Novel filtrate reducer as well as preparation method and application thereof

Abstract

The invention discloses a novel filtrate reducer as well as a preparation method and application thereof. The filtrate reducer is prepared from the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 27 to 90 parts of long-chain alkyl trimethyl ammonium chloride and 5 to 18 parts of alkali. A preparation method of the filtrate reducer comprises the following steps: S1, sequentially adding an isobutylene maleic anhydride copolymer and alkali, adding water, and stirring for dissolving to obtain a solution A; s2, adding long-chain alkyl trimethyl ammonium chloride into water, stirring and dissolving to obtain a solution B; s3, adding the solution B prepared in the step S2 into the solution A prepared in the step S1, and carrying out constant-temperature reaction; and S4, after the reaction liquid in the S3 is cooled to room temperature, filtering, washing the solid filtrate, and drying to obtain the novel filtrate reducer. The novel fluid loss additive is suitable for a gas-to-oil synthetic base drilling fluid system, has a good high-temperature and high-pressure fluid loss reduction effect, and solves the problems that the gas-to-oil synthetic base drilling fluid system is large in high-temperature fluid loss at 220 DEG C, poor in electrical stability and the like.

Description

Technical Field

[0001] The invention relates to a novel fluid loss reducer and a preparation method and application thereof. Background Art

[0002] Drilling fluid loss reducer is one of the most commonly used treatment agents in oil and gas field drilling, and occupies an important position in drilling fluid treatment agents. Adding a fluid loss reducer can adjust the performance of the drilling fluid, and can form a thin and dense filter cake on the well wall during drilling, which can reduce the impact of filtration on the formation and stabilize the well wall. In recent years, with the acceleration of oil exploration and the improvement of drilling technology, the exploration and development of oil and gas resources has continued to develop in deep formations.

[0003] At present, the existing gas-to-liquid synthetic-based drilling fluid fluid loss reducers are mainly divided into asphalt, humic acid and high molecular polymer types. Among them, asphalt-based fluid loss reducers have the advantages of wide material availability and low price, and have been widely used in the past. However, asphalt-based fluid loss reducers have the disadvantages of reducing drilling speed, polluting the environment and requiring large addition amounts. Their use has been restricted in the formulation of gas-to-liquid synthetic-based drilling fluids in environmentally sensitive areas in China and most parts of the world. Humic acid amine-based fluid loss reducers are environmentally friendly and can improve the rheology of drilling fluids and improve emulsification stability, but they are easily decomposed and lose their function under high temperature conditions. For example, the performance test results of the humic acid-based filtrate reducer prepared in the article "Development and Performance of a New High-Temperature Resistant Oil-Based Drilling Fluid Filter Loss Reducer" (Drilling Fluids and Completion Fluids, 2016, 33(01)) in high-temperature resistant and high-density oil-based drilling fluid showed that the high-temperature and high-pressure filtration loss of the filtrate reducer was 4.0 ml at 180°C and 8.6 ml at 220°C, indicating that the high-temperature resistance needs to be improved.

[0004] The polymer fluid loss reducer is a resin fluid loss reducer with a carbon-carbon structure as the main chain. It has good high-temperature and high-pressure fluid loss effect and long service life. However, at present, the polymer gas-to-liquid synthetic-based fluid loss reducer relies on imports and is expensive, which seriously limits its large-scale application. Therefore, it is urgent to develop a new fluid loss reducer with good fluid loss performance and low fluid loss. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a novel fluid loss reducer with good fluid loss reduction performance and low fluid loss under high temperature conditions, as well as a preparation method and application thereof.

[0006] As one aspect of the present invention, it relates to a novel fluid loss reducer, which comprises the following raw materials by weight: 20 parts of isobutylene maleic anhydride copolymer, 27-90 parts of long-chain alkyl trimethyl ammonium chloride, and 5-18 parts of alkali.

