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CN-121991675-A - Carbonate fracture-cavity type oil reservoir optimized foam system and preparation and profile control method thereof

CN121991675ACN 121991675 ACN121991675 ACN 121991675ACN-121991675-A

Abstract

The invention provides a carbonate fracture-cavity type oil reservoir optimized foam system, and a preparation and profile control method thereof, and relates to the technical field of oilfield chemistry. The preparation method of the carbonate fracture-cavity type oil reservoir optimized foam system comprises the following steps of mixing a surfactant with a solution to obtain a surfactant solution, mixing self-generated fibers with the obtained surfactant solution to obtain a solution, and enabling the obtained solution and gas to pass through a foam generator to generate foam. The method can form a stable sealing layer with a certain supporting capacity at the interface between the water layer and the foam to isolate the subsequent foam and the water layer, can improve the sweep range and the passing capacity of a foam system in a large-scale flowing space, and effectively improves the stratum sweep coefficient.

Inventors

  • HE LONG
  • WANG JIANHAI
  • YANG YINGDA
  • ZHANG XIAO
  • WU GUANGSHENG
  • Rong Gen

Assignees

  • 中国石油化工股份有限公司
  • 中国石油化工股份有限公司西北油田分公司

Dates

Publication Date
20260508
Application Date
20241104

Claims (18)

  1. 1. The preparation method of the carbonate fracture-cavity type oil reservoir optimized foam system is characterized by comprising the following steps of: S1, mixing a surfactant with a solution to obtain a surfactant solution; S2, mixing the autogenous fibers with the surfactant solution obtained in the step S1 to obtain a solution; And S3, enabling the solution obtained in the step S2 and the gas to pass through a foam generator to generate foam.
  2. 2. The method according to claim 1, wherein in step S1, the surfactant is an anionic-nonionic surfactant.
  3. 3. The method of claim 2, wherein the anionic-nonionic surfactant is YF-1.
  4. 4. The method of claim 1, wherein the concentration of the surfactant in the surfactant solution in step S1 is 0.2% -1%.
  5. 5. The method according to claim 4, wherein the concentration of the surfactant in the surfactant solution in step S1 is 0.5% to 1%.
  6. 6. The preparation method according to claim 1, wherein in the step S1, the mixing is performed at a temperature of 20-30 ℃, for a time of 1-2.5h, and at a speed of 400-600r/min.
  7. 7. The method according to claim 1, wherein in step S2, the concentration of the autogenous fibers in the solution is 0.5% -5.5%.
  8. 8. The method according to claim 7, wherein in step S2, the concentration of the autogenous fibers in the solution is 1% -5%.
  9. 9. The method according to claim 1, wherein in the step S2, the mixing is performed by stirring, wherein the step of stirring is performed by adding the self-fibers into the surfactant solution obtained in the step S1 in batches, the stirring temperature is 20-30 ℃, the stirring time is 3-6h, and the stirring speed is 400-600r/min.
  10. 10. The method according to claim 1, wherein in step S3, the gas is nitrogen.
  11. 11. The method according to claim 1, wherein in step S3, the mass of the foam is 60% -80%.
  12. 12. The method of claim 11, wherein in step S3, the foam has a mass of 68% -75%.
  13. 13. A carbonate fracture-cavity reservoir optimized foam system made by the method of any one of claims 1-12.
  14. 14. The carbonate fracture-cavity oil reservoir optimizing foam system according to claim 13, wherein the carbonate fracture-cavity oil reservoir optimizing foam system is injected in a slug injection mode, the volume of foam injected by the first slug is 0.01-0.1 PV, after the well is closed for 0.5-1.5h, continuous slug injection foam is continued, and the volume of foam injected by the continuous slug is 0.1-0.4 PV.
  15. 15. The carbonate fracture-cavity reservoir optimization foam system of claim 14, wherein the initial slug injection foam volume is 0.05PV-0.08PV, and the continuous slug injection foam is continued after the well is shut in for 0.5-1.5 hours, and the continuous slug injection foam volume is 0.2PV-0.35PV.
  16. 16. The flooding method of the carbonate fracture-cavity oil reservoir optimization foam system prepared by the preparation method of any one of claims 1 to 12, which specifically comprises the following steps: and (3) taking a well at the low top of the oil reservoir as an injection well, taking a well at the low position as a production well, injecting foam pre-generated by a slug from the injection well, closing the well for 0.5-1.5h, and continuously injecting the foam.
  17. 17. The flooding method of claim 16, wherein the injection well is a vertical well and the production well is a horizontal well or a vertical well.
  18. 18. The flooding method of claim 16, wherein the production well is located at an oil-water transition zone.

