Viscosity-improving filtrate reducer as well as preparation method and application thereof

Abstract

The invention provides a viscosity-improving filtrate reducer as well as a preparation method and application thereof. The viscosity-improving filtrate reducer is a polymerization product of modified corncob powder and a polymer, the modified corncob powder is corncob powder modified by an alkaline compound. The viscosity-improving and filtrate-reducing agent has the advantages of environmental protection, tackifying property and filtrate-reducing property, is low in production cost, and is a low-cost drilling fluid treating agent with tackifying property, filtrate-reducing property and environmental protection property.

Description

Technical Field

[0001] The present invention belongs to the technical field of oilfield chemicals, and in particular relates to a viscosity increasing and fluid loss reducing agent, a preparation method thereof, and an application thereof. Background Art

[0002] In addition to harming formation water, reservoirs, and construction workers, traditional drilling fluids also produce drilling waste that pollutes surface water, damages soil structure, affects plant and animal growth, and endangers human health. Therefore, the development of natural, biodegradable, and heavy metal-free environmentally friendly drilling fluid treatment agents is urgent. Natural materials such as lignin, tannin extracts, tannins, starch, cellulose, lignite, and plant gums are highly favored by oilfield chemists. Modified products obtained through carboxylation and sulfonation have become important oilfield chemical materials. While there are many examples of fluid loss additives prepared from natural plant materials, they still face challenges such as high cost, insufficient biodegradability, and inability to inhibit clay hydration expansion, which need to be addressed. Summary of the Invention

[0003] One aspect of the present invention provides a viscosity-enhancing and fluid loss-reducing agent, which is a polymerization product of modified corncob powder and a polymer; the modified corncob powder is corncob powder modified by an alkaline compound.

[0004] According to a specific embodiment of the present invention, the mass ratio of the corncob powder to the polymer is 10:1.

[0005] According to a specific embodiment of the present invention, the particle size of the corncob powder is not higher than 40 mesh.

[0006] According to a specific embodiment of the present invention, the alkaline compound is sodium hydroxide and / or potassium hydroxide.

[0007] According to a specific embodiment of the present invention, the polymer includes at least one of polyacrylamide, polyethylene terephthalate, polybutylene terephthalate and polymethyl methacrylate.

[0008] According to a specific embodiment of the present invention, the corncob powder is obtained by crushing corncobs;

[0009] Preferably, the corn cob is an air-dried corn cob.

[0010] It should be noted that the present invention is not particularly limited to the variety of corn from which the corncob is obtained. Generally, commercially available corncobs derived from any variety of corn can be used in the present invention.

[0011] The second aspect of the present invention provides a method for preparing the viscosity-enhancing and fluid loss-reducing agent according to the first aspect of the present invention, which comprises the following steps:

[0012] 1) grinding corn cobs to obtain corn cob powder;

[0013] 2) modifying the corncob powder with the alkaline compound to obtain the modified corncob powder;

[0014] 3) dispersing the modified corncob powder in an inorganic salt solution to obtain a modified corncob powder dispersion;

[0015] 4) causing the polymer to undergo a polymerization reaction with the modified corncob powder in the modified corncob powder dispersion to obtain the viscosity-enhancing fluid loss reducer.

[0016] The present invention utilizes alkaline compounds to modify corn cob powder. The alkaline compounds destroy the molecular structure of the corn cob powder and provide an alkaline environment, which is beneficial for maintaining the stability of the modified corn cob powder and the polymer during the reaction process; and using an inorganic salt solution as the reaction environment for the polymerization reaction of the modified corn cob powder and the polymer is beneficial for increasing the reaction rate of the polymerization reaction.

[0017] According to a specific embodiment of the present invention, in step 1), the corn cob is crushed and then sieved to obtain the corn cob powder;

[0018] Preferably, the corn cob is air-dried and then crushed;

[0019] Preferably, the particle size of the corncob powder is not higher than 40 mesh.

