(1. China Institute of Petrochemical Engineering and Technology, Beijing10010/; 2. China Petroleum Exploration and Development Research Institute, Beijing100083; 3. China Youshi University (Beijing), Beijing 102249
With the drilling of more and more low-pressure formations, the shortage of density-reducing materials in China is becoming more and more obvious, especially the research on high-performance hollow glass microspheres with high pressure bearing capacity. The author investigates the research on hollow microspheres in related fields at home and abroad, and thinks that although the research in this field is in the leading position abroad, there is no relevant report on the preparation theory of high-performance hollow microspheres at present. When the composition and particle size of hollow glass beads are similar, the higher the density, the greater the compressive strength of the beads. When the composition and density are similar, the smaller the particle size, the greater the compressive strength. According to its physical nature, the preparation methods of hollow microspheres can be divided into three types: chemical deposition, solution drying and powder melting. For the development of high-performance hollow microspheres, the author suggests studying the chemical composition of hollow microsphere shells in order to obtain well-cemented high-temperature resistant shells; In this process, it is suggested to adopt high temperature melting and aeration. The molten state can make the spherical shell structure more compact, and the hollowness and size of the spherical shell can be better controlled by controlling the feeding and gas supply rates.
Hollow glass beads; Density reducing material; Low density cement slurry; Low density drilling fluid; oil and gas wells
Research Progress of Low Density Hollow Glass Beads
Mu Haipeng 1, 2, 3, Ma Jiahua 1, Ding Shidong 1, Zhou Shiming 1
(1. China Petrochemical Petroleum Engineering Research Institute, Beijing10010/; 2. China Petrochemical Exploration and Development Research Institute, Beijing100083; 3. China Shiyou University, Beijing 102249, China)
With the increase of low-pressure strata drilled, the shortage of low-density materials research is more obvious. In view of this problem, the author summarizes the research on hollow glass beads in related fields and draws the latter conclusion. The research level of high strength hollow glass beads is still very low, which needs further study. When some hollow glass beads have similar composition and particle size, the beads with higher density have higher strength. When the composition and density of some hollow glass beads are similar, the smaller the particle size, the higher the strength of the beads. There are three methods to prepare hollow glass beads, such as electroless plating, solution drying and powder melting. The preparation process of hollow glass beads includes layered chemical composition, spheronization and hollow structure. In order to study high-strength hollow glass beads, the author puts forward the following suggestions: first, study the chemical composition of the material to obtain a good high-temperature resistant adhesive layer; Secondly, use the molten material and blow air, because this will make the lamella denser and it will be easier to control the hollowness and lamella thickness.
Research on cementing and completion technology of marine carbonate rocks, a major national science and technology project, the project number is 2008zx05005-006-004.
Keywords hollow glass super head; Weight loss materials; Lightweight cement slurry; Light mud; oil and gas wells
Over-drilling and exploitation of oil for more than a century has caused most of the world's oil to be stored in deep layers, and energy sources are exhausted. Although oil reserves are still very rich, but the underground energy is low, it is difficult to exploit these oil and gas. Underbalanced drilling technology is a drilling technology to keep the wellbore pressure lower than the formation pressure during drilling [1 ~ 3], which has dual functions of preventing leakage and protecting oil and gas reservoirs, so it is a better drilling method to develop these low-pressure reservoirs. The drilling fluid and cementing slurry used in this drilling method must be a low-density system with stable density under high pressure.
High-performance hollow glass beads are the main materials to achieve density stability in low-density systems under high pressure. At present, most of these materials used in domestic petroleum engineering field are HGS series products of foreign 3M company. Based on the research results of hollow glass beads at home and abroad, the author puts forward the research idea of high performance hollow glass beads.
Application of 1 hollow microspheres in petroleum engineering at home and abroad
At present, the application of hollow glass beads in petroleum engineering is mainly reflected in two aspects: low-density drilling fluid technology and low-density cementing slurry technology.
1. 1 low density drilling fluid technology
Although low-density drilling fluid systems with a density of about 0.85g/cm3 can be obtained by water-in-oil method, oil-in-water method and aeration or foam method, these systems all have serious defects [4]. For example, the main material of water-in-oil or oil-in-water drilling fluid is diesel, which has serious environmental pollution problems; Aerated or foamed drilling fluid has great compressibility, which will greatly attenuate downhole pulse signals, seriously restricting the field application of MWD, LWD and other technologies. Compared with these two low-density drilling fluid systems, the low-density drilling fluid obtained by hollow glass beads will not pollute the environment on the one hand and has environmental protection advantages; On the other hand, due to its incompressibility [5, 6], it will not affect the transmission of downhole pulse signals, and then it can be better applied to drilling with complex structure by using technologies such as MWD and LWD.
