RU2237797C1 - Method for isolating water influx areas in a well - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method includes consecutive feeding into influx area of polymer compound and cement suspension, polymer compound has hardening time 90-120 minutes, feeding of cement suspension is performed after pumping of separator liquid having concurrently properties of hardening agent for polymer compound and accelerating agent for hardening of cement suspension, and before and after separating liquid additionally pumped are intermediate bodies of fresh water.

EFFECT: higher effectiveness of isolation of water influx areas by means of increasing stability of isolating border.

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Description

The invention relates to the oil industry, in particular to the isolation of water inflow zones in a well.

A known method of isolating zones of water inflow in the well, including the injection into the well of a cement mortar [1].

The disadvantage of this method is that due to the direct contact of the cement with the produced water in the zone of water inflow, its initial concentration is violated and, as a result, the insulating barrier is destroyed.

Closest to the proposed invention is a method of isolating water inflow in a well, comprising sequentially injecting a viscoelastic composition and cement mortar into the water inflow zone [2].

The disadvantage of this method is that in the process of stopping the injection (holding), inter-reservoir flow occurs and the viscoelastic composition is diluted with produced water, as a result, the initial concentration of the viscoelastic composition is violated and, as a result, the stability of the resulting insulating barrier is impaired.

An object of the invention is to increase the efficiency of isolation of zones of water inflow by increasing the stability of the insulating barrier.

The problem is solved in that in a method for isolating water inflow zones in a well, comprising sequentially injecting a polymer composition and a cement slurry into the water inflow zone, according to the invention, the polymer composition has a curing time of 90-120 minutes, the cement slurry is injected after injecting the release fluid, which simultaneously exhibits hardener properties the polymer composition and the accelerator of setting the cement slurry, moreover, before and after the separation liquid, they additionally pump fresh water pads.

It is known that the most effective layers of intra-pore water can be suppressed by monomeric compounds, which are able to actively penetrate into the free volume of pores or into layers of loose-bound water and hold water firmly on the inter-pore surface of the rock [3]. To do this, use low-viscosity (not more than 15-20 MPa · s), easily filtered, water-limiting polymer compositions provided that they are cured in the pores of the formation and not cured in the wellbore. Ideally, it is necessary to quickly cure the monomer compound to the polymer state immediately after it enters the water-saturated part of the formation. However, for technological reasons, the curing time is selected in the range of 90-120 minutes. According to the recovery curves [4], the duration of pressure reduction after injection and, accordingly, the time for inter-reservoir flow to stop and mixing the injected fluids in the bottomhole formation zone is 15-30 minutes (1000-2000 s). That is, this is the time before which it is necessary to complete the curing process. Otherwise, the monomer compound will inevitably be diluted with formation water. Even worse is the case with a cement slurry, the setting time of which is 6-8 hours, and the end is 16-24 hours. The essence of the invention is the in-situ mixing of the polymer composition containing a standard hardener, with an additional amount of hardener to accelerate curing and prevent erosion of formation water. Almost at the same time, the leading edge of the injected cement slurry is mixed with the separation fluid (setting accelerator), which prevents erosion of the crust of the cement slurry. This is achieved by sequential and continuous injection of a polymer composition, a separation fluid (which simultaneously exhibits hardener and accelerator properties) and a cement slurry. Thus, this proposal eliminates the technical contradiction caused by the need to have a technologically safe curing time of the polymer composition - 90-120 minutes, and the need to quickly cure the polymer composition until the process of mixing the formation fluids is completed within 15-30 minutes. The same applies to cement slurry.

An example of a specific implementation. According to the reference book or empirically, a separation liquid is selected that exhibits both the properties of the hardener and the accelerator. For example, for acetone-formaldehyde resin according to TU 2228-006-48090685-2002, the standard hardener is an aqueous solution of alkali NaOH. At the same time, the same alkali solution is an accelerator for setting cement slurry [5]. For a pair of organosilicon compounds - cement slurries, the separating liquid, which simultaneously exhibits the properties of hardener and accelerator, is an aqueous solution of aluminum chloride. For a pair of urea-formaldehyde resin - cement suspension, the separation liquid is also an aqueous solution of aluminum chloride. A polymer composition is preliminarily prepared with a curing period (90-120 min), which ensures the safety of injection into the well. The required volume of the polymer composition and cement slurry for isolating and disconnecting individual layers and formations is determined empirically, based on the development conditions and the geological structure of the productive formations (permeability of the productive formation and the water-flooding layer, the degree of their fracturing and formation pressure values, the productivity of the reservoir and perforated parts thereof, etc.). For example, for the conditions of the oil fields of OAO TATNEFT when isolating formation water flowing through the annulus, the volume of polymer composition is selected according to the table.

The selected volume of the polymer composition, a pillow of 0.2 m fresh water, is then pumped into the well, then a release liquid in a volume equal to half the volume of the polymer composition. For a pair of acetone-formaldehyde resin - a suspension of cement, this will be an aqueous solution of NaOH, which simultaneously exhibits the properties of a hardener and a setting accelerator. To prepare 1.5 m ^{3 of the} polymer mixture with a cure time of 90-120 min, 1.35 m ^{3 of} acetone-formaldehyde resin must be taken and 0.15 m ^{3 of a} 10% aqueous NaOH solution added. In this case, the volume of separation liquid from a 10% aqueous NaOH solution will be 0.75 m ³ . When the polymer composition is mixed in the pores of the formation with an additional amount of hardener, it rapidly cures. The curing time of 1.5 m ^{3 of the} polymer composition with the addition of an additional 0.6 m ^{3 of} hardener will be from 1 to 3 minutes. Then a pillow of 0.2 m ^{3 of} fresh water and the calculated amount of a suspension of cement are pumped. A cement slurry is more sensitive to setting accelerator additives. A fresh water cushion is only necessary to prevent the components from mixing in the filling pipe. Otherwise, the proposed method does not differ from the standard technology for the injection of waterproofing materials.

Sourse of information

1. Molchanov A.G. Underground well repair. - M .: Nedra, 1986, p.198.

2. RF patent No. 2111337, Е 21 В 33/13, 05/20/98, BI No. 14.

3. Kleshenko II, Grigoryev AV, Telkov AP, Insulation work at the end and the operation of oil wells. - M .: Nedra Publishing House OJSC, 1998, p.26, 2nd paragraph.

4. Vasiliev V.N., Petrov A.I. Technique and technology for determining the parameters of wells and reservoirs. Reference worker. M .: Nedra, 1989, p.119, fig. 53-b.

5. Danyushevsky B.C., Aliyev P.M., Tolstykh I.F. Reference guide for cementing materials. - 2nd ed., Revised. and add. - M .: Nedra, 1987, p.198, table 4.1.

Claims (1)

A method of isolating water inflow zones in a well, including sequential injection of a polymer composition and a cement slurry into the water inflow zone, characterized in that the polymer composition has a curing time of 90-120 minutes, the cement slurry is injected after injecting a dividing fluid, which simultaneously exhibits the properties of a hardener of a polymer composition and an accelerator setting the cement slurry, and before and after the release liquid, they additionally pump fresh water pads.