[0020] According to a specific embodiment of the present invention, in step 2), the alkaline compound is prepared into an alkaline compound solution and then mixed with the corn cob powder, subjected to the modification, and filtered to obtain the modified corn cob powder;

[0021] Preferably, the volume of the alkaline compound solution is sufficient to disperse the corncob powder so as to ensure uniform modification of the corncob powder;

[0022] Preferably, to ensure that the corn cob powder can be uniformly modified in the alkaline compound solution, the solid-liquid ratio of the corn cob powder to the alkaline compound solution is 1:10;

[0023] Preferably, the mass of the alkaline compound solution is taken as 100%, and the concentration of the alkaline compound is 20 wt %;

[0024] Preferably, the solvent in the alkaline compound solution is water.

[0025] According to a specific embodiment of the present invention, in step 3), the solid-to-liquid ratio of the modified corncob powder to the inorganic salt solution is 1:3;

[0026] Preferably, the mass of the inorganic salt solution is taken as 100%, and the concentration of the inorganic salt is 20 wt %;

[0027] Preferably, the inorganic salt in the inorganic salt solution includes at least one of calcium chloride, ammonium chloride, zinc chloride and sodium nitrate;

[0028] Preferably, the solvent in the inorganic salt solution is water.

[0029] According to a specific embodiment of the present invention, in step 2), the modification temperature is 80° C.; and / or the modification time is not less than 30 min; and / or

[0030] The step 3) is carried out at 70° C.; and / or

[0031] In step 4), the polymerization reaction temperature is 70° C. and / or the duration is not less than 30 minutes;

[0032] Preferably, the entire process from step 2) to step 4) is carried out under stirring.

[0033] According to a specific embodiment of the present invention, in step 4), the polymerization product obtained by the polymerization reaction is dried to obtain the viscosity-enhancing fluid loss reducer.

[0034] Use of the viscosity increasing and fluid loss reducing agent according to one embodiment of the present invention or the viscosity increasing and fluid loss reducing agent prepared by the method according to the second embodiment of the present invention in preparing drilling fluid.

[0035] Beneficial effects of the present invention:

[0036] To address the problems of existing fluid loss additives made from natural plant materials, such as high cost, insufficient degradability, and inability to inhibit clay hydration expansion, the present invention provides a viscosity-enhancing fluid loss additive, its preparation method, and application. Compared with existing technologies, the present invention has at least the following advantages:

[0037] 1. The viscosity-enhancing and fluid-loss reducer provided by the present invention uses corncob powder as a main raw material, which is modified with an alkaline compound to obtain modified corncob powder. The modified corncob powder and a polymer are then polymerized in an inorganic salt solution to obtain the viscosity-enhancing and fluid-loss reducer. The mass ratio of corncob powder to polymer used is as high as 10:1. The large amount of corncob powder used and the significant reduction in the amount of polymer used enhance the biodegradability of the viscosity-enhancing and fluid-loss reducer and endow it with environmentally friendly properties. After the viscosity-enhancing and fluid-loss reducer enters the formation along with the drilling fluid, it will not damage the formation and can protect the formation.

[0038] 2. The modified corncob used in the viscosity-enhancing and fluid-loss additive provided by the present invention contains a large amount of cellulose, starch, and heteropolysaccharides, which is beneficial for improving the viscosity-enhancing performance of the viscosity-enhancing and fluid-loss additive. Adding 5% of the viscosity-enhancing and fluid-loss additive to the modified starch drilling fluid can achieve a viscosity increase rate of 45%.

[0039] 3. The viscosity-enhancing fluid loss reducer provided by the present invention combines chemical fluid loss reduction and physical fluid loss reduction, specifically:

[0040] The cellulose, starch, and polysaccharides in the modified corncob can also enhance the adsorption of the viscosity-enhancing fluid loss agent on the surface of clay particles in the drilling fluid, inhibiting clay hydration and expansion, reducing the fluid loss of the drilling fluid, and exerting a chemical fluid loss reduction effect. The modified corncob powder itself can block the pores of the filter cake formed by the drilling fluid, playing a physical fluid loss reduction role. The physical and chemical fluid loss reduction effects complement each other, giving the viscosity-enhancing fluid loss agent good fluid loss reduction performance. Adding 5% of the viscosity-enhancing fluid loss agent to the modified starch drilling fluid can achieve a fluid loss reduction rate of 55%.

[0041] 4. Corn cob powder with a particle size of no more than 40 mesh can be used in the present invention. In addition, corn cob powder with different particle sizes can achieve different modification effects. The viscosity-increasing and fluid loss-reducing properties of the final viscosity-increasing and fluid loss-reducing agents prepared are also different. Corn cob powder with different particle sizes can be used as the main raw material to prepare the viscosity-increasing and fluid loss-reducing agents provided by the present invention as needed.

