RU2296858C1 - Method for well bottom zone treatment - Google Patents

Abstract

FIELD: oil and gas well production, particularly methods for stimulating production by forming crevices or fractures.

SUBSTANCE: method for pulsed thermal treatment of well bottom involves applying gas-and-steam mixture pressure pulses to producing reservoir, wherein the pulses have amplitude and duration enough to create micro-crevices in the reservoir; performing thermal producing reservoir treatment with gas-and-steam mixture after micro-crevice formation. Well is repeatedly treated with 5-6 alternating pressure and thermal pulses. Pulse durations are 1.5-3 and pulse strengths are 4.0-1.25 MW. Pulse repetition period is selected as 30-60 s. Reservoir is thermally treated with gas-and-seam mixture at 200-700°C between pulse application.

EFFECT: increased output from exhausted and marginal wells.

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Description

The invention relates to the field of operation of oil and gas wells and can be used to treat the bottom-hole zone of the formation to increase the productivity of low-production and recovery of worked wells.

It is known that after a certain period of production, the productivity of oil and gas wells drops significantly due to a decrease in the permeability of reservoirs caused by the clogging of pores with various organic and inorganic substances.

A known method of impulse treatment of the bottom-hole zone of the formation (RU No. 2106485, CL. EVB 43/263, 1998), which includes creating excess pressure in the well by exposing the formation of solid fuel powder charges to the formation with gaseous products of combustion, while creating overpressure in the well, at least two consecutive pressure pulses with an amplitude and duration of the first pulse sufficient to open natural cracks and create microcracks, and the amplitude and duration of the second pulse, at least equal to the amplitude and duration of the first impulse and sufficient for the development of these cracks and microcracks, while the second pressure impulse is created when the pressure in the well from the first impulse is equal to 0.5 rock pressure.

However, in this method, there are drawbacks associated with the fact that the treatment of the formation is carried out by powder charges, creating problems for well safety. In addition, pulse processing does not provide sufficient fluidity of the extracted product, which reduces its production.

There is also known a method of heat treatment of the bottom-hole zone of the well (RU No. 2182656, Cl. ЕВВ 43/25, 2002), based on the use of a slowly burning charge, which is delivered in a container on the bondage and set fire to it 0.5-1.0 m below the productive formation to increase fluidity of the fluid. Simultaneously with the heating of the cracks and pores of the formation, heated hydrochloric acid is pushed into them, the well is kept for 1.0-1.5 hours, then an implosive device is lowered into the well, with which the reaction products are sucked from the cracks and pores of the formation.

The disadvantage of this method is the duration of the processing of the bottom-hole zone of the well and, therefore, the high cost of its application.

The prototype of the invention is a method of pulse-heat treatment of the bottomhole zone of the well (RU No. 2157885, Cl. ЕВВ 43/25, ЕВВ 43/117, Е21В 43/24, 2000), which includes a one-time exposure of the reservoir with explosive pressure pulses with amplitude and duration sufficient to create microcracks in the formation, and heat treatment of the reservoir after the formation of microcracks in it. Before burning the heat source, the space above it is shielded, and then after heat treatment, an implosive treatment (solvent washing of microcracks) of the well is performed.

The disadvantage of this method is its insufficient productivity due to a one-time pulse and thermal effects on the formation and the need for subsequent washing of the microcracks of the formation.

The objective of the invention is to eliminate the disadvantages of the prototype.

The technical result is to increase the productivity of the method.

The technical result is achieved by the fact that in the method of pulse-heat treatment of the bottom-hole zone of the well, which includes exposing the reservoir to pressure pulses of a vapor-gas mixture with an amplitude and duration sufficient to create microcracks in the reservoir, and heat treating with a gas-vapor mixture of the reservoir after microcracks are formed in it, according to the invention, a multiple treatment of a well is carried out with a series of 5 ÷ 6 alternating pressure pulses and thermal pulses of a gas-vapor mixture, at the duration of the pressure pulses is chosen in the range of 1.5–3 s at a pulse power of 4.0–1.25 MW, the pulse repetition period is selected in the range of 30–60 s, and in the interval between pulses, the formation is heat-treated with a gas-vapor mixture at a temperature of 200 ÷ 700 ° C.

Multiple treatment of a well with a series of alternating pressure pulses and thermal pulses of a gas-vapor mixture, respectively, allows maintaining microcracks in the productive layer in the open state while maintaining fluidity of the product due to thermal heating in the period between pressure pulses. The selected range of parameters of pressure pulses (pulse power 4.0–1.25 MW and pulse duration 1.5–3 s) is rational for opening and maintaining open microcracks in the productive layer. The lower value of the pulse power corresponds to the expansion of existing microcracks, and the upper value corresponds to the creation of new cracks in the reservoir. An increase in pulse power of more than 4.0 MW with a pulse duration of less than 0.15 s is impractical due to the possibility of damage to the well, and a decrease in pulse power of less than 1.25 MW with a pulse duration of 1.5 s is not enough to open microcracks due to its insufficiency energy. The follow-up period of pressure pulses is chosen less than the relaxation time (closing of microcracks) and is 30–60 s depending on the pressure in the reservoir. The parameters of heat treatment with a gas-vapor mixture in the period between pressure pulses are selected from the condition of thermal melting of asphaltene-resinous-paraffin deposits (AFS) and ensuring fluidity of the fluid. A decrease in the temperature of heat treatment below 200 ° C does not ensure the removal of asphaltene - resinous-paraffin deposits from microcracks. An increase in the temperature of heat treatment of a gas-vapor mixture over 700 ° C can lead to sintering of clay particles in the microcracks of the productive layer and reduce the permeability of the latter.

