth such that the rubber disc (11) is located on the head of the additional production column (3) of the side wellbore to cover the annular space of the wellbore, and then pump the acid solution at a pressure exceeding the permissible pressure on the production column. Well fluid with reaction products is collected in a trough container until the pH value of the formation reaches 6-7.

EFFECT: increased efficiency of acid treatment of the bottomhole zone and subsequent development of a production well with a lateral, increased production capacity of the well.

1 cl, 2 dwg, 1 ex

Description

The invention relates to the oil producing industry, in particular to methods of acid treatment and subsequent development of oil producing wells.

A method for treating the bottomhole zone of a well is known, which includes pumping an acid solution into the formation (Sh.K. Gimatudinov. Reference book on oil production. Moscow, "Nedra", 1974, pp. 420-432).

The disadvantages of this method include the need to lower a column of process pipes through which the acid solution is pumped, which increases the duration of repairs.

A method for treating the near-wellbore zone of wells to intensify oil and gas production is known (RU Patent No. 2696686, IPC E21B 43/25, published 05.08.2019, Bulletin No. 8). This method involves unseating a pump from its support using a truck crane mounted on a vehicle chassis, thereby ensuring the passage of fluid into the cavities of the tubing, and injecting a calculated volume of hydrocarbon solvent through the tubing into the near-wellbore zone of the formation. Next, using a truck crane, the pump is seated in the support, after which the hydrocarbon solvent in the near-wellbore zone of the formation is drained using a horizontal drilling machine. Following this, technical acid solutions are injected and drained in the same sequence, and the well is then left to react with the acid composition. After the well has been kept in response, the well is put into operation using the existing well drilling equipment with the liquid being withdrawn to a trough tank, followed by neutralization of the acid reaction products to the pH of the formation.

The disadvantages of this method are:

- a narrow scope of application only for wells with receiving formations due to the impossibility of injecting acid into poorly receiving formations due to the injection pressure being limited by the permissible pressure on the production casing;

- long development time due to the need to extract the volume of liquid in the inter-tube space;

- corrosion damage to sucker rod pump components during acid solution injection, leading to fluid leaks, failure of downhole pumping equipment and oil losses.

The closest method is the development of an oil producing well after processing the bottomhole formation zone (RU patent no. 2698354, IPC E21B 43/26, published on 08/26/2019, bulletin no. 24), which includes the stages of acid treatment of the bottomhole formation zone, during which an acid solution is pumped into the bottomhole formation zone, a period of time is waited for the acid solution to react with the rock of the bottomhole formation zone, during which a swabbing device is lowered onto the tubing to a depth of 5-10 meters above the artificial or current bottomhole, a swab is lowered into the well, a fluid medium is withdrawn from the well in the amount of at least 1 volume of the production string + 1.5 volumes of working fluids injected into the formation, and the fluid medium, moving from the perforation interval down the intertube and then through the shoe up the tubing, is removed both from the formation and from the well sump.

According to the description, this method can be implemented by lowering a locking joint onto the tubing prior to acid treatment, depending on the well's production capacity. This joint, which corresponds to the size of the pump being lowered, serves as a vibration control. After acid injection (while the acid reacts), the locking joint is lowered further onto the tubing to a depth of 5-10 meters above the artificial or current bottomhole, and the pumping equipment is lowered into the well. The recovered fluid, containing oil, formation water, and acid reaction products, is sent to an oil tanker. When the recovered fluid reaches a pH of 4 to 7, the flow line is connected to the oil pipeline. If necessary, the pumping equipment is raised to the optimal depth, depending on the well's production capacity and dynamic level.

The disadvantages of this method are:

- limited application due to the impossibility of pumping acid into formations with low injectivity due to the injection pressure being limited by the permissible pressure on the production casing;

- long development time due to the need to extract the volume of liquid in the inter-tube space;

- corrosion damage to the lower part of the pipe column and support immersed in an acid solution, which leads to fluid leaks, failure of deep-well pumping equipment and failure to achieve the planned effect;

- low efficiency of using a swab in wells with sidetracks due to significant leaks and the risk of cable breakage;

- insufficient efficiency of the known method.

The technical result is an increase in the efficiency of acid treatment of the bottomhole zone and the subsequent development of a production well with a sidetrack.

