RU2790071C1 - Well treatment method - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to the oil industry and can be used in the technological processing of wells. According to the method, a production well is stopped. The well is disconnected from the manifold line. The exposed carbonate reservoirs are saturated with process fluid along the well annulus until the well annulus is completely filled with the process fluid. The hydrochloric acid treatment of the bottomhole zone along the annulus of the well is carried out by pumping the hydrochloric acid composition into the annulus at the rate of 1 m³ of the hydrochloric acid composition TATOL/TATOL-SKS grade HCI-15/2500 per 1 m of the perforated strata. The hydrochloric-acid composition is forced into the productive formations with a process fluid with a process soaking of the well for 2 days. The well is connected to the manifold line and the well is put into operation.

EFFECT: simplification of the method without reducing the efficiency of well treatment with a simultaneous expansion of the arsenal of technical means that can be used for technological well treatment.

3 cl, 3 dwg

Description

The invention relates to the oil industry and can be used in the technological processing of wells.

The proposed treatment method can be effectively applied, mainly in wells, the reservoir layers of which are represented by carbonate rocks with low reservoir pressures.

A known method of processing the bottomhole zone of the well, including the injection into the formation of an acid solution [Sh.K. Gimatudinov. Reference book on oil production. M., "Nedra". 1974, pp. 420-432].

The disadvantage of this method is a relatively narrow scope, which makes it possible to use it effectively only in combination with additional operations.

There is also a method [RU 2483201 C1, E21B 43/20, 05/27/2013], based on the periodic injection of the working agent into injection wells, which are used as part of the production wells at a late stage of development of the deposit by transferring them to injection, moreover, injection of the working agent agent is produced with a gradual, over several months, increase in pressure, excluding its breakthrough into neighboring wells and up to a value that is twice the formation pressure at the time of transfer of production wells to injection wells, and after the volume of injected working agent becomes equal to the volume of extracted from the production well fluid for the entire period of development until the transfer of production wells to injection wells, abruptly, from the condition of closing the fractures of the reservoir layers, the injection of the working agent into the injection wells is stopped, while the working agent is the bottom water formed during the operation of the production wells.

The disadvantage of this method is a relatively narrow scope, since it can be used for some production wells at a late stage of deposit development.

In addition, there is a method of reservoir treatment [RU 2135760 C1, E21B 43/25, 27.08.1999], including interval injection of a reagent into the bottomhole zone, while pre-fixing the volume of the treatment interval relative to the bottom of the well, the injection of the reagent is carried out in a pulsating mode: injection at reagent intake pressure by perforation interval - process soaking at atmospheric pressure, the regime is repeated with a decrease in the reagent injection pressure until the working injectivity pressure of the well is reached, the remaining volume of the reagent is injected at a steady pressure, process soaking is carried out and the reaction products and pollutants are removed by swabbing until fluid is withdrawn in a volume exceeding at least three times the volume of the injected reagent.

The known method allows to increase the permeability of the bottomhole zone of the well, however, the method is not effective enough in a number of practical cases, for example, when processing heavily clogged bottomhole zones.

The closest to the proposed method in its technical essence is the method of treating the bottomhole zone of a well with low reservoir pressure [RU 2537433 C1, E21B 43/27, 01/10/2015], including injection into the bottomhole zone of a reagent, which is used as a solution of hydrochloric acid, technological holding for reaction and extraction of reaction products by swabbing, at the same time, prior to pumping the hydrochloric acid solution, the well is flushed with fresh water, the perforations of the productive formation are renewed at the rate of 10 holes per linear meter of the well and the formations are saturated with fresh water up to 6 MPa, then the solution is injected hydrochloric acid into the well in a volume of 2.0 ^m portions in a volume of 2.0 m ³ in the mode cycle, including 1 min injection at a pressure of 1-6 MPa, exposure 5 min for reaction, and the final injection of the hydrochloric acid solution volume in a constant mode, at the second stage, a 6-fold impulse injection of the second portion of the hydrochloric acid solution into the formation in a volume of 3 is performed, 0 m ³ in the cycle mode, including 1 min injection at a pressure of 1-6 MPa, exposure 5 min for reaction, and complete the injection of the volume of acid in a constant mode, after which a technological exposure of 3 hours is performed for reaction, at the third stage, injection is carried out into the reservoir the third portion of the hydrochloric acid solution at the rate of 0.5 m ³ per linear meter of the productive formation in continuous mode at a pressure of 1-6 MPa and perform a technological exposure to react for 3 hours, and at the fourth stage, a 6-fold impulse injection of the fourth portion of the solution into the formation is carried out hydrochloric acid at a rate of 1.0 ^m after which they complete the injection in a continuous mode, perform a technological exposure for a reaction of 3 hours and proceed to the extraction of reaction products by swabbing.