[0042] 5. The raw materials used in the viscosity-enhancing and filtration-loss-reducing agent provided by the present invention mainly include corn cob powder, as well as a small amount of alkali, inorganic salts and common polymers. The raw materials are cheap and easy to obtain, and a large amount of discarded corn cobs are also utilized, which greatly reduces the raw material cost. In terms of the preparation steps, the preparation method of the viscosity-enhancing and filtration-loss-reducing agent is simple. It only requires modifying the corn cob powder and then reacting it with the polymer in an inorganic salt solution. It also reduces manpower and equipment costs, and achieves an overall reduction in the cost of preparing drilling fluid agents using natural plant materials.

[0043] In summary, the viscosity increasing and fluid loss reducing agent provided by the present invention is a drilling fluid treatment agent that has both viscosity increasing properties, fluid loss reducing properties and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The X-ray diffraction pattern of the modified corncob powder obtained in step 2) of Example 1 and the X-ray diffraction pattern of the viscosity-enhancing and fluid loss reducer prepared in step 4) are shown, wherein spectrum line 1 is the X-ray diffraction pattern of the modified corncob powder, and spectrum line 2 is the X-ray diffraction pattern of the viscosity-enhancing and fluid loss reducer. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to examples. However, the examples are merely illustrative and do not limit the present invention in any way.

[0046] Corn cobs used in Examples 1 to 5 were purchased from Shihezi Jinshi Seed Co., Ltd.

[0047] Polyacrylamide used in Example 1 and Example 5 was purchased from Kunshan Rongzhiyu Fine Chemical Co., Ltd.

[0048] The polyethylene terephthalate used in Example 2 and the polybutylene terephthalate used in Example 3 were purchased from Shanghai Xuhuitong Plastics Co., Ltd.

[0049] The polymethyl methacrylate used in Example 4 was purchased from Jinan Linsheng Chemical Co., Ltd.

[0050] The amino inhibitor used in the evaluation of the fluid loss reduction and viscosity-increasing performance of the viscosity-enhancing fluid loss reducer was purchased from Xinxiang Zhengyang Chemical Co., Ltd., the modified starch fluid loss reducer was purchased from China National Petroleum Corporation Bohai Drilling Engineering Co., Ltd., the liquid lubricant RH-220 was purchased from Korla Mingyang Industry and Trade Co., Ltd., and the solid lubricant RAN-01 was purchased from Shanghai Bohei Biotechnology Co., Ltd.

[0051] Example 1

[0052] 1) The corn cobs are naturally air-dried, crushed using a ball mill, and then graded using a standard test sieve according to mesh size (from coarse to fine) to obtain corn cob powder (including 40-80 mesh corn cob powder, 80-120 mesh corn cob powder, 120-160 mesh corn cob powder, 160-200 mesh corn cob powder, and corn cob powder of 200 mesh or above, and each grade of corn cob powder is sealed in a sealed bag for use). Corn cob powder with a particle size of no more than 40 mesh can be used in the embodiments of the present invention. Here, 40-80 mesh corn cob powder is exemplarily used for the subsequent steps;

[0053] 2) Weighing 100 g of the 40-80 mesh corncob powder obtained in step 1) and adding it to 1000 mL of a sodium hydroxide aqueous solution (the mass of the sodium hydroxide aqueous solution is calculated as 100%, and the mass of the sodium hydroxide accounts for 20 wt%) at a solid-to-liquid ratio of 1:10, and modifying the corncob powder by stirring at 6000 rpm for 30 min at 80° C. After modification, filtering the mixture, collecting the filter residue, and washing it with deionized water to obtain modified corncob powder;

[0054] 3) mixing the modified corncob powder obtained in step 2) with a calcium chloride aqueous solution (the mass of the calcium chloride aqueous solution is calculated as 100%, and the mass of the calcium chloride accounts for 20 wt%) at a solid-to-liquid ratio of 1:3 (i.e., 3 mL of the calcium chloride aqueous solution is dispersed per gram of modified corncob powder), and stirring at 6000 rpm at 70° C. to uniformly disperse the modified corncob powder to obtain a modified corncob powder dispersion;

[0055] 4) Adding 10 g of polyacrylamide to the modified corncob powder dispersion obtained in step 3) at 70° C. while stirring, and continuing stirring for 30 minutes to carry out a polymerization reaction. After the reaction is completed, the reaction product is dried to obtain a viscosity-enhancing and fluid loss-reducing agent.

