CN101717625A - Clay stabilizing agent suitable for low-permeability oil pool - Google Patents

Abstract

The invention discloses a clay stabilizer suitable for low-permeability oil reservoirs, which is made of the following component raw materials according to mass percentage: 0.8-98% of 2-hydroxyethyltrimethylammonium chloride, 0-20% Inorganic salt containing ammonium or potassium ions, and the balance is tap water or oil field reinjection sewage; the clay stabilizer can effectively prevent clay from swelling, and the anti-swelling rate can reach more than 90%, and it has good compatibility with oil field reinjection sewage containing HPAM , does not produce flocs, has a low damage rate to the reservoir, and is suitable for low-permeability reservoirs developed by reinjecting sewage from HPAM oilfields.

Description

A Clay Stabilizer Suitable for Low Permeability Reservoirs

Technical field:

The invention relates to a clay stabilizer used in clay-containing low-permeability oil reservoirs.

Background technique:

Low permeability reservoirs during oilfield development, often containing clay minerals, are water sensitive. Among them, clay minerals expand, disperse, migrate, and block pore throats, which greatly reduces the original low permeability, which not only affects the productivity of oil wells, but also has a very bad and irreversible impact on the later development of oil fields.

Injecting clay stabilizers is an effective method to protect water-sensitive reservoirs. The cationic polymer clay stabilizer widely used in oil fields in recent years has high positive charge density, less dosage and long-lasting effect. However, this kind of clay stabilizer has a large molecular weight. Although it can achieve the purpose of anti-swelling and stabilization, it will cause great damage to low-permeability reservoirs and block pore throats. In addition, when the clay stabilizer with a large molecular weight is mixed with the oilfield reinjection sewage containing HPAM (polyacrylamide), the HPAM in the oilfield reinjection sewage is precipitated, causing the injection water to be turbid, reducing the quality of the injection water, and also causing a rise in water injection pressure. High, under-injection of wells and other issues. Therefore, for low-permeability water-sensitive reservoirs developed by injecting wastewater from HPAM-containing oilfields, a clay stabilizer that can effectively prevent clay swelling and has good compatibility with HPAM-containing oilfield wastewater is needed.

Invention content:

The technical problem to be solved by the present invention is to provide a method that can effectively prevent clay swelling and has good compatibility with reinjected sewage from HPAM-containing oilfields, and is suitable for the development of reinjected sewage from oilfields containing HPAM. Clay stabilizer for low permeability reservoirs.

For realizing above-mentioned purpose of the invention, technical scheme of the present invention is:

A clay stabilizer suitable for low-permeability reservoirs, made from the following raw materials in terms of mass percentage:

2-Hydroxyethyltrimethylammonium chloride 0.8～98%

Inorganic salt containing ammonium or potassium ions 0～20%

The balance is tap water or oilfield reinjection sewage

Wherein the ammonium ion or potassium ion inorganic salt is a kind of potassium chloride, ammonium chloride, potassium formate, ammonium formate, potassium acetate, ammonium acetate, potassium nitrate.

Preferably, the ammonium ion or potassium ion inorganic salt is one of potassium chloride or potassium formate.

A clay stabilizer suitable for low-permeability reservoirs is preferred, and its composition and mass percentage are as follows:

2-Hydroxyethyltrimethylammonium chloride 30～40%

Inorganic salts containing ammonium or potassium ions 5-15%

The balance is tap water or oilfield reinjection sewage

More preferably, the composition and mass percent of the clay stabilizer are as follows:

2-Hydroxyethyltrimethylammonium chloride 30%

Potassium Chloride 10%

Tap water or oil field reinjection sewage 60%

When the clay stabilizer of the present invention is applied to water flooding operations in low-permeability water-sensitive oil reservoirs, it is only necessary to mix the clay stabilizer of the present invention with oilfield reinjection sewage in a certain proportion. The mass percentage concentration of trimethyl ammonium chloride and potassium salt or ammonium salt is 0.8-2.5%.