The disadvantage of the closest technical solution is the relatively high complexity and relatively low efficiency.

It is known that the productivity of a well is largely determined by the permeability of the bottomhole zone. Existing methods, including the method of hydrochloric acid treatments of the bottomhole zone of wells chosen as the closest technical solution, are characterized by high complexity and relatively high costs with relatively low efficiency.

The problem solved in the invention is to create a simpler and less expensive method of well treatment, without reducing the efficiency of treatment while expanding the arsenal of technical means that can be used for technological treatment of wells.

The required technical result is to simplify the method without reducing the efficiency of the well treatment.

The problem is solved, and the required technical result is achieved by the fact that in the method of technological well treatment, the production well (screw pump or pumping unit) is stopped, the well is disconnected from the manifold line, the exposed carbonate reservoirs are saturated with process fluid (associated produced water from oil wells, with a density of 1.15 g/cm ³ or fresh water with a density of 1.02 g/cm ³ ) along the annulus of the well until the annulus of the well is completely filled with process fluid, hydrochloric acid treatment of the bottomhole zone is carried out along the annulus of the well by pumping a hydrochloric acid composition into the ^annulus at the rate of 1 m days and with subsequent connection of the well to the manifold line and putting the well into operation that.

The illustrative materials show:

In FIG. 1 example of successful bottom-hole treatment (BHT) along the annulus with a small amount of acid in well No. 8500;

In FIG. 2 is an example of a successful BHT on the annulus with a small volume of acid after filling with fresh water at well No. 8490;

In FIG. Figure 3 is an example of a successful large-volume BHT along the annulus after filling with fresh water at well No. 1248.

The proposed method of technological treatment of wells is implemented as follows.

With a full cycle of well treatment, the production well is shut down (screw pump or pumping unit), the well is disconnected from the manifold line, the exposed carbonate reservoirs are saturated with process fluid (produced water from oil wells, density 1.15 g/cm ³ or fresh water with a density of 1.02 g/cm ³ ) along the well annulus until the well annulus is completely filled with process fluid, the hydrochloric acid treatment of the bottomhole zone along the well annulus is carried out by pumping a hydrochloric acid composition into the annulus at the rate of 1 m ³ hydrochloric acid composition TATOL/TATOL-SKS grade HCI-15/2500 per 1 m of perforated strata and its displacement into productive formations with process fluid with process soaking of the well for 2 days and subsequent connection of the well to the manifold line and launch of the well in work.

In the proposed processing method, the process fluid is produced water (produced water from oil wells, density 1.15 g/cm ³ ) or fresh water (density 1.02 g/cm ³ ). The hydrochloric acid composition TATOL/TATOL - SCS brand HCI-15/2500 of the oilfield service company NPC-KARAT LLC is used as an acid. This hydrochloric acid formulation is a blend of synthetic hydrochloric acid, corrosion inhibitor, demulsifier, iron stabilizer, complexing dispersant and surfactants. The number 2500 indicated in the name means the ability of the acid composition to stabilize Fe ³⁺ ions in an amount up to 2500 ppm to Fe ²⁺ . The volume of acid required for large-volume hydrochloric acid treatment is determined based on the ratio: 1 m ³ of hydrochloric acid composition (TATOL/TATOL-SKS brand HCI-15/2500) per 1 m of perforated thickness.

Pre-saturation of the well contributes to the complex treatment of productive formations. The hydrochloric acid composition is not absorbed by highly permeable formations with washed zones, but reacts in the bottomhole zone under pressure, slowly penetrating deep into the productive formation. Highly permeable caverns saturated with water no longer absorb acid and its entire volume will fully react in the bottomhole zone of the well.

The use of water instead of a variety of gels to "seal" high-permeability caverns is more cost-effective. In this case, the redistribution of water and oil in the reservoirs occurs, and the consequences of water injection are minimal - the water cut is restored to values close to the values before the treatment of the bottomhole zone (BHT). The use of hydrochloric acid composition TATOL/TATOL-SKS brand HCI-15/2500 instead of the usual hydrochloric acid composition HCI-15 helps to prevent the formation of insoluble iron hydroxide during the BHT and, thereby, eliminates clogging and a decrease in the permeability of the bottomhole formation zone. Due to the large volume of acid, the impact coverage on the formation is increased, forming migration channels to the untouched oil-saturated areas of productive formations. Savings in this treatment method also lies in the fact that minimal efforts and time are required to prepare the well for the BHT, since it is not necessary to raise the downhole pumping equipment and lower the special equipment for the BHT. The need for a full workover workover (WOC) is eliminated and the downtime of the well is ensured to a minimum.

