RU2658854C1 - Well operation method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the oil and gas industry and can be used to increase the productivity of wells, that work with the accumulation of liquid and sand plugs on the bottom. Method of operating the well comprises the following successive steps. First, the liquid and sand plugs are removed by dosing the foaming agent to the bottom of the well. Foaming agent is pumped into the annulus at the wellhead without additional tubes being slaughtered in the amount, calculated according to the following mathematical expression: M_fa=m_udπR²(L+(P_form-ΔP_g-P_w)/(cos(α)ρ_fg)), where M_fa – the amount of foaming agent necessary for foaming all the fluid stored in the well, kg; m_ud – amount of blowing agent, which is necessary for foaming 1 m³ liquid impurities in the well, kg/m³; R is the internal radius of the production well string, m; L – length of the well from the bottom edge of the elevator column to the current face, m; P_form – the formation pressure applied to the lower edge of the column, Pa; ΔP_g – the pressure drop due to the weight of the gas column in the borehole, it can be calculated from the barometric formula, Pa; P_w – pressure at the wellhead, Pa; α – the angle of the borehole deviation from the vertical, deg; ρ_f – density of water, kg/m³; g – acceleration of gravity, m/s². Then, the well is put into operation at a gas flow rate, which ensures the removal of impurities from the well to the disposal plant of its products. After reducing the concentration of impurities in the gas stream to the permissible values, the well is transferred to gas field work. Stable borehole regime is ensured by a constant supply of a foaming agent with a flow calculated according to the following mathematical expression: Q_fa=m_ud(q_at+q_c), where Q_fa – foaming agent consumption, which is necessary to maintain stable operation of the well, kg/day; m_ud – amount of blowing agent necessary for foaming 1 m³ fluid in the well, kg/m³; q_at – consumption of liquid impurities entering the well from the formation, m³/day; q_c – consumption of liquid impurities condensing from the vapor phase in the gas flow during its movement along the lift column, m³/day.

EFFECT: proposed method allows effectively remove liquid and sand plugs from the bottom of the well and to ensure its further operation without accumulation of liquid.

1 cl, 1 dwg, 1 ex

Description

The invention relates to the field of the oil and gas industry and can be used to increase the productivity of wells operating with the accumulation of liquid and sand plugs at the bottom, including for deposits at a late stage of operation.

It is known that the accumulation of liquid plugs at the bottom of the wells, partially or completely covering the perforation interval, reduces the productivity of the wells until they stop completely, and also accelerates the destruction of the rock skeleton. This problem is most relevant for wells in gas fields at a late stage of operation, when low reservoir pressure does not provide the necessary gas velocity for the removal of fluid from the bottom. Mechanical particles in the products lead to erosive wear of the equipment of the wells, which requires further limitation of the productivity of the wells to safe gas flow rates at which the specific content of mechanical impurities in the production of the wells does not adversely affect the downhole equipment. To restore normal operation of a gas well, sand and water plugs should be removed, which, for example, at low reservoir pressures at a late stage of development is quite difficult to implement.

Known methods of operating gas wells with the removal of fluid from the wells with the shutdown of the well: by blowing the well into the atmosphere, stopping the well to absorb fluid by the formation, etc. [Muravyov V.M. Operation of oil and gas wells. M .: Nedra, 1978. p. 368].

The disadvantages of these methods are the need for staff to go to the well, temporarily disconnect the well from the gas collection network and the resulting loss of gas production. The release of gas into the atmosphere leads to significant irretrievable losses of gas and harm to the environment.

A known method of washing a sand plug in a gas well at low reservoir pressures, including installing a coiled tubing installation, installing blowout preventer and pumping equipment, an ejector, lowering a flexible pipe into the well, preparing a foaming washing liquid and flushing the well in the sand plug formation zone [RU 2188304 MPK E21B 37/00, ЕВВ 19/22, publ. 08/27/2002].

