RU2533783C1 - Well completion method - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method comprises the lowering and cementation of a production casing, with installation of a shoe in a cap base surface, drilling out of cement column with the subsequent forming of borehole in the productive formation interval. In the thick productive formation interval several caverns separated by girts are formed. In the girts before forming of caverns a probe perforation is performed with the location of punched channels along the perimeter in the same plain. Forming of cavity of caverns is performed in a borehole from above downwards from the cap.

EFFECT: well operation with the maximum production rate, with conservation of integrity of mine walls.

3 dwg

Description

The invention relates to the mining industry and is intended before the formation of a stable extended borehole, mainly in formations with weakly cemented rocks.

Known design of the producing well (I).

The design of the wellbore in the reservoir is determined by the type of reservoir, its hydrodynamic characteristics, the stability and strength of the rock, their tendency to fracture, and the thickness (thickness) of the reservoir.

The most acceptable, from the point of view of maximum well productivity, is the design of the bottom hole zone with an open bore, the diameter of which is determined from the conditions of maximum theoretical productivity and economic feasibility.

It is possible to achieve an increase in well productivity by expanding the bore, given that the diameter of the cavity can be 2–3 times larger than the diameter of the borehole, depending on the rock strength of the reservoir.

However, with its sufficiently large power, with the cylindrical shape of the cavity, collapse of the walls of the cavity is possible, with a sharp decrease in the permeability of the bottom-hole zone and the production capacity of the well.

A well-known design of wells, with an expanded section (II), where the expansion of the barrel is carried out to the required, or technically feasible rational radius of the cavity. According to the well-known data for a particular well, the diametrical sizes of the cavity obtained over the entire thickness of the reservoir can vary over a wide range. In this case, the dimensions of the cavity in height depend on the strength of the rock and can reach values of R _R ≈100 cm, with a reservoir thickness of H = 8 m.

The obtained dimensions of the cavity using hydrodynamic expanders depend on the strength of the rock layers and are random in depth and height.

To prevent the destruction of the rock layers, compulsory filling of the cavity with a sand-gravel mixture is carried out. An increase in the height of the cavity, with such diametrical dimensions, can lead to collapse of the walls and a decrease in well productivity.

A well-known new technology for completion of wells (III) is known when, when opening the reservoir and deepening the well, wall shedding and collapse of the open bottom occur.

The essence of the method - when completing a well, create a cavity at the boundary of the reservoir and tire, with the determination of the mechanical, physical and strength parameters of the reservoir, formation fluid, etc.

Based on these data, a calculation formula is proposed to determine the diametrical dimensions of the cavity at which collapse is excluded. However, the substitution of known data into the formula and calculations show that the diameter to which the cavity needs to be expanded is beyond the scope of the technique. The design of the open conical face, with the estimated diametric dimensions, according to the authors, will allow the well to be operated without complications. But it is impossible to achieve such cavity sizes due to the restrictions imposed by the expander designs, and the method has only theoretical significance.

The same applies to the design of the disk-shaped cavity, the diameter of which is calculated taking into account the conditions for preventing collapse of overlying rocks. At the same time, such a factor as the thickness (thickness) of the productive formation, the influence of which on the collapse of the walls of the cavity, does not play an important role.

A known method of completing wells (IV).

The method includes lowering and cementing the casing string, before opening the reservoir, with the installation of the shoe of the production string in the sole of the tire covering the reservoir. Then drill a cement cup, followed by descent of the tubing and development of wells.

The disadvantages of the method of application include:

- low efficiency of its use in loose or weakly cemented reservoirs, especially of high power, where when opening the upper part of the reservoir, the upper part of the walls of the cavity having a cylindrical shape over the entire thickness of the reservoir is shed and collapsed.

The collapse of the walls of the cavity, when opening the reservoir, occurs almost immediately, or to prevent this event, it is necessary to use special technological methods for fixing and maintaining the stability of the walls of the well. Even with an insignificant impact on the rock, which exists at the time of opening of the reservoir, when due to the instability of the walls of the mine, its collapse is possible.

The use of such a completion method on an old well stock can be considered problematic, since the formation of an expanded cavity in rocks having unknown physical and mechanical characteristics, when additional stresses arise in the rock skeleton composing the formation, during production and overhaul of wells. In this regard, there is a sharp decline in well productivity. It is difficult to restore the productivity of wells by expanding the wellbore, especially in high-power formations, due to the possibility of collapse of the walls of the cavity.

