RU2813414C1 - Method for killing horizontal gas wells - Google Patents

Abstract

FIELD: oil, gas and coke-chemical industry.

SUBSTANCE: invention relates to oil and gas industry, namely to technology of killing gas wells with horizontal end after hydraulic fracturing, due to provision of hydrodynamic equilibrium in the well-formation system using equipment for performance of works at controlled pressure. Method includes pumping of killing fluid to borehole bottom via tubing string, blocking of perforation interval by supply of blocking compound to horizontal borehole in volume required for overlapping of perforation interval zone. Then killing fluid is supplied, specific density of which is lower than specific density of blocking composition. At that, volumes of pumped killing fluid portions are calculated so that the height of the column of the killing fluid portion relative to the surface of the blocking composition in the tubing string is equal to the height of the column of killing fluid relative to the surface of the blocking composition located in the annular space. Pumping of killing fluid is carried out through coiled tubing string to the interval of the liner hanger with control of flow rate and gradual compression of the throttle. At the same time pumping is continued until the inflow is stopped and equilibrium is established in the well-formation system. Coiled tubing string is lowered into the horizontal section of the borehole to the borehole bottom with pressure control and throttle control. After that, the design volume of the blocking composition is pumped with simultaneous lifting of the coiled tubing string to the level of the liner hanger. Then liquid packer is installed.

EFFECT: increased efficiency of killing of gas wells with normal and abnormally high formation pressures.

1 cl, 11 dwg

Description

The invention relates to the oil and gas industry, namely to the technology of killing gas wells with a horizontal end after hydraulic fracturing, by ensuring hydrodynamic equilibrium in the well-reservoir system using equipment for carrying out work at controlled pressure.

There is a known method for blocking productive formations during major and underground repairs, as well as when putting wells into operation after drilling (RF patent No. 22174 C1, published on November 27, 2003), consisting of sequential injection of a buffer, a blocking fluid - an invert emulsion containing a hydrocarbon phase, an aqueous solution of sodium or calcium chloride, emultal or chalk, and kill fluids with a density lower than the density of the blocking fluid.

The disadvantage of this technology is the reduction in well productivity after development due to the forcing of killing fluid into the productive formation.

There is a known method for killing gas wells with abnormally low reservoir pressures during underground and major repairs (RF patent No. 2188308 C1, published on August 27, 2002), including pushing the well fluid into the formation by pumping gas through tubing, followed by the supply of a blocking composition – grouting material with a component in its composition that ensures chemical destruction, pumped with gas through the tubing, and crushing the well with portions of process fluid. The driving fluid is pumped in after the cementing material has hardened.

The disadvantage of this method is its inapplicability to wells with normal and abnormally high reservoir pressure, as well as a decrease in well productivity due to the use of cementing material.

There is a known method for gentle killing of wells with abnormally low reservoir pressures (RF patent No. 2322573 C1, published on April 20, 2008), which contain a circulation valve; a method can be used that involves pumping killing fluid through flexible tubing (CT) into the perforation interval blocking solution, lifting the pipes above the perforation interval and pumping the kill fluid while simultaneously bleeding gas from the annulus to the flare.

The disadvantage of this method is the impossibility of its use in wells with normal and abnormally high formation pressure, characteristic of the completion of wells in gas fields being put into operation.

There is a known method for installing several blocking packs, one of which plays the role of a “liquid” packer (RF patent No. 2487909 C1, published July 20, 2013). The efficiency of opening and temporarily blocking the productive formation is increased through the use of a gas-liquid mixture formed from the proposed composition with increased stability, high inhibitory properties and low filtration and density values.

The disadvantage of the technology is the impossibility of using foams for wells with normal and abnormally high reservoir pressures due to insufficient hydrostatic pressure of the foam column.

There is a known method for killing wells with abnormally low formation pressure (RF patent No. 2439296, published on January 10, 2012), adopted as a prototype. In this method, the perforation interval is blocked by injecting a blocking composition and a portion of driving fluid to create back pressure on the formation. In this case, before supplying the blocking composition to the bottom of the well, an additional portion of driving fluid is pumped through the tubing string in a volume that ensures equality of the columns of driving fluid above the blocking solution in the tubing and in the annulus of the well.

The disadvantages of this method are the absence in the technology of equipment for regulating pressure in the well-formation system, which makes the technology difficult to implement, its applicability exclusively to wells with abnormally low formation pressure, and the impossibility of use in the case of a horizontal wellbore in the productive horizon interval.

