RU2271441C2 - Well completion method and device - Google Patents

Abstract

FIELD: oil production, particularly to create spoke-ring crack in oil saturated rock.

SUBSTANCE: method involves boring well; casing the bell with casing pipes and cementing thereof; lowering selective cumulative rock-drilling machine, which comprises n sections with each section provided with separate cumulative charge; creating undercut in rock; performing hydraulic reservoir fracturing; expanding and fixing crack. Well borehole is drilled transversely to rock stratification direction. Telescopic device with central connection pipe and longitudinal stiffening ribs is arranged in casing pipe to be lowered in place of following crack creation. The undercut is performed in plane transversal to well axis and arranged at central pipe by combining cumulative charges with undercut plane in sections; serially throwing the charges and creating channel fan in the reservoir. Device comprises central connection pipe to be installed in casing pipe. The connection pipe is provided with longitudinal stiffening ribs for connection pipe wall reinforcement and telescopic connection units, which are connected to upper and lower casing pipe parts. The device also has cumulative rock-drilling machine comprising n sections, wherein each section provided with separate cumulative charge. Each next rock-drilling machine section is turned through angle divisible by 2π/n value relative to previous one. Method for well completion involves choosing the well having reservoir penetration angle near to 90° to reservoir layer inclination; lowering selective cumulative perforator having n sections, wherein each section is provided with separate cumulative charge; creating undercut in rock to create channel fan in plane transversal to well axis by aligning the cumulative charges with undercut plane in sections and serially throwing the charges; transversally cutting casing pipe below undercut plane; performing hydraulic reservoir fracturing and fixing the obtained crack; closing the undercut area with filtering connection pipe.

EFFECT: increased operational quality and reduced costs.

3 cl, 13 dwg

Description

The invention relates to oil and gas production, in particular, to a method for creating a radially annular crack, a conducting fluid in saturated rock.

The application of the method is preferable in formations with complex geological and technical conditions, associated, as a rule, with low permeability of the rock and with the need to control the shape and radius of the crack propagation near the gas and water-oil contacts.

It is known that, during drilling, there is an irreversible deterioration in the reservoir properties (the effect of formation damage). In the radius of up to - 1 m of the bottomhole zone, the pore ducts become clogged and reduced, in a radius of up to ~ 10 m clay may swell or disperse with fresh water entering the formation, formation of an emulsion. In addition, the process of high-speed drilling, accompanied by a significant mechanical impact on the rock and the appearance of a free surface in it, leads to the formation of a dilated softening and fracturing zone around the wellbore, which aggravates the damage to the formation, and the fracture is higher, the lower the initial porosity. The authors of [1] estimate the size of this zone with a radius of ~ 3 m.

The main method entrusted with solving the problem of creating channels of hydrodynamic communication with the unaffected zone of the formation is cumulative perforation. However, the possibilities of cumulative perforation are limited, since it is known that with the current technological level of manufacture of cumulative charges, the penetration depth over the rock is theoretically limited to 25 charge diameters. Existing charges have a penetration depth of not more than 1 m.

Thus, the most effective way (and for low-permeability non-fractured collectors with a plastic matrix is often the only possible way) to penetrate the affected area is to create a crack in the rock that extends beyond the affected area.

Obviously, preference should be given to a radially annular (horizontal) crack due to a number of geological and technological advantages. It is known that horizontal cracks form in open-hole wells at depths of up to 800 m. It is also known that horizontal lithostatic pressures increase faster than vertical ones with depth, therefore horizontal fracturing occurs much deeper in deeper formations [2].

For the successful implementation of the method at medium depths, it is necessary to solve the following problems related to the transition from the Lame stress state to the state in which a pre-formed crack propagates when its banks are loaded with pressure:

1) Posting the wellbore along the productive horizon should be carried out at a low speed to reduce mechanical damage. It is obvious that hydraulic fracturing immediately after high-speed drilling will not lead to the successful creation of a radial crack, since crack propagation in the dilated fracture zone will occur randomly. The development of a radial crack will be possible only after rheological "healing" of the fracture after a considerable period of time (about one year) after cementing.

