Plugging agent with temperature-resistant, salt-resistant and high-expansion for plugging large fractures and preparation method thereof

Abstract

A plugging agent with temperature-resistant, salt-resistant and high-expansion for plugging large fractures and a preparation method thereof of the present disclosure are provided, the plugging agent system consists of the following components: main agent: 6%10%, cross-linking agent: 0.6%1%, initiator: 0.006%0.01%, additive: 6%14%, and the rest being water; the preparation method includes the following steps: adding montmorillonite to water to prepare a montmorillonite dispersion system; adding the main agent, the cross-linking agent and the initiator to the montmorillonite dispersion system to prepare a main agent solution; putting the main agent solution into an oven with a temperature range with 9020 C. for 948 h to obtain gelation, the adhesive strength of the agent system can reach grade H, with 5080 expansion multiple, good strength after being expanded and good water plugging effect under the condition of a temperature of 140 C. and 250,000 degree of mineralization.

Claims

1. A plugging agent with temperature-resistant, salt-resistant and high-expansion for plugging large fractures, consisting of the following raw materials by mass ratio: main agent: 6%10%, cross-linking agent: 0.6%1% initiator: 0.006%0.01%, additive: 6%14%, and the rest being water; and wherein the main agent is composed of monomer 1 and acrylamide with an equal mass ratio, the monomer 1 is a mixture of acrylic acid and 2-acrylamide-2-methylpropylsulfonic acid; the additive is montmorillonite, the cross-linking agent is phenolic cross-linking agent prepared by phenol and formaldehyde at a mass ratio of 1:9, and the initiator is azo initiator.

2. A preparation method of the plugging agent with temperature-resistant, salt-resistant and high-expansion for plugging large fractures as claimed in claim 1, wherein the method comprises the following steps: A1, preparing a montmorillonite dispersion system: slowly adding the montmorillonite to stirred water and stirring for 4 h5 h at a stirring speed of 200300 r/min to obtain the montmorillonite dispersion system; A2, preparing a main agent solution: adding the main agent, the cross-linking agent and the initiator to the montmorillonite dispersion system and then stirring evenly to obtain the main agent solution; and A3, preparing a plugging agent: putting the main agent solution into an aging tank to be sealed, and then placing the aging tank under a temperature condition with 90120 C. to gelatinize for 948 hours, so as to obtain the plugging agent with temperature-resistant, salt-resistant and high-expansion for plugging large fractures.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an expansion schematic view of a plugging agent with 250,000 degree of mineralization in accordance with a first embodiment of the present disclosure;

(2) FIG. 2 is a schematic pressure change view of a large fracture model plugged with the plugging agent before and after.

DETAILED DESCRIPTION

(3) In order to more clearly understand and implement the present disclosure for one of ordinary skill in the related art, the principles and characteristics of the present disclosure are described on the basis of these drawings and embodiments; the examples cited are provided only to interpret the present disclosure, but not to limit the scope of the present disclosure.

(I) Embodiment

A First Embodiment

(4) Step A1: Preparing a Montmorillonite Dispersion System

(5) Adding 10 g montmorillonite to 82.2 g water solution being stirred in an agitator for 5 h, with the agitator running at 200 r/min, so that the montmorillonite can thoroughly mix into the water to obtain the montmorillonite dispersion system.

(6) Step A2: Preparing a Main Agent Solution

(7) The main agent prepared by 3 g acrylamide (AM), 2 g acrylic acid (AA) and 1 g 2-acrylamide-2-methylpropylsulfonic acid (AMPS), 0.8 g phenolic cross-linking agent and 1 g azobisisobutylene initiator with a concentration of 1% is added to the montmorillonite dispersion prepared in the step A1, the main agent, the cross-linking agent and the initiator can be dissolved into the montmorillonite dispersion system by stirring evenly with a glass rod so as to obtain a main agent solution.

(8) Step A3: Preparing a Plugging Agent

(9) Putting the prepared solution into an aging tank, and tightening the aging tank by bolts for sealing the prepared solution, and then putting the aging tank into an oven with a temperature of 120 C. for reaction, recording changes of adhesive strength, observing complete gelatinization, and then granulating with a grinding machine to obtain sample 1.

