Multi-slug deep fluid diversion method and application thereof

Abstract

The present application relates to the technical field of oilfield exploitation, and particularly relates to a deep liquid flow diversion method of multiple segment plugs and application thereof, steps of which comprise: (1) injecting crosslinking retarder into the formation through the injection well to form a front segment isolation plug; (2) injecting deep liquid flow diversion agent into the formation through the injection well to form a main agent plug; (3) injecting crosslinking retarder into the formation through the injection well to form a rear segment isolation plug; (4) injecting water into the formation through the injection well to form a water injection plug. The front segment isolation plug and the rear segment isolation plug of the present application prevent the deep liquid flow diversion agent from absorbing water in advance, and the rear segment isolation plug and the water injection plug jointly push the main agent plug forward, in which the deep liquid flow diversion agent blocks the water channeling channel during the pushing process, and the long-term blocking effect is good, the water flow can be broken through again after blocking, the blocking position is movable, and deep placement can be realized.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, specifically to a deep fluid flow diversion method for multi-segment plugs and its application. Background Technology

[0002] In oilfield development, water injection is often used for water drive development. This involves setting up water injection wells around the production wells and injecting water into the formations around the production wells to maintain or increase the reservoir pressure and push the oil in the formations to the vicinity of the production wells, thereby improving the oilfield recovery rate.

[0003] However, after water-driven oil recovery reaches a certain stage, the heterogeneity of high water-cut reservoirs increases. Water more easily penetrates areas of high permeability within the oil layer, gradually forming dominant water channels, or water channeling channels. Oil in low-permeability areas is not easily advanced, creating many dead zones that water injection cannot reach. When water channeling channels reach a certain scale, water flooding can easily occur. Large amounts of water injected through injection wells can quickly flow to production wells through these channels, causing a significant increase in water cut in the production wells, sometimes even reaching 100%. Consequently, the oil in the reservoir cannot be fully extracted, affecting the recovery rate.

[0004] In existing technologies, water channeling is blocked by injecting a flow diverting agent into the oil reservoir. This flow diverting agent, after being injected into the desired oil reservoir, forms a gel in areas of high permeability, thereby blocking the water channeling and redirecting subsequently injected water to areas of relatively low permeability. This alters the flow direction, allowing more oil to move towards the production well.

[0005] However, existing methods of injecting flow diverting agents to redirect fluid flow have several technical problems: the flow diverting agents easily react and swell with formation water after injection; large dosage is required, affecting long-term sealing effect; the sealing is easily breached, creating new water channeling channels; and the sealing location is fixed, only able to seal water channeling channels in the oil layer around the injection point. Summary of the Invention

[0006] To address the technical problems of existing technologies using flow diverting agents to seal water channeling, such as easy reaction and swelling with formation water after injection affecting long-term sealing effectiveness, easy re-breakthrough after sealing, and fixed sealing position, this invention provides a deep flow diverting method using a multi-segment plug. In the formation, a front isolation segment plug, a main agent segment plug, a rear isolation segment plug, and a water injection segment plug are sequentially formed. The front and rear isolation segments prevent the deep flow diverting agent from prematurely absorbing water. The rear isolation segment plug and the water injection segment plug together advance the main agent segment plug forward. During the advancement process, the deep flow diverting agent seals the water channeling. This method provides good long-term sealing effect, can re-seal even after water flow breakthrough, and allows for movable sealing positions and deep placement.

[0007] In a first aspect, the present invention provides a deep fluid flow diversion method for a multi-segment plug, comprising the following steps: (1) A cross-linking retarder is injected into the formation through a water injection well to form a front isolation slug. The front isolation slug can isolate the deep fluid flow diverting agent from the formation water, thus preventing the deep fluid flow diverting agent from absorbing a large amount of formation water and swelling in advance. (2) Deep fluid flow diverting agent is injected into the formation through the injection well to form the main agent slug. The deep fluid flow diverting agent in the main agent slug absorbs the formation water in the water channel as it advances in the formation, generating elastic particle gel to block the water channel. (3) Inject crosslinking retarder into the formation through water injection well to form a rear isolation slug. The rear isolation slug can isolate the deep fluid flow diverting agent from the later water injection, preventing the deep fluid flow diverting agent from absorbing a large amount of the later water injection and swelling in advance. At the same time, it can push the main agent slug forward so that it can enter the deep bottom layer. (4) Water is injected into the formation through the injection well to form an injection block. The injection block continues to push the main agent block forward, enters the water channel, and the water injected through the isolation block is absorbed by the deep liquid flow deflecting agent in the main agent block to generate elastic particle gel, which further blocks the water channel.