2) The direction of the trunk should be perpendicular to the angle of inclination of the layers, since the development of a horizontal crack is carried out, as a rule, in the layering plane, and failure to comply with this requirement will lead to breakage of the column when the crack expands.

3) To successfully create a radial crack, a circular subcut of the rock is produced before hydraulic fracturing. In the area of the collar, firstly, you must have a telescopic connection in the casing. The absence of such a connection will prevent the expansion of the crack during hydraulic fracturing; such a gap will lead rather to compaction of the rock in the near-wellbore zone or, in the best case, to the development of a vertical crack. Secondly, the production of the collar is associated with a significant weakening of the casing. The operation of a formation with a radially annular crack can be accompanied by plastic flow of the matrix in the crack zone and crushing of the column weakened in the column underneath, if measures are not taken to strengthen it.

4) In the production of a circular cut, there is also a weakening (cracking) of the cement stone above and below the plane of the cut, so the method of its creation should include the requirement of a minimum high-impact impact on the cement stone.

A known method of hydraulic fracturing associated with the creation in the rock of an artificial circular "cut" (the same as a subcut) by sandblasting perforation using a depth rotator [3]. The disadvantage of this method is low efficiency and productivity due to a sharp increase in hydraulic resistance to flow with increasing pressure in the cutting zone. At a distance of ~ 0.1 m, abrasive cutting of the rock is replaced by leaching of the cavity.

Closest to the proposed method and device is a method of jet-pulse hydraulic fracturing, which includes drilling a well to a predetermined depth, casing a well with pipes, cementing the annulus, lowering the device for directional fracturing to an appropriate depth ..., circular single perforation with a ring drill, pulse hydraulic fracturing of the reservoir ... and injection into the crack fluid with a fastener [4].

The disadvantage of this method is that the annular cumulative pipe cutter used to create the cut is, at best, able to cut the column and practically does not go deep into the annular cement stone, and even more so into the formation rock. Currently available technologies for the manufacture of ring shaped charges do not allow to increase the radius of its action. In addition, the ring charge has a significant high-explosive effect, leading to deformation of the column and cracking of cement stone in the cutting zone.

A known method of perforating formations, which includes first creating one perforation channel, then the second channel, which is located at a very close distance parallel to the first or even partially enters it. When the second cumulative charge is triggered, the layer formed from the compacted material in the second channel will be removed into the first perforation channel under the action of the force of this cumulative jet.

A perforating device is known to be lowered on an armored electric cable, which mainly consists of a body with two disconnected cumulative charges, an electric switch chamber and a rod with a limiter attached to the body of the perforator, as well as a packer element, which is lowered together with the perforator into the casing. The puncher is designed for lumbago as one pair of holes, or several at the same time in a given interval, in the latter case, several pairs of charges are mounted in the punch case, the punching technique remains the same [5].

The specified method allows you to create an effective subcut in the longitudinal plane of the well for subsequent fracture fracturing. The disadvantage of this method is that it does not allow you to create a radial-annular crack in the rock, which has several advantages if it is necessary to control the position and radius of the crack propagation in the reservoir, for example, when hydraulic fracturing is carried out near the water or gas-oil contact.

The purpose of the invention is the development of a method and device that improves the quality of work and reduces costs when completing a well with a radial annular crack.