In the early 1960s, the Soviet Union used hollow glass beads as density reducer to prevent leakage [7]. After 1990s, the United States began to use hollow glass beads to prepare low-density drilling fluid [8]. In recent years [9], hollow glass bead low-density drilling fluid has been successfully applied in many low-pressure oil and gas wells and underbalanced drilling in the United States and Russia. In recent years, with the popularization of deep and ultra-deep well technology, the downhole pressure is getting higher and higher [9 ~ 1 1]. Therefore, high-strength hollow glass beads with high bearing capacity are helpful to ensure the stability of low-density drilling fluid under the action of high downhole pressure, and have good application and popularization value. The test of Houston Drilling Research Center shows that [12], the crushing rate of high-strength hollow glass beads after passing through the nozzle of drill bit is very low, and the wear of hollow glass beads can be reduced by adjusting the nozzle angle.
In 2007, Meng Shangzhi and others used HGS products with densities of 0.32g/cm3 and 0.38g/cm3 to obtain low-density drilling fluid systems with densities of 0.78g/cm3 and 0.8g/cm3. The obtained system not only has excellent rheological properties, filtration loss reduction characteristics and lubrication characteristics, but also has high bearing capacity, which can be used for drilling in 1700m and 2800m wells respectively. The density reducing material HGS used in the system has a very small particle size, so it can be ensured that it will not affect the use of solid control equipment in field application. In 2008, Geng [10] and others prepared a low-density drilling fluid system with a density lower than 0.83 g/cm3, and applied this system to the development of Fuyang low-permeability reservoir in the periphery of Daqing. In 2009, Chen Siwu [13] applied the HGS oil-in-water drilling fluid with the density of 0.83g/cm3 to the drilling of Shen 289 well, which realized the artificially induced underbalanced drilling technology of low-pressure buried hill oil and gas reservoirs and achieved the purpose of protecting oil and gas reservoirs. The application of this technology can effectively reduce the density of drilling fluid, and at the same time, the existence of hollow glass beads ensures that the drilling fluid is in pure liquid state in the drill string, which solves the problem that conventional measuring instruments while drilling can not effectively transmit signals in multiphase flow.
1.2 low density cement slurry technology
After 2 1 century, American 3M company developed HGS series hollow glass beads with compressive strength exceeding 100MPa. With the appearance of this technology, the micro-silica microbeads composite low-density cement slurry system has achieved an ultra-low-density cement slurry system with a density of about 1.0g/cm3 and high strength and pressure stability. In recent years, in order to meet the requirements of drilling operation and adapt to the complex wellbore structure, the requirements for low-density drilling fluid have been continuously improved, which makes the technology of microbead-gas foam low-density cement slurry gradually mature. In recent years, many foreign companies have adopted the low-density cement slurry technology based on microbead low-density cement slurry [14 ~ 16], and further reduced the cement slurry density through foam technology. There are serious drilling problems in Samaria area in south-central Mexico, where the fracture pressure gradient is very low (0.879 ~ 1. 198g/cm3). Firstly, microbead cement slurry with the density of 1.32 ~ 1.44 g/cm3 was prepared, and then the cement slurry was expanded to the density of 0.998g/cm3. Since the introduction of micro-bead foam low-density cement slurry technology, construction workers have been able to successfully circulate cement slurry above the liner, thus improving the cementing quality in this area.
In 2006, Zhang Hongjun et al. [17] developed an ultra-low density cement slurry system with the density of 1.04 ~ 1.20g/cm3 using HGS hollow glass beads produced by 3M Company, and successfully applied it to the tower depth 1 well of key deep exploration wells in China Petrochemical Company. In 2007, Sun Fuquan et al. [18] developed an ultra-low density cement slurry system with a density of 0.96g/cm3 based on the research of new compressive hollow microspheres and the particle grading theory. The system has good stability, and the strength of cement at 70℃ for 48h is not lower than 18MPa. In 2009, Sun Xinhua et al. [19] developed an ultra-low density cement slurry system with the density of 1.0 ~ 1.30 g/cm3 by using glass beads with high strength, good sphericity and uniform particle size under the guidance of close packing theory.