A well-known method of well completion (see US Pat. RF No. 2326232, M., class. E21B 43/02, application No. 2006109837/03 of 03/29/2006, published. 06/10/2008) - prototype.

The invention is intended for the construction of wells in weakly cemented and loose reservoirs, with low rock strength. The implementation of the method, according to the authors, ensures the operation of wells without sand removal and eliminates the causes of collapse of the side walls of the open face in the reservoir.

Implementation of the method - lowering and cementing the production casing before opening - the reservoir, with the installation of the shoe on the sole - the tire, overlapping the reservoir. Next, check the tightness of the production casing and drill a cement glass, which is known and applied.

Then, before lowering the tubing, a cavity is created at the boundary of the reservoir and tire, which is expanded horizontally to achieve a size, the necessary value of which is determined by the analytical expression.

The disadvantages of the method include:

- since the opening of the reservoir occurs after the launch of the production string, the diameter of the wellbore below the shoe cannot be larger than the inner diameter of the casing pipes. This event occurs until the cavity expands. Moreover, according to the calculation formula, the diameter of the cavity, after substituting the initial data, can reach many meters, which is absolutely unrealistic.

It is unclear how to obtain complete geophysical information about the rock of the reservoir, the properties of the reservoir fluid, without having drilled the wellbore of a particular well, with a core taken and its investigation in laboratory conditions.

It is incorrect to use geophysical data obtained when drilling neighboring wells, which may differ in a fairly wide range of parameters.

It is not clear what is meant by the value of h - the thickness of the overlying rocks overlying the reservoir layer, which, according to the authors, is determined by the data of geophysical studies.

Creation of a cavity of the natural form that loose rock takes under the influence of gravity and the force of interaction with the fluid in the reservoir. This means that there is a reservoir, which occurs without external intervention and control, which makes it impossible to determine the size of the cavity.

The implementation of the method by which it determines the size of the cavity by mathematical dependence, namely, only its diametrical dimensions, with its subsequent expansion to several tens of meters. If you believe the calculation formula, then such an extension of the barrel is impossible to carry out!

The technical result that can be obtained by implementing the invention is reduced to the following:

- the possibility of increasing the flow rate of the well by expanding the wellbore in the interval of the reservoir, with obtaining caverns of the calculated diameter, while maintaining the stability of the walls of the cavity formed over the entire thickness of the reservoir, with caverns separated by bridges;

- the ability to reduce the pressure gradient on the walls of the cavity and increase the flow rate of the well;

- the possibility of increasing the permeability of the rock of the reservoir at the location of the jumpers, by creating deep perforation channels located at the same level around the perimeter in each jumper.

The technical result is achieved by creating a trunk in the interval of the reservoir and cavity, expanded in the horizontal direction, after the descent and cementing of the production string, with the installation of the shoe in the sole of the tire.

After creating a trunk in a productive formation of high power, several caverns are created, separated by jumpers, the height of which is determined from the condition of maintaining the integrity of the trunk.

The height of the jumpers is determined by the formula

where: h _n - the height of the jumper, m;

φ is the angle of natural cleavage of the rock of the reservoir;

c is the coefficient of adhesion of the rock, MPa;

g is the acceleration of gravity, m / s ² ;

D _article - the diameter of the wellbore, m;

P _p - rock density, kg / m ³ ;

P _f - the density of the reservoir fluid, kg / m ³ ;

,n is the expansion coefficient;

,

moreover, in each jumper, before creating the cavity, probe perforation is carried out, and the expansion of each cavity is carried out from top to bottom.

The design of the well, made by the protected method, is shown in the figures, where:

- figure 1 - construction of the bottom of the well after drilling the well, in the interval of the reservoir and the creation of deep perforation channels, in the place of existence of jumpers;

- figure 2 - construction of the bottom of the well, when forming the cavity;

- figure 3 is a cross section of a wellbore at the location of the perforation channels in the jumper.

In figures 1, 2, and 3, item 1 indicates a casing installed in the wellbore 2. In the interval of the reservoir with a capacity of H _PL , caverns 3 are made, separated by lintels 4, in which perforation channels 5 are placed uniformly around the perimeter in one plane.

The method of completing a well in oil and gas fields, with poorly cemented rocks composing a reservoir with a capacity of H _PL , is carried out in the following sequence of technological operations.

