RU2485284C1 - Method for reinforcement of bottom-hole zone and prevention of sand carryover from well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for reinforcement of a bottom-hole zone and prevention of sand carry-over from a well involves pumping to the well of polyurethane pre-polymer. Before polyurethane pre-polymer is pumped to the well, isopropyl alcohol is pumped, and after pre-polymer is pumped, buffer marketable Devonian oil is pumped and forced-through with water with density of 1000-1200 kg/m³. At that, forcing-through is performed at maximum allowable speed for formation of a polymer film fixing sand grains of the bottom-hole zone.

EFFECT: invention allows increasing the time of absence of polyurethane pre-polymer contact with water, which allows providing the required treatment radius of the formation bottom-hole zone, increasing sand fixing ability of the compound at maintaining permeability and productivity of the oil formation.

Description

The invention relates to the field of oil and gas industry and can be used for fastening the bottom-hole zone of sand-producing wells.

A known method of preventing the removal of sand and reduce water inflow into the well with low reservoir temperature (US Pat. RU No. 2413067, IPC ЕВВ 43/22, Е21В 43/24, publ. 02/27/2009, bull. No. 6), including heating the bottom-hole zone formation by injecting quartz sand with a fraction size from 0.05 to 2 mm in natural bitumen preheated to a temperature of 60 ° C, having a viscosity at a given temperature of at least 60 MPa · s, and then pumping into the bottomhole zone of the formation heated to a temperature of at least 90 ° C saturated aqueous solution of mineral salt having a difference in rast Vorimy more than 700 g / l in the temperature range from 20 ° C to 90 ° C.

The disadvantages of this method are the complexity and high energy costs in its implementation: heating bitumen to 60 ° C, as well as heating to a temperature of at least 90 ° C of a saturated aqueous solution of mineral salt.

A known method of fastening the bottom-hole zone of sand-producing wells (US Pat. RU No. 2387806, IPC E21B 33/138, publ. 04/27/2010, bull. No. 12), including creating a filter by preparing and injecting the polymer composition and hydrochloric acid, followed by exposure to curing the polymer composition. First, the polymer composition is injected, and then hydrochloric acid in the form of a 10-15% aqueous solution in a ratio of 1: 1 to the polymer composition with a bottomhole zone diameter of at least 1.8 m each, the polymer composition is prepared by mixing urea-formaldehyde resin with acetone-formaldehyde resin in a ratio of 4: 1, respectively, and aluminum powder in an amount of 0.05-0.2% by weight of the polymer composition.

The disadvantages of this method are the multicomponent composition and an additional operation - the injection of hydrochloric acid in order to create a filter for the influx of oil.

The closest in technical essence and the achieved result to the proposed technical solution is a method of controlling sand occurrences in oil and gas wells (US Pat. RU No. 2285791, IPC E21B 43/22, publ. 10/20/2006, bull. No. 29) by injection into the well of an anhydrous fluid containing a polyurethane prepolymer and a solvent in an amount equal to 0.5-1.5 pore volumes, then injection of water in an amount of 0.4-5.0 pore volumes for a time not exceeding 3 hours, after which injection stop and shutter under static conditions for at least 10 hours for erzhdeniya.

The disadvantage of this method is the limited time for injection of reagents - within 3 hours, which can lead to an emergency in case of unforeseen equipment stops during injection of reagents to prevent sand from the well.

The technical task of the proposal is to create an effective and safe way to prevent sand from the well by increasing the time that the polyurethane prepolymer is not in contact with water, which ensures the required radius of treatment of the bottomhole formation zone, increasing the sand-bonding ability of the composition while maintaining the permeability and productivity of the formation in oil.

The problem is solved by the proposed method of securing the bottom-hole zone and preventing the removal of sand from the well, including the injection of a polyurethane prepolymer into the well.

New is that before the polyurethane prepolymer is injected, isopropyl alcohol is pumped into the well, and after the prepolymer is injected, a buffer of marketable Devonian oil is pumped and then pressed with water with a density of 1000-1200 kg / m ³ , and the injection is carried out at the maximum permissible speed for the formation of the polymer film fastening the grain of sand of the bottomhole zone.

The essence of the proposal consists in sequentially pumping a polyurethane prepolymer into the bottomhole zone of the well through the tubing, and isopropyl alcohol, which is a drying agent that dissolves water unlimitedly, is pumped to pump the prepolymer to prevent it from contacting with produced water. Next, a polyurethane prepolymer is pumped, which envelops the grains of sand, forming a film on their surface, and a buffer of marketable Devonian oil to prevent premature curing of the prepolymer in contact with water, which is a hardener of the polyurethane prepolymer. The required amount of polyurethane prepolymer, isopropyl alcohol and commercial Devonian oil is determined by calculation, taking into account the porosity, thickness of the fixed formation and the diameter of the bottomhole zone coverage of each of these reagents for at least 1.5 m. reagents with water with a density of 1000-1200 kg / m ³ and incubated for 12 hours until the prepolymer is completely cured. Selling is carried out at the maximum permissible speed, which does not exceed the permissible pressure on the production string, so that the sand grains are only moistened with a polyurethane prepolymer to form adhesion between the sand grains after contact with water, and excess prepolymer is squeezed from the bottomhole zone into the formation. Allowable pressure on production casing wells is determined by the geological and physical parameters of the fields and is specified by the technological services of oil and gas production departments when performing work. When the polyurethane prepolymer is cured, a thin polymer film is formed in the places where the sand grains come in contact, which bonds the sand well in the bottomhole zone, while the formation does not become clogged, its permeability and oil productivity remain.

