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CN-121975061-A - Modified starch-based temporary plugging agent suitable for oil-based drilling fluid, and preparation method and application thereof

CN121975061ACN 121975061 ACN121975061 ACN 121975061ACN-121975061-A

Abstract

The invention provides a modified starch-based temporary plugging agent suitable for oil-based drilling fluid, and a preparation method and application thereof. The preparation method of the modified starch-based temporary plugging agent comprises the steps of adding sodium starch octenyl succinate into water, stirring uniformly, then adding acrylamide, butyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N, N' -methylenebisacrylamide, stirring uniformly, adjusting pH to 6-8 to obtain a water phase, adding an emulsifying agent into white oil, stirring uniformly to obtain an oil phase, adding the water phase into the oil phase, emulsifying to obtain emulsion, adding an initiating agent into the obtained emulsion, reacting to obtain a reaction solution, adding ethanol into the obtained reaction solution, precipitating, centrifuging, washing, drying and grinding to obtain the modified starch-based temporary plugging agent. The temporary plugging agent disclosed by the invention is stable in dispersion in an oil-based drilling fluid system, has strong high-temperature plugging capability, can be used for efficiently plugging a hypertonic channel and automatically degrading, and meets the plugging and reservoir protection requirements of deep well oil-based drilling fluids.

Inventors

  • LV KAIHE
  • HUANG XIANBIN
  • LIU JINGPING
  • LI GONGRANG
  • CHEN PANPAN
  • LI JIAN
  • SUN JINSHENG
  • LIAO BO
  • JIN JIAFENG
  • LI MEICHUN
  • BAI YINGRUI
  • WANG JINTANG

Assignees

  • 中国石油大学(华东)

Dates

Publication Date
20260505
Application Date
20251226

Claims (10)

  1. 1. The preparation method of the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid is characterized by comprising the following steps of: (1) Adding sodium starch octenyl succinate into water, stirring uniformly, then adding acrylamide, butyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N, N' -methylenebisacrylamide, stirring uniformly, and regulating the pH to 6-8 to obtain a water phase; (2) Adding the emulsifier into the white oil, and uniformly stirring to obtain an oil phase; (3) Adding an initiator into the obtained emulsion to react to obtain a reaction solution; (4) Adding ethanol into the reaction liquid obtained in the step (3) for precipitation, and obtaining the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid through centrifugation, washing, drying and grinding.
  2. 2. The method for preparing a modified starch-based temporary plugging agent suitable for oil-based drilling fluids according to claim 1, wherein in the step (1), the mass ratio of the sodium starch octenyl succinate to water is 0.1-0.6:1, preferably 0.3-0.5:1; In the step (1), the temperature of stirring the sodium starch octenyl succinate after adding the sodium starch octenyl succinate into water is 55-65 ℃, and the stirring time is 20-40 min.
  3. 3. The preparation method of the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid according to claim 1, wherein in the step (1), the mass ratio of the sodium starch octenyl succinate, the acrylamide, the butyl acrylate, the 2-acrylamido-2-methylpropanesulfonic acid and the N, N' -methylenebisacrylamide is 4-12:4-12:2-8:8-15:0.05-0.15, preferably 5-7:5-7:3-6:10-13:0.08-0.1, and further preferably 6:6:4:11:0.09; In the step (1), 10-30% by mass of sodium hydroxide aqueous solution is used for adjusting the pH to 6-8.
  4. 4. The preparation method of the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid according to claim 1, wherein in the step (2), the emulsifier is a combination of span 80 and tween 80, the mass ratio of span 80 to tween 80 in the emulsifier is 8-10:1, the white oil is 5# white oil, 7# white oil or 10# white oil, and the mass ratio of the emulsifier to the white oil is 0.01-0.04:1, preferably 0.02-0.035:1.
  5. 5. The method for preparing the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid according to claim 1, wherein in the step (3), the mass ratio of the water in the water phase to the white oil in the oil phase is 0.2-0.6:1, preferably 0.25-0.48:1, and the emulsifying step is that the water in the water phase and the white oil in the oil phase are emulsified for 2-5 min in a high-speed emulsifying machine at the rotating speed of 10000-15000 rpm.
  6. 6. The preparation method of the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid, which is disclosed in claim 1, is characterized in that in the step (3), the initiator is azo initiator, the azo initiator is azobisisobutyronitrile, azobisisoheptonitrile or dimethyl azobisisobutyrate, the mass of the initiator is 0.1-0.4% of the total mass of sodium starch octenyl succinate, acrylamide, butyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N, N' -methylenebisacrylamide, the initiator is in the form of an initiator oil solution, the initiator is dropwise added into a system under the condition of nitrogen atmosphere and 40 ℃, the temperature of the system is controlled to be increased at a speed of not higher than 0.5 ℃ per minute in the dropwise adding process, the temperature of the dropwise added system is not higher than 80 ℃, the dropwise adding rate of an initiator oil solution is 10-30 g/h, the initiator oil solution is obtained by adding the initiator into white oil, and the mass fraction of the white oil solution is 5-20% as that of the white oil in the step (2).
  7. 7. The method for preparing the modified starch-based temporary plugging agent applicable to the oil-based drilling fluid, which is characterized in that in the step (3), after the initiator is added, the constant-temperature reaction is continued for 4-6 hours, and the reaction is carried out under the nitrogen atmosphere.
  8. 8. The preparation method of the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid, which is disclosed in claim 1, is characterized in that in the step (4), the mass ratio of the volume of ethanol to the sodium starch octenyl succinate is 3-8 mL/1 g, the centrifugation is carried out for 5-10 min under the condition that the rotating speed is 7000-9000 rpm, the washing is carried out for 3-5 times by using deionized water, and the drying is carried out under the condition that the vacuum drying is carried out at 60-80 ℃ until the weight is constant.
  9. 9. A modified starch-based temporary plugging agent suitable for oil-based drilling fluids, characterized in that it is prepared by the preparation method according to any one of claims 1-8.
  10. 10. The use of the modified starch-based temporary plugging agent for oil-based drilling fluids according to claim 9 in oil-based drilling fluids as temporary plugging agent in oil well drilling processes.