The disadvantage of this method is that it does not allow to wash the sand plug in a gas well with an abnormally low reservoir pressure (below 0.3 from the initial one) due to the significant absorption of flushing fluid by the reservoir, as well as the high cost of work and the inability to use in wetlands in the absence of access roads. In addition, the fluid can again accumulate at the bottom of the well, and the resulting positive effect can be quite short-term.

A known method of washing a sand plug in a gas well at low reservoir pressures, including installing a coiled tubing installation, installing blowout and pumping equipment, an ejector, lowering a flexible pipe into the well, preparing a washing foam-forming liquid, a booster installation and a gas separator [RU 2341644 C1, IPC E21B 37/00, publ. December 20, 2008].

The disadvantage of this method is the need to connect equipment to an adjacent well or pipeline, which is not possible with a single arrangement of wells that are not grouped into well pads, as well as its high cost for the continuous operation of wells operating with constant accumulation of liquid at the bottom.

A known method of operating gas wells, comprising dosing a foaming substance into a gas-liquid stream by forcing it through a portion of the gas stream, for which lift pipes are filled with foam substance, which are lowered below the perforation interval, and the pressure of the bypassed gas is regulated depending on the pressure of the gas-liquid stream at the wellhead [a.s. SU No. 1062376, IPC Е21В 43/00. publ. 12/23/1983].

The disadvantage of this method is the need to lower the elevator column below the perforation interval. But in the vast majority of gas wells, the lower end of the lift columns is located in the perforation interval or above it. Therefore, to implement the method will require significant capital costs.

The objective of the invention is to develop a method for the effective removal of liquid and sand plugs from the bottom of the well and ensuring its further operation without accumulation of liquid.

The technical result of the claimed invention is to improve the operating conditions of gas wells, ensuring their stable and safe operation, including under conditions of abnormally low reservoir pressures, increasing gas production and increasing the reliability of the operation of the well.

The task and the technical result are achieved by the fact that in the method of operating a gas well, including removing liquid and sand plugs by dosing a foaming agent to the bottom of the well, according to the invention, the foaming agent is pumped into the annulus at the wellhead without lowering additional pipes to the bottom and its required number is calculated according to the formula:

- количество пенообразователя, необходимое для вспенивания всей жидкости, накопленной в скважине, кг;Where

- the amount of foaming agent necessary for foaming all the fluid accumulated in the well, kg;

- количество пенообразователя, необходимое для вспенивания 1 м³ жидких примесей в скважине, кг/м³;

- the amount of foaming agent required for foaming 1 m ³ liquid impurities in the well, kg / m ³ ;

R is the inner radius of the production casing of the well, m;

L is the length of the well from the bottom edge of the lift string to the current bottom, m;

- пластовое давление, приведенное к нижнему краю лифтовой колонны, Па;

- reservoir pressure reduced to the lower edge of the elevator column, Pa;

- перепад давления, обусловленный весом столба газа в скважине, может быть рассчитан по барометрической формуле, Па;

- pressure drop due to the weight of the gas column in the well can be calculated by the barometric formula, Pa;

P _y - pressure at the wellhead, Pa;

α is the angle of deviation of the wellbore from the vertical, degrees;

ρ _W - the density of water, kg / m ³ ;

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

after which the well is put into operation with a gas flow rate, which ensures the removal of impurities from the well, first to the unit for utilization of its products, after reducing the concentration of impurities in the gas stream to acceptable values, the well is put into operation in the gas field, ensuring a stable mode of operation by constantly supplying a foaming agent with flow rate calculated by the formula:

where Q _by is the flow rate of the foaming agent necessary to maintain stable well operation, kg / day;

- количество пенообразователя, необходимое для вспенивания 1 м³ жидкости в скважине, кг/м³;

- the amount of foaming agent required for foaming 1 m ³ fluid in the well, kg / m ³ ;

q _in - the flow rate of liquid impurities entering the well from the reservoir, m ³ / day;

q _to - the flow rate of liquid impurities condensing from the vapor phase in the gas stream when it moves along the elevator column, m ³ / day.

