RU2425960C1 - Development method of bottom-hole zone - Google Patents

Abstract

FIELD: oil and gas industry. ^ SUBSTANCE: according to the method the connection to distant formation zone is established so that its coverage by draining is increased, and complications caused by rock caving after perforation are prevented. Perforation is performed downwards with increased perforation density with cumulative charges of lower power where there is not any nearest water-bearing formation or water-oil contact. After perforation the chlorhydric acid treatment of open hole is performed. At that, increase in formation pressure and preservation of water content on the same level is accepted as result of the performed treatment. ^ EFFECT: higher well productivity. ^ 1 ex, 3 tbl, 1 dwg

Description

The invention relates to the oil industry and may find application in the processing of the bottom-hole zone of an open-hole well.

A well-known method of well completion, in which the well is supplied with a casing to the roof of the reservoir. At the same time, oil-saturated layers are determined in the well. Extend the open hole in the zones of oil-saturated interlayers and at the same time washed with oil. After that, the expanded wellbore is treated with a hydro-jet supply of an acid solution through a nozzle for hydro-sand-jet perforation (RF Patent No. 2182651, publ. 05.20.2002).

The disadvantage of this method is the technological complexity and high cost. It is a method of completing a well after drilling. The method has all the disadvantages of sandblasting, the effectiveness of which depends on many factors. The proposed method is simple to implement and low cost. It provides high SCR efficiency and can be used during the operation of the well until the development of recoverable oil reserves.

Closest to the proposed invention in technical essence is a method of processing an injection well, comprising sampling the rock from the productive thickness of the injection well or the closest well to it. On the selected rock samples, the rock compression conditions are simulated, which operate in the bottomhole zone for various designs of the bottom hole and various depressions in the well. The stresses are reproduced at which deformation occurs with cracking, loosening of rock samples and an irreversible increase in their permeability. Determine the design of the bottom of the injection well with perforations or a horizontal slot in the open hole. Create an installed well bottom design. At the bottom of the well, a depression is created that is not less than established according to the simulation of rock samples. This depression is maintained until the well is put into injection mode (RF patent No. 2213852, publ. 10/10/2003 - prototype).

The method is not effective enough and leads to a slight increase in well productivity.

The proposed invention solves the problem of increasing well productivity.

The problem is solved in that in the method for processing the bottom-hole zone of a well, including perforation of an open wellbore, according to the invention, perforation is performed “top-down” with an increased density of perforation by low-power cumulative charges, after perforation, hydrochloric acid treatment of the open wellbore is performed.

SUMMARY OF THE INVENTION

The production fund includes open hole wells. This type of well is characteristic of homogeneous stable (solid) reservoirs. It is believed that such a design has the best hydrodynamic perfection. But the practice of operating such wells suggests otherwise. Wells under the same operating conditions, having an open borehole (bottom), are often comparable or inferior in productivity to wells with cased and perforated production intervals.

The production rate and rate of its decline in open-hole wells do not correspond to the idea of the productivity of wells committed by the nature of opening. This is also confirmed by hydrodynamic studies. Often, open-hole wells have a positive skin factor.

Thus, it can be concluded that the productivity of open-hole wells is reduced due to significant changes in the bottom-hole zone during the initial opening of productive horizons and subsequent operation, such as mudding, penetration of mud filtrates into the bottom-hole zone, and mechanical impurities during flushing and killing wells.

Currently, as an effective method for stimulating open-hole wells, generally accepted methods of hydrochloric acid treatment of the bottomhole zone in various designs are actively used, such as hydrochloric acid baths, directional hydrochloric acid treatment, hydrochloric acid treatment using a hydraulic nozzle, etc. P.

But an analysis of the effectiveness of the applied stimulation methods showed that there are a number of wells in which the ongoing activities either do not bring positive results, or have a short-term effect.

To explain the reasons, it is necessary to consider in more detail the mechanism of decolmatization of the bottomhole formation zone.

The analysis of the inflow profiles of the productive carbonate formation shows that its working part often does not exceed 30-50%. When using the existing methods of treating the formation with hydrochloric acid, the latter is absorbed by the drained zones of the formation, and the inactive areas remain untreated.

Thus, the depth of the effective impact of the applied methods for processing the bottom-hole zone in the existing version is not sufficient to create a hydrodynamic connection between the wellbore and the non-working productive part of the formation, i.e. when processing the bottom-hole zone, uniform processing of the immediate near-wellbore zone occurs without affecting its peripheral part. Open hole processing is ultimately the processing of the borehole walls and existing active channels.

For hydrochloric acid treatment of non-working sections of the formation, a tool is needed to create acid delivery channels to them.

