1. 2. Synthetic polymers
Phenolic resin and vinyl polymer are representative of the synthesis of polymer like fluid loss agents, which have many characteristics, such as excellent performance and easy structure adjustment.

2.1 sulfonated phenolic resins
The sulfonated phenolic resin products include SMP, sulfonated lignin sulfonated phenolic resin < SLSP) and urea modified sulfonated phenolic resin < SPU. Among them, SMP is widely used in deep well brine slurry, and the three sulfonated drilling fluid system with SMP as an important component has been used for many years, Amps, AA, am and SMP were prepared. The temperature resistance of APR was 240 ℃ and the salt resistance was better than that of SMP, The amphoteric sulfonated phenolic resin asp-1 was obtained, which improved the fluid loss reduction effect of the product and inhibited the formation expansion and dispersion better. Sulfonated hydroxymethylphenol was synthesized by one-step method under alkaline conditions, and its temperature resistance was significantly improved and its performance was better than that of smp-1.

2.2 vinyl polymer fluid loss reducer
Vinyl polymer fluid loss reducer is usually polymerized by two or more monomers containing double bond. It can improve the temperature and salt resistance of target products through molecular design, and meet the requirements of drilling fluid high temperature performance in deep wells, ultra deep wells, horizontal wells and other complex wells, More and more attention has been paid to the preparation of polymer filtrate reducer by vinyl monomers. The common monomers are am, AA, N-vinyl-2-pyrrolidone < NVP), styrene sulfonic acid < SS), amps, dimethyldiallylammonium chloride < DMDAAC, etc, Anionic vinyl polymers and zwitterionic vinyl polymers can be obtained by monomer copolymerization. Since the desulfonic acid group in amps is a typical strong hydration group, it can increase the temperature and salt resistance of the polymer, and its copolymers are the focus of current research.

2.3 anionic vinyl polymer
The main anionic vinyl polymers are as follows: amps-am binary copolymer with high temperature and salt resistance was synthesized by oxidation-reduction initiator system, and AMPS / AM / VAC, am / AMPS / MAA terpolymer filtrate reducer, The synthetic geopolymer has good filtration reduction effect in fresh water, saturated brine and calcium containing slurry, and has a certain effect of temperature and salt resistance. Two copolymers, dilp527 and mp488, were synthesized by copolymerization of sodium 2-acryloyloxy-2-vinylmethylpropane sulfonate < aoems), acryloyloxybutylsulfonic acid < AOBS), DMAM, am and AA, The drilling fluid system composed of them has good high temperature stability and no high temperature thickening. The high temperature and high pressure filtration rate can be controlled within 15ml through formula optimization. The polymer synthesized by ANPs and DMAM is optimized by uniform design. The polymer has strong filtration reduction and viscosity increasing ability in freshwater salt drilling fluid, After aging at 220 ℃, the effect of filtrate reduction is obvious.

A novel high temperature resistant multi polymer fluid loss reducer JHW was synthesized by using amps and other monomers as raw materials. The temperature resistance of JHW reached 210℃, with excellent salt resistance, calcium and magnesium resistance. The optimum synthesis conditions were determined by orthogonal experiment. The filtrate loss of the polymer had little change before and after aging at 180℃.

The results show that AMPS / AM / itaconic acid < IA) terpolymer has good temperature resistance
Its decomposition temperature is less than 240 ℃, which is much higher than that of AMPS homopolymer. At the condition of 220℃,meanwhile, the mechanism of high temperature stability of AMPS / AM / ia copolymer mud is discussed.

