In the construction of oil and gas exploration and development, workover is an important link. Oil and gas wells may break down at any time in the process of flowing, pumping or water injection, resulting in production reduction or even production stop. Such as: sand plugging in oil wells, serious wax and salt deposition in the wellbore, reservoir plugging, permeability reduction, oil, gas and water layer collusion, production reservoir depletion and other faults of the oil well itself; downhole oil production equipment failures such as tubing connection tripping, abnormal oil pump operation, etc. After the fault occurs, only through the downhole operation to remove the fault, replace the downhole equipment, adjust the parameters of the oil well, and resume the normal production of the oil well.

Oil plays a very important role in the development of various countries in contemporary society, and the corresponding oil drilling and production technology is also developing rapidly. Various chemical treatment agents have also been developed. China's oil drilling and production technology is still at a relatively backward level: one is that there is no good chemical treatment agent; the other is that there is no good drilling technology; good mud treatment agent plays an important role in oil drilling and production.

Fluid loss reducer is a kind of mud treatment agent, which is used to ensure the stability of drilling fluid performance, reduce the loss of harmful liquid to the formation, stabilize the well wall and ensure the regular diameter.

The filtrate reducer mainly works through the following mechanisms:

(1) The capillary channels in the mud cake are blocked in an all-round way to make it smooth and dense;

(2) The negative charge density of mud cake is increased to form a strong polarized water layer;

(3) Adsorption on the side of clay crystal particles forms a bridge to reduce the capillary pore size;

(4) Increase the viscosity of filtrate;

The wettability of pores of mud cake was changed.

Among the various filtrate reducer currently used, the first mechanism is represented by pre gelatinized starch, while the second and third mechanisms are mainly represented by strong anions such as NH, hpan and smp-i. for the fourth mechanism, CMC and PAC can not be ignored, but other types of fluid loss agents can be ignored. Only asphalt has the fifth mechanism The mechanism is as follows. In general, the action mechanism of fluid loss additive is usually based on one mechanism, supplemented by other mechanisms. According to the molecular structure characteristics of the fluid loss additive, the effect of fluid loss control can be improved by chemical modification or proper combination, which can not only retain the strong points of the action mechanism of the fluid loss additive, but also make up for the weak point of the action mechanism.

There are two main types of filtrate reducer used in China: one is the derivative of natural material; the other is the modified product with waste acrylic fiber as raw material. The former has a wide range of raw materials, but the product has a single role in drilling fluid, and the added amount is relatively large. The raw material source of the latter is limited, and the salt resistance and calcium resistance of the product are poor. Jst501 was synthesized by copolymerization of acrylamide, sodium allyl sulfonate, potassium acrylate and calcium acrylate under certain conditions. Polymer is one of the largest amount of fluid loss additive, and its development speed is fast. This kind of polymer is mainly composed of acrylic acid and acrylamide copolymer. The hydrolysate of acrylic fiber waste is a kind of acrylic copolymer with medium molecular weight and low price, and its cost is only one third of that of pure synthetic polymer. Therefore, its dosage has been dominant in drilling fluid. This kind of product has hydrolyzed polyacrylonitrile calcium (cpan), hydrolyzed polyacrylonitrile sodium, ammonium, potassium salt, etc.

Sulfonated starch, lignite and carboxymethyl cellulose are the first filtrate reducer used in drilling fluid. With the deepening of the research and the increasingly complex formation conditions, the existing natural and natural modified fluid loss additive can not meet the needs of drilling, which promotes the research and development of synthetic polymer fluid loss additive. In recent years, with the continuous development of mud technology, people focus on the development of amphoteric composite ionic polymer and new sulfonic monomer polymer with good comprehensive performance, and have made gratifying progress. Cationic and / or amphoteric composite ionic mud fluid loss control agents have incomparable advantages over anionic ones in terms of filtration control agent capacity, salt resistance, temperature resistance and collapse prevention effect.

In recent years, drilling practice shows that anionic drilling fluid system has more and more limitations on modern high-pressure jet drilling and optimized drilling, such as strong static structural force of mud, high energy consumption in water hole, insufficient inhibition ability of hydration and dispersion of drilling cuttings and clay, etc., which has become a prominent problem in optimized drilling. Based on the synthesis of anionic treating agents, a new amphoteric anionic composite ionic polymer coated fluid loss reducer fa-367, which can be compatible with anionic mud system, was developed by the Institute of petrochemistry and Southwest Petroleum Institute, which further realized the multi-function of mud treatment agent. The excellent performance of amphoteric composite ionic polymer treatment agent also promoted the research work of amphoteric ionic plastic copolymer fluid loss reducer.

With the increase of drilling special wells, ultra deep wells and complex wells, higher requirements are put forward for drilling fluid technology. The original drilling fluid treatment agent can not meet the needs of the development of drilling fluid technology. This prompted oilfield chemists to develop new drilling fluid additives. With the wide application of drilling fluid additives, a large number of waste drilling fluid additives enter the environment. Some of them can not or are difficult to be degraded by microorganisms in nature. These additives stay in the environment during the production period. The light ones pollute the environment, affect the growth of animals and plants, and even poison people and livestock. Synthetic polymer is one of the most widely used filtrate reducer for drilling fluid, and it is also the most concentrated and active field for domestic oilfield chemists to study and explore. The results show that the temperature resistance and high valence ion pollution resistance of polymer treatment agents can be improved by copolymerization of new monomers with acrylic acid and acrylamide. Since the late 1990s, more and more attention has been paid to the "double protection" (environmental protection and production layer protection) activities in oilfield exploitation. It is precisely after recognizing the many advantages of the modified natural materials that they began to pay attention to the oilfield chemicals of natural raw materials. Natural raw materials are rich in sources and low in price. Natural materials such as starch, cellulose, humic acid, tannin extract (tannin), lignin and other natural materials have biodegradability after modification. They are environmental protection materials and have broad prospects for use as multifunctional new oilfield chemicals.

Great progress has been made in the research and application of drilling fluid loss control agents in China, and the drilling fluid technology is becoming more and more perfect. The existing fluid loss additives can basically meet the needs of drilling fluid loss control, and some experience has been accumulated in the research of new treatment agents.