阅读说明：本技术 一种薄隔层稠油油藏下层水堵水方法及使用的堵水剂体系 (Water plugging method for lower layer water of thin-interlayer heavy oil reservoir and water plugging agent system used in same ) 是由 赵长喜 耿超 王瑞 毛为成 余倩 张喜玲 王孟江 于 2020-04-14 设计创作，主要内容包括：本发明涉及一种薄隔层稠油油藏下层水堵水方法及使用的堵水剂体系,属于石油开采技术领域。该堵水方法包括如下步骤：向出水油层注入氮气泡沫段塞,以抑制下层水侵入隔层；然后注入隔层凝胶段塞,隔层凝胶段塞主要由水玻璃、水玻璃交联剂、水组成,隔层凝胶段塞进入隔层,成胶后对隔层内孔隙进行封堵；再注入封堵凝胶段塞,封堵凝胶段塞主要由碱木质素、碱木质素交联剂、水组成,封堵凝胶段塞进入油层与隔层边界,成胶后对油层与隔层边界形成封堵。本发明的薄隔层稠油油藏下层水堵水方法,采用三个段塞主要针对油层下部、隔层、水层上部进行封堵,抑制下层水窜进油层,改善薄隔层稠油油藏的开发效果。(The invention relates to a water plugging method for a lower layer of a thin-interlayer heavy oil reservoir and a water plugging agent system used by the same, and belongs to the technical field of oil exploitation. The water plugging method comprises the following steps: injecting a nitrogen foam slug into the water-out oil layer to inhibit the water in the lower layer from invading the interlayer; then injecting an interlayer gel slug which mainly comprises water glass, a water glass cross-linking agent and water into the interlayer, wherein the interlayer gel slug enters the interlayer and plugs the pores in the interlayer after gelling; and injecting a plugging gel slug, wherein the plugging gel slug mainly comprises alkali lignin, an alkali lignin cross-linking agent and water, enters the boundary between the oil layer and the interlayer, and forms plugging on the boundary between the oil layer and the interlayer after gelling. The invention relates to a method for blocking water in the lower layer of a thin-interlayer heavy oil reservoir, which adopts three slugs to mainly block the lower part of an oil layer, an interlayer and the upper part of a water layer, inhibits the water in the lower layer from entering the oil layer and improves the development effect of the thin-interlayer heavy oil reservoir.)

1. A method for blocking water in a lower layer of a thin-layer heavy oil reservoir is characterized by comprising the following steps:

determining an oil layer water outlet section, and injecting a nitrogen foam slug to inhibit the lower-layer water from invading the interlayer; then injecting an interlayer gel slug which mainly comprises water glass, a water glass cross-linking agent and water into the interlayer, wherein the interlayer gel slug enters the interlayer and plugs the pores in the interlayer after gelling;

and injecting a plugging gel slug, wherein the plugging gel slug mainly comprises alkali lignin, an alkali lignin cross-linking agent and water, enters the boundary between the oil layer and the interlayer, and forms plugging on the boundary between the oil layer and the interlayer after gelling.

2. The method for blocking water in the lower layer of the thin-layer heavy oil reservoir according to claim 1, wherein the thin-layer gel plug is composed of the following components in percentage by mass: 1 to 30 percent of water glass, 0.1 to 2 percent of water glass cross-linking agent and the balance of water.

3. The thin-partition heavy oil reservoir lower layer water plugging method according to claim 1 or 2, characterized in that the water glass cross-linking agent is one or more of ethyl formate, ethyl acetate, methyl acetate, ammonium chloride and methanol.

4. The thin-partition heavy oil reservoir lower layer water plugging method according to claim 1, wherein the plugging gel slug consists of the following components in percentage by mass: 3-20% of alkali lignin, 3-10% of an alkali lignin cross-linking agent and the balance of water.

5. The thin-partition heavy oil reservoir lower layer water plugging method according to claim 1 or 4, wherein the alkali lignin cross-linking agent is one or more of formaldehyde, phenol, resorcinol and urotropine.

6. The method for blocking water in the lower layer of the thin-partition heavy oil reservoir according to claim 1, wherein the nitrogen injection foam slug is in a form of injecting nitrogen first and then injecting foaming liquid.

7. The thin-partition heavy oil reservoir lower layer water plugging method according to claim 1 or 6, wherein the nitrogen foam slug is formed by nitrogen and foaming liquid, and the foaming liquid comprises the following components in percentage by mass: 0.5 to 2 percent of foaming agent, 0.1 to 3 percent of foam stabilizer and the balance of water.