In general, the application of the proposed method allows to increase the productivity of low-yield and well-developed wells and, as a result, the level of their profitability.

According to the invention, the pulse-heat treatment of the well is carried out with a hermetically sealed wellhead by installing a heat shield in its upper part. Then, a pressure pulse generator and a heat generator are successively installed in the well at the bottomhole zone level in time. After installing the pressure pulse generator, it is ignited on command from the surface of the earth. In this case, due to the selection of the volume and burning rate of the combustible substance of the generator, a pressure pulse is generated with a duration of 1.5 ÷ 3 s and a pulse power of 4.0 ÷ 1.25 MW. Due to the impact on the bottom hole, the rock skeleton is destroyed and a network of additional microcracks is formed that increase the permeability of the bottom zone of the formation. After the formation of microcracks, a heat generator is installed in place of the burnt pulse generator with the volume of the combustible substance and its burning rate, providing a temperature of 200-700 ° C of the gas-vapor mixture in the bottomhole zone and burning it for 30 ÷ 60 s. In this case, the paraffin deposits are removed from the microcracks and sufficient fluidity of the product is ensured from the bottomhole zone. Simultaneously after the end of the action of the first pressure impulse, a natural swim (relaxation) of microcracks occurs under the influence of its own weight (shrinkage) of rocks in the well. This time is from 3 to 10 minutes, depending on the friability and depth of the bottomhole zone of the well. Therefore, before the end of the microcrack swim, the next pressure pulse generator is fed into the perforation zone, which restores the floating microcracks to the open state. Next, the well treatment process is repeated.

Examples of specific implementation of the method.

Example 1. The treatment was carried out on the decommissioned well LLC "LUKOIL-Nizhnevolzhskneft" of the Volgograd region. The impact of the Melikessky horizon. During testing, the annular space of the well above the bottomhole zone was sealed by installing a PRYAMO type heat shield, designed to hold pressure up to 700 atm. and temperatures up to 700 ° C. The pressure pulse generator and the heat generator were solid propellant. The volume of the gas-generating composition and the burning rate of the pressure pulse generator of the gas-vapor mixture were determined from the condition of ensuring its burning time for 1.5 s at a pulse power of 1.25 MW. For this, the gas generating composition of the pulse generator included in wt.%: Granulated ammonium nitrate of grade B-72; potassium dichromate - 5; epoxy resin brand ED-20 with hardener polyethylene polyamine in a ratio of 10: 1-23. The heat generator is configured to create a temperature in the bottomhole zone of 200 ° C. For this, the gas-generating composition of the heat generator included potassium perchlorate, aluminum powder, SKF-32 fluororubber and technological additives providing the required burning speed and temperature. The mass of the heat generator was selected from the condition of its burning time of 30 s. The bottom-hole treatment was carried out by a series of 6 alternating pressure pulses and thermal pulses of a gas-vapor mixture. At the same time, the increase in oil production after processing its bottom-hole zone increased by 240%.

Example 2 was carried out according to example 1 in a neighboring well with an increased burning rate of the gas generating compositions of the generators due to the increased percentage of oxidizing agent in the gas generating compositions. The output parameters of the pulse generator were: pulse power 4.0 MW and a time of 3 s, and the parameters of the heat generator - 700 ° C with a burning time of 1 min. The increase in oil production in this case amounted to 350%.

The present invention is not limited to the above examples of its implementation. In the framework of the present invention, it is possible to use to implement the proposed method not only separate pressure pulse generators and heat generators, replaced as they burn, but also a combined controlled generator. For example, it is possible to use the nitrogen generator of Kompomash GIRS OJSC (Gubar V.A. et al. New equipment and technologies for repair and restoration of a low-production and inactive well stock // Collection of abstracts at the Congress of Russian Oil and Gas Industrialists. - Ufa, 1998, p. .14) subject to appropriate refinement for operation in pulsed and thermal conditions.

The experiments showed the feasibility of using the proposed method on the tested wells to restore their efficiency and the possibility of oil production of at least 1.8 t / day from one well.

Claims (1)

A method of treating a bottom-hole zone of a well, including applying pressure pulses of a vapor-gas mixture to the reservoir with an amplitude and duration sufficient to create microcracks in the reservoir, and heat treating with a gas-vapor mixture of the reservoir after microcracks are formed in it, characterized in that the well is repeatedly treated with a series of 5 ÷ 6 alternating pressure pulses and thermal pulses of the vapor-gas mixture, while the duration of the pressure pulses is chosen in the range of 1.5 ÷ 3 s at pulse power of 4.0-1.25 MW, the pulse repetition period is selected in the range of 30-60 s, and in the interval between pressure pulses, the formation is heat-treated with a vapor-gas mixture at a temperature of 200-700 ° C.