Geopolymer was prepared by AMPS / am third monomer, which had good filtration reduction effect, temperature and salt resistance. Shale rolling recovery and inhibition of bentonite dispersion showed that the geopolymer had certain anti sloughing performance. Then, the Quaternary copolymer of diammonium methacrylamide < MAM) / AA / AMPS was prepared. The preliminary evaluation of mud performance showed that the polymer had good filtration control performance, temperature and salt resistance, It is suitable for field well slurry in Zhongyuan Oilfield. rqyn14ZNXIN-vinyl-2-pyrrolidone < NVP) has five membered rings in its molecule
The results show that NVP as polymer monomer can increase the molecular stiffness of polymer, which has a positive significance for improving the temperature resistance of polymer. The ternary polymers NJ-1 and WH-1 were synthesized by using NVP, amps and am as the main raw materials. They have good filtration reduction effect in fresh water, compound brine and sea water drilling fluid, and have good compatibility with conventional treatment agents, emxvxotoco showed good resistance to temperature and calcium and magnesium, and achieved good results in field application
Similar to the above terpolymer, ocl-jb was synthesized by using amps, am, AA and nvp4 monomers as raw materials. The fluid loss additive can not only reduce the filtration rate of drilling fluid, but also regulate the flow pattern of drilling fluid. The temperature resistance of ocl-ja prepared by mixing with humic acid derivatives can reach above 200 ℃, and the viscosity effect is not obvious, It has good compatibility with other drilling fluid additives.

Because the relative molecular weight of polymer is more than several hundred thousand, the apparent viscosity and other rheology of mud system are affected
In order to reduce the viscosity effect, a non tackifying low molecular weight polymer fluid loss additive with low molecular weight was synthesized from unsaturated monomers such as amps and am. The laboratory evaluation results showed that the polymer fluid loss reducer had good filtration reduction, temperature resistance and pollution resistance.

All the above studies were carried out by aqueous solution polymerization. The three component polymer was prepared by super concentrated inverse emulsion polymerization. It has not only good filtration loss capability, good compatibility with conventional treatment agents, strong resistance to temperature, salt and calcium pollution, but also has good application prospects in field application.

2.2 zwitterionic vinyl polymer
Amphoteric vinyl polymers have both anionic and cationic groups. Its inhibition ability is better than that of anionic polymer. In this aspect, the study includes: a kind of AMPS / trimethylallylammonium chloride < MTAAT) / am terpolymer AMPS / AM/2-hydroxy-3-methylacrylamide oxypropyl trimethylammonium chloride <HMOPTA) copolymer, which has good temperature and salt resistance, especially high valence ion resistance, and good collapse prevention effect.

Although DMDAAC has low polymerization activity, it is often used in the synthesis of drilling fluid additives. For example, terpolymers with different compositions obtained by copolymerization of amps and DMDAAC with other monomers show good temperature resistance, salt tolerance and fluid loss reduction, and have good collapse prevention effect. The amphoteric ion terpolymer aod-1 synthesized from AMPS / am / allylmethylammonium chloride has strong salt paste resistance, It can keep the drilling fluid performance stable, and the filtration rate is small. During the drilling process, the borehole is stable, and the tripping and casing running are very smooth . The AM / sulfomethylacrylamide / cationic monomer HMC-1 amphoteric copolymer filtrate reducer can not only reduce the filtration rate of drilling fluid, but also improve the rheological property of drilling fluid, reduce the consistency of drilling fluid, and has good salt and calcium resistance.

At present, vinyl polymer is the most active in the study of fluid loss additive. Although most of the polymers obtained in the study have good temperature and salt resistance, there is little difference in the properties of each polymer. The relationship between polymer structure and performance is less studied, At the same time, most of the studies only stay in the laboratory pilot stage. Because of the high viscosity of this kind of polymer, the effect of reaction amplification is obvious, Therefore, the successful industrialization of the product and the field application examples are few. How to industrialize the treatment agent with good performance is the focus of future research.

2. Development trend
In view of the current situation, the next step in the development of fluid loss agents should focus on the corresponding relationship between polymer structure and the performance of fluid loss reducer, develop new monomers, improve the temperature and salt resistance of polymer, take into account the environmental friendliness and the formation of industrial production capacity, and pay attention to the compound use of additives, The development direction is mainly reflected in the following three aspects: euts8zqvrd
(1) At the same time, it is necessary to pay attention to the salt and calcium resistance, collapse prevention and formation and environmental pollution
(2) Improve the properties of existing polymers, and further improve the high temperature resistance and collapse resistance of biopolymer and zwitterionic polymer fluid loss additive.

(3) In order to reduce the polymerization, we should develop new monomers and carry out the research on inorganic organic polymer treatment agents
The cost of the complex and the development of some filtrate reducer with good effect of reducing fluid loss and without increasing viscosity were developed.