The technical result is the killing of gas wells with normal and abnormally high reservoir pressures.

The technical result is achieved by the fact that the injection of kill fluid is carried out through flexible tubing into the liner suspension interval with flow control and gradual tightening of the throttle, while the injection is continued until the inflow stops and equilibrium is established in the well-reservoir system, the flexible tubing is lowered pipes into the horizontal section of the wellbore to the bottom of the well with pressure control and throttle control, after which the calculated volume of the blocking composition is pumped in with the simultaneous lifting of flexible tubing to the level of the liner suspension, and then a liquid packer is installed.

The method is illustrated by the following figures:

fig. 1 – diagram of the piping of the Xmas tree with a coiled tubing unit and equipment for pressure control;

fig. 2 – throttling block diagram;

fig. 3 – lowering of flexible tubing to the liner suspension interval and injection of kill fluid;

fig. 4 – injection of blocking solution with simultaneous lifting of flexible tubing;

fig. 5 – creation of backpressure on the bottom;

fig. 6 – initial pressure distribution in the well;

fig. 7 – initial temperature distribution in the well;

fig. 8 – pressure distribution along the wellbore when the calculated wellhead pressure is reached;

fig. 9 – pressure distribution after running the tool;

fig. 10 – pressure distribution in a plugged well;

fig. 11 – pressure on the throttle during the shutdown process, where:

1 – flare outlet;

2 – coiled tubing unit;

3 – blowout prevention equipment;

4 – coiled tubing lubricator;

5 – fountain fittings;

6 – output line;

7 – throttling block;

8 – flexible tubing (coiled tubing);

9 – annulus monitoring line;

10 – pipe head;

11 – high pressure gauge;

12 – column head;

13 – adjustable throttle;

14 – Coriolis flow meter;

15 – check valve;

16 - exit to the separator;

17 – technological pump and compressor pipes;

18 – pipe holder;

19 – pipe head;

20 – shank suspension;

21 – horizontal section of the trunk;

22 – blocking solution;

23 – productive formation;

24 – liquid packer;

24 – killing fluid.

The method is carried out as follows. The equipment is installed (Fig. 1). The well operates at flare outlet 1. The coiled tubing unit 2 is installed, the preventers 3 and the coiled tubing lubricator 4 are installed on the Xmas tree 5, the output line 6 is connected to the throttling unit 7. A downhole pressure gauge is installed at the end of the coiled tubing 8. Bottomhole pressure monitoring during well killing is carried out continuously. Information about bottomhole pressure is transmitted via coiled tubing 8 via a cable communication channel to the control station. The annulus is controlled through the annulus control line 9, connected to the pipe head 10. The annulus pressure is monitored through a high-pressure pressure gauge 11 installed on the casing head 12 and continuously transmitting data to the control station.

An adjustable throttle 13, automatically controlled from the control station, a high-pressure pressure gauge 11 and a Coriolis flow meter 14 are installed on the throttling block (Fig. 2), information from which is transmitted to the control station, a check valve with a bleeder device 15 and an outlet to the separator 16.

The coiled tubing 8 (Fig. 3) is lowered into the process tubing 17, fixed to the pipe holder 18 of the pipe head 19 with flushing to the liner suspension interval 20. The wellhead and bottomhole pressures are measured. Based on the data obtained, the following technological parameters are calculated:

Back pressure on the throttle corresponding to the pressure of the volume of kill fluid required to pump the block composition after it enters the annulus:

Where – the volume of pipe space in the gas pipeline complex,, – density of the killing fluid, kg/, – internal diameter of the casing, m.

Pressure in the well-reservoir system during technological operations:

Where – hydrostatic pressure of the process fluid column, MPa; – pressure losses arising during circulation in the tubing, MPa; – piston effect that occurs when running coiled tubing, MPa.

Piston effect:

Where – maximum descent speed of equipment, m/s; – outer diameter of the descent equipment, m; And – dimensionless parameters; – length of the descent equipment, m.

After specifying the killing parameters, the killing fluid is pumped through coiled tubing 8 into the liner suspension interval with flow control and gradual tightening of the throttle. Injection is continued until the inflow stops and equilibrium is established in the well-reservoir system, after which, by gradually opening the throttle, the wellhead pressure is reduced to the value of the calculated back pressure at the throttle, taking into account the dynamic component that occurs when running the tool.