This goal is achieved by the fact that in the known method of completing a well, including drilling a well, casing a well with pipes, cementing the annulus, launching a selective cumulative perforator containing n sections with a separate cumulative charge in each section, creating a subcut in the rock, pulse fracturing, expansion and consolidation of the crack, the wellbore is perpendicular to the direction of layering, in the descent casing in the place of the alleged creation of the gap installed There is a telescopic device with a central branch pipe and longitudinal stiffeners, while the undercut is carried out in a plane perpendicular to the axis of the well and located in the zone of the central branch pipe by sectionally combining cumulative charges with the plane of the undercut, firing them sequentially and creating channel fans in the formation. The device includes a central nozzle installed in the casing with longitudinal stiffeners for reinforcing the nozzle wall and telescopic joints with the upper and lower parts of the casing and a selective cumulative perforator containing n sections with a separate cumulative charge in each section, in which the subsequent sections of the perforator are rotated relative to previous at an angle multiple of 2π / n, while the device provides the possibility of sequential sectional alignment of its cumulative charge in a central pipe for sequentially otstrelivaniya them in one plane. In the case when it is necessary to create a radial-annular crack in a previously drilled well, choose a well from their stock with an angle of its entry into the formation close to 90 ° to the angle of inclination of the layers, launching a selective cumulative perforator containing "n" sections with a separate cumulative charge in each section, creating a subcut in the rock with the formation of a fan of channels in the reservoir in a plane perpendicular to the axis of the well by sectionally combining cumulative charges with the plane of the subcut and sequentially firing them, transverse cut casing string below the plane of the collar, pulsed hydraulic fracturing, fixing a hydraulic fracture and overlapping of the collar zone and cutting with a filter nozzle. A comparison of the claimed technical solution with the prototype allows, according to the author, to establish compliance with its criterion of "novelty." The author is not aware of the use of the combination of distinctive features of the method and device in other areas of technology, which gives reason to believe that the proposed solution meets the criterion of "significant differences".

In the drawings, step by step illustrates one of the variants of the main method.

The figure 1 shows the wellbore 1, which is carried out perpendicular to the corner of the layering in the reservoir 2.

The figure 2 shows a section of the trunk and the bottomhole formation zone (PZP) with a descent casing, on which a telescopic device with a central pipe 3 is installed in the place of the proposed horizontal gap. The central pipe is connected to the lower and upper parts of the column by telescopic connections 4. Cross section of the central the pipe is enlarged shown in figure 3.1, which shows the vertical stiffening ribs 12, reinforcing the wall of the column. After the descent of the column, the annular space is fixed with cement stone 5. The gap δ between the movable parts of the telescopic device should be minimal to prevent cement from entering it when pumping the cement plug. The cavity ρ can be filled with air. The features of lowering the column into the wellbore are such that the top of the column in section R (see FIG. 1) is stretched and the bottom in section S is in a compressed state, so there is no need to fix the telescopic device in a compressed position.

In the PPP, it is possible to identify damaged zones 6 and 7, which separate the well from an intact reservoir 2.

In figures 3A (front view) and 3b (plan view) shows the stage of production of a circular cut. A selective perforator 8 is lowered into the well, containing n individual sections with a separate cumulative charge 10 each (shown in Fig. 3.1). Cumulative charges are combined sectionally with the plane of the cut and shoot them with the formation of a fan of cumulative channels 11. The angle between adjacent channels will be 2π / n. The distance between the ends of adjacent channels with a channel length of ~ 0.7 m and n = 36 will be about 80 mm. With such a mutual arrangement of the channels, a region of a connected annular crack 14 will appear in the plane of the undercut 14. The existing errors in the methods of attachment of the punch allow you to shoot all the charges in almost the same plane with a small spread Δ, as shown in figure 3.2. Obviously, the wall of the central pipe will be significantly weakened by cumulative holes 13, therefore, to prevent the column from being deformed at the subsequent stages of completion and during well operation, longitudinal stiffeners 12 are provided, which will reduce the depth of the channels that come to them and distort the boundary of the region 14.

After the completion of the undercut step, a pulse-type pressure generator is lowered into the well, for example, a powder generator 15 (see Figures 4a for a front view, 4b for a plan view). The pressure of the generator will act on the shores of area 14 and contribute to the spread of the horizontal fracture 16. At this stage, the crack can propagate outside the damaged zone, and if the powder generator contains finely divided non-combustible fraction, partial crack fixing and well operation are possible.

