RU2584194C1 - Method for prevention of behind-casing flows in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil and gas industry, namely to methods of overhaul of wells. Method involves performance of geophysical investigations with identification of intervals of inter-string flows. Casing string is equipped with pipes extensible to 24% with outer sealing elements. Casing string in upper part of expanded pipes from inside is equipped with hollow mandrel with seat for cementing plug, and below is with annular stop to stop mandrel. Expansion of casing string in range of flows is performed during cementing. Expanded by mandrel, which is moved under excess pressure in casing string, generated from wellhead. Movement of mandrel is performed by cementing plug after landing on mandrel, installed in specified interval of well.

EFFECT: technical result is increased efficiency of procedure due to reduction of material and time costs for elimination of behind-casing flows.

1 cl, 2 dwg

Description

The invention relates to the oil and gas industry, and in particular to methods for overhaul wells.

A known method of eliminating annular flows (patent RU No. 1813873, IPC ЕВВ 33/13, published on 05/07/1993, bull. No. 17), including sealing the channels of the flows, while in order to simplify the technology of work, the casing in the interval of flows or on individual areas expand beyond elastic deformations.

The disadvantages of this method:

- limited scope, since the casing is able to expand without breaking no more than 6%, after which the probability of its destruction increases significantly;

- the hydraulic anchor does not create an annular expansion around the entire perimeter of the pipe, which leads to low sealing efficiency of annular flows;

- the creation of very high pressures (100 MPa) requires the use of special pipes, machines, equipment and tools, which is associated with a significant increase in the cost of the process.

The closest in technical essence is the method of elimination of annular crossflows (patent RU No. 2537709, IPC E21B 33/10, 7/20 publ. 10.01.2015, bull. No. 1), including geophysical surveys in the well with the determination of the intervals of possible annular overflows, casing supply with expandable up to 24% pipes with external sealing elements located after lowering the casing opposite to the intervals of possible overflows, in the event of annular overflows, acting on the inner surface of the expandable pipes b, equipped with sealing elements, expand them in the entire flow interval, sealing the annulus, thereby completely eliminating the flow of fluid from the formation into the formation, in addition, expandable pipes with external sealing elements swelling under the action of the formation fluid are used.

The disadvantages of this method:

- the inability to prevent annular crossflows during the construction of the well, which leads to additional material and time costs, since it is necessary to stop the well for work on the elimination of annular crossflows;

- the need for additional tripping operations to expand the pipes and use additional equipment (flare), which leads to additional material and time costs.

The technical objective of the proposed method is to reduce additional material and time costs by preventing annular crossflows during the construction of the well, which eliminates the need to stop the wells for liquidation of annular crossflows and, accordingly, additional tripping operations to expand the pipes and use additional equipment .

The technical problem is solved by a method of preventing casing flow in the well, including geophysical surveys with determining casing flow intervals, supplying the casing with expandable pipes up to 24% with external sealing elements located after running the casing opposite the flow intervals, expanding the casing in the flow interval beyond elastic deformation by acting on the inner surface of expandable pipes provided with sealing elements.

It is new that the casing in the upper part of the expandable pipes is internally provided with a hollow mandrel with a saddle under the cement plug, and below it with an annular stop for stopping the mandrel, and the casing is expanded in the flow interval during cementing with the mandrel moving down to the stop after tight installation of a cement plug in it under the action of excess pressure in the casing created from the wellhead.

In FIG. 1 shows the descent into the well with flow from the formation to the formation of the casing in the upper part of the expandable pipes, equipped with a mandrel with a saddle for a cement plug, and below it an annular stop.

In FIG. 2 shows the elimination of overflows by expandable casing pipes using a mandrel and its fixation in an annular stop.

The method is carried out in the following sequence.

Based on the geological material and information on the presence of casing flows in neighboring wells, interval 1 (Fig. 1, 2) of casing flows is included in the well construction project, including casing string 2, expandable to 24%, pipe 3, equipped with sealing elements 4, located after lowering the casing 2 into the well 5 opposite the interval 1 flows. The casing 2 in the upper part 6 (Fig. 1) of the expandable pipes 3 (Figs. 1, 2) is internally provided with a hollow mandrel 7 with a seat 8 for a cement plug 9, and below it with an annular stop (stop ring) 10 to stop the mandrel.

The casing 2 is lowered into the well 5 (Fig. 1) with expandable pipes 3 provided with sealing elements 4, while the expandable pipes 3 are interconnected, for example, by threading or welding. The cementing of the well 5 is carried out in a known manner. During cementing of the well 5, when the cementing plug 9 reaches the hollow mandrel 7, it is hermetically installed in the seat 8. Moreover, due to the core 11 of the cementing plug 9 being made of metal, and the ledge 12 is made on the inner cavity of the mandrel 7, the probability of that the plug 9 will slip through the inner cavity of the mandrel 7. Under the influence of excess pressure in the casing 2 (Fig. 2) created from the mouth (not shown) of the well 5 during cementing, the hollow mandrel 7, acting on the inner surface of the expansion of pipes 3, provided with sealing elements 4, expands them in the entire interval 1 of the overflow, sealing the annulus 13 until the gaps 14 between the casing 2 and the wall 15 of the well 5 are eliminated, thereby completely eliminating the flow of fluids from the formation 16 into the formation 17 and vice versa .

Due to the fact that the expandable pipes 3 (Fig. 1) are made of steel, allowing their expansion to 24%, the existing gaps 14 between the casing 2 and the wall 15 of the well 5 are completely eliminated without possible destruction of the casing 2. After the hollow core 7 Fig. 2) an annular stop (stop ring) 10 in the lower part of the expandable pipes 3 on the manometer (not shown) at the wellhead 5, an increase in pressure is recorded, which is a signal to stop cementing of the well 5. After that, perforation (not shown) is made in product range clear formation 17 in a known manner. If it is necessary to involve the underlying formation (not shown) in the development of the well 5, drill the cementing plug 9, the hollow mandrel 7 and the ring stop (stop ring) 10 made for this purpose from easily drilled materials.

The proposed method allows to reduce additional material and time costs by preventing annular crossflows during the construction of the well, which eliminates the need to stop the well for liquidation of annular crossflows and, accordingly, additional tripping operations to expand the pipes and use additional equipment.

Claims (1)

A method of preventing annular crossflows in the well, including conducting geophysical studies with determining intervals of annular crossflows, supplying the casing string with expandable up to 24% pipes with external sealing elements located after lowering the casing string opposite the flow intervals, expanding the casing string in the flow interval beyond elastic deformation by on the inner surface of expandable pipes equipped with sealing elements, characterized in that the casing the casing in the upper part of the expandable pipes from the inside is equipped with a hollow mandrel with a saddle under the cement plug, and below it with an annular stop to stop the mandrel, and the casing in the flow interval is expanded during cementing by the mandrel, moving down to the stop after the cement plug is sealed in it under the action of excess pressure in the casing created from the wellhead.

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