(10) Samples 25 are respectively prepared by changing monomer ratios of each main agent according to the steps A1A3, and specific composition of samples 15 is shown in Table 1.

(11) TABLE-US-00001 TABLE 1 Formula table of samples 1~5 main agent mont- cross-linking AA AMPS AM water morillonite initiator agent group (g) (g) (g) (g) (g) (g) (g) sample 1 2 1 3 82.2 10 1.0 0.8 sample 2 2.3 1.2 3.5 81.2 sample 3 2.7 1.3 4 80.2 sample 4 3 1.5 4.5 79.2 sample 5 3.3 1.7 5 78.2

A Second Embodiment

(12) Step A1: Preparing a Montmorillonite Dispersion System

(13) Adding 6 g montmorillonite to 83.2 g water solution stirring for 5 h, so that the montmorillonite can thoroughly mix into the water to obtain the montmorillonite dispersion system.

(14) Step A2: Preparing a Main Agent Solution

(15) The main agent prepared by 4.5 g acrylamide (AM), 1.5 g 2-acrylamide-2-methylpropylsulfonic acid (AMPS) and 3 g acrylic acid (AA), 0.8 g phenolic cross-linking agent and 1 g azobisisobutylene initiator with a concentration of 1% is added to the montmorillonite dispersion prepared in the step A1, the main agent, the cross-linking agent and the initiator can be dissolved into the montmorillonite dispersion system by stirring evenly so as to obtain main agent solution.

(16) Step A3: Preparing a Plugging Agent

(17) Putting the prepared solution into an aging tank, and tightening the aging tank by bolts for sealing the prepared solution, and then putting the aging tank into an oven with a temperature of 120 C. for reaction, recording gelatinization during the reaction process, and when the gelatinization of the system did not change for a long time, the gelatinization is completed to obtain sample 6.

(18) Samples 710 are respectively prepared by changing the proportion of the montmorillonite and the water according to the steps A1A3, and specific composition of samples 610 is shown in Table 2.

(19) TABLE-US-00002 TABLE 2 Formula table of samples 6~10 main cross-linking agent water montmorillonite initiator agent group (g) (g) (g) (g) (g) sample 6 9 83.2 6 1.0 0.8 sample 7 81.2 8 sample 8 79.2 10 sample 9 77.2 12 sample 10 75.2 14

(II) Performance Text

(20) 1) Adhesive Strength Test

(21) The main agent solution in samples 110 is sealed in the aging tank and then put into the oven at 120 C. for gelation. Strength of each sample at different gelation times is shown in Table 3 and Table 4.

(22) TABLE-US-00003 TABLE 3 Adhesive strength table of samples 1-5 time ( h) group 2 7 9 15 24 48 72 96 sample 1 A B C D E F G H sample 2 A C D F G G H H sample 3 A C E G G G H H sample 4 B E F H H H H H sample 5 D E H H H H H H

(23) TABLE-US-00004 TABLE 4 Adhesive strength table of samples 6~10 time (h) group 2 7 9 15 24 48 72 96 sample 6 B B C E G H H H sample 7 B B C F G H H H sample 8 B C C E F H H H sample 9 B C D F H H H H sampe 10 C D D F H H H H

(24) It can be seen from Table 3 and Table 4 that the gelation time of the plugging agent of the present disclosure is above 9 h, and the final gelation strength can be controlled according to an amount of the montmorillonite and an amount of the main agent.

(25) 2) Expansion Multiple Test

(26) Samples with a same quality are taken from sample 1 to sample 10 and placed in an oven with a temperature 90 C. (the samples placed in penicillin bottles with clear water) for 4 hours and one day to test the expansion multiple. Specific results can be seen in Table 5:

(27) TABLE-US-00005 TABLE 5 Test of glue expansion multiple of sample 1 to sample 10 expansion multiple sample sample sample sample sample sample sample sample sample sample (g/g) 1 2 3 4 5 6 7 8 9 10 4 h 20 30 32 37 47 34 34 35 37 50 1 d 50 58 64 75 80 74 77 77 75 74

(28) It can be seen from the above two performance tests that the expansion multiple is mainly related to the mass fraction of the main agent; the higher the mass fraction of the main agent, the greater the expansion multiple of the system samples in a same time. A final gelation time is related to the amount of the main agent and the montmorillonite additive. The interaction between the montmorillonite additives and the particles of an original system and gaps filling can minimize the gaps, form a high concentration solid particle content system, increase van der Waals force between particles, and further increase the final gelation strength of the system. The final gelation time of the system can be reduced by increasing the concentration of the main agent or the montmorillonite.