After drilling a well, casing 1 is lowered and cemented, with a shoe located at the bottom of the tire, above the reservoir.

Check the tightness of the casing 1 and the lining of the well, followed by drilling a cement cup. Then drill a wellbore 2 wells, for the entire power (H _PL ) of the reservoir, with obtaining core material. In core studies, determine the average value of the coefficient of adhesion - C, in MPa, the value of the average density of the rocks of the reservoir.

By calculation, using the formula, determine the diametrical - D _cav and the transverse dimensions h _{cav of} each cavity 3, with the calculation of the size of the jumpers 4 between them. Set the intervals between the jumpers 4 and determine the location of the probe perforation in each jumper 4, with a uniform location along the perimeter of the perforation channels 5 in one plane. This is achieved by installing a hydraulic probe punch, a known design at the level of the intended location, for example, the first jumper 4.

Supply pressure of the working fluid into the perforator, with the exit of the probe with a nozzle in the reservoir, as the formation of the perforation channel 5.

The probe with the nozzle is returned to the perforator body.

Relieve pressure and rotate the drill pipe string, together with the case of the perforator at an angle of 120 °, install a perforator above a new point and create the next perforation channel 5 by supplying working fluid under pressure with a jet through the probe nozzle to the formation rock.

After performing the perforation channels in the first, starting from the top of the jumper 4, the drill pipe string with the perforator is moved to the location level of the next jumper 4 and the process of creating the perforation channels 5 is repeated by analogy with the above.

In this manner, probe perforation is carried out in all jumpers 4. The number of jumpers 4 and cavity 3 with known sizes of the latter depends on the thickness of the reservoir - H _pl .

After performing probe perforation of the jumpers 4, the device is removed to the surface, replaced by an expander, which is lowered into the well to a predetermined depth, with the location at the level of the first cavity 3, starting from the top. The working fluid is supplied under pressure to the drill pipe string, followed by rotation of the expander and the formation of a cavity 3 of a given diameter — D _cav and height — h _cav .

After the formation of the first cavity 3, the flow of fluid under pressure is stopped and the expander is returned to the transport position and, further, by moving the drill string down, the expander is placed at a new level to perform the operation to form the subsequent cavity 3, with the process of its formation being repeated, by analogy with the above.

The dimensions of the cavity 3 in height and inner diameter are determined from the condition of maximum productivity in the production of reservoir fluid, while maintaining the integrity of the walls of the mine.

The formation of caverns 3, alternating with jumpers 4, having an estimated geometric parameters, will ensure the stability of the mine during operation of a productive formation of high power, composed of fragile, weakly cemented rocks, without wall collapse and destruction of the reservoir, at the maximum possible flow rates.

The jumpers 4 between the caverns 3, play the role of stiffening rings that perceive rock pressure, which prevents the destruction of the pores of the reservoir.

Information sources

1. The exploitation of gas and gas condensate fields: a Reference manual. - M .: Nedra, 1988, p. 68-71. Authors: Gvozdev B.P., Gritsenko A.I., Kornilov A.E.

2. V.V. Zinoviev "Construction and repair of gas wells." Development. Implementation. - M .: Nedra, 2004, p.136-143.

3. M.V. Pyatakhin "Geochemical problems in the operation of wells." Ser. “Vesti gazovoy nauki” Moscow, OAO Gazprom, Gazprom VNII-GAZ, 2011. Chapter 8.

4. Babichev A.A. “Highly efficient completion of wells with open bottom at Nevsky PHN. A.A. Babichev et al. II V. sb. Underground gas storage. Problems and prospects. - M.: VNIIGAZ, 2003 S. 324-330.

5. Pat. RF №2.326.232, M., cl. E21B 43/02. The method of well completion. Application No. 2006109837/03 of March 29, 2006, publ. 06/10/2008 - a prototype.

Claims (1)

A method of completing wells, including launching and cementing a production casing, with a shoe in the sole of the tire, drilling a cement cup, followed by creating a trunk in the interval of the reservoir and a cavity expanded in the horizontal direction, characterized in that several cavities separated by bridges, moreover, in bridges, prior to the creation of caverns, probe perforations are carried out, with perforation channels perimeter etru in the same plane, and the formation of cavity cavities lead in the trunk from top to bottom from the tire.

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