To test and prove the effectiveness of the proposed method, BHT was carried out with a small volume of hydrochloric acid composition TATOL / TATOL-SKS brand HCI-15/2500 (3 m ³ for the entire perforated stratum - an average of 0.2 m ³ per 1 m perforated stratum) and without filling with process liquid at 7 wells (Nos. 8505, 8500, 8508, 8515, 8516, 8522, 673). On wells No. 8505, 8508, 8522, the effect of BHT was not obtained (in all wells, the initial injection pressure was 0 atm., the final injection pressure was 0 atm., the volume of injected acid was 3 m ³ for each well). Total additional production from 3 wells (Nos. 8500, 8515, 8516) amounted to 50.18 tons. 07 t/day, effect duration 37 days, initial injection pressure 0 atm., final injection pressure 0 atm., volume of injected acid was 3 m ³ , total perforated stratum 39.8 m). The least effect on well No. 8515 is 13.36 t (average oil flow rate before BHT 1.52 t/day, after BHT 1.74 t/day, effect duration 62 days, initial injection pressure 0 atm., final injection pressure 0 atm. ., the volume of injected acid was 3 m ³ , the total perforated thickness was 31.8 m). An example of a successful BHT with a small volume of acid along the annulus is shown in FIG. 1.

In all wells, the injection of the hydrochloric acid composition and its displacement into the formation took place without pressure on the unit, i.e. the entire hydrochloric acid composition was absorbed by highly permeable formations without significant impact on the bottomhole zone of the well. The dynamic levels in the wells remained at their original values. But still, additional production was obtained, but due to a slight increase in oil production, which stretched for a long time and was associated with the cleaning of well perforation zones. On average, the increase in well flow rate was 0.36 t/day for each day of the effect.

BHT with a small volume of hydrochloric acid composition TATOL/TATOL-SKS brand HCI-15/2500 (3 m ³ for the entire perforated stratum - an average of 0.2 m ³ per 1 m perforated stratum for all treated wells) after filling with fresh water was carried out on 10 wells (Nos. 8519, 1243, 1244, 1247, 1251, 1253, 1254, 8491, 8490, 8488). Of these, no effect was obtained at well No. 1254 (initial injection pressure 0 atm., final injection pressure 20 atm., the volume of injected acid was 3 m ³ , the total perforated stratum was 16.8 m). The least effect was obtained at well No. 1247 - 1.88 tons (average oil flow rate before BHT 0.78 t/day, after BHT 0.88 t/day, effect duration 20 days, initial injection pressure 0 atm., final injection pressure 50 atm., the volume of injected acid was ³ m effect 19 days, initial injection pressure 0 atm., final injection pressure 55 atm., the volume of injected acid was 3 m ³ , the total perforated thickness was 15 m). The total additional production by wells was 195.98 tons. The greatest effect was obtained at well No. 8490 - 55.34 tons (average oil flow rate before BHT 0.18 t/day, after BHT 0.64 t/day, effect duration 121 days and continues on the date of calculation, the initial injection pressure is 0 atm., the final injection pressure is 60 atm., the volume of injected acid was 3 m ³ , the total perforated stratum was 12.5 m). An example of a successful BHT with a small volume of acid over the annulus after filling with fresh water is shown in FIG. 2.

On average, the increase in well flow rate was 0.45 t/day for each day of the effect. The injection of acid and its displacement into the formations took place already in the presence of pressure on the unit, which indicates that the injected acid was not absorbed by the formations, but remained to react in the bottomhole zone of the well. But its volume was still insufficient for complete processing of the entire stratum exposed by perforation.

BHT with a large volume of hydrochloric acid composition TATOL/TATOL-SKS brand HCI-15/2500 (1 m ³ per 1 m of perforated stratum) after filling with fresh water was carried out on 11 wells (nos. 1248, 8510, 1247, 1251, 1242, 1252, 1253, 8508, 8518, 1237, 1238). Of these, no effect was obtained at well No. 1252 (initial injection pressure 0 atm., final injection pressure 20 atm., the volume of injected acid was 10 m ³ , the total perforated stratum was 10 m). For the rest of the wells, the total additional production was 355.94 tons. The greatest effects were obtained at well No. 8510 - 105.99 tons (average oil flow rate before BHT 0.81 t/day, after BHT 1.23 t/day, effect duration 91 days , initial injection pressure 0 atm., final injection pressure 60 atm., volume of injected acid was 15 m ³ , total perforated stratum 15 m) and well No. , after BHT 1.28 t/day, effect duration 138 days, initial injection pressure 0 atm., final injection pressure 60 atm., volume of injected acid was 14 m ³ , total perforated thickness 14 m). An example of a successful large-volume BHT along the annulus after filling with fresh water is shown in FIG. 3. The least effect on well No. 1247 is 3 tons (average oil flow rate before BHT 0.55 t/day, after BHT 0.98 t/day, effect duration 7 days, initial injection pressure 0 atm., final injection pressure 50 atm. ., the volume of injected acid was 10 m ³ , the total perforated thickness was 10 m). On average, the increase in well flow rate was 0.7 t/day for each day of the effect.

