A method for increasing viscosity of cationic guar gum fracturing fluid

Abstract

The present application relates to the field of oilfield chemical technology and discloses a method for increasing the viscosity of a cationic guar gum fracturing fluid. The method comprises adding sulfate to a cationic guar gum fracturing fluid, wherein the guar gum content is 0.3% to 0.7% by mass, and adding 0.1% to 3% sulfate and 0.2% to 0.5% cross-linking agent, with the remainder being water for preparing the fluid. The present application adds sulfate to the cationic guar gum fracturing fluid. The sulfate ions in the sulfate can, through electrostatic attraction, achieve secondary cross-linking of the hydroxypropyl guar gum fracturing fluid cross-linked with the organic cross-linking agent, thereby enhancing its cross-linking density. This is manifested as a significant increase in the viscosity of the fracturing fluid without increasing the concentrations of the guar gum and cross-linking agent. The present application is applied to, for example, low-permeability carbonate reservoirs. While maintaining the same viscosity of the fracturing fluid, the amount of guar gum and cross-linking agent can be reduced, thereby reducing the cost of the fracturing fluid. Furthermore, the reduced amount of guar gum can reduce the residue content of the fracturing fluid after gel breaking, thus having good application prospects.

Description

Technical Field

[0001] The present application relates to the field of oilfield chemical technology, and in particular to a method for increasing the viscosity of a cationic guar gum fracturing fluid. Background Art

[0002] Fracturing fluid is used during the extraction of fluid minerals (oil, gas, fresh water, brine, hot water, etc.) to achieve high yields by leveraging the conductive forces of the fluid. In recent years, with the rapid rise in oil and natural gas extraction, the workload of oilfield fracturing operations has continued to increase. In most oilfield fracturing operations, a guar gum-based fluid is first prepared, followed by the addition of various modifiers and crosslinking agents. However, in actual operations, this method suffers from the high viscosity of the guar gum-based fluid in the storage tank, resulting in high pump circulation resistance. This leads to unstable crosslinking and low viscosity of the fracturing fluid, compromising the stability and success rate of the fracturing operation.

[0003] Patent document CN104087282A discloses a fracturing fluid viscosity-increasing method, which enhances the cross-linking effect of guar gum fracturing fluid by adjusting the pH to alkaline, thereby increasing the viscosity of the prepared fracturing fluid. This method is simple to operate and easy to prepare. The prepared fracturing fluid has a certain salt resistance and low requirements for the preparation water. Even when using seawater (containing salt), it has a viscosity-increasing effect. However, research has found that the above-mentioned viscosity-increasing method and conventional viscosity-increasing methods both increase the viscosity of the fracturing fluid through a single cross-linking, and the viscosity-increasing effect is limited, which still makes it difficult to meet the requirements of the market's high-performance standards. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the purpose of the present application is to provide a method for increasing the viscosity of a cationic guar gum fracturing fluid.

[0005] To achieve the above objectives, this application adopts the following technical solutions:

[0006] A method for increasing the viscosity of a cationic guar gum fracturing fluid comprises the following steps: calculating by mass percentage, the guar gum content is 0.3% to 0.7%, adding 0.1% to 3% sulfate and 0.2% to 0.5% crosslinking agent, and the balance being water for preparing the fluid.

[0007] Preferably, the guar gum is hydroxypropyl guar gum trimethylammonium chloride, and the structural formula is shown in formula (1):

[0008]

[0009] Preferably, the sulfate ion content in the ion composition of the water used for the solution is less than 200 mg / L, the cation content is lower than the solubility of its sulfate, and the content of other anions is not limited.

[0010] Preferably, the sulfate is selected from one or more of sodium sulfate, potassium sulfate and ammonium sulfate.

[0011] Preferably, the cross-linking agent is selected from one or both of organic boron and organic zirconium.

[0012] Furthermore, the method for increasing the viscosity of the cationic guar gum fracturing fluid comprises the following steps: first dissolving sulfate in the preparation water (without precipitation or other incompatibility phenomena), then adding the guar gum to fully dissolve it, then adding the crosslinking agent, and stirring evenly to obtain the product.

[0013] In a preferred embodiment of the present application, the method for preparing the water for the solution is: adding 31.5 g / L of sodium chloride, 3 g / L of potassium chloride, 1.4 g / L of calcium chloride and 6 g / L of magnesium chloride to a beaker filled with distilled water.

[0014] In another preferred embodiment of the present application, the method for preparing the water for the solution is: adding 50 g / L of sodium chloride into a beaker filled with distilled water.

