Deep profile control system and preparation method thereof

Abstract

The invention discloses an in-depth profile control system. The in-depth profile control system is characterized by being prepared from the following raw materials: polyacrylamide with the concentration ratio of 0.3 to 0.5 percent, a phenolic aldehyde cross-linking agent with the concentration ratio of 0.3 to 0.5 percent and a cross-linking enhancer with the concentration ratio of 0.3 to 0.5 percent. Through complexation, hydrolysis and hydroxyl bridge effects, the plugging agent reacts with carboxyl and amido in polyacrylamide to form a three-dimensional net system, the viscosity is low before gel forming, the injection performance is good, a pipe column does not need to be moved during construction, the plugging agent preferentially enters a water channeling high flow guide channel, selective plugging is achieved, the pressure difference of an oil-water channel of a reservoir is adjusted after gel forming, and the streaming area is increased; the profile control agent has the advantages of being high in gelling strength, good in plugging effect, fast in pressure rising effect, small in dosage, short in construction period and capable of saving cost, and the prepared profile control agent is resistant to salt, scouring and shearing, good in stability and high in plugging capacity.

Description

Technical Field

[0001] The invention relates to the technical field of oil production, in particular to a deep profile control system and a preparation method thereof. Background Art

[0002] my country's oilfield industry is developing rapidly, and the difficulty of oilfield exploitation is increasing day by day. Higher exploitation technology is needed to ensure the steady development of the industry. As far as the current development of oilfields in my country is concerned, most oilfields rely on water injection technology for exploitation, but usually, the differences in water injection layers are huge. High permeability layers have strong water absorption capacity, while low permeability layers are just the opposite. This leads to the need for oilfield workers to increase water injection volume and oil recovery efficiency to ensure balanced water absorption in the profile.

[0003] All major oil fields have entered the high water content exploitation stage, and profile control and water plugging agents have shifted from conventional profile control technology to deep profile control (displacement) technology. So far, profile control agents have become an effective measure to adjust the heterogeneity of oil layers and block the dominant channels of water flow, and are a hot topic for domestic and foreign scholars to study the direction of improving oil recovery. The deep profile control technology of water injection wells can effectively improve the macroscopic sweep coefficient of injected water, significantly increase the crude oil recovery rate of the entire block, and achieve good results in increasing oil and reducing water. As a favorable means to control inefficient and invalid cycles, deep profile control technology has been widely used in composite flooding.

[0004] Therefore, in order to solve the above problems, a deep profile control system and a preparation method are proposed. Summary of the invention

[0005] The object of the present invention is to provide a deep profile control system, the raw materials of which include: polyacrylamide with a concentration of 0.3-0.5%, a phenolic crosslinking agent with a concentration of 0.3-0.5%, and a crosslinking enhancer with a concentration of 0.3-0.5%;

[0006] The preparation steps include:

[0007] Step 1: Weigh 200mL of tap water into a 500mL beaker, install a vertical stirrer, insert the stirring paddle into three-quarters of the liquid surface, start the vertical stirrer to make the prepared water form a vortex, and adjust the stirring speed of the vertical stirrer;

[0008] Step 2: Slowly and evenly add the weighed polyacrylamide with a concentration of 0.3%-0.5% into the vortex wall and stir for 1-2 hours until it is completely dissolved, then add the phenolic crosslinker with a concentration of 0.3%-0.5% and the crosslinking enhancer with a concentration of 0.3%-0.5% respectively, and continue to stir until it is completely dissolved, and the system solution is prepared;

[0009] Step 3: Pour the prepared solution into a high temperature resistant glass bottle, seal the solution, and place it in a 60°C electric blast drying oven within 30 minutes.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The invention reacts with the carboxyl group and the amide group in the polyacrylamide through complexation, hydrolysis and hydroxy bridge action to form a three-dimensional network system. The viscosity before gelation is low and the injection performance is very good. The construction does not require the moving of the pipe column. The plugging agent preferentially enters the water channeling high diversion channel and selectively plugs it. After gelation, the pressure difference of the oil-water channel of the reservoir is adjusted to increase the bypass area to achieve the purpose of controlling water and increasing oil. The invention has the advantages of high gelation strength, good plugging effect, fast pressure-starting effect, small dosage, short construction period and cost saving. In addition, the prepared profile control agent is salt-resistant, erosion-resistant, shear-resistant, stable and strong plugging ability.