8. The method for blocking water in the lower layer of the thin-partition heavy oil reservoir according to claim 7, wherein the foaming agent is one or more of sodium alpha-alkenyl sulfonate, sodium dodecyl sulfate, polyoxyethylene lauryl ether and sorbitan monooleate.

9. The thin-partition heavy oil reservoir lower layer water plugging method according to claim 7, wherein the foam stabilizer is one or more of polyacrylamide, hydroxypropyl guar gum, sodium carboxymethyl cellulose, bentonite, fly ash and calcium carbonate.

10. The water shutoff agent system used in the method for water shutoff of the lower layer of the thin-interval heavy oil reservoir according to any one of claims 1 to 9, which comprises a foaming liquid, an interval gel slug and a shutoff gel slug, wherein:

the foaming liquid comprises the following components: 0.5 to 2 percent of foaming agent, 0.1 to 3 percent of foam stabilizer and the balance of water;

the interlayer gel slug consists of: 1-30% of water glass, 0.1-2% of water glass cross-linking agent and the balance of water;

the plugging gel slug consists of: 3-20% of alkali lignin, 3-10% of an alkali lignin cross-linking agent and the balance of water, wherein the percentages are mass percentages.

Technical Field

The invention relates to a water plugging method for a lower layer of a thin-interlayer heavy oil reservoir and a water plugging agent system used by the same, and belongs to the technical field of oil exploitation.

Background

The implementation of the water plugging technology mainly comprises two important links of selecting and putting the water plugging agent into a well. After the suitable water shutoff agent is selected, the water shutoff agent needs to be solidified and gelatinized to play a water shutoff role, which is a key step for the good and bad effect of the water shutoff agent. The oil reservoir condition and the well completion mode influence the placement position of the plugging agent, particularly, the water outlet of the horizontal well mainly comprises bottom water and crack water seepage, a water logging part is tightly connected with an oil layer, and the modes of open hole well completion and the like enable more contact spaces to exist among a stratum, an annular part and a shaft. Generally, the water shutoff agent has strong rheological property, stability, safety, reliability and high shutoff strength; the water shutoff agent has stronger suspension stability before reaching a preset position, and cannot be deposited and solidified in the fluid; the water shutoff agent also has strong anti-scouring capability and can stably block the water outlet point for a long time.

The existing water shutoff agent mainly uses particle type, resin type, gel type and foam type plugging agents, the solid particle type plugging agent has poor migration capability, cannot pass through a sand control screen pipe and cannot realize deep plugging of stratum; the resin type plugging agent is sensitive to the environment, is not easy to control and has high cost; the foam type plugging agent has low plugging strength; the conventional gel type plugging agent uses polymers as main agents, has high base fluid viscosity and is not easy to enter a water channeling channel.

Thin interlayer heavy oil reservoir, lower floor's water energy is sufficient, because the interlayer is thin, possesses certain permeability simultaneously, along with the going on of notes vapour exploitation, lower floor's water very easily passes the interlayer and scurries into the oil reservoir, leads to the quick water logging of oil reservoir, and the high water production of most oil wells, steam scurries the passageway along water and gets into the water layer among the notes vapour process, and steam utilization is rateed lowly, when increasing manufacturing cost, influences the development effect of this type of oil well.

For a thin interlayer heavy oil reservoir, because the interlayer has a certain shielding effect on lower-layer water, the physical property of the oil reservoir is poorer, and a plugging agent with higher conventional viscosity is difficult to enter the interlayer, the plugging agent can only form plugging in the oil reservoir, secondary water channeling is easily formed after plugging, and the effect is poorer.

When the existing plugging agent system is used for plugging water of a thin interlayer heavy oil reservoir, the relationship between plugging strength and the viscosity of a plugging agent base fluid is difficult to balance, and the plugging effect on a water outlet point of the thin interlayer heavy oil reservoir is limited.

Disclosure of Invention

The invention aims to provide a method for blocking water in a lower layer of a thin interlayer heavy oil reservoir, which can form a slug combined in various forms aiming at the thin interlayer heavy oil reservoir, thereby improving the water blocking effect.

In order to achieve the aim, the specific technical scheme of the method for blocking water in the lower layer of the thin-interlayer heavy oil reservoir is as follows:

a method for blocking water in a lower layer of a thin-layer heavy oil reservoir comprises the following steps: determining an oil layer water outlet section, and injecting a nitrogen foam slug to inhibit the lower-layer water from invading the interlayer; then injecting an interlayer gel slug which mainly comprises water glass, a water glass cross-linking agent and water into the interlayer, wherein the interlayer gel slug enters the interlayer and plugs the pores in the interlayer after gelling; and injecting a plugging gel slug, wherein the plugging gel slug mainly comprises alkali lignin, an alkali lignin cross-linking agent and water, enters the boundary between the oil layer and the interlayer, and forms plugging on the boundary between the oil layer and the interlayer after gelling.