[0007] In a specific embodiment, the base is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0008] As another aspect of the present invention, it relates to a method for preparing the above-mentioned fluid loss reducer, wherein the method comprises the following steps:

[0009] S1, adding isobutylene maleic anhydride copolymer and alkali in sequence, adding water and stirring to dissolve, to prepare solution A;

[0010] S2, adding long-chain alkyl trimethylammonium chloride to water, stirring to dissolve, to obtain solution B;

[0011] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at a constant temperature;

[0012] S4. After the reaction liquid in S3 cools to room temperature, it is filtered, the solid filtered out is washed, and then dried to obtain a novel filtrate reducer.

[0013] In a specific embodiment, in S3, the reaction temperature is 80-95° C., and the reaction time is 1-3 h.

[0014] As another aspect of the present invention, it relates to the application of the novel fluid loss reducer in gas-to-liquid synthetic-based drilling fluid.

[0015] As another aspect of the present invention, it relates to a gas-to-liquid synthetic-based drilling fluid, wherein the gas-to-liquid synthetic-based drilling fluid contains the above-mentioned novel fluid loss reducer.

[0016] As another aspect of the present invention, it relates to an oilfield drilling process, wherein the drilling process uses the above-mentioned gas-to-liquid synthetic-based drilling fluid.

[0017] The novel fluid loss reducer provided by the present invention is suitable for a gas-to-liquid synthetic-based drilling fluid system, has good high-temperature and high-pressure fluid loss reducing effect, good temperature resistance, low fluid loss and the like, and solves the problems of large high-temperature fluid loss at 220°C and poor electrical stability of the gas-to-liquid synthetic-based drilling fluid system.

[0018] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the infrared spectrum of the fluid loss reducer prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with specific examples, and the protection scope of the present application is not limited by the following examples. Among them, the sources of materials mainly involved in the examples are shown in Table 1 below, and other materials not shown are conventional commercial products.

[0021] Table 1: Material source description

[0022] Serial number materials Specification factory 1 Isobutylene maleic anhydride copolymer self made 2 Sodium hydroxide ≥96％ Sinopharm Chemical Reagent Co., Ltd. 3 Octadecyltrimethylammonium chloride ≥98％ Sinopharm Chemical Reagent Co., Ltd. 4 Octaalkyltrimethylammonium chloride ≥99％ Shanghai MacLean Biochemical Technology Co., Ltd. 5 Potassium hydroxide ≥95％ Shanghai MacLean Biochemical Technology Co., Ltd. 6 Dodecyltrimethylammonium chloride ≥98％ Shanghai MacLean Biochemical Technology Co., Ltd. 7 Tetradecyltrimethylammonium chloride ≥99％ Shanghai MacLean Biochemical Technology Co., Ltd. 8 ammonia 25.0％ Sinopharm Chemical Reagent Co., Ltd. 9 Hexadecyltrimethylammonium chloride ≥97％ Shanghai MacLean Biochemical Technology Co., Ltd. 10 Dodecyltrimethylammonium chloride ≥99％ Shanghai MacLean Biochemical Technology Co., Ltd.

[0023] Based on the prior art, the inventors have further developed the raw material composition of high molecular polymer fluid loss reducers and provided Examples 1 to 6.

[0024] Example 1

[0025] The fluid loss reducer of this embodiment comprises the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 5 parts of alkali (sodium hydroxide), 150 parts of water, and 45 parts of long-chain alkyl trimethyl ammonium chloride (octadecyl trimethyl ammonium chloride).

[0026] The fluid loss reducer of this embodiment is prepared by the following steps:

[0027] S1, add 20 parts of isobutylene maleic anhydride copolymer, 5 parts of sodium hydroxide and 100 parts of water into a reaction bottle in sequence, stir and dissolve, to prepare solution A;

[0028] S2, take another reaction bottle, add 45 parts of octadecyltrimethylammonium chloride and 50 parts of water thereto in sequence, stir and dissolve, to prepare solution B;

[0029] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at a constant temperature of 80°C for 2h;

[0030] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0031] The infrared spectrum of the fluid loss reducer prepared in this example is as follows: Figure 1 shown.

