1. A selective water plugging method for a bottom water gas reservoir high water content gas well is characterized by comprising the following steps:

s1, determining the position of a water-gas layer caused by bottom water coning;

s2, injecting a foaming agent solution into the effluent gas layer;

s3, after the step S2 is completed, injecting nitrogen, enabling the nitrogen to enter a water production high-pressure layer, and forcing the water cone in the near wellbore zone to fall back;

s4, injecting a plugging agent into the water producing channel in a directional mode, forming an artificial partition plate on the water producing layer, plugging the bottom water upward channel, and inhibiting and relieving bottom water coning;

and S5, replacing by liquid nitrogen, and recovering and retaining the permeability of the near wellbore zone.

2. The method for selectively plugging a water-bearing gas well of a bottom water gas reservoir as defined in claim 1, wherein the method for determining the position of the water-bearing gas layer in step S1 is as follows: according to the geological condition of a water-seeing well or a water-flooded well and the dynamic data accumulated in the gas production process, comprehensive comparative analysis is carried out, and the water-yielding layer position is reasonably judged; and then, combining a fluid resistance measuring method, and determining a water layer position by using a resistance meter to measure a resistivity change curve of the fluid in the shaft when water flows into the gas well according to different conductivities of the water with high salinity and the water with low salinity.

3. The method for selectively plugging a water-high-water-content gas well in a bottom water gas reservoir according to claim 1, wherein the foaming agent solution is an aqueous solution of an ionic foaming agent, and the concentration of the ionic foaming agent solution is controlled to be 0.5-1.2%.

4. The method for selectively plugging a water in a bottom water gas reservoir high water-bearing gas well according to claim 3, wherein the ionic foaming agent is sodium lauryl sulfate or an amino acid foaming agent.

5. The method for selectively plugging a water-bearing gas well in a bottom water gas reservoir according to claim 4, wherein a foam stabilizer, such as polyacrylamide or polyvinyl alcohol, is further added to the foaming agent solution.

6. The method for selectively plugging a water-bearing gas well in a bottom water gas reservoir as defined in claim 1, wherein the nitrogen injection rate in step S3 is 600-900Nm³/h。

7. The method for selectively plugging the bottom water gas reservoir high water-bearing gas well according to claim 1, wherein in step S4, the plugging agent is a delayed in-situ polymerized gel, and the breakthrough pressure gradient of the gel in the core is greater than 9 MPa/m.

Background

Gas well water production is an inevitable problem in the development of oil and gas fields. With the exploitation of gas fields, the number of water outlet wells and water flooded wells is increased day by day, so that the yield of the gas wells is reduced, even the gas wells are completely flooded, the final recovery ratio of the gas fields is reduced, which is one of the main reasons for the deterioration of the economic benefit of the gas wells, and a matched water drainage and gas production and water plugging process needs to be provided for the water flooded wells.

The drainage and gas recovery mode mainly comprises the following steps: the method is characterized in that a plurality of drainage modes such as a drainage well, mechanical drainage, foam drainage, gas lift + foam drainage, plunger + foam drainage and the like are deployed, but water blocking measures are necessary for some wells which have high cost in a drainage and gas production process or have serious flooding without drainage and gas production process conditions on site. The water plugging is mainly realized by mechanical water plugging or chemical water plugging. The mechanical water plugging is based on that the water outlet point is clear, the position of produced water in the gas well is firstly found, then the produced water position is plugged, and the water output is controlled. The chemical water plugging process is mainly used for plugging a water outlet layer by injecting a plugging agent into a stratum. The commonly used plugging agents at present comprise non-selective chemical plugging agents and selective chemical plugging agents. The non-selective water plugging process is suitable for wells with clear water outlet layers, and the water outlet layers are permanently plugged by the plugging agent. The selective water plugging refers to a chemical water plugging method for injecting a proper selective water plugging agent into a production layer through a gas well to plug a stratum and reduce the water phase permeability without plugging the gas layer or having small influence on the gas phase permeability.

The water plugging technology is a key technology for controlling water and stabilizing oil, and plays an important role in improving the development effect of a gas field and increasing the ultimate recovery ratio of the gas field. The water plugging technology can not only reduce the treatment cost and increase the economic benefit, but also avoid the treatment of large-volume effluent in the drainage gas production process, and reduce the phenomena of environmental pollution, formation sand production, pipeline corrosion, scaling and the like.