The technical result is achieved by a method of acid treatment of the bottomhole zone and development of a production well with a sidetrack, a main production string and an additional production string of the sidetrack, including lowering a string of tubing with a lock support, pumping an acid solution into the bottomhole zone of the formation, lowering a rod pump on a string of sucker rods with a seat in the lock support, collecting well fluid with reaction products in a trough tank and subsequent connection of the flow line to the oil pipeline.

What is new is that the following assembly is first installed on the tubing string below the lock support, from top to bottom: a tubing pipe, a metal branch pipe with two metal disks, between which a rubber disk is placed, a sub, a fiberglass pipe shank with upper and lower fiberglass branches with rubber centralizers at the ends of the shank, while the diameter of the rubber disk of the assembly is selected smaller than the internal diameter of the main production string, but larger than the internal diameter of the additional production string of the sidetrack, the tubing string is lowered into the well so that the rubber disk is located 1-2 m above the head of the additional production string of the sidetrack, an acid solution is brought through the tubing string with a squeezing fluid to the formation, 4 after this the tubing string with the assembly is lowered to such a depth that the rubber disk is located on the head of the additional production string of the sidetrack to close the annular space of the well, and then inject an acid solution at a pressure exceeding the permissible pressure on the production casing, the well fluid with the reaction products is withdrawn into a trough tank until the pH value of the formation reaches 6-7.

Fig. 1 shows a diagram of pumping an acid solution, Fig. 2 shows a diagram of development and subsequent operation after processing the bottomhole zone, where 1 is a formation, 2 is the main production casing, 3 is an additional production casing of the sidetrack, 4 is a tubing string, 5 is a lock support, 6 is a rod pump, 7 is a column of pump rods, 8 is a tubing pipe, 9 is a metal branch pipe, 10 is metal disks, 11 is a rubber disk, 12 is a sub, 13 is a shank made of fiberglass pipes, 14 is an upper fiberglass branch pipe, 15 is a lower fiberglass branch pipe, 16, 17 are rubber centralizers.

The method of acid treatment of the bottomhole zone and development of a production well with a sidetrack is implemented as follows.

First, the following assembly is installed on the tubing string 4 (Fig. 1) below the lock support 5, from top to bottom: tubing pipe 8, metal branch pipe 9 with two metal disks 10, between which a rubber disk 11 is placed, sub 12, fiberglass pipe shank 13 (hereinafter referred to as the shank) with an upper fiberglass branch pipe 14 installed above the shank 13, and a lower fiberglass branch pipe 15 installed below the shank 13, with rubber centralizers 16 and 17, respectively, at both ends. The tubing string 4 with the assembly is lowered into the well.

The diameter of the rubber disk 11 is chosen to be smaller than the internal diameter of the main production string 2, but larger than the internal diameter of the additional production string of the sidetrack 3. The metal disks 10 are fixed at the top by a coupling (not shown in Fig. 1, 2), connecting the pipe 8 and the metal branch pipe 9, and at the bottom by a sub 12.

The lower fiberglass pipe 15 with rubber centralizers 17 (at least two) ensures the assembly can enter the additional production string of the sidetrack 3 without complications. The upper fiberglass pipe 14 with rubber centralizers 16 ensures the centering of the rubber disk 11 to ensure the inter-annular space is closed. The rubber centralizers 16, 17 are secured to the body of the fiberglass pipes 14, 15 by couplings (not shown in Figs. 1, 2) installed at both ends of the pipes 14, 15.

At the first stage, the tubing string 4 with the assembly is lowered to such a depth that the rubber disk 11 is located 1-2 m above the head of the additional production string of the sidetrack 4 of the well, then the required amount of acid solution is brought through the tubing string 4 with the displacement fluid to the formation 1.

Next, the tubing string 4 with the assembly is lowered to such a depth that the rubber disk 11 is placed on the head of the additional production string of the sidetrack 4 to block the inter-tube space of the well.

The acid solution is injected directly into the wellbore zone at a pressure exceeding the permissible pressure of the production casing. The fiberglass construction of liner 13 allows for extended exposure to the acid solution during injection, and especially during development, without any adverse effects, as fiberglass is not susceptible to corrosion.

After pumping the acid solution, the rod pump 6 (Fig. 2) is lowered onto the rod string 7, seated in the locking bearing 5, and the unit is started. The wellbore fluid and reaction products are withdrawn into a trough tank until the formation pH reaches 6-7 (a lower pH indicates an acidic environment and must be adjusted to a near-neutral pH). The flow line is then connected to the oil pipeline, and production resumes. Seal the annular space with a rubber disk also helps reduce well completion time.