The 2-hydroxyethyltrimethylammonium chloride in the formula of the present invention contains a strong polar group (hydroxyl group) in its structure, and its use feature is that it can be miscible with water in any proportion, and it can be mixed with oilfield reinjection sewage containing HPAM It has good compatibility, HPAM and 2-hydroxyethyltrimethylammonium chloride in sewage can still be dissolved in water after neutralization, and no flocs appear in water; and because 2-hydroxyethyltrimethylammonium The molecular weight (139.5) of ammonium chloride is very small, and 2-hydroxyethyltrimethylammonium chloride per unit mass contains more positive charges. Good ability to prevent clay swelling. 2-Hydroxyethyltrimethylammonium chloride is a strong polar molecule with positive charge and hydroxyl group. It has the function of cementing clay particles and preventing the migration of clay particles. Therefore, when the oil field reinjection sewage containing the clay stabilizer of the invention enters the oil reservoir containing clay, it can inhibit the swelling of the clay and protect the oil reservoir.

Technical effect of the present invention is:

1. The clay stabilizer involved in the present invention has a good anti-swelling effect, and the anti-swelling rate can reach more than 90%.

2. The clay stabilizer involved in the present invention has good compatibility with HPAM-containing oil field reinjection sewage, and does not produce flocs.

3. The clay stabilizer involved in the present invention has a low damage rate to oil reservoirs and is suitable for low-permeability oil reservoirs.

4. The clay stabilizer involved in the present invention is colorless, odorless, non-toxic and harmless, and has stable properties.

5. The clay stabilizer involved in the present invention has good weather resistance, acid and alkali resistance, good water solubility, and is convenient for on-site application.

Detailed ways:

Example 1

Add 5.7 tons of 70% liquid 2-hydroxyethyltrimethylammonium chloride in a ^10m mixing tank, then add 4.3 tons of tap water, mix well, and filter to obtain 10 tons of clay stabilizer products with a solid content of 40%.

Wherein 2-hydroxyethyltrimethylammonium chloride is commonly called as choline chloride, and 70% liquid 2-hydroxyethyltrimethylammonium chloride is a commercially available industrial grade product.

During use, be mixed with the clay stabilizer solution that contains the above-mentioned clay stabilizer product and be respectively 2%, 3%, 4%, 5%, 6% (mass percentage) with HPAM oil field reinjection sewage, its anti-swelling rate is shown in the table 1.

The anti-swelling rate is determined according to SY/T 5971-94 evaluation method of clay stabilizer for water injection.

Table 1 embodiment 1 clay stabilizer solution anti-swelling rate

Concentration/% 2 3 4 5 6 Anti-expansion rate/% 63.7 75.1 84.9 88.7 90.3

It is stipulated that when the anti-swelling rate of the clay stabilizer is greater than 60%, it is considered to meet the requirements. It can be seen from Table 1 that the use of 2-hydroxyethyltrimethylammonium chloride alone can meet the anti-swelling requirements.

Especially when the above-mentioned clay stabilizer solution is 6%, the anti-swelling rate reaches 90.3%.

Example 2

Add 5 tons of 20% potassium chloride solution to a ^10m3 mixing tank; then add 4.3 tons of 70% liquid 2-hydroxyethyltrimethylammonium chloride, then add 0.7 tons of tap water, mix well, and filter to obtain the solid content 10 t of 40% clay stabilizer.

20% potassium chloride solution: commercially available industrial grade solid potassium chloride is prepared by adding tap water.

With reference to the usage method of Example 1, the clay stabilizer solutions containing the above-mentioned clay stabilizer are respectively prepared as 2%, 3%, 4%, 5%, 6% (mass percentage), and its anti-swelling rate is shown in Table 2.

Table 2 embodiment 2 clay stabilizer solution anti-swelling rate

Concentration/% 2 3 4 5 6 Anti-expansion rate/% 67.9 80.6 88.6 91.4 92.5

As can be seen from Table 2, the clay stabilizer solution compounded with inorganic salt potassium chloride has better anti-swelling rate than the product of Example 1.

The principle is that potassium chloride and 2-hydroxyethyltrimethylammonium chloride have synergistic and complementary effects. Potassium ions enter the clay layer to prevent swelling, and 2-hydroxyethyltrimethylammonium chloride acts as charge neutralization on the periphery of clay particles, thereby achieving the purpose of swelling prevention. Has a high anti-expansion rate.