[0008] Furthermore, the cross-linking retarder includes one or more combinations of mannitol, sodium gluconate, sorbitol, galactose, galactomannan, and betaine derivatives.

[0009] Furthermore, deep fluid diverting agents include organic gel systems or combinations of organic gel systems and inorganic gel systems.

[0010] Furthermore, the organic gel system includes polymers and crosslinking agents. The polymers include polyacetamide, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, and biopolymers. The crosslinking agents include organochromium crosslinking agents, organozirconium crosslinking agents, and organoaluminum crosslinking agents. The inorganic gel system includes modified bentonite inorganic gel system and lithium magnesium silicate gel system.

[0011] Furthermore, the injection volume of the crosslinking retarder in the front isolation slug: the injection volume of the deep fluid flow diverting agent in the main agent slug: the injection volume of the crosslinking retarder in the rear isolation slug = (0.5-2): 1: (0.5-2).

[0012] Furthermore, the injection volume of the crosslinking retarder in the front isolation slug is 1:1:1, while the injection volume of the deep fluid flow diverting agent in the main agent slug is 1:1:1.

[0013] Furthermore, in step (2), the raw materials of the deep fluid flow diverting agent are loaded and transported by tank truck. When in use, the raw materials of the deep fluid flow diverting agent loaded in the tank truck are transported to the mixing tank. The deep fluid flow diverting agent is prepared and diluted in the mixing tank. Then, the deep fluid flow diverting agent in the mixing tank is pumped to the injection wellhead by a pump truck. This facilitates the preparation and arrangement and shortens the time for setting up the instrument.

[0014] Furthermore, the mixing tank is equipped with a stirring device, which can mix the deep liquid flow diverting agent evenly through stirring.

[0015] Secondly, the present invention provides an application of the above-mentioned deep fluid flow diversion method in oilfield water drive development.

[0016] The beneficial effects of this invention are as follows: 1. This invention employs a sequence of injecting a crosslinking retarder, followed by a deep fluid flow diverting agent, then another crosslinking retarder, and finally water into the formation. This sequentially forms a front-stage isolation slug, a main agent slug, a rear-stage isolation slug, and a water injection slug in the formation. The front-stage isolation slug isolates the formation water from the main agent slug, preventing the deep fluid flow diverting agent from prematurely absorbing and swelling from the formation water. The deep fluid flow diverting agent in the main agent slug forms a gel to seal water channeling. The rear-stage isolation slug isolates the main agent slug from the water injection slug, preventing the deep fluid flow diverting agent from absorbing subsequent water injection and swelling. This method offers high sealing efficiency for water channeling and excellent long-term sealing performance.

[0017] 2. In this invention, the deep flow diverting agent in the main slug does not prematurely absorb water and swell under the protection of the front and rear isolation slugs. Therefore, after sealing the water channel, some deep flow diverting agent that has not absorbed water and swelled to form a gel still exists in the bottom layer. During subsequent waterflooding development, if the water flow breaks through the rear isolation slug to form a new water channel, the remaining deep flow diverting agent can absorb this water, sealing the new water channel again, further extending the action time of the deep flow diverting agent and improving the sealing efficiency.