[0056] Example 2

[0057] 1) The corn cobs are naturally air-dried, crushed using a ball mill, and then graded using a standard test sieve according to mesh size (from coarse to fine) to obtain corn cob powder (including 40-80 mesh corn cob powder, 80-120 mesh corn cob powder, 120-160 mesh corn cob powder, 160-200 mesh corn cob powder, and corn cob powder of 200 mesh or above, and each grade of corn cob powder is sealed in a sealed bag for use). Corn cob powder with a particle size of no more than 40 mesh can be used in the embodiments of the present invention. Here, 80-120 mesh corn cob powder is exemplarily used for the subsequent steps;

[0058] 2) Weighing 100 g of the 80-120 mesh corncob powder obtained in step 1) and adding it to 1000 mL of a sodium hydroxide aqueous solution (the mass of the sodium hydroxide aqueous solution is calculated as 100%, and the mass of the sodium hydroxide accounts for 20 wt%) at a solid-to-liquid ratio of 1:10, and modifying the corncob powder by stirring at 6000 rpm for 30 min at 80° C. After modification, filtering, collecting the filter residue, and washing it with deionized water to obtain modified corncob powder;

[0059] 3) mixing the modified corncob powder obtained in step 2) with an aqueous ammonium chloride solution (the mass of the aqueous ammonium chloride solution is calculated as 100%, and the mass of the ammonium chloride accounts for 20 wt%) at a solid-to-liquid ratio of 1:3 (i.e., 3 mL of the aqueous ammonium chloride solution is used to disperse each gram of the modified corncob powder), and stirring at 6000 rpm at 70° C. to uniformly disperse the modified corncob powder to obtain a modified corncob powder dispersion;

[0060] 4) Adding 10 g of polyethylene terephthalate to the modified corncob powder dispersion obtained in step 3) at 70° C. while stirring, and continuing stirring for 30 minutes to carry out a polymerization reaction. After the reaction is completed, the reaction product is dried to obtain a viscosity-enhancing and fluid loss reducer.

[0061] Example 3

[0062] 1) The corn cobs are naturally air-dried, crushed using a ball mill, and then graded using a standard test sieve according to mesh size (from coarse to fine) to obtain corn cob powder (including 40-80 mesh corn cob powder, 80-120 mesh corn cob powder, 120-160 mesh corn cob powder, 160-200 mesh corn cob powder, and corn cob powder of 200 mesh or above, and each grade of corn cob powder is sealed in a sealed bag for use). Corn cob powder with a particle size of no more than 40 mesh can be used in the embodiments of the present invention. Here, 120-160 mesh corn cob powder is exemplarily used for the subsequent steps;

[0063] 2) Weighing 100 g of the 120-160 mesh corncob powder obtained in step 1) and adding it to 1000 mL of a sodium hydroxide aqueous solution (the mass of the sodium hydroxide aqueous solution is calculated as 100%, and the mass of the sodium hydroxide accounts for 20 wt%) at a solid-to-liquid ratio of 1:10, and modifying the corncob powder by stirring at 6000 rpm for 30 min at 80° C. After modification, filtering, collecting the filter residue, and washing it with deionized water to obtain modified corncob powder;

[0064] 3) mixing the modified corncob powder obtained in step 2) and a zinc chloride aqueous solution (the weight of the zinc chloride aqueous solution is calculated as 100%, and the weight of the zinc chloride accounts for 20 wt%) at a solid-liquid ratio of 1:3 (i.e., 3 mL of the zinc chloride aqueous solution is dispersed per gram of the modified corncob powder), and stirring at 6000 rpm at 70° C. to uniformly disperse the modified corncob powder to obtain a modified corncob powder dispersion;

[0065] 4) Adding 10 g of polybutylene terephthalate to the modified corncob powder dispersion obtained in step 3) at 70° C. while stirring, and continuing stirring for 30 minutes to carry out a polymerization reaction. After the reaction is completed, the reaction product is dried to obtain a viscosity-enhancing and fluid loss reducer.

