SU1567761A1 - Method of terminating borehole exposing unsteady productive strata - Google Patents

Abstract

The invention relates to methods for completing geothermal, as well as oil, gas and other wells, which reveal unstable reservoirs. In order to increase the stability of unstable rocks in the zone of the reservoir at high water speeds, the method of completing a geothermal well includes opening the reservoir and creating a sump below it by drilling from under the casing of the well, creating a cylindrical cavity by expanding the open wellbore under cemented casing and placement of filter material in this cavity. A cement-sand mixture is pumped between the cavity wall and the slotted shank, after its hardening, the cement-sand stone behind the gaps of the shank against the high-permeability interval of the formation is crushed, creating a thick network of filtration cracks and microcracks in it. In order to improve the quality of cementing the cavity, when the cement-sand mixture is pumped, the slit section of the shank is lowered into the sump of the well, and after placing the mixture in the cavity and above the cavity behind the shank, the latter is raised and its slit section is positioned against the high-permeability interval of the formation. Moreover, the cement-sand mixture is pumped to take into account the compensation of the volume of pipes extracted from the wells when lifting the sump from the sump after the mixture is pumped. 2 hp f-ly, 4 ill.

Description

The invention relates to the oil and gas industry, namely, methods for uncovering unstable and weakly cemented productive sandstones and completing the construction of geothermal as well as oil, gas and other wells drilled to such reservoirs.

The purpose of the invention is to increase the efficiency of fixing unstable rocks in a geothermal well.

in the zone of bedding at high rates of produced water.

Figures 1 and 2 depict the moment of injection of the cement-sand mixture into the cavity behind the slotted shank; in FIGS. 3 and 4, the zone is fixed at the bottom of the zone.

Pa 1 and 2 depicts KHVOSTORIK 1 with a gap 2, lowered on a drill string 3 with a ball-type disconnector 4 into 5 when pumping DSP into cavity 6 created by rubbing an open shaft skazhipyp under production column 7, including the interval of occurrence of a thermovascular formation 8

The ball disconnector consists of a housing 9§ of a coupling funnel 10, interconnected by a ball-lock 11 whose balls are spring-loaded with an elastic element 12 (for example, a flat spring). A sleeve 14 is installed in the housing on the shear pins 13, locking the cavity of the ball lock, and in this sleeve on the middle pins 15 there is an internal sleeve 16 overlapping the flushing windows 17. On the outer surface of the case longitudinal grooves 18 are chosen that pass through the ball lock cavity into the cavity of the coupling funnel. The housing in the upper part is connected to the drill pipe string 3, and in the lower part - to the nozzle 19 containing a check valve 20. Other designs of disconnectors can be used.

The technology of operations using the well completion method is as follows.

Smoking the wells to the roof (water seal) of the productive formation 8 are made according to a known technology, the production column 7 is lowered down to the bottom and cemented. After the cement has hardened behind the column 7, the latter is pressed to the design pressure, the bit is lowered and the well is deepened by drilling with opening the formation 8 and creating a sump 5 under it. The depth of the empamp 13 should be calculated from the condition of providing its volume V3 equal to not less than half the volume of the rock Vn) p chosen when increasing the diameter of the expanding interval h field (between the shoe of column 7 and the bottom of the reservoir 8) from the nominal bit diameter dAOA to diameter D FLOOR of an expanded cylindrical cavity, i.e.

 ff / П7А1 Ц

V, 7 / gt (POGd-Ldol) -p

2 4

Considering that

fi 4

YA "L- 1g

where 1- is sump depth, you can easily determine that

1l

(VLSL- dAOA)

3 7 LPOL

d; u

.

 , .Q jj jn 25

.

35

50

55

After the sump is created, the chisel is lifted from the well and a rape tool (jetting or mechanical expander) is lowered (up to the shoe of column 7).

By intensive flushing with rotation and slow delivery of the drill string, the interval of the well from the shoe of column 7 to the bottom of the formation 8 is widened to create a cavity close to cylindrical with diameter Opo. At the same time, part of the rock washed out from the walls is carried out from the well by the washing fluid, and some part of the washed out rock that is not carried out of the well (due to insufficient velocity of the washing fluid rising in the cavity) is deposited in the well sump.

The correspondence of the diameter of the created cavity to the calculated one and its profile is checked by electrometric or acoustic methods, preliminarily lifting the drill string with the expander from the well.

