RU2276250C2 - Method to install bridge for oil reservoir isolation - Google Patents

Abstract

FIELD: oil and gas well building, particularly to perform isolation works in cased wells.

SUBSTANCE: method involves depositing sand column, which closes perforation interval; injecting plugging composition above sand column. The plugging composition comprises aqueous dispersion including fresh water and water-swelling polymeric powder based on water-absorbing polymer. The polymeric powder is taken in amount of 1.5 parts by weight per 100 parts of fresh water. Gel aggregates of water-swelling polymer are added in amount of not more than 5% by fresh water weight.

EFFECT: improved technology of bridge creation.

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Description

The invention relates to the field of construction of oil and gas wells, in particular, to the field of insulating work in cased wells.

Known widely used method of installing a cement bridge over the roof of the underlying reservoir. To do this, tubing pipes (tubing) with an open end to a depth of 50-100 m above the top of the reservoir are lowered into the well. The cement mortar is pumped and the necessary time is waiting for it to cure. A hardened cement pillar cuts off the oil reservoir from the rest of the well. However, this method has disadvantages. At high injectivity of the underlying formation, the bridge goes down under overpressure in the well. In this case, the cement slurry in some cases drops to the perforation interval, enters the reservoir and reduces its productivity. In other cases, the cement mortar does not reach the underlying formation, but in the process of lowering it is diluted with water and the cement cup cannot be obtained with a qualitatively cut-off cement bridge. Fluid passes through it.

The closest technical solution adopted for the prototype is a method of installing a bridge that cuts off the underlying layer from the overlying ones, including the reclamation of a column of sand that overlaps the perforation interval, and the injection of grouting composition above it [2].

According to this method, sand is first washed into the well through deflated tubing. A pillar is created from sand, filling the perforation interval and exceeding it by 3-10 m. Then, through the tubing installed above the barrel of sand, a bridge of cement mortar is installed. In this case, the cement mortar at the contact with the sand forms a filter cake and does not leak below. Thus, the installation of the cement bridge at a predetermined depth is ensured and the lowering and penetration of the cement mortar into the underlying productive formation with the damage to its productivity is excluded. However, this method has the disadvantage that it is necessary to spend time installing a cement bridge, an OZZ, drilling it with the time it takes to lower a tubing with a downhole motor, raise it when you have to return to the operation of the underlying reservoir.

The objective of the invention is to reduce the time required to install the bridge by improving the technology for its creation. The problem is solved by the method of installing a bridge that cuts off the underlying oil formation from the overlying formations, including the washing up of a column of sand, covering the perforation interval, and the injection of grouting composition above it, characterized in that as a component of the grouting composition, an aqueous dispersion of fresh water and a powder of a swellable polymer is used - GNP based on AK-639 in the ratio of 1.5 weight parts per 100 parts of fresh water with the introduction of GNP gel aggregates into the dispersion in an amount up to 5% by weight of the fresh water of the dispersion.

The invention consists in the following.

In the well, a sand bridge is washed through the open tubing with an open end, covering the interval of perforation of the underlying oil reservoir. Then, through them, water dispersion from GNP is pumped into the well with the inclusion of large aggregates from GNP. As GNP use AK-639 (TU 6-02-00209912-59-96).

An aqueous dispersion is prepared by mixing powder from GNP - AK-639 in fresh water with a polymer concentration of 1.5% in it, introducing aggregates of GNP into it with a size not exceeding the inner diameter of the tubing. Putting more than 1.5% of GNP powder into the water is technologically limited by the ability of pumping by the CA-320 pump. GNP aggregates are dense gel particles with a polymer concentration in the range of 5-20%.

The volume of dispersion of GNP powder is determined in advance based on technical plans. Usually it does not exceed 10-20 m in the casing. For casing diameters of 146 and 168 mm, 200 l is usually taken.

The introduction of aggregates from GNP into an aqueous dispersion of GNP powder in an amount of up to 5% by weight of fresh water ensures the transition of the whole mass after 4 hours into a dense gel formed into a total mass. Entering 5% of GNP units is admissible by the ability of the TsA-320 pumps to pump it.

The table shows data on the selection of the optimal combination of dispersion of GNP powder and aggregates of GNP in the form of a dense gel with a polymer concentration of up to 10% in it.

Composition based on GNP, weight. parts Sample Condition Water GNP powder GNP unit Holding time, hour one hundred 0.5 5 four Weak gel, scattered particles of aggregates one hundred 1,0 5 four Gel gelatinous, separate units one hundred 1,5 5 four Dense gel, continuous in a single mass with aggregates one hundred 2 5 2 Due to the high density, it is not technologically advanced when pumped

To install the bridge, first a sand column is washed in the well with previously lowered tubing, covering the perforation interval in the cut-off formation. Then the tubing is set above the boundary of the column of sand. The cementing unit ЦА-320 is connected to the injection line of the well, and through a small capacity establishes a connection with a tanker filled with fresh water. After that, a buffer from fresh water is pumped into the well to flush the tubing and part of the casing from produced water. Then, a dispersion of GNP powder in fresh water in a volume of 200 l is injected into the well with the introduction of GNP gel aggregates into it. At the same time, fresh water is supplied from the tanker to the small cavern CA-320, then GNP powder and GNP gel aggregates are introduced into it. The composition is squeezed before exiting the tubing and left to swell for 4 hours. The tubing rises to the roof of the overlying formation. A perforator descends through the tubing and perforation of the overlying formation is carried out, its development and operation. If it is necessary to re-preserve the well, the tubing is pulled down and the bridge is removed from the GNP and the sand bridge by washing.

The advantage of the proposed method over the known one is to increase the efficiency of isolation work by reducing the time required to cut off the underlying oil reservoir from the overlying ones, which allows, practically without stopping at the OZC and carrying out tripping operations, to perforate through the tubing in the overlying reservoir, mastering it to determine it productivity or exploitation.

The proposed method provides without the use of downhole motors with a bit, the production of de-preservation of the lower oil reservoir, if the transition to its operation.

Literature

1. The reference book on the current and capital repair of wells. M .: Nedra, 1979. The chapter “Isolation of the Upper Waters” (p. 239).

2. Instructions for the repair of well support RD-39-1-843-82. Page 28 clause 4.123, appendix 8.

Claims (1)

A method of installing a bridge that cuts off the underlying oil reservoir from the overlying reservoirs, including depositing a column of sand overlapping the perforation interval, and pumping grouting composition above it, characterized in that as components of the grouting composition, an aqueous dispersion of fresh water and a powder of water-swelling polymer (GNP) is used based on AK-639 in a ratio of 1.5 weight. including 100 parts of fresh water with the introduction of GNP gel aggregates into the dispersion in an amount of up to 5% by weight of the fresh water of the dispersion.