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Alkyl glycosides (APG) are mainly used in many industries such as daily chemical products, textile, leather auxiliaries, paper making auxiliaries, etc. The application of alkyl glycosides in drilling fluids was first reported in 1994 abroad, and the research on the application of alkyl glycosides in drilling fluids was started in 1996 in China. The first alkyl glycoside studied and applied in drilling fluids is methyl glycoside (MEG), and then there are ethyl glycoside, propyl glycoside, dodecyl glycoside, trimethylsilyl glycoside, carboxymethyl glycoside, etc. Among them, the most widely used alkyl glycoside is MEG.
Since the added volume of alkyl glycosides should be not less than 35% to give full play to its effect, the domestic research and development of modified alkyl glycoside derivatives based on alkyl glycosides has been carried out for the problems of high cost, inhibition and temperature resistance of alkyl glycosides in drilling fluid applications, and the application of modified alkyl glycoside derivatives in drilling fluids has gradually gained attention, and sulfo-methyl alkyl glycosides, polyether alkyl glycosides, cationic Among them, the most studied and widely used alkyl glycoside derivatives are cationic alkyl glycoside (CAPG) and polyether amine alkyl glycoside (NAPG).
1 Research on the application of alkyl glycosides in drilling fluids
1.1 Methyl glycoside
EG is made from glucose and methanol under certain conditions. Zhang Yan et al. were the first to find that MEG could improve the lubricating and inhibiting properties of drilling fluids, and also gave the first theoretical basis that MEG could form an adsorption film on the well wall. Ding Tongwei et al. further showed that MEG stabilizes shale by film formation, permeation and dehydration, and exhibits unique inhibition, lubrication and reservoir protection properties. Lei Zumeng et al. found that: MEG can adsorb and form a film on the clay surface; the film efficiency of MEG on the mud shale surface is related to the MEG concentration and soaking time; the higher the MEG concentration and the shorter the soaking time, the higher the film efficiency; MEG inhibits clay hydration and improves the film efficiency together to achieve well wall stabilization through adsorption and film formation. Lv Kaihe et al. found that MEG reduces the water activity of drilling fluid, improves the membrane efficiency of mud shale, reduces the leaching of drilling fluid filtrate into the formation, and finally achieves collapse prevention.
MEG can play different roles in different drilling fluid systems. adding MEG to ultra-low permeability drilling fluid systems can reduce the filtration loss of drilling fluid while improving the inhibition, lubricity and solid phase capacity of drilling fluid. adding MEG to silicate drilling fluid systems, its micelles adsorb on the surface of treating agent and solid phase particles to form a water-repellent barrier, which can prevent or reduce the interaction between silicate and barite surface and silicate This improves the rheology of silicate drilling fluids and significantly reduces the high-temperature and high-pressure filtration loss of drilling fluids.
In 1999, the first field test of MEG was conducted in Sha 113 well, and the results showed that the drilling fluid with MEG had good inhibition, outstanding reservoir protection performance and wall building and wall protection, effectively solved the problem of well wall collapse in strong water-sensitive formations, the well diameter was regular, the electric core testing was successful once, and the average mechanical drilling speed was 47. 8% higher than that of neighboring wells. Subsequently, field tests of MEG were carried out in Daqing, Shengli and Zhongyuan oilfields, and the application results showed that the drilling fluid with MEG has better lubricating performance, while the reservoir protection and collapse inhibition are outstanding.
1.2 Other alkyl glycosides
In addition to MEG, domestic research on the application of other alkyl glycosides in drilling fluids was carried out indoors at the same time, but there are fewer reports of such products actually being applied in field drilling fluids.
Xia Xiaochun et al. used starch and ethanol to synthesize ethyl glycoside (ETG), and when ETG was added at 20%, the reduction rate of lubrication coefficient and linear swelling reduction rate of the base slurry were greater than 60%. Zhao Suli et al. used starch and ethanol to synthesize ethyl glycoside, which could significantly improve the recovery of shale rolling by more than 50% at 2% addition, and the resistance temperature could reach 150℃. Lei Zumeng et al. synthesized ethyl glycoside from glucose and anhydrous ethanol, which was well-matched with conventional treating agents such as SD I-17W and LV-CMC, and could improve its high temperature resistance. Cai Lishan et al. found that the addition of ethyl glycoside into the silicate drilling fluid system further enhanced the ability of the system to form a film on the shale surface, improved the lubricating ability of the system, and improved the shale inhibition effect.
Wang Ruli made ethyl glycoside from glucose and ethylene glycol could enter the interlayer of montmorillonite through the action of displacement and hydration, etc., and replace the interlayer water of montmorillonite, which destroyed the hydration film in montmorillonite and inhibited the hydration swelling of clay.
Jiang Juan et al. synthesized n-propyl glycoside (BEG) and isopropyl glycoside (PEG) from corn starch. Indoor studies showed that when 7% of BEG or PEG was added to the drilling fluid, the shale rolling recovery of the drilling fluid reached more than 95%, the lubrication coefficient was 0.029, and the permeability recovery value was greater than 90%, and it also had certain resistance to salt contamination.
Zhang Huahui synthesized DTG I1, a polyhydroxy glycoside anti-collapse agent, from starch and fatty alcohols, which has certain effects of inhibiting mud shale hydration and swelling and dispersion, and can effectively improve the film efficiency of mud shale and reduce the water activity of drilling fluid. DTG-1 has a certain effect of reducing filtration loss and has a good effect of regulating flow pattern in high-density drilling fluid, which can effectively reduce the apparent viscosity and dynamic shear of high-density drilling fluid and make high-density drilling fluid have good flow performance.