[0032] Example 2

[0033] The fluid loss reducer of this embodiment comprises the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 15 parts of alkali (potassium hydroxide), 200 parts of water, and 83 parts of long-chain alkyl trimethyl ammonium chloride (hexadecyl trimethyl ammonium chloride).

[0034] The fluid loss reducer of this embodiment is prepared by the following steps:

[0035] S1, add 20 parts of isobutylene maleic anhydride copolymer, 15 parts of potassium hydroxide and 100 parts of water into a reaction bottle in sequence, stir and dissolve, to prepare solution A;

[0036] S2, take another reaction bottle, add 83 parts of hexadecyltrimethylammonium chloride and 100 parts of water thereto in sequence, stir and dissolve, to prepare solution B;

[0037] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at 95°C for 3h;

[0038] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0039] Example 3

[0040] The fluid loss reducer of this embodiment comprises the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 18 parts of alkali (ammonia water), 150 parts of water, and 27 parts of long-chain alkyl trimethyl ammonium chloride (octaalkyl trimethyl ammonium chloride).

[0041] The fluid loss reducer of this embodiment is prepared by the following steps:

[0042] S1, add 20 parts of isobutylene maleic anhydride copolymer, 18 parts of ammonia water and 100 parts of water into a reaction bottle in sequence, stir and dissolve, to prepare solution A;

[0043] S2, take another reaction bottle, add 27 parts of octadecyltrimethylammonium chloride and 50 parts of water thereto in sequence, stir and dissolve, to prepare solution B;

[0044] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at 80°C for 1h;

[0045] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0046] Example 4

[0047] The fluid loss reducer of this embodiment includes the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 12 parts of alkali (5 parts of sodium hydroxide, 7 parts of potassium hydroxide), 200 parts of water, and 73 parts of long-chain alkyl trimethyl ammonium chloride (tetradecyl trimethyl ammonium chloride).

[0048] The fluid loss reducer of this embodiment is prepared by the following steps:

[0049] S1, add 20 parts of isobutylene maleic anhydride copolymer, 5 parts of sodium hydroxide, 7 parts of potassium hydroxide and 100 parts of water into a reaction bottle in sequence, stir and dissolve, to prepare solution A;

[0050] S2, take another reaction bottle, add 73 parts of tetradecyltrimethylammonium chloride and 100 parts of water thereto in sequence, stir and dissolve, to prepare solution B;

[0051] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at 95°C for 3h;

[0052] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0053] Example 5

[0054] The fluid loss reducer of this embodiment includes the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 10 parts of alkali (sodium hydroxide), 200 parts of water, and 66 parts of long-chain alkyl trimethyl ammonium chloride (dodecyl trimethyl ammonium chloride).

[0055] The fluid loss reducer of this embodiment is prepared by the following steps:

[0056] S1, add 20 parts of isobutylene maleic anhydride copolymer, 10 parts of sodium hydroxide and 100 parts of water into a reaction bottle, heat to raise the temperature, stir and dissolve, to prepare solution A;

[0057] S2, take another reaction bottle, add 66 parts of dodecyltrimethylammonium chloride and 100 parts of water thereto in sequence, heat to raise the temperature, stir to dissolve, and prepare solution B;

[0058] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at 95°C for 3h;

[0059] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0060] Example 6

[0061] The fluid loss reducer of this embodiment comprises the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 5 parts of alkali (sodium hydroxide), 200 parts of water, and 30 parts of long-chain alkyl trimethyl ammonium chloride (decyl trimethyl ammonium chloride).