Figures 5a and 5b illustrate the final stage, including the descent and installation of downhole equipment 17 (enlarged shown in Fig.5.1), further expansion of the fracture 16 and fixing it with sand 18.

Figures 6a and 6b show a method implemented in a previously drilled well, at the stage of fixing the fracture and installing the filter nozzle.

After the circular cut is carried out, the casing is transversely cut to form a gap 19. Next, a pulsed hydraulic fracturing is carried out, the crack 16 is expanded and its sand is fixed with sand 18. Then, the filter pipe 20 is lowered into the well and installed, for example, by means of cutting with overlapping of the cutting and cutting zones .

Implementation of the method in a production environment will allow the development of reservoirs classified as "dry" and can provide significant savings compared with the technology of horizontal wells and wells with re-cut boreholes.

Literary sources

1. Gaivoronsky I.N., Leonenko G.N., Zamakhaev B.C. Oil and gas collectors in Western Siberia, their autopsy and testing. - M .: Geoinformmark CJSC. 2000 (ISBN 5-9000357-16-3), p. 204.

2. Nikolaevsky V.N. Geomechanics and fluid dynamics. - M .: Nedra, 1996 (ISBN 5-247-03675-1), p. 126.

3. Usachev P.M. Hydraulic fracturing. Textbook for students of vocational education and workers in the workplace. - M .: Nedra, 1986, p. 65.

4. Impulse fracture of rocks. Mikhalyuk A.V., Voitenko Yu.I. Repl. ed. Danilenko V.A .; Academy of Sciences of Ukraine. Institute of Geophysics named after S.I.Subbotina, - Kiev: Science. Dumka, 1991 (ISBN 5-12-002063-1), p. 170 (prototype).

5. Schuster Nick A. Methods for perforating an earth formation [Schlumberger Techology Corp.]. Pat. USA, class 166-297 (E 21 B 43/117), No. 3706340.

Claims (3)

1. A method of completing a well, including drilling a well, casing a well with pipes, cementing an annulus, launching a selective cumulative perforator containing n sections with a separate cumulative charge in each section, creating a cut in the rock, pulsed hydraulic fracturing, expansion and consolidation of the crack, characterized the fact that the wellbore is perpendicular to the layering direction, a telescopic device is installed in the descent casing in the place of the alleged creation of the gap GUSTs with central pipe and longitudinal ribs, wherein the pull up is performed in a plane perpendicular to the borehole axis and situated in the central zone of the nozzle, by combining Multiple Feature Select shaped charges with the plane pull up, and sequential firing of creating channels in the formation of the fan. 2. A device comprising a central pipe installed in the casing with longitudinal stiffeners for reinforcing the pipe wall and telescopic connection nodes to the upper and lower parts of the casing and a selective cumulative perforator containing n sections with a separate cumulative charge in each section, in which subsequent sections rotary hammers are rotated relative to the previous ones by an angle multiple of 2π / n, while the device provides the possibility of sequential sectional alignment of its cumulative series with a central socket for serial otstrelivaniya them in one plane. 3. A method of completing a well, including selecting a well from its stock with an angle of its entry into the formation close to 90 ⁰ to the angle of inclination of the layers, launching a selective cumulative perforator containing n sections with a separate cumulative charge in each section in which subsequent sections of the perforator are rotated relative to the previous ones by an angle multiple of 2π / n, creating a subcut in the rock with the formation of a channel fan in the formation in a plane perpendicular to the axis of the well, by sectionally combining cumulative charges with the plane of the subcut and atelnogo their firing, the transverse cutting of the casing below podrubit plane pulse fracturing, fracturing and fracture fixation overlap zone and pull up the cutting nozzle filter.

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