[0066] Example 4

[0067] 1) The corn cobs are naturally air-dried, crushed using a ball mill, and then graded using a standard test sieve according to mesh size (from coarse to fine) to obtain corn cob powder (including 40-80 mesh corn cob powder, 80-120 mesh corn cob powder, 120-160 mesh corn cob powder, 160-200 mesh corn cob powder, and corn cob powder of 200 mesh or above. Each grade of corn cob powder is sealed in a sealed bag and ready for use). Corn cob powder with a particle size of no more than 40 mesh can be used in the embodiments of the present invention. Here, 160-200 mesh corn cob powder is exemplarily used for the subsequent steps;

[0068] 2) Weighing 100 g of the 160-200 mesh corncob powder obtained in step 1) and adding it to 1000 mL of a sodium hydroxide aqueous solution (the mass of the sodium hydroxide aqueous solution is calculated as 100%, and the mass of the sodium hydroxide accounts for 20 wt%) at a solid-to-liquid ratio of 1:10, and modifying it at 6000 rpm and 80° C. for 30 min. After completion, filtering, collecting the filter residue, and washing it with deionized water to obtain modified corncob powder;

[0069] 3) mixing the modified corncob powder obtained in step 2) and a sodium nitrate aqueous solution (the mass of the sodium nitrate aqueous solution is calculated as 100% and the mass of the sodium nitrate is calculated as 20 wt%) at a solid-to-liquid ratio of 1:3 (i.e., 3 mL of the sodium nitrate aqueous solution is dispersed per gram of the modified corncob powder), and stirring at 6000 rpm at 70° C. to uniformly disperse the modified corncob to obtain a modified corncob powder dispersion;

[0070] 4) Adding 10 g of polymethyl methacrylate to the modified corncob powder dispersion obtained in step 3) at 70° C. while stirring, and continuing stirring for 30 minutes to carry out a polymerization reaction. After the reaction is completed, the reaction product is dried to obtain a viscosity-enhancing and fluid loss reducer.

[0071] Example 5

[0072] 1) The corn cobs are naturally air-dried, crushed using a ball mill, and then graded using a standard test sieve according to mesh size (from coarse to fine) to obtain corn cob powder (including 40-80 mesh corn cob powder, 80-120 mesh corn cob powder, 120-160 mesh corn cob powder, 160-200 mesh corn cob powder, and corn cob powder of 200 mesh or above. Each grade of corn cob powder is sealed in a sealed bag and ready for use. Corn cob powder with a particle size of no more than 40 mesh can be used in the embodiments of the present invention. Here, corn cob powder of 200 mesh or above is exemplarily used for the subsequent steps;

[0073] 2) Weighing 100 g of the corncob powder with a mesh size of 200 or larger obtained in step 1) and adding it to 1000 mL of a sodium hydroxide aqueous solution (the mass of the sodium hydroxide aqueous solution is calculated as 100%, and the mass of the sodium hydroxide accounts for 20 wt%) at a solid-to-liquid ratio of 1:10, and modifying the corncob powder by stirring at 6000 rpm for 30 min at 80° C. After modification, filtering the mixture, collecting the filter residue, and washing it with deionized water to obtain modified corncob powder;

[0074] 3) mixing the modified corncob powder obtained in step 2) and a calcium chloride aqueous solution (the mass of the calcium chloride aqueous solution is calculated as 100%, and the mass of the calcium chloride accounts for 20 wt%) at a solid-liquid ratio of 1:3 (i.e., 3 mL of the calcium chloride aqueous solution is dispersed per gram of modified corncob powder), and stirring at 6000 rpm at 70° C. to uniformly disperse the modified corncob powder to obtain a modified corncob powder dispersion;

[0075] 4) Add 10 g of polyacrylamide to the modified corncob powder dispersion obtained in step 3) at 70°C while stirring, and continue stirring for 30 minutes to carry out polymerization reaction. After the reaction is completed, the reaction product is dried to obtain a viscosity-enhancing fluid loss reducer. X-ray diffraction pattern determination of modified corncob powder and viscosity-enhancing fluid loss reducer

[0076] The modified corn cob powder prepared in step 2) and the viscosity-enhancing and fluid loss-reducing agent prepared in step 4) in Examples 1 to 5 were respectively subjected to X-ray diffraction pattern measurement, and Example 1 is used as an example for detailed description.