The proposed method of operating the well is as follows.

Based on the results of gasdynamic and geophysical studies, a well is selected whose productivity has decreased due to accumulation of liquid and sand in the faces (high level of liquid in a stopped well, increased removal of liquid and sand at high gas flow rates for research, etc.). A foaming agent is pumped into the annulus at the wellhead without lowering additional tubes to the bottom, the required amount of which is calculated by the formula (1). This formula requires the foaming of all the fluid at the bottom, and its maximum amount that can accumulate in a well that has almost stopped for this reason, when the magnitude of the depression on the formation and friction losses during the movement of the gas-liquid flow in the elevator string can be neglected.

After the foaming agent arrives at the bottom, the well is put into operation with a gas flow rate that ensures the removal of impurities from the well to the disposal unit, and the concentration of impurities in the gas stream is monitored. As the field experience with the use of foaming agents has shown, foaming of the liquid at the bottom ensures intensive removal of both liquid and solid impurities from the well. After cleaning the well from the main volume of impurities and reducing their concentration to acceptable values at which the normal functioning of the equipment is ensured, the well is transferred to work in the gas field.

After the well is put into operation, liquid impurities from the reservoir begin to continuously flow into the gas stream, as well as liquid impurities that condense during the movement of gas through the lift column from the vapor phase contained in the gas stream. To exclude their accumulation and maintain stable operation of the well, impurities are transported first to the utilization unit, and then to the gas field, a foaming agent is constantly fed into it with a flow rate that ensures removal of these impurities, and the flow rate of the foaming agent is calculated by the formula (2).

During the operation of the well in the gas field, control of the concentration of impurities in the gas stream is maintained and, as it decreases below an acceptable level, gas consumption is increased.

In practice, the method is applied as follows (for example, well No. 602 of the Medvezhye field).

According to the results of gas-dynamic and geophysical studies at well No. 602 of the Medvezhye field, it was determined that its productivity decreased due to accumulation of liquid and sand at the bottom (a high level of liquid was measured in a stopped and a working well, a sand-clay plug overlaps part of the perforation, increased fluid removal and sand at high gas flow rates for research). At the same time, the field is at a late stage of development, and the low reservoir pressure no longer provides a well flow rate sufficient to remove liquid and sand plugs from the bottom without additional geological and technical measures. Based on this information, it was decided to operate the well with a foaming agent.

для начальной загрузки с целью вспенивания всей жидкости, накопленной на забое скважины при следующих исходных данных:According to the formula (1), the amount of foaming agent was calculated

for initial loading with the aim of foaming all the fluid accumulated at the bottom of the well with the following initial data:

- количество пенообразователя, необходимое для вспенивания 1 м³ жидких примесей в скважине;

- the amount of foaming agent required for foaming 1 m ³ liquid impurities in the well;

R = 0.1 m - the inner radius of the production casing of the well;

L = 58 m - the length of the well from the bottom edge of the elevator string to the current bottom;

- пластовое давление, приведенное к нижнему краю лифтовой колонны;

- reservoir pressure reduced to the lower edge of the elevator column;

- перепад давления, обусловленный весом столба газа в скважине;

- pressure drop due to the weight of the gas column in the well;

P _y = 0.79 MPa - pressure at the wellhead;

α = 0 - angle of deviation of the wellbore from the vertical, degrees;

ρ _W = 1000 kg / m ³ - the density of the well fluid;

g = 9.81 m / s ² - acceleration of gravity.

, которое необходимо для вспенивания накопленной в скважине жидкости.As a result of the calculation, the amount of foaming agent is obtained

, which is necessary for foaming the fluid accumulated in the well.

According to the formula (2) was calculated flow rate Q _of foaming agent required for removing liquid impurities, constantly entering the wellbore from the formation and movement of gas condensable in the process of the production tubing of a gas contained in the vapor stream, with the following initial data:

- количество пенообразователя, необходимое для вспенивания 1 м³ жидких примесей в скважине;

- the amount of foaming agent required for foaming 1 m ³ liquid impurities in the well;

q _in = 0 m ³ / day - flow rate of liquid impurities entering the well from the formation;

q _k = 0.3 m ³ / day — flow rate of liquid impurities condensing from the vapor phase in the gas stream as it moves along the lift column, m ³ / day.