Description

Modified starch-based temporary plugging agent suitable for oil-based drilling fluid, and preparation method and application thereof Technical Field The invention relates to a modified starch-based temporary plugging agent suitable for oil-based drilling fluid, and a preparation method and application thereof, and belongs to the technical field of oil-gas drilling. Background For unconventional oil and gas reservoirs and high-temperature deep wells, oil-based drilling fluids are widely used by virtue of their excellent inhibition and lubricity, but during the drilling process, high permeability channels such as cracks, pores and the like are often present in formations around the wellbore, which may lead to drilling fluid loss and reservoir contamination. For this reason, temporary blocking agents are often used to temporarily block these channels. The traditional temporary plugging agent is solid particles such as calcium carbonate, petroleum resin and the like, the materials cannot be accurately matched with the size of the pore throat of the stratum in the actual drilling process, the requirement of the whole well section is difficult to meet, and the traditional temporary plugging agent still faces the challenges of particle hydrophobic modification and dissolution controllability in the oil-based drilling fluid. In recent years, with the improvement of recovery ratio and the improvement of environmental protection requirements, degradable polymer temporary plugging agents are receiving a great deal of attention. Meanwhile, the self-adaptive shielding temporary plugging agent containing hydrophilic groups and hydrophobic chains can automatically adjust the plugging form according to pore throats, however, the system is designed aiming at water-based drilling fluid, has poor dispersion in an oil-based drilling fluid system, is incompatible with an oil phase, and is difficult to effectively clean after well completion. For example, china patent CN120555034A discloses a plugging material which comprises, by mass, 3-5% of starch, 2-6% of vegetable gum, 16-25% of a polymer monomer compound, 5-8% of a pH regulator, 0.05-0.1% of a curing agent, 4-12% of a gelling agent, 3.2-9.6% of a gelling auxiliary agent, 1-4% of a dispersing agent, 0.05-1% of an initiator, 3-5% of a capsule breaker and the balance of water. Although the plugging material is a multi-component composite plugging system, the system components are complex, the in-situ polymerization and colloid crosslinking mechanisms are not demonstrated enough, and the key performance can not give out sufficient control data or system evaluation results under high-temperature and high-pressure conditions. Chinese patent document CN120310541a provides a plugging agent for oil-based drilling fluids, comprising a rigid material, pregelatinized tapioca starch, inorganic fibers, gel particles and a base oil, wherein the raw materials for preparing the gel particles comprise allyl glycidyl ether, alkyl primary amine, short-chain acrylate, long-chain acrylate, styrene and unsaturated silane. But the addition amount of the plugging agent is high, up to 10wt%, and the plugging performance lacks high-temperature high-pressure authentication results. Therefore, the development of the degradable temporary plugging agent which is stably dispersed in the oil-based drilling fluid has important significance. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a modified starch-based temporary plugging agent suitable for oil-based drilling fluid, and a preparation method and application thereof. The modified starch-based temporary plugging agent is a degradable temporary plugging agent, is stable in dispersion in an oil-based drilling fluid system, has strong high-temperature plugging capability, and can solve the problems that the traditional temporary plugging agent is poor in dispersion in the oil-based drilling fluid and is easy to remain after plugging. The modified starch-based temporary plugging agent can not only efficiently plug a hypertonic channel, but also be automatically degraded, thereby meeting the plugging and reservoir protection requirements of deep well oil-based drilling fluid. In order to achieve the above purpose, the technical scheme of the invention is as follows: The preparation method of the modified starch-based temporary plugging agent suitable for the oil-based drilling fluid comprises the following steps: (1) Adding sodium starch octenyl succinate into water, stirring uniformly, then adding acrylamide, butyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid and N, N' -methylenebisacrylamide, stirring uniformly, and regulating the pH to 6-8 to obtain a water phase; (2) Adding the emulsifier into the white oil, and uniformly stirring to obtain an oil phase; (3) Adding an initiator into the obtained emulsion to react to obtain a reaction solution; (4) Adding ethanol into the reaction liquid obtained in the step