In 2008, Wan Wei et al. [20] developed an ultra-low density cement slurry system with the density of1.10 ~1.50g/cm3 based on the particle grading theory, which has the advantages of high stability, no shrinkage of cement volume and stable high temperature resistance. In 2009, an ultra-low density cement slurry system with the density of 1. 15g/cm3 was developed by compounding foreign HGS 18000 glass beads with ordinary floating beads. In 2008, Cheng et al. [2 1] introduced the fractal geometry theory into the particle grading model and established the particle group fractal grading model. On this basis, a low-density cement slurry system with the density of 1.4g/cm3 was developed and applied to deep wells in Tarim. A low-density cement slurry system with the density of 1. 10g/cm3 was further developed by using 3M microbeads and superfine cement.
It can be seen that most of these low-density and ultra-low-density systems choose HGS products from 3M Company as lightening agents. At present, there is no report on the field application of hollow glass beads in China, so it is necessary to strengthen the research in this field.
2 Research status of high strength hollow microspheres at home and abroad
2. 1 Study on Hollow Glass Beads Abroad
At present, the production technology of hollow glass beads is mainly mastered by several foreign manufacturers [12], such as 3M, PQ, Emerson, Asahi Glass Company of Japan, etc. Among them, the products of American 3M Company occupy most of the domestic and foreign petroleum engineering markets. After years of research, American 3M Company has formed several series of hollow bead products and seven HGS series of high-performance hollow glass bead products [15]. Table 1 shows the performance of high-performance hollow glass beads of 3M company, and Table 2 shows the main glass bead products of 3M company.
Table/Properties of High Performance Hollow Glass Beads of Kloc-0/3M Company
From the table 1, it can be seen that the main component of high-performance hollow glass beads of 3M company is alkali lime silicate glass, which has stable chemical properties and softening temperature as high as 600℃, so it has the characteristics of high temperature resistance.
Table 2 Performance Comparison of HGS Series Hollow Glass Beads of 3m Company
As can be seen from Table 2:
1) HGS 2000-HGS 6000, the particle size distribution of these five products is very close, and their compressive strength is related to density. The higher the density, the greater the compressive strength of the product. Therefore, when the particle size of microspheres is similar, the bearing capacity of microspheres is related to their density, and the greater the density, the greater the compressive strength of microspheres.
2) 2) The densities of HGS10000 and HGS 18000 are both 0.6g/cm3, and the HGS 18000 with relatively small particle size has high strength. Therefore, under the same density of microspheres, the bearing capacity of microspheres is related to their particle size. The larger the particle size, the greater the compressive strength of microspheres.
2.2 Study on China Hollow Glass Beads
The domestic research on low-density and high-strength hollow glass beads is still very lacking, and it is almost completely dependent on imports. Although in the 1970s, domestic scientific research institutes began to develop hollow glass beads [22 ~ 24] by furnace melting, but it has not been able to form large-scale production. In the early 1990s, some domestic manufacturers introduced a hollow glass bead production line with huge investment, but the performance of the beads produced was too poor to meet the requirements of high performance.
At present, only the Institute of Physical and Chemical Technology of Chinese Academy of Sciences has reported the research of high-performance hollow glass beads. Pan Shunlong et al. [22], Institute of Physical and Chemical Technology, Chinese Academy of Sciences, developed a new production process of hollow glass microspheres based on soft chemistry method, which can not only improve the properties of microspheres, but also improve the bead formation rate of microspheres. Table 3 shows the pressure-bearing performance of the developed hollow glass beads.
Table 3 Properties of China Hollow Glass Beads
It can be seen from Table 3 that when the density is 0.2 1g/cm3 and the pressure is 12MPa, the crushing rate of glass beads is as high as 40.6%. When the density reaches 0.50g/cm3, the crushing rate is only 5. 1% under the pressure of 12MPa. This shows that with the increase of the density of hollow glass beads, the bearing capacity increases. As can be seen from the comparison table 2, there is still a big gap in the research of high-performance hollow glass beads at home and abroad.
3 theoretical research on hollow microspheres at home and abroad
At present, the main methods for preparing hollow glass beads at home and abroad are template method, emulsion method, spray drying method, powder method, droplet method and xerogel method [25 ~ 30], but the preparation theory of hollow glass beads has not been systematically reported [3 1 ~ 34]. Based on the physical essence of these methods, the author divides them into three categories: one is chemical precipitation; The second is the solution drying granulation method; The third method is powder melting granulation.