[0077] Figure 1 There are two spectra, 1 and 2. Among them, spectrum line 1 is the X-ray diffraction spectrum of the modified corncob powder. It can be seen that the modified corncob powder has obvious diffraction peaks at 11.7°, 20.3° and 21.7°, corresponding to the cellulose (110), (110) and (020) crystal planes, respectively. The peaks are sharp. This is because the corncob powder was treated with alkali, resulting in a transformation of its crystal structure. Spectrum line 2 is the X-ray diffraction spectrum of the viscosity-enhancing and filtration-reducing agent. It can be seen that after grafting polyacrylamide, the relative intensity of the peaks of the crystal planes at 12.4° and 21.4° of the viscosity-enhancing and filtration-reducing agent is significantly weakened. This also indicates that grafting and copolymerization condensation reactions occurred in the crystalline region of the viscosity-enhancing and filtration-reducing agent, resulting in the destruction of its crystal structure, thereby obtaining an amorphous copolymer product.

[0078] After measuring and analyzing the X-ray diffraction patterns of the modified corncob powder prepared in step 2) of Examples 2 to 5 and the viscosity increasing and fluid loss reducing agent prepared in step 4), the X-ray diffraction patterns of the modified corncob powder prepared in step 2) of Examples 2 to 5 are similar to those of the modified corncob powder prepared in step 4). Figure 1 The spectrum line 1 in the figure is basically consistent. Since the corn cob powder is subjected to alkali treatment, the crystalline structure of the corn cob powder has changed. According to the measurement results of the X-ray diffraction patterns of the viscosity-enhancing and fluid loss reducers prepared in Examples 2 to 5, it is known that the crystalline region of the viscosity-enhancing and fluid loss reducers prepared in any of the examples has undergone grafting and copolymerization condensation reactions, resulting in the destruction of its crystalline structure, and the obtained product is also an amorphous copolymer.

[0079] Evaluation of fluid loss reduction and viscosity-increasing performance of viscosity-enhancing fluid loss reducers

[0080] The viscosity-enhancing and fluid-loss-reducing agent was added to the modified starch drilling fluid, and the apparent viscosity and high-temperature and high-pressure fluid loss were measured to evaluate the viscosity-enhancing and fluid-loss-reducing performance of the viscosity-enhancing and fluid-loss-reducing agent. The specific steps are as follows.

[0081] (1) Preparation of modified starch drilling fluid

[0082] Mixing water, clay, sodium carbonate, sodium hydroxide, an amino inhibitor, calcium oxide, a modified starch fluid loss additive, a liquid lubricant RH-220, and a solid lubricant RAN-01 to obtain a modified starch drilling fluid, wherein the mass of water is taken as 100%, the clay is used in an amount of 4 wt%, the sodium carbonate is used in an amount of 0.2 wt%, the sodium hydroxide is used in an amount of 0.5 wt%, the amino inhibitor is used in an amount of 1 wt%, the calcium oxide is used in an amount of 0.25 wt%, the modified starch fluid loss additive is used in an amount of 2 wt%, the liquid lubricant RH-220 is used in an amount of 2 wt%, and the solid lubricant RAN-01 is used in an amount of 2 wt%;

[0083] (2) Preparation of test samples

[0084] Take 100 g of the modified starch drilling fluid prepared in (1), add 5 g of the viscosity-enhancing and fluid-loss-reducing agent prepared in Example 1, and stir evenly to obtain the test sample-1;

[0085] The viscosity-increasing and fluid loss reducer prepared in Example 1 was replaced with the viscosity-increasing and fluid loss reducers prepared in Examples 2 to 5 of equal mass, and the mixture was stirred evenly to obtain test samples-2 to-5;

[0086] (3) Apparent viscosity measurement

[0087] The apparent viscosity was determined according to 6 of the national standard GB / T16783.1-2006 "Field testing of drilling fluids in the petroleum and natural gas industry Part 1: Water-based drilling fluids". First, the modified starch drilling fluid prepared in (1) was used as a blank control sample, and its apparent viscosity at room temperature (i.e., 25°C) was measured using a direct-reading viscometer. The specific steps are as follows:

[0088] 3-1. Inject the blank control sample into the container and immerse the drum just to the scale line;

[0089] 3-2. Measure and record the temperature of the blank control sample;

[0090] 3-3. Make the drum rotate at 600r / min. After the dial reading stabilizes, read and record the dial reading R at 600r / min. 600 ;

[0091] 3-4. Calculate the apparent viscosity η according to formula (I) A .