[0015] In another preferred embodiment of the present application, the method for preparing the water for the solution is: adding 100 g / L of sodium chloride into a beaker filled with distilled water.

[0016] Compared with the prior art, this application has the following beneficial effects:

[0017] (1) The present application adds sulfate to the cationic guar gum fracturing fluid. The sulfate ions in the sulfate can achieve secondary crosslinking of the hydroxypropyl guar gum fracturing fluid crosslinked with an organic crosslinker through the action of electrostatic gravitons, thereby enhancing its crosslinking density. This is manifested as a significant increase in the viscosity of the fracturing fluid without increasing the concentration of guar gum and crosslinker.

[0018] (2) The present invention is applied to, for example, low-permeability carbonate reservoirs. While maintaining the same viscosity of the fracturing fluid, the amount of guar gum and cross-linking agent can be reduced, thereby reducing the cost of the fracturing fluid. Moreover, the reduction in the amount of guar gum can reduce the residue content after the fracturing fluid breaks, which has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0020] Figure 1 The present invention provides the rheological curves of fracturing fluids with different concentrations of sodium sulfate added in simulated seawater when fracturing fluids are prepared with 0.6% hydroxypropyl guar trimethyl ammonium chloride and 0.4% organoboron, and when fracturing fluids are prepared with 0.5% hydroxypropyl guar trimethyl ammonium chloride and 0.3% organoboron.

[0021] Figure 2The rheological curves of fracturing fluids containing 0.5% hydroxypropyl guar trimethylammonium chloride, 0.4% organic boron and different concentrations of sodium sulfate were added to a 5% sodium chloride solution.

[0022] Figure 3 The rheological curves of fracturing fluids containing 0.6% hydroxypropyl guar trimethylammonium chloride, 0.4% organic boron and different concentrations of sodium sulfate were added to a 10% sodium chloride solution.

[0023] Figure 4 The present invention provides the rheological curves of fracturing fluids with different concentrations of ammonium sulfate added in simulated seawater when fracturing fluids are prepared with 0.3% hydroxypropyl guar gum trimethyl ammonium chloride and 0.2% organic zirconium, and when fracturing fluids are prepared with 0.7% hydroxypropyl guar gum trimethyl ammonium chloride and 0.5% organic zirconium. DETAILED DESCRIPTION

[0024] The present application is described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present application, but are not intended to limit the present application in any form. It should be noted that those skilled in the art may make several variations and improvements without departing from the scope of the present application. These all fall within the scope of protection of the present application.

[0025] Example 1

[0026] The specific preparation process of simulated liquid water includes the following steps:

[0027] (1) Add distilled water to a beaker.

[0028] (2) Add 31.5 g / L sodium chloride, 3 g / L potassium chloride, 1.4 g / L calcium chloride, and 6 g / L magnesium chloride to a beaker containing distilled water.

[0029] (3) Add a rotor to the beaker and place the beaker on a magnetic stirrer to stir thoroughly for 15 minutes.

[0030] (4) After sufficient stirring, the simulated liquid water can be obtained.

[0031] The fracturing fluid viscosification and preparation process includes the following steps:

[0032] (1) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the simulated solution water and stir thoroughly.

[0033] The structural formula of hydroxypropyl guanidine trimethylammonium chloride is as follows:

[0034]

[0035] (2) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0036] Example 2

[0037] The water used for the simulated liquid preparation was the same as that in Example 1.

[0038] The fracturing fluid viscosification and preparation process includes the following steps:

[0039] (1) Add 1% sodium sulfate to the simulated solution water and stir thoroughly.

[0040] (2) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0041] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0042] Example 3

[0043] The water used for the simulated liquid preparation was the same as that in Example 1.

[0044] The fracturing fluid viscosification and preparation process includes the following steps:

[0045] (1) Add 2% sodium sulfate to the simulated solution water and stir thoroughly.

[0046] (2) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0047] The structural formula of hydroxypropyl guanidine trimethylammonium chloride is as follows:

[0048] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0049] The obtained fracturing fluid was placed in a rheometer to measure its rheological curve at 90°C.

[0050] Example 4

[0051] The water used for the simulated liquid preparation was the same as that in Example 1.

[0052] The fracturing fluid viscosification and preparation process includes the following steps:

[0053] (1) Add 3% sodium sulfate to the simulated solution water and stir thoroughly.

[0054] (2) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0055] The structural formula of hydroxypropyl guanidine trimethylammonium chloride is as follows:

[0056] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0057] Example 5

[0058] The water used for the simulated liquid preparation was the same as that in Example 1.