[0062] The fluid loss reducer of this embodiment is prepared by the following steps:

[0063] S1, add 20 parts of isobutylene maleic anhydride copolymer, 5 parts of sodium hydroxide and 100 parts of water into a reaction bottle, heat to raise the temperature, stir and dissolve, to prepare solution A;

[0064] S2, take another reaction bottle, add 30 parts of dodecyltrimethylammonium chloride and 100 parts of water thereto in sequence, heat to raise the temperature, stir to dissolve, and prepare solution B;

[0065] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at 95°C for 3h;

[0066] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0067] According to the constituent raw materials and preparation method of the fluid loss reducer of the present invention, the inventors obtained the following comparative examples by adjusting the dosage of some raw materials, which are given as comparative examples 1 to 2.

[0068] Comparative Example 1

[0069] The filtrate reducer of this comparative example comprises the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 2 parts of alkali (sodium hydroxide), 150 parts of water, and 45 parts of long-chain alkyl trimethyl ammonium chloride (octadecyl trimethyl ammonium chloride).

[0070] The fluid loss reducer of this comparative example is prepared by the following steps:

[0071] S1, add 20 parts of isobutylene maleic anhydride copolymer, 2 parts of sodium hydroxide and 100 parts of water into a reaction bottle in sequence, stir and dissolve, to prepare solution A;

[0072] S2, take another reaction bottle, add 45 parts of octadecyltrimethylammonium chloride and 50 parts of water thereto in sequence, stir and dissolve, to prepare solution B;

[0073] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at 80°C for 2h;

[0074] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0075] Comparative Example 2

[0076] The filtrate reducer of this comparative example comprises the following raw materials in parts by weight: 20 parts of isobutylene maleic anhydride copolymer, 10 parts of alkali (sodium hydroxide), 200 parts of water, and 15 parts of long-chain alkyl trimethyl ammonium chloride (octadecyl trimethyl ammonium chloride).

[0077] The fluid loss reducer of this comparative example is prepared by the following steps:

[0078] S1, add 20 parts of isobutylene maleic anhydride copolymer, 10 parts of sodium hydroxide and 100 parts of water into a reaction bottle in sequence, stir and dissolve, to prepare solution A;

[0079] S2, take another reaction bottle, add 15 parts of octadecyltrimethylammonium chloride and 100 parts of water thereto in sequence, stir and dissolve, to prepare solution B;

[0080] S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at 95°C for 3h;

[0081] S4, after the reaction solution in S3 is cooled to room temperature, filtering, washing the solid filtered product and drying it to obtain the filtrate reducer.

[0082] The fluid loss reducers prepared in the above Examples 1 to 6 and Comparative Examples 1 to 2 are applied to the oilfield drilling process to prepare drilling fluids. According to the conventional drilling fluid preparation method in the industry, Application Examples 1 to 6 and Comparative Examples 1 to 2 are given.

[0083] Application Example 1

[0084] The drilling fluid of this application example includes the following components in parts by weight: 80 parts of gas-to-liquid (185V) + 20 parts of CaCl2 aqueous solution (mass concentration is 20%) + 3 parts of primary emulsifier (DR-EM) + 2 parts of auxiliary emulsifier (DR-CO) + 2 parts of organic soil (HF-120) + 4 parts of filtrate reducer (Example 1) + 2 parts of calcium oxide + 250 parts of barite.

[0085] Application Example 2

[0086] The difference from Application Example 1 is that the fluid loss reducer prepared in Example 2 is used instead of the fluid loss reducer in Application Example 1.

[0087] Application Example 3

[0088] The difference from Application Example 1 is that the fluid loss reducer prepared in Example 3 is used instead of the fluid loss reducer in Application Example 1.

[0089] Application Example 4

[0090] The difference from Application Example 1 is that the fluid loss reducer prepared in Example 4 is used instead of the fluid loss reducer in Application Example 1.

[0091] Application Example 5

[0092] The difference from Application Example 1 is that the fluid loss reducer prepared in Example 5 is used instead of the fluid loss reducer in Application Example 1.