Preparation of hollow spheres by chemical precipitation method
Chemical precipitation method mainly uses materials to deposit on a preset template, and then removes the template to obtain hollow spheres. First, select specific substances as templates [24 ~ 27] (such as hard template microspheres such as polystyrene microspheres and silica, and soft templates such as micelles and emulsions). By controlling the assembly, adsorption and precipitation reactions of precursors on the template surface, the surface coating shell is formed by physical and chemical methods such as sol-gel method, and then the template is removed by dissolution, heating or chemical reaction, so as to obtain hollow structural microspheres of the required materials.
Figure 1 is a schematic diagram of hollow microspheres prepared by chemical precipitation method. It mainly includes three steps: (1) Select a spherical solid ball with appropriate size as a template; (2) using sol-gel method, layer-by-layer self-assembly method, interface reaction method and other methods to precipitate on the surface of the solid ball to form a shell; (3) removing the template in the shell by methods such as dissolution, heating or chemical reaction.
Figure 1 principle of preparing hollow spheres by chemical precipitation method.
The method can control the thickness of the shell by controlling the increase of reactants; The size of the cavity is controlled by selecting the size of the preset template ball.
3.2 Preparation of Hollow Spheres by Solution Drying Method
Drop method, emulsification method and spray drying method [28 ~ 3 1] all belong to this kind of method. The raw materials used in this method must be water-soluble. First, the material is dissolved in water to form a stable system. Then, the solution is dropped into a dryer or a high-temperature shaft furnace by a droplet generator, and air is blown in the falling process to form a hollow ball; It is then dried, refined, cooled and collected (Figure 2). The main equipment of this method includes vertical droplet furnace and droplet generator.
Fig. 2 schematic diagram of preparation of hollow spheres by solution drying method
3.3 Preparation of hollow spheres by powder melting
Hot-melt method is mainly to make the material reach high-temperature melting state, and the molten particles form spheres under the action of surface tension, and then they are blown or foamed internally to form hollow spheres (Figure 3). The commonly used powder metallurgy method and xerogel method [32 ~ 34] all belong to this kind of method.
Principle of preparing hollow spheres by melting method.
Although the above theoretical methods are different in process, they mainly include two theories: one is balling theory; The second is the theory of hollowing out. There are mainly three kinds of balling theories: using preset spherical template, droplet gravity balling and molten surface tension balling. There are also three kinds of hollowing out theories: eliminating the preset core, inflating it into hollowing out, and foaming it into hollowing out.
4 Conclusions and suggestions
4. 1 conclusion
1) With the popularization of deep well and ultra-deep well technology and the increase of energy-exhausted formations, the technology of low-density drilling fluid and low-density cement slurry with stable density under high pressure has been applied more and more. However, most of the high-performance hollow glass beads used in China are products of foreign 3M companies, which requires strengthening the research and development of high-performance hollow glass beads.
2) When the composition of hollow glass beads is similar, the bearing capacity is related to many factors such as density and particle size. When the particle size of microspheres is similar, the bearing capacity of microspheres is related to their density. The greater the density, the greater the compressive strength of microspheres. Under the same density of microspheres, the bearing capacity of microspheres is related to their particle size. The larger the particle size, the greater the compressive strength of microspheres.
3) At present, there are three main principles for making hollow spheres: chemical precipitation, solution drying and powder melting. Although the processes of these theoretical methods are different, they mainly include spheroidization theory and hollowing theory. There are mainly three kinds of spheroidization theory and three kinds of hollowing theory.
4.2 Suggestions
Through investigation and analysis, it is suggested to study high-performance hollow bead density-reducing materials from the following aspects:
1) The chemical composition of hollow microsphere shells was studied in order to obtain high temperature resistant shells with good cementation.
2) In the process of pelletizing, it is suggested to adopt high-temperature melting pelletizing method. Compared with chemical precipitation and solution drying, the structure formed by materials in high temperature melting state will be denser.
3) In the hollow process, it is suggested to adopt the method of inflation, and control the hollow degree and size of the spherical shell by controlling the feed and gas supply. The method of presetting nuclei is more suitable for chemical precipitation; In the internal foaming method, the foaming size is not easy to control, and it is easy to make the shell uneven.
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