As a result of the calculation, the foaming agent flow Q was obtained _at = 3.45 kg / day to maintain stable operation of the well during its operation.

и поступления его на забой запустили скважину в работу с расходом газа 110-120 тыс. м³/сут, обеспечивающим вынос примесей из скважины на установку утилизации с периодическим контролем концентрации примесей в газовом потоке. Также с помощью пневмонасоса обеспечили подачу в скважину пенообразователя с расходом Q_по=3,45 кг/сут для вспенивания постоянно поступающей в нее жидкости.After supplying the amount of blowing agent

and its entry into the face launched the well into operation with a gas flow rate of 110-120 thousand m ³ / day, which ensures the removal of impurities from the well to a disposal unit with periodic monitoring of the concentration of impurities in the gas stream. Also, with the help of a pneumatic pump, a foaming agent was supplied to the well with a flow rate of Q _by = 3.45 kg / day for foaming the fluid constantly entering it.

The parameters of the well are shown in the drawing.

As can be seen from the graph, during the well development from 10/16/2015 to 10/21/2015, there was a significant removal of solid impurities, which pose a serious danger from the point of view of abrasive wear of the equipment. At the field, the development project defined a criterion for the maximum allowable specific solids content equal to 2 mm ³ / m ³ (volume of mechanical impurities in one cubic meter of natural gas). This value of the specific content of solid impurities was achieved on 10/21/2015 with a decrease in well production to the level of 50 thousand m ³ / day, at which liquid and solid impurities are still carried to the surface. With such a flow rate, the well was put into operation in a gas field with a control of the concentration of impurities in the gas stream. As can be seen from the graph, further cleaning of the well during its operation allowed to increase the flow rate to 80 thousand m ³ / day without exceeding the permissible level of solid impurities in the well production.

Thus, the use of the proposed method allows you to effectively remove fluid and sand plugs from the bottom of the well and ensures its further operation without accumulation of fluid. As a result, stable and safe well operation is ensured, including in conditions of abnormally low reservoir pressures.

Claims (18)

A method of operating a well, including removing liquid and sand plugs by dosing a foaming agent to the bottom of the well, characterized in that the foaming agent is pumped into the annulus at the wellhead without lowering additional tubes to the bottom and its required amount is calculated by the formula:

Where

- the amount of foaming agent necessary for foaming all the fluid accumulated in the well, kg;

- the amount of foaming agent required for foaming 1 m ³ liquid impurities in the well, kg / m ³ ; R is the inner radius of the production casing of the well, m; L is the length of the well from the bottom edge of the lift string to the current bottom, m;

- reservoir pressure reduced to the lower edge of the elevator column, Pa;

- pressure drop due to the weight of the gas column in the well can be calculated by the barometric formula, Pa; P _y - pressure at the wellhead, Pa; α is the angle of deviation of the wellbore from the vertical, degrees; ρ _W - the density of water, kg / m ³ ; g is the acceleration of gravity, m / s ² , after which the well is put into operation with a gas flow rate, which ensures the removal of impurities from the well, first to the unit for utilization of its products, after reducing the concentration of impurities in the gas stream to acceptable values, the well is put into operation in the gas field, ensuring a stable mode of operation by constantly supplying a foaming agent with flow rate calculated by the formula:

where Q _by is the flow rate of the foaming agent necessary to maintain stable well operation, kg / day;

- the amount of foaming agent required for foaming 1 m ³ fluid in the well, kg / m ³ ; q _in - the flow rate of liquid impurities entering the well from the reservoir, m ³ / day; q _to - the flow rate of liquid impurities condensing from the vapor phase in the gas stream when it moves along the elevator column, m ³ / day.

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