[0059] The fracturing fluid viscosification and preparation process includes the following steps:

[0060] (1) Add 0.5% hydroxypropyl guanidine trimethylammonium chloride to the simulated solution water and stir thoroughly.

[0061] (2) Add 0.3% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0062] The obtained fracturing fluid was placed in a rheometer to measure its rheological curve at 90°C.

[0063] Example 6

[0064] The water used for the simulated liquid preparation was the same as that in Example 1.

[0065] The fracturing fluid viscosification and preparation process includes the following steps:

[0066] (1) Add 2% sodium sulfate to the simulated solution water and stir thoroughly.

[0067] (2) Add 0.5% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0068] The structural formula of hydroxypropyl guanidine trimethylammonium chloride is as follows:

[0069] (3) Add 0.3% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0070] The fracturing fluids obtained in Examples 1 to 6 were placed in a rheometer to measure their rheological curves at 90°C. Figure 1 shown.

[0071] Example 7

[0072] The specific preparation process of simulated liquid water includes the following steps:

[0073] (1) Add distilled water to a beaker.

[0074] (2) Add 50 g / L of sodium chloride to a beaker containing distilled water.

[0075] (3) Add a rotor to the beaker and place the beaker on a magnetic stirrer to stir thoroughly for 15 minutes.

[0076] (4) After sufficient stirring, the simulated liquid water can be obtained.

[0077] The fracturing fluid viscosification and preparation process includes the following steps:

[0078] (1) Add 0.5% hydroxypropyl guanidine trimethylammonium chloride to the simulated solution water and stir thoroughly.

[0079] (2) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0080] Example 8

[0081] The water used for the simulated liquid preparation was the same as that in Example 7.

[0082] The fracturing fluid viscosification and preparation process includes the following steps:

[0083] (1) Add 0.5% sodium sulfate to the simulated solution water and stir thoroughly.

[0084] (2) Add 0.5% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0085] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0086] Example 9

[0087] The water used for the simulated liquid preparation was the same as that in Example 7.

[0088] The fracturing fluid viscosification and preparation process includes the following steps:

[0089] (1) Add 1% sodium sulfate to the simulated solution water and stir thoroughly.

[0090] (2) Add 0.5% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0091] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0092] Example 10

[0093] The water used for the simulated liquid preparation was the same as that in Example 7.

[0094] The fracturing fluid viscosification and preparation process includes the following steps:

[0095] (1) Add 2% sodium sulfate to the simulated solution water and stir thoroughly.

[0096] (2) Add 0.5% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0097] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0098] The fracturing fluids obtained in Examples 7 to 10 were placed in a rheometer to measure their rheological curves at 90°C. Figure 2 shown.

[0099] Example 11

[0100] The specific preparation process of simulated liquid water includes the following steps:

[0101] (1) Add distilled water to a beaker.

[0102] (2) Add 100 g / L of sodium chloride to a beaker containing distilled water.

[0103] (3) Add a rotor to the beaker and place the beaker on a magnetic stirrer to stir thoroughly for 15 minutes.

[0104] (4) After sufficient stirring, the simulated liquid water can be obtained.

[0105] The fracturing fluid viscosification and preparation process includes the following steps:

[0106] (1) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the simulated solution water and stir thoroughly.

[0107] (2) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0108] The obtained fracturing fluid was placed in a rheometer to measure its rheological curve at 90°C.

[0109] Example 12

[0110] The water used for the simulated liquid preparation was the same as that in Example 11.

[0111] The fracturing fluid viscosification and preparation process includes the following steps:

[0112] (1) Add 0.5% sodium sulfate to the simulated solution water and stir thoroughly.

[0113] (2) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0114] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0115] Example 13

[0116] The water used for the simulated liquid preparation was the same as that in Example 11.

[0117] The fracturing fluid viscosification and preparation process includes the following steps:

[0118] (1) Add 1% sodium sulfate to the simulated solution water and stir thoroughly.

[0119] (2) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0120] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0121] Example 14

[0122] The water used for the simulated liquid preparation was the same as that in Example 11.

[0123] The fracturing fluid viscosification and preparation process includes the following steps:

[0124] (1) Add 2% sodium sulfate to the simulated solution water and stir thoroughly.

[0125] (2) Add 0.6% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0126] (3) Add 0.4% of organic boron to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0127] The fracturing fluids obtained in Examples 11 to 14 were placed in a rheometer to measure their rheological curves at 90°C. Figure 3 shown.

[0128] Example 15

[0129] The water used for the simulated liquid preparation was the same as that in Example 1.