Polyurethane prepolymers (oligomers capable of participating in chain growth or crosslinking reactions to form high molecular weight linear and cross-linked polymers) are obtained by the reaction between hydroxyl-containing polyesters or isocyanates. They are mixed in ratios providing an excess of isocyanate, resulting in the formation of a prepolymer with terminal reactive isocyanate groups (-NCO). Polymers obtained on the basis of polyurethane prepolymers with terminal NCO groups are characterized by high strength, tear resistance, wear, benz, and frost resistance while maintaining highly elastic properties in a wide temperature range.

Reagents used in the proposal:

- isopropyl alcohol according to GOST 9805-84;

- polyurethane prepolymer BFM-19;

- Commodity Devonian oil;

- water with a density of 1000-1200 kg / m ³ .

The method in the field is carried out in the following sequence. The tubing is lowered into the sand-producing well, the shoe of which is set above the perforation interval.

The required amount of polyurethane prepolymer, isopropyl alcohol and Devonian crude oil is determined by calculation, depending on the porosity, thickness of the fixed formation and the diameter of the bottomhole zone coverage of each of these reagents at least 1.5 m. When reducing the diameter of the treatment less than 1.5 m, the strength of the created filter for oil inflow is insufficient to withstand the pressure drops existing during well operation. An increase in the processing diameter of more than 1.5 m does not affect the efficiency of the method, but is impractical due to the increase in costs of the reagents used. Then, isopropyl alcohol, a polyurethane prepolymer, and marketable Devonian oil are pumped sequentially through tubing. Then, the injected reagents are pressed into the reservoir with water with a density of 1000-1200 kg / m ³ with a maximum permissible speed that does not exceed the permissible pressure on the production string, which is determined by the technological services of the oil and gas production departments, to form a polymer film that holds the sand grains of the bottomhole zone.

The well is left for aging until the polymer composition has cured for 12 hours. After aging, without additional operations, a durable natural filter with good permeability for oil flow is obtained. Then the well is put into operation.

Tests of the sand-bonding ability of the composition according to the proposed method was carried out in laboratory conditions on reservoir models 10 cm long and 6 cm inner diameter filled with quartz sand of a 0.15-0.25 mm fraction, which allow simulating the injection of reagents into the reservoir and continuously monitoring their flow rate by scheme: “well-reservoir” and “reservoir-well”. Initially, tests were carried out on a water-saturated reservoir model. Water was pumped through the reservoir model, its flow rate was measured, and the initial permeability of the model was determined. Then, isopropyl alcohol, a polyurethane prepolymer, and a buffer from marketable Devonian oil were pumped sequentially through the model. It was left to hold for a period of 10 to 24 hours. Then, mineralized formation water was pumped through the reservoir model and the model permeability was determined by the Darcy formula. A similar procedure was performed with the oil-saturated model, having previously determined the oil permeability. The test results are presented in the table.

As can be seen from the table, the bonding of sand occurs both in the water-saturated and oil-saturated models, the decrease in water permeability in the water-saturated model is 71.4-88.2% compared to 36.4-84.6% in the prototype, and the decrease in permeability by oil in the oil-saturated model is insignificant and amounts to 4.8-13.3%. When the models are aged for 6 hours, the sand does not bond well, and water permeability decreases slightly, so the optimal time required for curing the polyurethane prepolymer is 10-14 hours, the additional time slightly affects the effectiveness of the method.

The results of model tests of the proposed method No. Holding time, h Before processing After processing Sand removal Sand condition Sq, Mkm ² Kn, Mkm ² Sq, Mkm ² Kn, Mkm ² one 6 0.40 0.35 0.36 0.34 there is poorly bonded 2 10 0.35 0.42 0.10 0.40 no fastened 3 fourteen 0.23 0.34 0.06 0.32 no fastened four eighteen 0.19 0.11 0.05 0.10 no fastened 5 22 0.44 0.26 0.09 0.23 no fastened 6 24 0.51 0.15 0.06 0.13 no fastened Note: Kv - water permeability coefficient; Кн - oil permeability coefficient.

Thus, the result is achieved - the creation of an effective and safe way to prevent the removal of sand from the well by increasing the time of absence of contact of the polyurethane prepolymer with water. that allows you to provide the required radius of the treatment of the bottom-hole zone of the formation, increasing the sand-bonding ability of the composition while maintaining the permeability and productivity of the formation in oil.

Claims (1)

A method of fixing the bottom-hole zone and preventing sand from the well, including the injection of a polyurethane prepolymer into the well, characterized in that isopropyl alcohol is pumped into the well before the polyurethane prepolymer is injected, and after the prepolymer is injected, a buffer from marketable Devonian oil is pressed through with water with a density of 1000- 1200 kg / m ³ , and the squeezing is carried out at the maximum permissible speed for the formation of a polymer film that holds together the sand grains of the bottomhole zone.