[0092] η A =R 600 / 2 formula (Ⅰ)

[0093] Among them, R 600 The dial reading is 600r / min;

[0094] η A is the apparent viscosity.

[0095] 3-5. According to steps 3-1 to 3-4, the blank control sample was replaced with the test samples-1 to test samples-5 prepared in (2), and the apparent viscosity was measured respectively. Combined with the apparent viscosity of the blank control sample, the apparent viscosity growth rate of the test samples-1 to test samples-5 relative to the blank control sample was calculated. The results are shown in Table 1.

[0096] Table 1. Viscosity-enhancing properties of fluid loss additives

[0097] Example Example 1 Example 2 Example 3 Example 4 Example 5 Sample number to be tested Sample to be tested-1 Sample to be tested-2 Sample to be tested-3 Sample to be tested-4 Sample to be tested-5 Apparent viscosity growth rate / % 16 45 38 30 25

[0098] As can be seen from Table 1, after adding 5 wt% of the viscosity-enhancing and fluid loss reducer prepared in Examples 1 to 5, the viscosity of the modified starch drilling fluid increases by between 16% and 45%, indicating that the viscosity-enhancing and fluid loss reducer provided by the present invention can be effectively increased when added to the drilling fluid. In addition, the viscosity of the drilling fluid can be controlled by adjusting the addition ratio of the viscosity-enhancing and fluid loss reducer in the drilling fluid to meet different requirements of actual production.

[0099] (4) High temperature and high pressure filtration loss measurement

[0100] First, the modified starch drilling fluid prepared in (1) was used as a blank control sample, and the high-temperature and high-pressure filtration loss was determined according to 7.3.2 of the standard GBT 16783.1-2014 "Field testing of drilling fluids in the petroleum and natural gas industry Part 1: Water-based drilling fluids";

[0101] The blank control sample was replaced with the test samples-1 to test samples-5 prepared in (2), and the high-temperature and high-pressure filtration loss was measured respectively. Combined with the high-temperature and high-pressure filtration loss of the blank control sample, the filtration loss reduction rate of the test samples-1 to test samples-5 relative to the blank control sample was calculated. The results are shown in Table 2.

[0102] Table 2. Fluid loss reduction properties of viscosity-enhancing and fluid loss reducers

[0103] Example Example 1 Example 2 Example 3 Example 4 Example 5 Sample number to be tested Sample to be tested-1 Sample to be tested-2 Sample to be tested-3 Sample to be tested-4 Sample to be tested-5 Fluid loss reduction / % 20 40 55 45 43

[0104] As can be seen from Table 2, the viscosity-enhancing and fluid loss reducers prepared in Examples 1 to 5 can be added to the modified starch drilling fluid to effectively reduce the high-temperature and high-pressure fluid loss of the modified starch drilling fluid. When 5% of the viscosity-enhancing and fluid loss reducer is added to the modified starch drilling fluid, the fluid loss is reduced by 20%-55%.

[0105] Combining Table 1 and Table 2 with the formula of the viscosity-enhancing and fluid loss reducer provided by the present invention, the viscosity-enhancing and fluid loss reducer provided by the present invention can have at least the following advantages:

[0106] 1. The viscosity-enhancing and fluid-loss reducer provided by the present invention uses corncob powder as its main raw material, with a mass ratio of corncob powder to polymer as high as 10:1, and the amount of polymer used is very small. The large amount of corncob powder used enhances the environmental friendliness of the viscosity-enhancing and fluid-loss reducer. Compared with existing viscosifiers and fluid-loss reducers, it has better biodegradability and will not damage the formation after entering the formation with the drilling fluid, thus helping to protect the formation.