Example 3

Add 7.0 tons of 27% ammonium chloride solution into a 10m ³ mixing tank; then add 3.0 tons of 70% liquid 2-hydroxyethyltrimethylammonium chloride, mix well, and filter to obtain a stable clay with a solid content of 40% Agent 10 tons.

27% ammonium chloride solution: commercially available industrial grade solid ammonium chloride is prepared by adding tap water.

With reference to the usage method of Example 1, the clay stabilizer solutions that contain the above-mentioned clay stabilizer are respectively prepared as 2%, 3%, 4%, 5%, 6% (mass percentage), and its anti-swelling rate is shown in Table 3.

Table 3 embodiment 3 clay stabilizer solution anti-swelling rate

Concentration/% 2 3 4 5 6 Anti-expansion rate/% 60.7 74.6 80.7 85.1 88.0

As can be seen from Table 3, the anti-expansion rate of the product of Example 3 compounded with ammonium chloride can also meet the anti-expansion requirements. There is also synergy between ammonium chloride and 2-hydroxyethyltrimethylammonium chloride.

Example 4

Clay stabilizer composition and ratio: 0.16 tons of 50% 2-hydroxyethyltrimethylammonium chloride, 9.84 tons of oilfield reinjection sewage.

The clay stabilizer is directly applied to the water flooding operation of the low-permeability water-sensitive reservoir, and the anti-swelling ratio is measured to be 63.7%, which meets the anti-swelling requirement.

Example 5

The composition and proportion of the clay stabilizer: solid 2-hydroxyethyltrimethylammonium chloride with a concentration of 98% by mass.

With reference to the usage method of Example 1, it is prepared as a clay stabilizer solution containing 0.8% (mass percentage) of the above clay stabilizer.

The anti-swelling rate was determined to be 63.0%.

Example 6

Table 4 Comparison of anti-swelling ratio of clay stabilizer composed of different water quality

Composition and ratio of clay stabilizer 5 tons of 70% 2-hydroxyethyltrimethylammonium chloride; 2.5 tons of 20% potassium chloride solution; 2.5 tons of tap water. 5 tons of 70% 2-hydroxyethyltrimethylammonium chloride; 2.5 tons of 20% potassium chloride solution; 2.5 tons of oilfield reinjection sewage. Concentration of clay stabilizer solution/% 2 2 Anti-expansion rate/% 66.7 67.1

It can be seen from the above table that the clay stabilizer prepared by using oilfield reinjection sewage is beneficial to improve the anti-swelling effect due to the high salinity of oilfield reinjection sewage.

Example 7

Clay stabilizers made of different inorganic salts were formulated with reference to the usage method of Example 1 to be 5.0% (mass percentage) clay stabilizer solutions containing the following clay stabilizers.

The anti-swelling rate of the clay stabilizer that table 5 different inorganic salts constitute

clay stabilizer 30% A10% potassium formate; the balance is tap water. 30% A; 10% ammonium formate; the balance is tap water. 30% A; 10% potassium acetate; the balance is tap water. 30% A; 10% ammonium acetate; the balance is tap water. 30% of A; 10% of potassium nitrate; the balance is tap water. Anti-expansion rate% 90.6 84.3 87.5 81.9 87.1

Note: A in Table 5 represents 2-hydroxyethyltrimethylammonium chloride.

As can be seen from Table 5, potassium formate, ammonium formate, potassium acetate, ammonium acetate, and potassium nitrate can all be used in combination with 2-hydroxyethyltrimethylammonium chloride. Among them, the effect of potassium salt is better than that of ammonium salt.

Example 8

PDMDAAC (polydimethyldiallylammonium chloride) is a polyquaternium clay stabilizer widely used in oil fields. Get PDMDAAC (solid content 37%; Intrinsic viscosity number 145mL/g), each 10.0g of the clay stabilizer that embodiment 1 and embodiment 2 make respectively, then take the HPAM oil field containing HPAM in the No. Reinject sewage 190g, be mixed with the clay stabilizer solution that is 5% (mass percentage) containing clay stabilizer, the anti-swelling rate of the PDMDAAC clay stabilizer solution at this moment is 84.7%; After stirring 30min, filter with 0.45 μm filter membrane , dried to constant weight, and the content of suspended matter is shown in Table 6. Suspended solids content is measured with reference to SY/T 5329-94.