[0018] 3. The present invention can advance the downstream isolation blocker through the water injection blocker, thereby advancing the main agent blocker, so that the main agent blocker continuously blocks the water channeling along the way during the advancement process. The blocking position is movable, which can realize the deep placement of the main agent blocker. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0020] Example 1 A deep fluid flow diversion method for a multi-segment plug, comprising the following steps: (1) A cross-linking retarder is injected into the formation through a water injection well to form a front isolation slug. The cross-linking retarder includes one or a combination of mannitol, sodium gluconate, sorbitol, galactose, galactomannan, and betaine derivatives. (2) Deep fluid flow diverting agent is injected into the formation through a water injection well to form a main agent slug. The deep fluid flow diverting agent includes an organic gel system or a combination of an organic gel system and an inorganic gel system. The organic gel system includes a polymer and a crosslinking agent. The polymer includes polyacetamide, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, and biopolymers. The crosslinking agent includes an organic chromium crosslinking agent, an organic zirconium crosslinking agent, and an organic aluminum crosslinking agent. The inorganic gel system includes a modified bentonite inorganic gel system and a magnesium lithium silicate gel system. The injection method of deep fluid flow diverting agent is as follows: the raw materials of deep fluid flow diverting agent are loaded and transported by tank truck. When in use, the raw materials of deep fluid flow diverting agent loaded in the tank truck are transported to the mixing tank. The deep fluid flow diverting agent is prepared and diluted in the mixing tank. Then, the deep fluid flow diverting agent in the mixing tank is pumped to the injection wellhead by a pump truck. The mixing tank is equipped with a stirring device. (3) Inject cross-linking retarder into the formation through water injection wells to form a downstream isolation slug; (4) Water is injected into the formation through injection wells to form injection sluices.

[0021] Example 2 An application of the deep fluid flow diversion method of Example 1 in oilfield waterflooding development: Eight oil production wells are located around the injection well. After water flooding, the water cut of the surrounding oil production wells rises to 100%. The method of Example 1 is used to treat the injection well, including the following steps: (1) A cross-linking retarder is injected into the formation through a water injection well. The cross-linking retarder is galactomannan, and the injection volume is 20 m³, forming a front isolation slug. (2) A deep fluid flow diverting agent is injected into the formation through a water injection well to form a main agent slug. The injection volume of the deep fluid flow diverting agent is 20 m³. The deep fluid flow diverting agent is an organic gel system, and the raw materials are polyacrylamide and organic chromium crosslinking agent. By mass, the concentration of organic chromium crosslinking agent in the deep fluid flow diverting agent is 3%, and the concentration of polyacrylamide is 0.3%. The injection method for deep fluid flow diverting agent is as follows: Polyacrylamide and organochromium crosslinking agent are loaded and transported separately using tank trucks. The polyacrylamide and organochromium crosslinking agent loaded in the tank trucks are then transferred to a mixing tank equipped with a stirring device. Under the stirring of the stirring device, the deep fluid flow diverting agent is prepared. Then, 20 m³ of the deep fluid flow diverting agent is pumped to the injection wellhead using a pump truck and injected into the formation, forming a main agent slug in the formation. (3) A cross-linking retarder is injected into the formation through a water injection well. The cross-linking retarder is galactomannan, and the injection volume is 20 m³, forming a downstream isolation slug. (4) Water is injected into the formation through injection wells to form injection sluices.

[0022] One month after treatment, the average water content of the oil wells surrounding the injection well decreased from 100% to 83.3%. Within one year of treatment, the average water content of the surrounding oil wells decreased to a minimum of 35.8%. Within one year of treatment, the average daily oil increase per well in the surrounding oil wells was 0.75 t / d, and the maximum daily oil increase per well was 1.85 t / d. After 14 months of treatment, the average water content of the surrounding oil wells was 69.7%, and the average daily oil increase per well was 0.87 t / d.