Among them, patent CN104929568B discloses a method for controlling water in a gas reservoir, which comprises injecting gas into the gas reservoir, pushing the invaded water in the gas layer to a far well, configuring gel with delayed cross-linking ability, and atomizing the gel to form gas-phase dispersed gel. Injecting the gas-phase dispersion gel and gas into the gas reservoir, continuously injecting the gas to realize the migration and dispersion of the gel in the gas layer, and then carrying out soaking. The method can realize the atomization of the gel plugging agent, obviously reduce the injection pressure and is suitable for medium-low permeability gas reservoirs. But the sweep range of the gel is limited, and the method cannot effectively solve the problem of exploitation of a bottom water gas reservoir high-water-content gas well after water production.

Therefore, the development of a selective water plugging method for a bottom water gas reservoir high-water-content gas well is urgently needed to solve the problem that the yield of the gas well is sharply reduced after the gas reservoir meets water.

Disclosure of Invention

The invention aims to provide a selective water plugging method for a bottom water gas reservoir high water content gas well, aiming at the problem of difficult water plugging of the bottom water gas reservoir high water content gas well.

The invention provides a selective water plugging method for a bottom water gas reservoir high-water-content gas well, which comprises the following specific steps of:

and S1, determining the position of the water-gas layer caused by the coning of the bottom water. The specific method comprises the following steps: according to the geological condition of a water-seeing well or a water-flooded well and the dynamic data accumulated in the gas production process, comprehensive comparative analysis is carried out, and the water-yielding layer position is reasonably judged; and then, combining a fluid resistance measuring method, and determining a water layer position by using a resistance meter to measure a resistivity change curve of the fluid in the shaft when water flows into the gas well according to different conductivities of the water with high salinity and the water with low salinity.

And S2, injecting a foaming agent solution into the water-gas outlet layer. The foaming agent solution is an aqueous solution of an ionic foaming agent, and the concentration of the ionic foaming agent solution is controlled to be 0.5-1.2%. The ionic foaming agent is sodium lauryl sulfate or an amino acid foaming agent. Preferably, a foam stabilizer polyacrylamide or polyvinyl alcohol can be added into the foaming agent solution. After the foaming agent solution is injected, foam is formed in the gas-producing layer, and the water-producing layer or the water flooded layer does not generate foam due to no gas phase, so that automatic fixed-point temporary plugging can be realized to protect the potential gas-producing layer.

S3, after the step S2 is completed, injecting nitrogen at a high speed and a high pressure, wherein the nitrogen injection speed is 600-900Nm³Allowing nitrogen to enter a water production high-pressure layer to force a water cone in a near wellbore zone to fall back; the purpose of pressing the cone is realized, and simultaneously, conditions are created for the subsequent plugging agent to enter.

S4, injecting the plugging agent into the water producing channel in a directional mode, forming an artificial partition plate on the water producing layer, plugging the bottom water upward channel, and inhibiting and relieving bottom water coning. The plugging agent is delayed in-situ polymerized gel, and the breakthrough pressure gradient of the gel in the rock core is more than 9 MPa/m.

And S5, replacing with liquid nitrogen, recovering and retaining the permeability of the near-wellbore region, and facilitating the recovery of the gas well yield.

Under the combined action of the steps, intelligent selective water plugging of the bottom water gas reservoir high-water-content gas well can be realized, and the problem that the yield of the gas well is sharply reduced after the gas reservoir meets water is solved.

Compared with the prior art, the invention has the following beneficial effects:

(1) and injecting a foaming agent solution into the water-gas outlet layer at a high speed, forming foam in the gas-producing layer by using gas in the gas layer, and generating no foam in the water-producing layer or the water-flooded layer due to no gas phase or too little gas phase. In the non-water flooded layer, the foam stability is better, and the plugging capability is stronger, thereby preventing or reducing the entering of the plugging agent. Therefore, the potential gas producing layer can be protected by automatic temporary blocking at fixed points.

(2) And injecting nitrogen at high speed and high pressure to make the nitrogen enter a water production high-pressure layer, so that a water cone in a near-wellbore area is forced to fall back, the purpose of cone pressing is realized, and meanwhile, conditions are created for the subsequent entering of a plugging agent.

(3) The water cone is pressed by adopting a foam and nitrogen cone pressing system, then a partition plate is established by adopting an intelligent gel matching partition plate system, and the water cone is effectively controlled by compounding the cone pressing system and the partition plate.

(4) And the liquid nitrogen replaces the unbroken foam and the plugging agent to the stratum, so that the permeability of the near-wellbore area is quickly recovered, and the recovery of the gas well yield is facilitated.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a schematic diagram of foam generated by mixing with formation gas after injection of a foaming agent solution, the foam temporarily blocking the protective gas production zone.

FIG. 2 is a schematic diagram of the nitrogen implantation after the end of the cone.

Fig. 3 is a schematic illustration of the formation of an artificial separator after injection of a plugging agent.