[0093] Application Example 6

[0094] The difference from Application Example 1 is that the fluid loss reducer prepared in Example 6 is used instead of the fluid loss reducer in Application Example 1.

[0095] Application Comparative Example 1

[0096] The difference from Application Example 1 is that the filtrate reducer prepared in Comparative Example 1 is used instead of the filtrate reducer in Application Example 1.

[0097] Application Comparative Example 2

[0098] The difference from Application Example 1 is that the filtrate reducer prepared in Comparative Example 2 is used instead of the filtrate reducer in Application Example 1.

[0099] In addition, taking asphalt-based fluid loss reducers and humic acid amine-based fluid loss reducers in the prior art as examples, oil-based drilling fluids are prepared for use in oilfield drilling processes, which are also used as comparative examples of the present invention. Comparative examples 3 to 4 are given.

[0100] Application Comparative Example 3

[0101] The drilling fluid of the comparative example of this application includes the following components, measured by weight: 80 parts of gas-to-liquid (185V) + 20 parts of CaCl2 aqueous solution (mass concentration is 20%) + 3 parts of primary emulsifier (DR-EM) + 2 parts of auxiliary emulsifier (DR-CO) + 2 parts of organic soil (HF-120) + 4 parts of fluid loss reducer - asphalt + 2 parts of calcium oxide + 250 parts of barite.

[0102] Application Comparative Example 4

[0103] The drilling fluid of the comparative example of this application includes the following components, measured by weight: 80 parts of gas-to-liquid (185V) + 20 parts of CaCl2 aqueous solution (mass concentration is 20%) + 3 parts of primary emulsifier (DR-EM) + 2 parts of auxiliary emulsifier (DR-CO) + 2 parts of organic soil (HF-120) + 4 parts of filtrate reducer - humic acid amine + 2 parts of calcium oxide + 250 parts of barite.

[0104] The above application examples 1 to 6 and application comparison examples 1 to 4 were applied to oilfield drilling technology, and the following performance tests were performed. According to the relevant methods described in the national standard GB / T16783.2 "Field Test of Drilling Fluids in the Petroleum and Natural Gas Industry", the test results were recorded in the following Table 2.

[0105] Table 2: Drilling fluid performance evaluation results

[0106]

[0107] It can be seen from the experimental results in Table 2 that: Application Comparative Example 3 and Application Comparative Example 4 are gas-to-oil synthetic-based drilling fluid systems prepared with asphalt-based fluid loss reducers and humic acid amine-based fluid loss reducers, respectively. After high-temperature aging at 220°C, the high-temperature and high-pressure fluid loss of the synthetic-based drilling fluid system of Application Comparative Example 3 is 14.8 ml. Excessive fluid loss can easily cause accidents such as well wall instability and collapse. Therefore, the asphalt-based fluid loss reducer is not suitable for use as a fluid loss reducer for a temperature-resistant 220°C gas-to-oil synthetic-based drilling fluid system. After high-temperature aging at 220°C, the high-temperature and high-pressure fluid loss of the synthetic-based drilling fluid system of Application Comparative Example 4 is 10.5 ml. The fluid loss is better than that of the asphalt-based fluid loss reducer, and the demulsification voltage of 971V is better than that of the asphalt-based fluid loss reducer drilling fluid system of 824V, indicating that the electrical stability of the humic acid amine-based fluid loss reducer under high-temperature conditions of 220°C is better than that of the asphalt-based fluid loss reducer product. However, the high-temperature and high-pressure filtration loss of 10.5 ml is too large, which can also easily cause wellbore instability. Therefore, it cannot be directly used as a filtration loss reducer for 220℃ high-temperature gas-to-liquid synthetic-based drilling fluid system.