[0130] The fracturing fluid viscosification and preparation process includes the following steps:

[0131] (1) Add 0.3% hydroxypropyl guanidine trimethylammonium chloride to the simulated solution water and stir thoroughly.

[0132] The structural formula of hydroxypropyl guanidine trimethylammonium chloride is as follows:

[0133] (2) Add 0.2% organic zirconium to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0134] Example 16

[0135] The water used for the simulated liquid preparation was the same as that in Example 1.

[0136] The fracturing fluid viscosification and preparation process includes the following steps:

[0137] (1) Add 0.1% ammonium sulfate to the simulated solution water and stir thoroughly.

[0138] (2) Add 0.3% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0139] (3) Add 0.2% organic zirconium to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0140] Example 17

[0141] The water used for the simulated liquid preparation was the same as that in Example 1.

[0142] The fracturing fluid viscosification and preparation process includes the following steps:

[0143] (1) Add 1% ammonium sulfate to the simulated solution water and stir thoroughly.

[0144] (2) Add 0.3% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0145] (3) Add 0.2% organic zirconium to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0146] Example 18

[0147] The water used for the simulated liquid preparation was the same as that in Example 1.

[0148] The fracturing fluid viscosification and preparation process includes the following steps:

[0149] (1) Add 0.7% hydroxypropyl guanidine trimethylammonium chloride to the simulated solution water and stir thoroughly.

[0150] The structural formula of hydroxypropyl guanidine trimethylammonium chloride is as follows:

[0151] (2) Add 0.5% organic zirconium to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0152] Example 19

[0153] The water used for the simulated liquid preparation was the same as that in Example 1.

[0154] The fracturing fluid viscosification and preparation process includes the following steps:

[0155] (1) Add 0.1% ammonium sulfate to the simulated solution water and stir thoroughly.

[0156] (2) Add 0.7% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0157] (3) Add 0.5% organic zirconium to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0158] Example 20

[0159] The water used for the simulated liquid preparation was the same as that in Example 1.

[0160] The fracturing fluid viscosification and preparation process includes the following steps:

[0161] (1) Add 1% ammonium sulfate to the simulated solution water and stir thoroughly.

[0162] (2) Add 0.7% hydroxypropyl guanidine trimethylammonium chloride to the solution and stir thoroughly.

[0163] (3) Add 0.5% organic zirconium to the uniformly stirred guar gum base liquid and stir thoroughly to obtain the product.

[0164] The fracturing fluids obtained in Examples 15 to 20 were placed in a rheometer to measure their rheological curves at 90°C. Figure 4 shown.

[0165] The above describes the specific embodiments of the present application. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the substantive content of the present application.

Claims

1. A method for increasing the viscosity of a cationic guar gum fracturing fluid, characterized in that: In terms of mass percentage, the cationic guar gum content is 0.3% to 0.7%, the sulfate content is 0.1% to 3%, and the cross-linking agent content is 0.2% to 0.5%. The balance is water for preparing the solution. The sulfate ion content in the ion composition of the water for preparing the solution is less than 200 mg / L. The sulfate ions in the sulfate achieve secondary cross-linking of the hydroxypropyl guar gum fracturing fluid cross-linked by the cross-linking agent through electrostatic attraction. The cationic guar gum is hydroxypropyl guar gum trimethylammonium chloride, and its structural formula is shown in formula (1): ， The viscosity increasing method comprises the following steps: firstly dissolving sulfate in liquid preparation water, then adding guar gum to fully dissolve it, then adding a cross-linking agent, and stirring evenly.

2. The method for increasing the viscosity of the cationic guar gum fracturing fluid according to claim 1, wherein: The sulfate is selected from one or more of sodium sulfate, potassium sulfate and ammonium sulfate.

3. The method for increasing the viscosity of a cationic guar gum fracturing fluid according to claim 1, wherein: The cross-linking agent is selected from one or two of organic boron and organic zirconium.

4. The method for increasing the viscosity of a cationic guar gum fracturing fluid according to claim 1, wherein: The water for the solution is prepared by adding 31.5 g / L of sodium chloride, 3 g / L of potassium chloride, 1.4 g / L of calcium chloride, and 6 g / L of magnesium chloride into a beaker filled with distilled water.

5. The method for increasing the viscosity of a cationic guar gum fracturing fluid according to claim 1, wherein: The method for preparing the water for the solution is as follows: adding 50 g / L of sodium chloride into a beaker filled with distilled water.

6. The method for increasing the viscosity of a cationic guar gum fracturing fluid according to claim 1, wherein: The method for preparing the water for the solution is as follows: adding 100 g / L of sodium chloride into a beaker filled with distilled water.

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