Suspended matter content after adding clay stabilizer in table 6 sewage

Types of Clay Stabilizers PDMDAAC Example 1 product Example 2 product Suspended matter content/mg·L ^-1 101.4 7.5 9.6

It can be seen from Table 6 that the clay stabilizer of the present invention has good compatibility with the HPAM-containing oil field reinjection sewage. Although charge neutralization exists, it does not lead to the precipitation of HPAM.

Example 9

With reference to SY/T 5358-2002 Reservoir Sensitivity Flow Experimental Evaluation Method, investigate the damage of the clay stabilizer of the present invention to the rock core.

Put the extracted and measured air permeability K _g core into the flow experiment device, simulate the formation temperature at 45°C, inject 2PV finely filtered brine, and after the pressure is stable, measure the flow rate, record the pressure difference, and calculate the permeability K ₁ . Instead of injecting clay stabilizer solution with a mass concentration of 5.0%, after injecting 5PV, change to injecting water. After injecting 5PV, measure the flow rate and pressure difference, and calculate the permeability K ₂ .

Calculation formula of core damage rate D _k : D _k = (1-K ₂ /K ₁ )×100%

Select PDMDAAC, the product of Example 1 and the product of Example 2, and use oilfield reinjection sewage to make a solution containing a clay stabilizer with a mass concentration of 5% respectively; use Daqing Sa zero group rock cores, and inject finely filtered brine and clay stabilizer solution in sequence and oilfield reinjection sewage, according to the change of core permeability, the adaptability of three clay stabilizers to low-permeability core was investigated. The test results are shown in Table 7.

Table 7 Core flow test results of three clay stabilizers

It can be seen from Table 7 that the core damage rate is very high, reaching 82.63%, without adding clay stabilizer and directly injecting oilfield reinjection sewage for development; Rock cores do more damage. This is because PDMDAAC has a large hydrodynamic volume, which blocks the pore throat; on the other hand, PDMDAAC has a slow molecular diffusion rate, and water molecules preferentially contact clay minerals to cause hydration expansion, resulting in a decrease in core permeability. However, the products of Example 1 and Example 2 with smaller molecular weights have less damage to low-permeability rock cores, and the damage rates are only 17.85% and 16.45%, indicating that the clay stabilizer of the present invention has better adaptability to low-permeability oil reservoirs.

Illustrate that clay stabilizer of the present invention has better ability to prevent clay swelling by above embodiment and experiment, the damage rate to the lower Daqing Sa zero group rock core of permeability is less, and the oil field sewage that contains HPAM in Daqing has better effect. compatibility. The invention provides a clay stabilizer product with excellent performance for developing clay-containing low-permeability oil reservoirs.

Claims (4)

1. clay stabilizer that is applicable to low-permeability oil pool, make by following component raw material by mass percentage:

2-hydroxyethyl trimethyl ammonium chloride 0.8～98%

The inorganic salt 0～20% that contain ammonium or potassium ion

Surplus is tap water or oil field return water

The inorganic salt that wherein contain ammonium or potassium ion are a kind of of Repone K, ammonium chloride, potassium formiate, ammonium formiate, potassium acetate, ammonium acetate or saltpetre.

2. according to the described clay stabilizer that is applicable to low-permeability oil pool of claim 1, the inorganic salt that contain ammonium or potassium ion wherein are a kind of in Repone K or the potassium formiate.

3. according to the described clay stabilizer that is applicable to low-permeability oil pool of claim 1, its composition and mass percent are as follows:

2-hydroxyethyl trimethyl ammonium chloride 30～40%

The inorganic salt 5～15% that contain ammonium or potassium ion

Surplus is tap water or oil field return water

4. according to the described clay stabilizer that is applicable to low-permeability oil pool of claim 1, its composition and mass percent are as follows:

2-hydroxyethyl trimethyl ammonium chloride 30%

Repone K 10%

Tap water or oil field return water 60%.