[0012] The system base fluid of the present invention is a pure viscous fluid with low initial viscosity, no normal stress, excellent deep migration ability, and can undergo polymerization and grafting reactions underground. Due to its adjustable gelation time, deep profile control and water plugging can be achieved, thereby improving the problems of short effective period and short plugging radius of conventional profile control technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram showing the change in viscosity of Example 1 of the present invention with the amount of initiator added;

[0014] Figure 2 is a schematic diagram of the reaction changes of different initiator addition amounts in Example 1 of the present invention;

[0015] Figure 3 Schematic diagram showing the change of viscosity with polyacrylamide feed ratio in Example 1 of the present invention;

[0016] Figure 4 is a parameter diagram of the thermal stability of the system of Example 1 of the present invention;

[0017] Figure 5 is a schematic diagram of thermal stability at different temperatures of Example 1 of the present invention;

[0018] Figure 6 is a schematic diagram of the experimental results of core plugging in Example 1 of the present invention;

[0019] Figure 7 This is a graph showing the change in plugging rate versus permeability in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The present invention provides a deep profile control system, the raw materials of which include: polyacrylamide with a concentration of 0.3-0.5%, a phenolic cross-linking agent with a concentration of 0.3-0.5%, and a cross-linking enhancer with a concentration of 0.3-0.5%;

[0022] The preparation steps include:

[0023] Step 1: Weigh 200mL of tap water into a 500mL beaker, install a vertical stirrer, insert the stirring paddle into three-quarters of the liquid surface, start the vertical stirrer to make the prepared water form a vortex, and adjust the stirring speed of the vertical stirrer;

[0024] Step 2: Slowly and evenly add the weighed polyacrylamide with a concentration of 0.3%-0.5% into the vortex wall and stir for 1-2 hours until it is completely dissolved, then add the phenolic crosslinker with a concentration of 0.3%-0.5% and the crosslinking enhancer with a concentration of 0.3%-0.5% respectively, and continue to stir until it is completely dissolved, and the system solution is prepared;

[0025] Step 3: Pour the prepared solution into a high temperature resistant glass bottle, seal the solution, and place it in a 60°C electric blast drying oven within 30 minutes.

[0026] Embodiment 1:

[0027] The effects of different addition amounts of polyacrylamide, crosslinking agent and crosslinking enhancer concentration ratio on the gelling properties were studied.

[0028] Polyacrylamide 0.3-0.5%, phenolic crosslinking agent 0.3-0.5%, crosslinking enhancer 0.3-0.5%, gel is prepared according to the above experimental method for preparing gel, and the single variable method is used to detect the influence of the content of each component on the experimental results.

[0029] A: In this experiment, the polyacrylamide concentration was fixed at 0.3%, the reaction temperature was set at 60°C, and the concentration range of the crosslinking agent and the crosslinking enhancer was 0.3%-0.5%.

[0030] Figure 1 It is a schematic diagram of the change of viscosity with the amount of initiator added;

[0031] Figure 2 It is a schematic diagram of the reaction changes with different initiator addition amounts;

[0032] Depend on Figure 1 It can be seen from the curve that at first, as the ratio concentration increases, the rate of free radical generation accelerates, which is beneficial to the growth of the chain and the acceleration of the polymerization reaction, and the viscosity of the product gradually increases. However, when the ratio concentration is too high, too many free radicals will be triggered. According to the kinetics and steady-state theory of free radical polymerization reaction, the grafting rate will be sharply reduced, and the viscosity of the formed jelly system will decrease. The recommended ratio concentration is 0.3%.