The invention relates to a method for blocking water in the lower layer of a thin-interlayer heavy oil reservoir, which adopts three slugs to mainly block the lower part of an oil layer, an interlayer and the upper part of a water layer so as to inhibit the water in the lower layer from entering the oil layer. The first slug is nitrogen foam, and is injected into the water layer, a foam plugging slug is formed between the upper boundary of the water layer and the lower boundary of the interlayer, and the water cone is pressed to prevent the lower layer water from flowing into the interlayer; the second section plug is an interlayer gel section plug and is used for gelling in interlayer pores to improve the shielding performance of the interlayer; the third slug is a plugging gel slug and is used for playing a role of sealing, forming strong plugging on the boundary of the oil layer and the interlayer, improving the thickness of the plugging layer, preventing steam from scouring the interlayer gel slug and the nitrogen foam slug, and improving the plugging strength and the plugging validity period. In addition, it is often necessary to inject a post-injection slug to displace the slug out of the screen and near-wellbore zone to prevent it from consolidating near the near-wellbore to block the steam injection and production passages.

The plugging agent is a low-viscosity system, and can effectively enter the interlayer to realize interlayer plugging; the viscosity of the plugging agent is close, the fingering phenomenon caused by viscosity difference can be avoided in the process of injecting the section plug, and the section plugs can be sequentially arranged according to the injection sequence; the nitrogen foam system firstly injects nitrogen to push water in the water channeling channel to the deep part, and then injects a foam liquid slug, and in the production process, the nitrogen and the foam liquid generate foam in the porous medium in the process of transporting from a water layer to the interlayer, and the aim of inhibiting the lower water from invading an oil layer through the interlayer is realized by utilizing the Jamin effect. The system viscosity is low, the pressure is low in the injection process, and the thin interlayer damage caused by high-pressure construction is avoided; the plugging agent is easy to enter a water channeling channel, avoids entering an oil-containing channel, reduces plugging of an oil-containing area, and has certain selectivity.

In order to achieve a better plugging effect, the plugging agent needs to be effectively retained in the water layer, the interlayer and part of the oil layer so as to increase the effective plugging thickness.

The nitrogen foam slug adopts a mode of firstly injecting nitrogen and then injecting foaming liquid, so that the nitrogen foam slug effectively forms foam in a water layer, blocks the upper part of the water layer and inhibits the lower-layer water from entering into an interlayer, and the adopted gel slugs are high-strength and low-viscosity gel systems, are easy to enter into a water channeling area to form high-strength blocking and effectively prevent the lower-layer water from entering into an oil layer. After the steam huff-and-puff well is injected into the plugging system, the oil reservoir water channeling channel can be plugged, steam is effectively inhibited from entering a water layer, the steam heating efficiency is improved, meanwhile, high water content of an oil well caused by lower-layer water channeling is prevented, and the oil reservoir development effect is improved.

After the water plugging method for the lower layer water of the thin-interlayer heavy oil reservoir is adopted for water plugging on site, the comprehensive water content of the produced oil is obviously reduced, the effective water plugging period is long, and the oil yield is obviously increased.

The interlayer gel slug consists of the following components in percentage by mass: 1 to 30 percent of water glass, 0.1 to 2 percent of water glass cross-linking agent and the balance of water.

Under the stratum environment, the water glass forms a network silicic acid gel under the action of a water glass cross-linking agent, generally, the water glass modulus is selected to be 2.5-3.5, and the content of effective substances is 30-40%.

The interlayer gel slug base liquid formed by the water glass has low viscosity, is convenient for pumping and injection, has high generated gel strength, and can effectively prevent backflow after condensation so as to improve the plugging performance. In addition, the water glass has low price and is suitable for large-scale application.

The water glass cross-linking agent is selected from substances capable of promoting the water glass to form gel, such as one or more of ethyl formate, ethyl acetate, methyl acetate, ammonium chloride and methanol.

The plugging gel slug consists of the following components in percentage by mass: 3-20% of alkali lignin, 3-10% of an alkali lignin cross-linking agent and the balance of water.