[0108] The high molecular polymer fluid loss reducer with branched chains prepared in Examples 1-6 of the present invention is used to prepare a gas-to-oil synthetic-based drilling fluid system, and the high temperature and high pressure fluid loss after aging at 220°C is in the range of 3.6 to 4.2 ml, indicating that the high molecular polymer fluid loss reducer of the present patent has excellent high temperature and high pressure fluid loss performance, and meets the technical requirements of high temperature and high pressure fluid loss performance of a 220°C high temperature gas-to-oil synthetic-based drilling fluid system. The demulsification voltage of the gas-to-oil synthetic-based drilling fluid system prepared in Examples 1-6 of the present invention is above 1234V, which is much higher than the 400V required at the drilling construction site, indicating that the high molecular polymer fluid loss reducer prepared in the present invention is beneficial to the electrical stability of the synthetic-based drilling fluid system. The high molecular polymer fluid loss reducer of the present invention can effectively solve the problem of large high temperature and high pressure fluid loss of a 220°C high temperature gas-to-oil synthetic-based drilling fluid system.

[0109] The high-temperature and high-pressure filtration loss of the gas-to-liquid synthetic-based drilling fluid prepared with the high-molecular polymer filtration reducer prepared in Comparative Examples 1 to 2 was 5.6 ml and 6.0 ml respectively, and the filtration performance was significantly better than the high-temperature and high-pressure filtration loss performance of the gas-to-liquid synthetic-based drilling fluid prepared with the asphalt filtration reducer and the humic acid amine filtration reducer, but lower than the high-temperature and high-pressure filtration loss performance of the high-molecular polymer filtration reducer prepared in Examples 1 to 6 of the present invention. It can be explained that: too high or too low an addition amount of each material is not conducive to the filtration performance of the polymer filtration reducer.

[0110] The above are only preferred feasible embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Various modifications or applications made according to the above embodiments are within the protection scope of this technical solution.

[0111] Although the specific embodiments of the present invention have been described in detail, it will be understood by those skilled in the art. According to all the teachings disclosed, various modifications and replacements can be made to those details, and these changes are all within the protection scope of the present invention. The full scope of the present invention is given by the attached claims and any equivalents thereof.

Claims

1. A novel fluid loss reducer, characterized in that: The composition comprises the following raw materials by weight: 20 parts of isobutylene maleic anhydride copolymer, 27-90 parts of long-chain alkyl trimethyl ammonium chloride and 5-18 parts of alkali.

2. The novel fluid loss reducer according to claim 1, characterized in that: The number of carbon atoms of the long-chain alkyl group in the long-chain alkyl trimethylammonium chloride is selected from one of C8, C10, C12, C14, C16 or C18.

3. The novel fluid loss reducer according to claim 1, characterized in that: The alkali is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water.

4. A method for preparing the novel fluid loss reducer according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: S1, adding isobutylene maleic anhydride copolymer and alkali in sequence, adding water and stirring to dissolve, to prepare solution A; S2, adding long-chain alkyl trimethylammonium chloride to water, stirring to dissolve, to obtain solution B; S3, adding solution B prepared in S2 to solution A prepared in S1, and reacting at a constant temperature; S4. After the reaction liquid in S3 cools to room temperature, it is filtered, the solid filtered out is washed, and then dried to obtain a novel filtrate reducer.

5. The method for preparing the novel fluid loss reducing agent according to claim 4, characterized in that: In the step S3, the reaction temperature is 80-95° C. and the reaction time is 1-3 hours.

6. Use of the novel fluid loss reducer as claimed in any one of claims 1 to 5 in gas-to-liquid synthetic-based drilling fluid.

7. A gas-to-liquid synthetic-based drilling fluid, characterized in that: The gas-to-liquid synthetic-based drilling fluid contains the novel fluid loss reducer as claimed in claim 6.

8. An oilfield drilling process, characterized in that: The drilling process uses the gas-to-liquid synthetic-based drilling fluid as described in claim 7.

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