To solve this problem and increase the effectiveness of measures to stimulate the work of open-hole wells operating carbonate reservoirs, we propose to use cumulative perforation with increased perforation density with low-power cumulative charges. Perforation density is considered to be increased when the number of perforations is more than 10 per linear meter of perforation interval. Cumulative charges of low power, as a rule, are charges capable of creating perforation channels up to 350 mm long in cased hole conditions.

Perforation channels provide a hydrodynamic connection between the reservoir and the wellbore, i.e. additional active channels are connected to drainage, and also serve to create paths for acid penetration deep into the formation. Thereby, the area of effective impact on the sealed area of the reservoir is significantly increased. Thus, the main goal of the work is to connect inactive zones of the formation by creating additional fracture systems and involving them in active drainage.

The proposed range of works has many positive aspects, but also has its limitations.

The main advantage is the relative cheapness and simplicity of the work. It should also be borne in mind that when perforating in an open wellbore in the absence of a metal column and cement stone, all energy is directed to the formation of the channel, and its depth is significantly increased.

The main danger when perforating in an open hole is the possibility of destruction of the walls of the boreholes and grabbing the tool. However, the high density of carbonate rocks and the use of caseless perforators virtually eliminate this possibility.

Also, when conducting perforation in an open hole, an important condition for the efficiency of work is the absence of a nearby aquifer or water-oil contact.

To prevent negative consequences, we propose the following progress:

1. Selection of wells with suitable geological and physical characteristics.

2. Hydrodynamic studies of the well before the event.

3. Perforation of the open trunk. In order to avoid shedding of the open bore and seizure of perforating equipment, it is recommended that the interval be opened by the top-down technology using caseless perforators with cumulative charges of low power and increased perforation density.

4. Hydrodynamic studies of the well after perforation.

5. Hydrochloric acid treatment of the bottomhole zone.

6. Hydrodynamic studies of the well after treatment;

Concrete example

Perforation followed by treatment with hydrochloric acid was performed at well No. 8230 of NGDU Elkhovneft with an open bottom hole.

The well is operating carbonate reservoirs of the Tournaisian stage (Kizelovsky-Cherpetsky horizon) of deposit No. 51 of the Novo-Elkhovsky field.

Well No. 8230 was drilled and put into operation on March 10, 2004, with a flow rate of 6.2 m ³ / day for liquid, 5.5 t / day for oil and a water cut of 2%.

With further operation, the oil flow rate decreased and in February 2008 amounted to 1.5 tons / day. In March 2008, hydrochloric acid treatment of the bottom-hole zone was carried out at the well. The measures carried out brought a short-term effect. The oil production rate increased to 4.4 tons / day, however, 4 months after the work on processing the bottom-hole zone, it decreased to 1.4 tons / day.

The open hole interval is 24 m (1208.0-1231.0 m). The absolute permeability of the reservoir is on average 4 mD, the average porosity is 12.1%. At the time of perforation, followed by acid treatment, the fluid flow rate was 1.7 m ³ / day with a water cut of 4%.

This well is selected based on the most suitable conditions for testing the proposed complex of conditions, namely:

1) the well has an oblique directional profile (horizontal wells have not been considered at the moment due to the high risk of rock collapse and tool sticking);

2) the open hole interval is drilled in the carbonate reservoir of the Tournaisian stage;

3) earlier work on the treatment of the bottom-hole zone was ineffective.

For perforation of the open section of the barrel, a disposable perforator on a steel plate PRK-42C was used (Table 1), which is characterized by low power, which will prevent the occurrence of possible complications arising from shedding of rocks after perforation works. The calculated value of the channel depth for this perforation system was 653 mm with the declared breakdown capacity in the casing - concrete layer system equal to 311 mm. To increase the processing efficiency, an increased perforation density of 12 holes / pm was applied.

After perforation, the acid treatment was carried out by injection of a 12% aqueous hydrochloric acid solution at the rate of 1 m ³ / m of the productive formation, technological exposure for 3 hours and washing the well with produced water.

The performed perforation of open hole No. 8230 showed that the combined use of cumulative perforation in an open table with subsequent treatment of the bottom-hole zone with hydrochloric acid was highly effective.