Reference numbers in the figures: the gas well comprises a 1-gas well, a 2-foaming agent, a foam blocking layer, a 3-water producing layer, a 4-gas producing layer and a 5-artificial clapboard, wherein the foam blocking layer is generated after the 2-foaming agent is mixed with formation gas.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

The invention provides a selective water plugging method for a bottom water gas reservoir high-water-content gas well, which adopts the technical idea that: the foaming agent solution is injected into the gas-water interface of the gas well at a high speed to be mixed with the gas of the gas layer to form foam, and the foam is not generated in the water producing layer or the water flooded layer due to no gas phase, so that the potential gas producing layer can be protected by temporary plugging at an automatic fixed point. Then nitrogen is injected at high speed and high pressure, the water cone in the near wellbore area is pressed downwards to communicate the natural gas at the far end, the gas phase seepage capability is increased, and meanwhile, conditions are created for the subsequent entering of the plugging agent. And then injecting a plugging agent into the water outlet layer, wherein the foaming agent is injected in advance to temporarily plug and protect a potential gas production layer and the pressure cone effect of nitrogen gas, so that the subsequently injected plugging agent is forced to directionally enter a water production channel, an artificial partition plate is formed at a proper position of the water production layer to plug a bottom water upward channel, the bottom water coning is inhibited and relieved, and finally, the permeability of a near-wellbore area is recovered and kept through liquid nitrogen displacement, thereby being beneficial to the recovery of the yield of the gas well.

In this embodiment, the water shutoff method includes the following specific steps:

1. determining the water outlet position of the gas well; and carrying out comprehensive comparative analysis according to the geological condition of the water-seeing well or the water-flooded well and the dynamic data accumulated in the gas production process, and reasonably judging the water-yielding layer position. And then, combining a fluid resistance measuring method, and determining a water layer position by using a resistance meter to measure a resistivity change curve of the fluid in the shaft when water flows into the gas well according to different conductivities of the water with high salinity and the water with low salinity.

2. As shown in fig. 1, a blowing agent solution is injected into the water vapor-evolving layer at a high velocity. The foaming agent in the foaming agent solution is sodium lauryl sulfate with the mass percentage concentration of 1 percent, the foam stabilizer is polyvinyl alcohol with the concentration of 0.2 percent, and the foaming agent solution is used for increasing the stability of foam and forming a foam system with high quality and controllable half-life period. After the foaming agent solution is injected, the gas in the gas layer is utilized to form foam in the gas producing layer, and the water producing layer or the water flooded layer does not generate foam because no gas phase or too little gas phase exists. The reason is that the water saturation in the water flooded layer is high, so that the foam stability is poor, the blocking agent injected subsequently can still enter smoothly, and in the water flooded layer, the foam stability is better, and the blocking capability is stronger, so that the blocking agent is prevented or reduced from entering. Therefore, the potential gas producing layer can be protected by automatic temporary blocking at fixed points.

3. As shown in fig. 2, nitrogen is injected at high speed and high pressure, so that the nitrogen enters a water production high-pressure layer, a water cone in a near wellbore zone is forced to fall back, the purpose of cone pressing is achieved, natural gas at a far end is communicated, the gas phase seepage capability is increased, and meanwhile, conditions are created for the subsequent entering of a plugging agent. During construction, the nitrogen consumption is calculated by the state equation PV ═ nRT, and the injection speed is controlled at 600-³Pressure is greater than formation pressure.

4. As shown in fig. 3, under the combined action of steps 1-3, a plugging agent is injected, and the plugging agent adopts the temperature-resistant, salt-tolerant and high-temperature-resistant self-crosslinking in-situ polymerized water plugging gel disclosed in patent CN 104449618B. The plugging agent is directionally introduced into the water producing layer and transversely extends to increase the plugging radius of the chemical agent and form an artificial partition plate at a proper position. The viscosity of the gel is close to that of water, the initial viscosity of the gel is low, the injectability is good, the selectivity is good, the liquid production amount of a high-permeability layer can be greatly reduced, and the liquid production amount of a low-permeability layer can be rapidly increased. The breakthrough pressure gradient of the gel in the rock core is more than 9MPa/m, and the plugging rate reaches 99 percent.

5. Liquid nitrogen replaces unbroken foam and the plugging agent to the stratum, so that the permeability of the near-wellbore area is quickly recovered and reserved, and the recovery of the yield of the gas well is facilitated.

Under the combined action of the steps, intelligent selective water plugging of the bottom water gas reservoir high-water-content gas well can be realized, and the problem that the yield of the gas well is sharply reduced after the gas reservoir meets water is solved.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.