When the expanded cavity 6 is in satisfactory condition, the shank 1 is lowered on the drill string with disconnector 4 (in Fig. 1 - ball disconnector) so that the interval of its slots is sump 5 well in cavity 6, and the disconnector itself - above the shoe - is operational string 7, and the distance IK from the shoe of the production string 7 to the flushing ports 17 of the separator 4 should provide the volume Vk of the fluid in the annular space between the shank 1 and the string 7 on this length of not less than the total volume VT of the pipes extracted from the well, the stumps follow (after DSP injection) to raise the shank to accommodate its gaps against the productive interval of the formation, i.e. If we denote: dK - inner diameter of the casing

columns, m;

Dx - outer diameter of the shank, m;

dr is the outer diameter of the drill string pipes, m;

1 is the total length of the drill string pipes that are extracted from the well when the shank is lifted after the onset of the DSC for the installation of an interpal section of its well against the reservoir, m,

that

f-wl-dj) l

to

Mc

from where

(df-dj)

Consequently, the arrangement shown in Fig. 1 is lowered into the well. So that the spacing of the legs of the shank 1 is in the sump 5, and the disconnector is in the column 7 at a distance from its boot

1k.1t ()

Then, the distance from the upper edge of the shank slots to the disconnector will be

dr LT () + hr

pl

The above ratios for calculating 1K and lg provide the possibility of filling the cavity of the DSP and guarantee the condition that the shoe of the column 7 does not stand out from the DSP when the shank is raised up (to the productive interval of the formation) after the injection of the DSC.

Then a light buffer fluid is pumped into the well, joint with the reservoir fluid (for example, produced water) in the volume of cavity 6, and then the DSP is pumped in the volume

1B 1,

Vhnc woo

VK);

where Vn6 /, - the volume of the cavity in the well between the wall of the cavity 6 and the shank I; V is the volume of the annular space between the column 7 and the shank;

K - coefficient taking into account

loss of DSP during its pumping through the drill string due to mixing with the fluid in the well, sedimentation into the sump, etc. (K, 1, 2).

Following the DSP, a volume of squeezing fluid is pumped into the drill string 3, which is equal to the volume of the shank up to the interval of its slits (to displace the DSP by the liner), then the ball 21 is thrown into the column 3 (Fig. 1) and the slug is pumped. When the ball 21 is seated on the saddle of the inner sleeve 16 of the disconnector 4, the sleeve 16 cuts off the pins 15 and moves downward until the bottom 19 of the nozzle 19 is seated by opening the flushing windows 17 of the disconnector. By drilling a hole through these windows, the excess DSPS is removed over the liner, and then the piercing is stopped and, lifting the drill string with the liner, its slotted section is installed against the producing formation. The check valve 20 5 serves to prevent the DSP from flowing into the shank at. stop flushing.

After the DSP hardens, they throw a second ball (of larger diameter than the first 0), which sits on the saddle of the outer sleeve 14, and the latter cuts off the pins 13 and, moving downwards, also sits on the bottom of the nozzle 19, opening the ball lock, the spring-loaded 5 balls of which are poured in the pipe 19, which provides unloading of the shank with the sleeve-vosponka 10 on the cement-sand stone (as shown in Fig. 2), and the drill string with the remaining 0 elements of the disconnector is lifted from the well.

Then, the bit is lowered into the well on the drill string, and rotation and flushing work inside the shank to clean the portions of the DSP that remained in the shank during these operations and to model its channel, then raise the bit from the well. 0 By successive descents and explosions of string TDT1 type detonating torpedoes in the interval of the tail gap or pressure increase in the well by intensively pumping water into it, the cement – sand ring is crushed. When using torpedoes of the TDH type, the masses of detonating charges are chosen from the condition of creating an explosive force, which is necessary and sufficient for crushing the cement-sand stone against the slits of the shank without damaging its other intervals.

The technical and economic efficiency of the well completion method is to ensure their high production rate and injectivity due to the large filtration surface of the fluid, which is proportional to the cavity diameter, and significantly low in average.

five

with the known methods of fluid resistance in the transition zone between the well and the reservoir, as well as in the relative cost-effectiveness and manufacturability of work on fixing unstable and insufficiently stable (at high fluid velocities) pores in the zone of the reservoir bed, since the method does not require special equipment and materials fully fit into the existing well construction technology.

Claims (3)

1. A method for completing a well that reveals an unstable productive formation, including opening the plate and creating a sump under it by drilling from under the well casing, lowered to the top of the reservoir, creating a cylindrical cavity by expanding the open wellbore under the cemented casing and placing the filter material in this cavity in the gap between the borehole wall and the slotted shank, which is due to the fact that The goal is to increase the efficiency of fixing unstable rocks in the geothermal well in the zone of the reservoir bed at high rates of produced water, between the cavity wall and the slotted shank, as a filter material pumped the cement-sand mixture, after it hardens the cement-sand stone behind the crevice the highly permeable interval of the formation is crushed and a dense network of seepage cracks and microcracks is created in it. 2. A method according to claim 1, characterized in that, in order to improve the quality of the cementing cavity, when pumping the cement-sand mixture, the slit section of the shank is lowered into the sump of the well, and after placing the mixture in the cavity and above the cavity behind the shank, the latter is lifted and its slit section is positioned against the highly permeable formation interval. 3. Method according to Claims 1 and 2, characterized in that the cement-sand mixture is pumped with allowance made for compensation of the volume of pipes extracted from the well when lifting the sump from the sump after the mixture is pumped. vЈ  r 2 o “O .ai k iMiil Sfffj rj jTj (i г г 1 i гШ9Ш let .. h 1Ch - / .... 7 Ј & j