[0023] Example 3 An application of the deep fluid flow diversion method of Example 1 in waterflooding development of an oilfield. Eight oil production wells are located around the injection well. After water flooding, the water cut of the surrounding oil production wells rises to 91.5%. The method of Example 1 is used to treat the injection well, and the steps include: (1) A cross-linking retarder is injected into the formation through a water injection well. The cross-linking retarder is tallow-based dihydroxyethyl betaine, and the injection volume is 20 m³, forming a front isolation slug. (2) A deep fluid flow diverting agent is injected into the formation through a water injection well to form a main agent slug. The injection volume of the deep fluid flow diverting agent is 30 m³. The deep fluid flow diverting agent is a combination of an organic gel system and an inorganic gel system. The raw materials of the organic gel system are polyacrylamide and an organic chromium crosslinking agent, and the raw material of the inorganic gel system is lithium magnesium silicate. By mass, the concentration of the organic chromium crosslinking agent in the deep fluid flow diverting agent is 2%, and the concentration of the polyacrylamide is 0.15%. The injection method for deep fluid flow diverting agent is as follows: Polyacrylamide, organic chromium crosslinking agent, and lithium magnesium silicate are loaded and transported separately in tank trucks. The polyacrylamide, organic chromium crosslinking agent, and lithium magnesium silicate loaded in the tank trucks are then transported to a mixing tank equipped with a stirring device. Under the stirring of the device, the mixture is prepared as a deep fluid flow diverting agent. Then, 30 m³ of the deep fluid flow diverting agent is pumped into the injection wellhead using a pump truck and injected into the formation, forming a main agent slug in the formation. (3) A cross-linking retarder is injected into the formation through a water injection well. The cross-linking retarder is tallow-based dihydroxyethyl betaine, and the injection volume is 20 m³, forming a downstream isolation slug. (4) Water is injected into the formation through injection wells to form injection sluices.

[0024] One month after treatment, the average water content of the oil wells surrounding the injection well decreased from 91.5% to 17.2%. Within one year of treatment, the average water content of the surrounding oil wells decreased to a minimum of 16.7%. Within one year of treatment, the average daily oil increase per well in the surrounding oil wells was 1.2 t / d, and the highest daily oil increase per well was 2.14 t / d. After 16 months of treatment, the average water content of the surrounding oil wells was 33.3%, and the average daily oil increase per well was 1.2 t / d.

[0025] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A deep fluid flow diversion method for a multi-stage plug, characterized in that the steps include... include: (1) Inject crosslinking retarder into the formation through water injection wells to form a front isolation slug; (2) Inject deep fluid flow diverting agent into the formation through the injection well to form the main agent slug; Crosslinking retarder includes one or more of mannitol, sodium gluconate, sorbitol, galactose, galactomannan, and betaine derivatives; (3) Inject cross-linking retarder into the formation through water injection wells to form a downstream isolation slug; Deep fluid diverting agents include organic gel systems or combinations of organic gel systems and inorganic gel systems; (4) Water is injected into the formation through injection wells to form injection sluices.

2. The deep fluid flow diversion method as described in claim 1, characterized in that, Organic gel systems include polymers and crosslinking agents. Polymers include polyacetamide, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, and biopolymers. Crosslinking agents include organochromium crosslinking agents, organozirconium crosslinking agents, and organoaluminum crosslinking agents. Inorganic gel systems include modified bentonite inorganic gel systems and lithium magnesium silicate gel systems.

3. The deep fluid flow diversion method as described in claim 1, characterized in that, The injection volume of crosslinking retarder in the front isolation slug: the injection volume of deep fluid flow diverting agent in the main agent slug: the injection volume of crosslinking retarder in the rear isolation slug = (0.5-2): 1: (0.5-2).

4. The deep fluid flow diversion method as described in claim 3, characterized in that, The injection volume of crosslinking retarder in the front isolation slug: the injection volume of deep flow diverting agent in the main agent slug: the injection volume of crosslinking retarder in the rear isolation slug = 1:1:

1.

5. The deep fluid flow diversion method as described in claim 1, characterized in that, In step (2), the raw materials of the deep fluid flow diverting agent are loaded and transported using a tanker truck. When in use, the raw materials of the deep fluid flow diverting agent loaded in the tanker truck are transported to the mixing tank. The deep fluid flow diverting agent is prepared and diluted in the mixing tank. Then, the deep fluid flow diverting agent in the mixing tank is pumped to the injection wellhead using a pump truck.

6. The deep fluid flow diversion method as described in claim 5, characterized in that, The mixing tank is equipped with a stirring device.

7. The application of the deep fluid flow diversion method as described in claim 1 in oilfield water drive development.