The proposed method improves the efficiency of acid treatment of the near-wellbore zone and subsequent development of a sidetracked production well, increasing the well's production capacity. It also eliminates corrosion damage to the lower portion of the pipe string and support immersed in acid solution, which can lead to fluid leaks, failure of downhole pumping equipment, and failure to achieve the planned results.

An example of practical application.

Production well #1 with a sidetrack (horizontal section): main production casing (MPC) with a diameter of 146 mm (TBVK-146 pipes), running depth of 1,100 m (to the branch point), MPC shoe 1,100 m; additional production casing (sidetrack) with a diameter of 102 mm (TBP-102 pipes), length of 500 m (horizontal section), running depth from 1,100 m to 1,600 m, head of the additional casing (branch point) 1,100 m. Perforation interval: 1,400–1,600 m (horizontal section) with contamination: carbonate deposits (CaCO ₃ ) + clay cake. The following assembly was preliminarily installed on a 73 mm diameter tubing column below the lock support installed at 1,090 m: 73 mm tubing pipe (length 508 m, from 1,090 m to 1,598 m), a metal branch pipe with two metal disks with a rubber disk between them (the diameter of the rubber disk is 120 mm, less than the diameter of the OEK, equal to 146 mm, greater than the diameter of the additional production casing, equal to 102 mm), a sub, a 8 m long fiberglass pipe shank (from 1,098.5 m to 1,106.5 m) with upper and lower fiberglass branches with rubber centralizers of 100 mm diameter at both ends. The tubing string with the assembly was lowered to a depth of 1.598 m, the rubber disk was at a depth of 1.098.5 m (1.5 m above the head of the additional production string; in other examples, the installation was carried out at 1 m and 2 m above the head of the additional production string).

An acid solution (composition: 15% HCl + 0.5% urotropine (corrosion inhibitor) + 1% surfactant) with a volume of 4 m³ and an injection rate of 0.6 m³/min was added to the tubing string with a displacement fluid (composition: 2% ammonium chloride solution (NH ₄ Cl) with a volume of 2.5 m³ and a displacement rate of 0.8 m³/min to the formation. After this, the tubing string with the assembly was lowered to 1.5 m, placing the disk on the head of the additional production string (1.100 m). The acid solution was pumped at a pressure of 16 MPa (with an allowable pressure of 15 MPa for the OEK) into the bottomhole formation zone. The NN2A insertable sucker rod pump was lowered to 1.595 m on a string of pumping rods, and the unit was put into operation. Selection The wellbore fluid with reaction products was injected into the trough tank until the formation pH reached 6.5 (the initial pH was 2.0, and after 2.5 hours of sampling, the value increased to 6.5). Treatment zone: 1,400–1,600 m (90% CaCO ₃ dissolved). The flow rate before and after treatment was 6 m³/day (contaminated bottomhole zone) and 18 m³/day (24 hours after startup), respectively. A 3-fold increase in flow rate was recorded. A rubber disk at 1,100 m prevented the erosion of the OEK. The fiberglass liner (1,098.5–1,106.5 m) did not corrode.

Claims (1)

A method for acidizing the bottomhole zone and developing a production well with a sidetrack, a main production string and an additional production string of the sidetrack, including lowering a tubing string with a lock support, pumping an acid solution into the bottomhole zone of the formation, lowering a rod pump on the sucker rod string with a seat in the lock support, collecting well fluid with reaction products in a trough tank and then connecting the flow line to an oil pipeline, characterized in that the following assembly is preliminarily installed on the tubing string below the lock support from top to bottom: tubing, a metal branch pipe with two metal disks, between which a rubber disk is placed, a sub, a shank made of fiberglass pipes with upper and lower fiberglass branches with rubber centralizers at the ends of the shank, wherein the diameter of the rubber disk the assembly is selected smaller than the internal diameter of the main production string, but larger than the internal diameter of the additional production string of the sidetrack, the tubing string is lowered into the well so that the rubber disk is located 1-2 m above the head of the additional production string of the sidetrack, the acid solution is brought through the tubing string with the displacement fluid to the formation, after this the tubing string with the assembly is lowered to such a depth that the rubber disk is located on the head of the additional production string of the sidetrack to block the annular space of the well, and then the acid solution is pumped with a pressure exceeding the permissible pressure on the production string, the withdrawal of well fluid with reaction products into a trough tank is carried out until the hydrogen index pH of the formation is reached in the range of 6-7.