Description

Carbonate fracture-cavity type oil reservoir optimized foam system and preparation and profile control method thereof Technical Field The invention relates to the technical field of oilfield chemistry, in particular to a carbonate fracture-cavity type oil reservoir optimized foam system, and a preparation and profile control method thereof. Background Carbonate reservoirs play a very important role in global oil and gas resources. Due to the severe heterogeneity of reservoirs and the diversity of the communication modes of cracks and karst cave, the water displacement mechanism is more complex due to the factors, and the final displacement effect and the residual oil distribution are controlled by the communication degree and the communication condition between large cracks and large holes in a cave system. In the development process of fracture-cavity type carbonate reservoirs, a foam system is often matched for profile control and flooding. Foam is a profile control system which is applied to exploitation of heterogeneous oil reservoirs. The foam has the characteristics of stable water contact, defoaming when contacting oil, enhanced plugging capability along with the increase of permeability, and the like, so that the foam profile control system can play a good role in controlling fluidity, can effectively adjust the channeling problem of a heterogeneous stratum, and can effectively improve the utilization degree of a top oil layer due to relatively low gas phase density in the foam. Although the foam can adjust the injection profile to improve the recovery ratio of crude oil, the foam still belongs to a thermodynamically unstable system, the stability of the foam still is the biggest problem for restricting the application of foam fluid, and as the migration distance of the foam increases, the conditions of a surfactant structure, solubility, aggregation behavior, adsorption capacity on a gas/liquid surface and the like change, and all the changes affect the performance of the foam, so that when the foam flows in a fracture-cavity system, the overall flow performance of the foam is poor due to the severe stratum condition of high temperature and high salt of a fracture-cavity oil reservoir. Meanwhile, when the foam flows in the fracture-cavity medium, obvious layering phenomenon is caused by gravity differentiation, foam is broken and separated out, liquid is mixed with stratum water, so that most of water phases flow along the bottom of an oil reservoir in the foam profile control and flooding process, the dryness of the foam floating on the water surface is high, the fluidity is weak, and the middle upper part of the oil reservoir cannot be effectively swept. Therefore, the existing foam system has poor profile control and flooding effects for the seam holes with extremely strong permeability. Chinese patent CN116622359A provides a self-assembled gel foam oil displacement agent suitable for high-temperature high-salt fracture-cavity oil reservoirs and a preparation method thereof, and belongs to the technical field of oilfield chemistry. The oil displacement agent comprises 0.2-0.5% of quaternary amphiphilic hydrophobic association copolymer, 0.2-0.3% of betaine Gemini surfactant, 0.1-0.35% of amine oxide surfactant, 0.1-0.2% of heat-resistant polybasic acid anhydride, 0.02-0.07% of counter ion compound, 0.04-0.14% of chelating agent and the balance of water, wherein the content of inorganic salt in water is 10-22%, and the raw materials are prepared into the foam oil displacement agent by using a foam generator. The foam stability after foaming is obviously improved, the oil-water interfacial tension is obviously reduced by improving the fluidity of oil-water two-phase flow, expanding the swept volume, improving the oil washing efficiency, increasing the stratum energy and improving the seepage capability of oil phase liquid, thereby obviously improving the crude oil recovery ratio of a high-temperature high-salt fracture-cavity type oil reservoir. However, the foam oil displacement agent provided by the invention has complex formula preparation and higher cost. Chinese patent CN111484838a discloses a carbonate fracture-cavity type oil reservoir composite plugging agent and its preparation method. The preparation method comprises the steps of (1) adding an anionic-nonionic surfactant into water, stirring to obtain a surfactant solution, (2) enabling the obtained surfactant solution to be in full contact with gas through a foam generator to generate foam, and (3) adding rice hull ash into the generated foam to be fully mixed to obtain the composite plugging agent. The foam prepared by the preparation method provided by the invention carries the rice hull ash composite plugging agent, can effectively plug a high-permeability layer and improve the recovery ratio of crude oil, has a good plugging effect on longitudinal heterogeneity and plane heterogeneity, and can effectively adjust the water absorption