[0107] 2. Modified corncob powder contains a large amount of cellulose, starch, and heteropolysaccharides, which help to increase the viscosity of the fluid loss agent. In addition, these cellulose, starch, and heteropolysaccharides in the modified corncob powder can also enhance the adsorption of the viscosity-enhancing fluid loss agent on the surface of clay particles in the drilling fluid, inhibiting clay expansion, reducing the fluid loss of the drilling fluid, and exerting a chemical fluid loss reduction effect.

[0108] 3. Modified corncob powder particles can block the pores of the filter cake formed by drilling fluid, playing a physical role in reducing fluid loss, complementing the chemical fluid loss reduction effect, and giving the viscosity-enhancing fluid loss reducer good fluid loss reduction performance;

[0109] 5. Corn cob powder with a particle size of no more than 40 mesh can be used in the present invention. In addition, corn cob powders of different particle sizes have different modification effects, and the viscosity-increasing and fluid loss reduction properties of the final viscosity-increasing and fluid loss reducer prepared are also different. Corn cob powders of different particle sizes can be selected as the main raw material to prepare the viscosity-increasing and fluid loss reducer provided by the present invention as needed;

[0110] 4. The raw materials used in the viscosity-enhancing and fluid-loss-reducing agent provided by the present invention are cheap and readily available, and the preparation steps are simple, which greatly reduces the cost of preparing drilling fluid agents using natural plant materials as the main raw materials.

[0111] In summary, the viscosity increasing and fluid loss reducing agent provided by the present invention is a drilling fluid treatment agent that has both viscosity increasing properties, fluid loss reducing properties and environmental protection.

[0112] Although the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that various modifications may be made without departing from the true spirit and scope of the invention. Furthermore, the subject matter, spirit, and scope of the invention may be modified in various ways to adapt to specific circumstances, materials, combinations of materials, and methods. All such modifications are intended to be within the scope of the claims.

Claims

1. A viscosity-enhancing and fluid loss-reducing agent, which is a polymerization product of modified corncob powder and a polymer; the modified corncob powder is corncob powder modified with an alkaline compound.

2. The viscosity increasing and fluid loss reducing agent according to claim 1, characterized in that: The mass ratio of the corncob powder to the polymer is 10:

1.

3. The viscosity increasing and fluid loss reducing agent according to claim 1 or 2, characterized in that: The alkaline compound is sodium hydroxide and / or potassium hydroxide.

4. The viscosity increasing and fluid loss reducing agent according to any one of claims 1 to 3, characterized in that The polymer includes at least one of polyacrylamide, polyethylene terephthalate, polybutylene terephthalate, and polymethyl methacrylate.

5. A method for preparing the viscosity-enhancing and fluid loss-reducing agent according to any one of claims 1 to 4, comprising the following steps: 1) grinding corn cobs to obtain corn cob powder; 2) modifying the corncob powder with the alkaline compound to obtain the modified corncob powder; 3) dispersing the modified corncob powder in an inorganic salt solution to obtain a modified corncob powder dispersion; 4) causing the polymer to undergo a polymerization reaction with the modified corncob powder in the modified corncob powder dispersion to obtain the viscosity-enhancing fluid loss reducer.

6. The method according to claim 5, characterized in that In step 2), the alkaline compound is prepared into an alkaline compound solution, which is then mixed with the corncob powder, subjected to the modification, and filtered to obtain the modified corncob powder.

7. The method according to claim 5 or 6, characterized in that In step 3), the solid-to-liquid ratio of the modified corncob powder to the inorganic salt solution is 1:3; Preferably, the inorganic salt in the inorganic salt solution includes at least one of calcium chloride, ammonium chloride, zinc chloride and sodium nitrate.

8. The method according to any one of claims 5 to 7, characterized in that In step 2), the modification temperature is 80° C.; and / or the modification time is not less than 30 min; and / or In step 4), the polymerization reaction temperature is 70° C.; and / or the duration is not less than 30 minutes.

9. The method according to any one of claims 5 to 8, characterized in that In step 4), the polymerization product obtained by the polymerization reaction is dried to obtain the viscosity-enhancing fluid loss reducer.

10. Use of the viscosity-enhancing and fluid-loss-reducing agent according to any one of claims 1 to 4 or the viscosity-enhancing and fluid-loss-reducing agent prepared by the method according to any one of claims 5 to 9 in preparing drilling fluid.

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