(29) 3) Expansion Multiple Test of the Present Disclosure Under a High-Temperature and High-Salt Condition

(30) The sample 1 is selected as a test sample of the system with high-temperature and high-salt performances and then is dried and ground into particles, and 0.5 g particles are selected to be sealed in an ampere bottle with 250,000 degree of mineralization water. Furthermore, the sealed ampere bottle is put into an explosion-proof box, and then is put into the oven with 140C temperature to observe changes of the particles in the ampere bottle. The changes of the sample 1 are shown in FIG. 1.

(31) It can be seen that the expansion multiple of the particles under the condition of formation water with 250,000 degree of mineralization is more than 20 times, which is less than that under clear water on the whole. Under the conditions of 140 C. temperature and formation water with 250,000 degree of mineralization, the particles remained in the shape of particles after being placed for 90 days, without being broken, that is, under the condition of high-temperature and high-salt, the particles of the sample 1 still has a stable plugging control ability, which can meet a demand of profile control and water plugging in large fractures and strong heterogeneous reservoir.

(32) 4) Plugging Effect of the Present Disclosure in a Fracture Model

(33) According to the formation characteristics of a fractured reservoir, three rock cores are selected for the experiment. The core is completely slit along its diameter to obtain a fracture with a width of 2 mm. Water used in the experiment is formation water with 250,000 degree of mineralization. Experiment steps are as follows: first measuring a pore volume of the model with saturated water (rate: 1 mL/min) and then with saturated oil (rate: 0.5 mL/min), so as to record original oil saturation. And then, performing water flooding (rate: 0.5 ml/min) on the model to 98% moisture content; after completing water flooding, injecting plugging agent with a volume of 0.3 PV at a rate of 0.3 mL/min, and then performing subsequent water flooding on the model after being placed at a temperature of 90 C. for 24 h. Subsequent water flooding at 1 PV, 3 PV and 5 PV are carried out in three groups of experiments, respectively, to observe and compare the changes of the plugging performance after the system is scour by different injected fluids. At the same time, during the injection process, recording pressure changes during water flooding before and after, and recording the injection pressure change at every 0.1 PV, and the pressure changes of subsequent experiments with water flooding of 5 PV are shown in FIG. 2.

(34) The plugging rate of different subsequent water flooding volumes is shown in Table 6:

(35) TABLE-US-00006 TABLE 6 Changes of plugging rate under different subsequent water flooding volumes rock core original permeability after residual serial permeability plugging agent resistance plugging number K.sub.1 (mD) injection K.sub.2 (mD) factor (%) 1 2727.96 5.00 545.59 99.82 2 2843.16 5.59 505.62 99.80 3 2828.77 8.85 319.64 99.68

(36) From the above experiments, it can be seen that in the fracture model, the plugging agent has a good adsorption capacity in the fracture after gelation, a plugging rate of the fracture can reach more than 99% even if the subsequent water flooding up to 5 PV is performed after injecting the plugging agent, at the same time, the above experiment results also prove that the present disclosure is extremely scour resistant. The plugging rate can still reach more than 99% after being scouring by a large amount water flooding.

(37) The plugging agent system with temperature-resistant, salt-resistant and high-expansion for plugging large fractures of the present disclosure is to control the expansion multiple of the system by adjusting different proportions of monomers. The plugging system of the present disclosure is of a high expansion multiple and a strong gelation effect so that particles are hardly broken after the system is expanded under a condition of high-temperature and high-salt. Thus, the present disclosure not only can meet a required intensity of the experiments, but also is the key to realize water plugging operation with high-temperature, high-salt, large-fracture and strong heterogeneous reservoir, adjust reservoir heterogeneity and improve oil recovery.

(38) Although the features and elements of the present disclosure are described as embodiments in particular combinations, each feature or element can be used alone or in other various combinations within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.