An example of a specific implementation of the method of processing the bottomhole zone along the annulus of the well.

The bottom-hole zone of oil-producing well No. 1248 with a depth of 1098.0 m is treated. The well is operated by a screw rod pump. Productive layers are perforated in the intervals of 1059.0-1061.0 m; 1064.0-1066.0 m; 1075.0-1079.0 m; 1082.2-1089.0 and are represented by carbonate rocks of the Vereya horizon and the Bashkirian stage of the porous-fractured type. The total perforated thickness is 14 m. The density of the existing perforation is 10 holes per linear meter of the well. The well was decommissioned at a current liquid flow rate of 0.64 t/day, an oil flow rate of 0.63 t/day, and a water cut of 1.2%.

The well was shut in, the wellhead was disconnected and sealed from the manifold line. The well was filled with fresh water through a conduit located on the well pad. A water conduit was connected to the annulus of the well through the lower angle annular valve and filling began. The well was completely filled and saturated in 24 hours. The total volume of fresh water pumped into the well was 200 ^m3 , after which the flow of fresh water in the conduit stopped, the pressure in the well rose to 20 atm., the annulus of the well was completely filled with water.

The calculated volume of acid (TATOL/TATOL-SKS grade HCI-15/2500) per 14 m of total perforated thickness was 14 ^m3 (based on the ratio of 1 ^m3 of TATOL/TATOL-SKS grade HCI-15/2500 per 1 m ).

Acid was injected with a SIN-32 unit (acid well treatment unit). To do this, instead of a conduit, a SIN-32 unit was knocked into the annulus and pumping began. After pumping all the acid into the annulus of the well, it was forced into the formation with a calculated volume of fresh water - 6 m ³ . The initial injection pressure was 10 atm., the final injection pressure was 60 atm. The optimal injection pressure at bottomhole treatment is up to 60 atm. in this case, there is no critical impact on the downhole pumping equipment of the well.

After completion of the treatment, the well was left to react for 2 days, during these two days the injected acid completely reacted with the carbonate rocks of the reservoir.

The manifold line of the well was assembled and put into operation. After the BHT, the well began to work with the following parameters: liquid flow rate 2.2 t/day, oil flow rate 1.25 t/day, water cut 14%. At the same time, during the week, the well worked with a water cut of 98% (Fig. 3).

Empirically, it was found that it is inexpedient and inefficient to pump a hydrochloric acid composition into a well with carbonate productive formations without first filling the well with process fluid. In this case, the maximum positive effect is achieved when acid is injected with the calculation of 1 m ³ of hydrochloric acid composition per 1 m of the exposed stratum. When using a larger volume of acid, there is a risk of water breakthrough - at well No. 8503, when pumping acid with the calculation of 2 m ³ of hydrochloric acid composition per 1 m of the exposed stratum after BHT, the water cut of the production became equal and remains within 90%. The use of the hydrochloric acid composition TATOL/TATOL-SKS HCI-15/2500 prevents the formation of insoluble iron hydroxide during the BHT, while maintaining the reservoir properties of the bottomhole formation zone.

At the same time, the time from the moment the well is stopped and it is started is minimal - within one week. It is possible to carry out this type of BHT both in wells with screw pumps and with pumping units. All this makes it possible to carry out much more bottomhole treatment at the field without the involvement of workover crews, without a significant decrease in overall production and well downtime.

Thus, the proposed method achieves the desired technical result, which is to simplify the method without reducing the efficiency of well treatment. This has solved the task of creating a simpler and less costly way to treat a well without reducing the efficiency of treatment while expanding the arsenal of technical means that can be used for technological treatment of wells.

Claims (3)

1. The method of technological treatment of wells, according to which a production well is stopped, the well is disconnected from the manifold line, the exposed carbonate reservoirs are saturated with process fluid along the well annulus until the well annulus is completely filled with process fluid, hydrochloric acid treatment is carried out bottom-hole zone along the annulus by pumping a hydrochloric acid composition into the annulus at the rate of 1 m ³ of the hydrochloric acid composition TATOL/TATOL-SKS grade HCI-15/2500 per 1 m of the perforated stratum and its displacement into the productive formations with a process fluid with a process soaking of the well within 2 days and with subsequent connection of the well to the manifold line and putting the well into production. 2. The method according to p. 1, characterized in that as a process fluid used produced water from oil wells with a density of 1.15 g/cm ³ . 3. The method according to claim 1, characterized in that fresh water with a density of 1.02 g/cm ³ is used as the process fluid.

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