To assess the effectiveness of the measures taken at the well, a complex of hydrodynamic studies was carried out, including:

1. Removing the pressure recovery curve before events.

2. Removing the pressure recovery curve after perforation.

3. The removal of the curve after processing the bottom-hole zone.

4. Determination of fluid flow rate and water cut of products at each stage.

An analysis of the results of hydrodynamic studies of the well (Table 2) showed that as a result of the measures taken, significant changes occurred in the bottomhole zone of the well. There is an improvement in all the filtration characteristics of the formation. Moreover, after perforation, we observe an increase in parameters such as permeability and hydraulic conductivity, which indicates the creation of additional active channels in the bottomhole zone of the well, but, as can be seen from the results of the studies, the size of these channels only restored the connection between the well and the remote zone of the formation. The greatest effect was achieved by subsequent treatment of the bottom-hole zone, as evidenced by a significant increase in permeability and hydraulic conductivity.

You can visually evaluate the effectiveness of the measures taken according to the graph below comparing the rate of pressure recovery (see drawing).

In the drawing, curve 1 is the pressure recovery curve before events, curve 2 is after perforation, curve 3 is after perforation and hydrochloric acid treatment. As follows from the graphs in figure 1, after perforation and hydrochloric acid treatment, pressure is restored faster, and the pressure is large.

The complex use of perforation and hydrochloric acid treatment allowed not only to restore communication with the remote zone of the formation, but also to increase the coverage of the formation by drainage by connecting additional channels and fracture zones of the oil-bearing formation. This is also evidenced by an increase in reservoir pressure and maintaining the same percentage of water cut. Well productivity as a result of measures according to hydrodynamic studies of the well increased 10 times.

Table 1 Main parameters and characteristics of the PRK-42S puncher The name of indicators Units measuring Value Transverse dimension mm 46 Minimum tubing inner diameter mm 58 Perforation density hole / m 12 Phase orientation of charges degree 0 Maximum allowable hydrostatic pressure MPa 80 The most admissible temperature ° C 150 Exposure time at maximum settings h 2 The average penetration depth when firing at a combined target (casing - concrete layer) mm 311 The explosive mass of one cumulative charge g 6

table 2 The results of hydrodynamic studies of well No. 8230 Before events After perforation After perforation and hydrochloric acid treatment Bottomhole pressure, MPa 2.6 2.9 5,6 Reservoir pressure, MPa 6.7 6.8 7.8 Productivity coefficient, m ³ / day · atm 0,050 0,068 0.650 Productivity ratio 1.14 3.06 7.18 Skin factor -0.15 -3.55 -5.02 Hydraulic conductivity, D · cm / sPz 0.129 0.220 0.980 Piezoconductivity, cm ² / s 13.5 45 273 Permeability, MD 4.1 22.7 125 Estimated Q fluid, m ³ / day 1.7 2.6 14.3 Water cut,% four four four

The economic efficiency assessment is based on all the costs of the work (table 3). Two wells were taken as an example: on one of the wells, hydrochloric acid treatment was performed without perforation, and on the other, hydrochloric acid treatment in combination with perforation.

The economic effect in the case of perforation in combination with hydrochloric acid treatment is 4 times higher than the economic effect of processing using existing technologies. Net profit from the practical application of the proposed range of works at one well amounted to 934 thousand rubles.

After successful work on the directional well, cumulative perforation with hydrochloric acid treatment was performed on all open-hole wells, including horizontal ones, with a positive result.

Application of the proposed method will solve the problem of increasing well productivity.

Table 3 Initial data and calculation of economic effect Expenditures Units rev. Indicator values Hydrochloric acid treatment Hydrochloric acid treatment and perforation Initial data Growth t / day 2.7 8.0 Add. oil production in 4 months t 289.3 857.3 Operating ratio 0.893 0.893 Oil price rub / t 7016.0 7016.0 MET rub / t 3092,7 3092,7 Oil cost rub / t 1591.3 1591.3 Maintenance rub. 396,000.0 736875,0 Services of LLC AlGIS rub. 4928.2 94,749.0 Calculation of the economic effect The proceeds from the implementation of add. prey rub. 2029953.3 6014676.5 MET rub. 894,805.5 2651275.6 Oil cost rub. 460,425.6 1364224.0 Repair Costs rub. 396,000.0 736875,0 Services of LLC AlGIS rub. 4928.2 94,749.0 Retained earnings rub. 273,794.0 1167553.0 Income tax rub. 54,758.8 233510.6 Net profit rub. 219035,2 934042,4

Claims (1)

A method of treating a bottomhole zone of a well, including perforating an open wellbore, characterized in that they establish a connection with the remote zone of the formation with an increase in its coverage by drainage and prevent complications from shedding of rocks after perforation, which is carried out “top-down” with an increased density of perforation with low cumulative charges power in the absence of a nearby aquifer or water-oil contact, after perforation, hydrochloric acid treatment of the open trunk is carried out, while by treatment as an increase in pore pressure and maintaining water content at the same level.

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