[0033] B: The introduction of long chains of polyacrylamide can improve the strength of the gel. The concentration of crosslinker and crosslink enhancer was fixed at 0.3%, the reaction temperature was set at 60°C, the polyacrylamide feed ratio was changed, and 0.1-0.5% was added to the system to observe the gelation of the system. Figure 3 shown.

[0034] By the attached Figure 3 It can be seen that the greater the content of polyacrylamide, the stronger the gel viscosity, the shorter the gelation time, and the higher the cost. When the ratio is 0.3%, the homopolymerization reaction is obvious. Considering the system strength and cost, the best feed ratio is 1:1:1, that is, the concentrations of polymer, crosslinking agent, and crosslinking enhancer are 0.3%, 0.3%, and 0.3%, respectively.

[0035] C: Performance evaluation of deep profile control system: The experimental water was tap water, and the gelling performance at different temperatures of 40℃, 60℃, and 90℃ was used to carry out experimental research work such as gel performance parameter evaluation, gel system optimization, and process parameter optimization. The standards and enterprise standards of the petroleum and natural gas industry of the People's Republic of China were followed. The standards used are as follows: SY / T 5590-2004 Performance evaluation method of profile control agent, Q / SL 1421-1999 Gel-type water plugging and profile control agent and performance evaluation method.

[0036] 1. Conventional indicators:

[0037] Figure 4 is the thermal stability parameter of the system, Figure 5 is the thermal stability of the system at different temperatures;

[0038] The thermal stability of the system was tested. Figure 4 As shown: the gelation time is 2 days, the long-term stability of the system is good, and a high gelation strength is maintained within 12 days.

[0039] 2. Core sealing:

[0040] Core plugging experiments were carried out using core plugging equipment. After the working fluid gelled inside the core, it was displaced with formation water to test the breakthrough pressure and the plugging pressure after stabilization. The plugging property of the gel fluid was analyzed, and the permeabilities of 200mD, 500mD, and 1000mD were measured after standing for 24h + water drive breakthrough.

[0041] As attached Figure 6 , 7 The experimental results shown are core displacement experiments: after the gel was injected, the cores were all plugged. With the increase in the amount of gel injected, the displacement pressure rose faster and faster, the amplitude of the curve change increased, and the core plugging effect became better.

[0042] Utilizing the technical solution described in the present invention, or those skilled in the art designing a similar technical solution inspired by the technical solution of the present invention to achieve the above-mentioned technical effects, all fall within the protection scope of the present invention.

Claims

1. A deep profile control system, characterized by: The raw materials of the deep profile control system include: polyacrylamide with a concentration of 0.3-0.5%, a phenolic cross-linking agent with a concentration of 0.3-0.5%, and a cross-linking enhancer with a concentration of 0.3-0.5%.

2. The method for preparing a deep profile control system according to claim 1, characterized in that: The preparation steps include: Step 1: Weigh 200mL of tap water into a 500mL beaker, install a vertical stirrer, insert the stirring paddle into three-quarters of the liquid surface, start the vertical stirrer to make the prepared water form a vortex, and adjust the stirring speed of the vertical stirrer; Step 2: slowly and evenly add the weighed polyacrylamide with a concentration of 0.3%-0.5% into the vortex wall and stir until it is completely dissolved, then add the phenolic crosslinker with a concentration of 0.3%-0.5% and the crosslinking enhancer with a concentration of 0.3%-0.5% respectively, and continue stirring until it is completely dissolved, and the system solution is prepared; Step 3: Pour the prepared solution into a high temperature resistant glass bottle, seal the solution, and place it in a 60°C electric blast drying oven within 30 minutes.

3. The method for preparing a deep profile control system according to claim 2, characterized in that: In the step 2, the weighed polyacrylamide with a concentration of 0.3%-0.5% is slowly and evenly added into the vortex wall and stirred until it is completely dissolved for 1-2 hours.

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