Under the formation environment, the alkali lignin forms a high-strength crosslinked polymer under the action of an alkali lignin crosslinking agent, and generally, the molecular weight of the alkali lignin is between 1000-2000. The addition of the alkali lignin can also change the rheological property of the plugging gel block in the conveying process, so that pumping is facilitated. The plugging gel slug can resist the temperature of 350 ℃, and has good adaptability to the heavy oil thermal recovery high-temperature environment.

The plugging gel slug is selected from substances capable of promoting the cross-linking reaction of the alkali lignin, such as one or more of formaldehyde, phenol, resorcinol and urotropine.

The nitrogen injection foam slug adopts a form of firstly injecting nitrogen and then injecting foaming liquid.

The nitrogen foam slug is formed by nitrogen and foaming liquid, and the foaming liquid comprises the following components in percentage by mass: 0.5 to 2 percent of foaming agent, 0.1 to 3 percent of foam stabilizer and the balance of water.

The foaming liquid consists of a foaming agent and a foam stabilizer, and the foam formed by the foaming liquid has higher stability due to the presence of the foam stabilizer.

The foaming agent is selected from one or more of sodium alpha-alkenyl sulfonate, sodium dodecyl sulfate, polyoxyethylene lauryl ether and sorbitan monooleate.

The foam stabilizer is selected from substances with good foam stabilizing performance, such as one or more of polyacrylamide, hydroxypropyl guar gum, sodium carboxymethyl cellulose, bentonite, fly ash and calcium carbonate.

The foaming agent and the foam stabilizer have good compatibility, and respective foaming and foam stabilizing performances can be well maintained.

The total volume calculation formula of each slug is as follows: q2 RhL Φ, where Q is the total volume of the slug, in m³R is the plugging radius, the unit m, L is the length of the water outlet section, the unit m, h is the sum of the effective thickness of 1/2 oil layer, the thickness of the interlayer and the thickness of 1/3 water layer, the unit m and phi are the effective porosity. Specifically, the method for blocking water in the lower layer of the thin-layer heavy oil reservoir comprises the following steps:

1) determining the position of the water section: the position of the water outlet section is determined by using a temperature profile test, and a packer is used for clamping and sealing to ensure that a slug is injected into the water outlet section;

2) calculating the total consumption of the slugs, calculating the consumption of each slug by adopting a cuboid model, calculating the consumption of each slug by adopting the volume calculation formula according to the volume, wherein the underground volume ratio of nitrogen to foam is 1:1, calculating the underground volume of the nitrogen according to the total volume of the nitrogen foam, converting the underground volume of the nitrogen into the ground volume of the injected nitrogen by utilizing a Kerbelon equation PV (nRT), and calculating the standard condition volume of the required nitrogen by using the standard condition;

3) according to the result of the volume calculation of the slug, firstly injecting nitrogen, then injecting foaming liquid to form a nitrogen foam slug, then sequentially injecting an interlayer gel slug and a plugging gel slug, and selecting the proportion of the interlayer gel slug and the plugging gel slug according to the plugging strength requirement, namely the plugging thickness of the interlayer gel slug and the plugging gel slug can be randomly changed without considering the interlayer thickness, and the total strength can meet the requirement and simultaneously comprehensively consider the cost and the strength required by each stage;

4) and finally, injecting a post-positioned slug, usually water, replacing the slug out of the sieve tube and the zone close to the well bore, preventing the slug from being solidified near the well bore, blocking a steam injection channel and an oil extraction channel, and injecting steam.

The specific technical scheme of the water shutoff agent system used by the method for water shutoff of the lower layer of the thin-interlayer heavy oil reservoir comprises the following steps:

a water shutoff agent system used in a water shutoff method for a lower layer of a thin-interlayer heavy oil reservoir comprises foaming liquid, interlayer gel slugs and shutoff gel slugs, wherein: the foaming liquid comprises the following components: 0.5 to 2 percent of foaming agent, 0.1 to 3 percent of foam stabilizer and the balance of water; the interlayer gel slug consists of: 1-30% of water glass, 0.1-2% of water glass cross-linking agent and the balance of water; the plugging gel slug consists of: 3-20% of alkali lignin, 3-10% of an alkali lignin cross-linking agent and the balance of water, wherein the percentages are mass percentages.

The base liquid of each slug is obtained by mixing the components in proportion, the preparation process of each base liquid is simple and convenient to use, and the viscosity of the base liquid of each slug is less than 5mPa & s, so that the base liquid is easy to pump into a water channeling channel.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting.

First, the concrete embodiment of the water plugging method for the lower layer of the thin-layer heavy oil reservoir