The coiled tubing 8 is lowered into the horizontal section of the wellbore 21 to the bottom of the well with pressure control and throttle control in order to prevent absorption. At the same time, the supply of the blocking solution begins. The injection rate and descent speed must ensure that the blocking solution 22 begins to be pushed into the productive formation 23 simultaneously with the tool reaching the bottom. Next, the calculated volume of blocking composition is pumped in with simultaneous lifting of the coiled tubing to the level of the liner suspension (Fig. 4). After this, a liquid packer 24 is installed to separate the blocking solution and the kill fluid 25 (Fig. 5), after which an additional displacement volume of the kill fluid is completed to create back pressure in accordance with the standard values established by safety rules in the oil and gas industry.

After pumping the block composition, technical settling is performed for 12 hours, after which the level in the pipe space is measured.

The result of this method is a plugged well and ready for further work. The preservation of the productive characteristics of the reservoir layer is ensured by a blocking pack installed in the horizontal wellbore interval.

Example 1. Calculation of parameters and killing process.

The Python programming language and the Scipy and Numpy libraries for modeling physical processes are used for modeling. The mechanistic model of Hassan and Kabir is used to calculate multiphase flow. The operation of killing a gas condensate well at one of the fields in Eastern Siberia after development for several days is simulated. The following initial data are used for the calculation (Table 1):

Table 1 - Initial data for calculation

No. Parameter Meaning Reservoir pressure, MPa eleven Bottomhole pressure during mining, MPa 10 Killing fluid density, kg/m3 1020 Gas flow rate, thousand m ³ /day 151 Tubing internal diameter, mm 104 Diameter of coiled tubing, mm 44 Killing fluid consumption, l/s 15 Gas viscosity under normal conditions, mPa*s 0.016

Let us simulate the initial distribution of pressure (Fig. 6) and temperature (Fig. 7) in a gas well during production.

Let's calculate the reserve of back pressure on the throttle for pushing the block pack along the coiled tubing and compensating for the piston effect when running the tool according to dependencies 1-3. Let us determine the pressure value of the hydrostatic liquid column created by the volume of kill fluid in the coiled tubing:

Next, we determine the pressure arising due to the piston effect when running the coiled tubing:

Let us determine the pressure loss due to friction when pumping kill fluid from coiled tubing. To determine this, a single-phase flow is simulated in the developed software:

After this, we will determine the total additional pressure for running the coiled tubing with flushing:

Accordingly, the injection of kill fluid must be carried out until this pressure is reached at the wellhead. Let's simulate the injection of kill fluid into a well until a given wellhead pressure is reached. The download time was 138 s. The pressure distribution along the wellbore at this point in time is presented on the graph (Fig. 8).

Next, the coiled tubing is lowered to the bottom with flushing. During the descent, the throttle pressure is released, reaching atmospheric pressure at the end of the descent. The result of the tool run simulation is presented in the graph (Fig. 9).

Next, the block pack is pushed through with the assembly being lifted with the annulus closed. During this operation, the bottomhole pressure is not controlled, since the goal is to push the block pack into the bottomhole zone.

After installing the block pack, the well is pressurized to the standard bottomhole pressure values. For a well of this depth, the bottomhole pressure should be 1.05 formation pressure. The pressure in the well after the killing operation is presented on the graph (Fig. 10). The program for changing the pressure on the throttle during the work process is presented in the graph (Fig. 11).

The use of the claimed method makes it possible to complete and develop a gas or gas-condensate well after multi-stage hydraulic fracturing without reducing the productive characteristics of the reservoir.

Claims (1)

A method for killing horizontal gas wells, including pumping killing fluid to the bottom of the well through a tubing string, blocking the perforation interval by supplying a blocking composition into the horizontal wellbore in the volume necessary to block the perforation interval zone, then supplying killing fluid, the specific density of which is lower specific density of the blocking composition, while the volumes of pumped portions of the killing fluid are calculated in such a way that the height of the column of a portion of the killing fluid relative to the surface of the blocking composition located in the tubing string is equal to the height of the column of the killing fluid relative to the surface of the blocking composition located in the annulus, characterized in that the injection of kill fluid is carried out through flexible tubing into the liner suspension interval with flow control and gradual tightening of the throttle, while injection is continued until the inflow stops and equilibrium is established in the well-formation system, flexible tubing is lowered into a horizontal section of the wellbore to the bottom of the well with pressure control and throttle control, after which the calculated volume of the blocking composition is pumped in with the simultaneous lifting of flexible tubing to the level of the liner suspension, and then a liquid packer is installed.