Zhang Jie et al. showed that the combination of heteroglycoside KD I03 and hydrolyzed polyacrylonitrile salt can form a non-thickening drilling fluid system with significantly lower viscosity and improved performance.
Huijun Su and Dan Cai et al. synthesized trimethylsilyl glycoside (TSG) from glucose and trimethylsilyl chloride as raw materials, and the test results showed that TSG has a better effect of inhibiting clay hydration swelling and dispersion; the linear swelling rate of bentonite was only 54.62% and the anti-swelling rate was 79.07% in the aqueous solution of TSG with a mass fraction of 10%. Cai Dan et al. synthesized carboxymethyl glycosides by sodium chloroacetate and glucose, and the linear swelling of bentonite in 10.0% aqueous solution was 60.09% at 90 min; quaternary ammonium-type glycosides were synthesized by 2,3 monoepoxypropyltrimethylammonium chloride and glucose, and the linear swelling of bentonite in 10.0% aqueous solution was 56.11% at 90 min; bipartite glycosides were synthesized by glucose and epichlorohydrin The bentonite linear swelling rate was 56.37% in 10.0% aqueous solution at 90 min.
The dodecyl glycoside synthesized by Sun Ao can be used as the main emulsifier, together with the emulsion stabilizer lauryl alcohol and co-emulsifier Span I 20. The solid-free low-density water-in-oil drilling fluid formulated with this emulsifier can resist temperature up to 120°C and has good resistance to soil intrusion, crude oil intrusion and salt intrusion.
Xin Yinchang et al. found that the ionic compound foaming agent QR I1 prepared by alkyl glycoside, DM5512, betaine and 1631 can be used as a foaming agent for temperature- and salt-resistant and oil-resistant microfoaming system, and it can also maintain good performance in the base fluid with mineralization degree of 10×104 mg/L.
Gao Changhong found that the compounded alkyl glycoside APG-AB could significantly improve the high-temperature and high-pressure water loss of drilling fluids even with a small addition, and a 1% addition of APG-AB could reduce the high-temperature and high-pressure water loss of brine polymer base slurry from 36 mL to 8 mL, and also improve the temperature resistance of polymers in drilling fluids. According to Zhao Suli, alkyl glycosides are well-matched with conventional polymers, while they can synergistically improve the temperature resistance of polymers in drilling fluids, and can improve the solid phase capacity of drilling fluids, and can be used as drilling fluid viscosity reducers, cement slurry dispersants and retarders.
Zhao Hu et al. conducted an indoor study on calcium chloride monoalkyl glycoside drilling fluids. Alkyl glycosides can improve the temperature resistance and pollution resistance of polymers and solve the problems of difficult rheology and filtration loss control of calcium chloride drilling fluids, and the temperature resistance of calcium chloride monoalkyl glycoside drilling fluids reached 130°C with good inhibition and lubricity.
2 Research on the application of alkyl glycoside derivatives in drilling fluids
2.1 Sulfonated alkyl glycosides
The nonionic surfactant alkyl glycoside was modified to anionic surfactant sulfonated methyl ethyl glycoside by introducing sulfonated methyl on ethyl glycoside. The ability of this product to interact with bentonite is further enhanced compared with alkyl glycoside, and the viscosity reduction ability and anti-collapse inhibition are also further improved, and the satisfactory effect can be achieved with a small amount of addition, and the foaming property is weakened, and the temperature resistance can reach 180℃ due to the addition of sulfonyl methyl group, which can be widely used in medium-deep well or ultra-deep well drilling fluid.
The field application of sulfomethylethyl glycoside in five wells including Panshiao 5 in Shengli Oilfield shows that the new multi-hydroxyl polymer drilling fluid has good comprehensive performance, which can effectively inhibit the hydration swelling and dispersion of mud shale, prevent the collapse of the formation, with small friction coefficient and fast drilling speed, and can fully meet the requirements of complex wells such as deep wells and special process wells. Among them, the design construction period of Panshui 5 well is 50 d, but the actual construction period is only 28 d, which greatly shortens the construction period and saves the drilling cost.
2.2 Polyether alkyl glycosides
Polyether alkyl glycosides were synthesized by cetyl alcohol, glucose, ethylene oxide and propylene oxide, which have no acute skin toxicity and no fish toxicity as thick oil emulsion viscosity reducers, and are environmentally friendly emulsion viscosity reducers. When the mass fraction of emulsifying viscosity reducer is O.3%, the oil-water interfacial tension can reach the order of 10-3 mN/m, and the viscosity reduction rate can reach 92.1%, which has a very good viscosity reduction effect.
2.3 Cationic alkyl glycosides
Through molecular design, Si Xiqiang et al. synthesized cationic alkyl glycosides based on alkyl glycosides for the first time. The product has 99.15% primary shale recovery, 0.088 extreme pressure lubrication coefficient for 2% CAPG aqueous solution, 483 500×10-6 EC50 value and 150°C temperature resistance. CAPG product has good compatibility with conventional water-based drilling fluid system.
Currently, CAPG has been applied to more than 40 wells in the field. After using CAPG in Jingnan 72-13H1 well, the average mechanical drilling speed of the horizontal section is 9.71 m/h, which is 72% higher than the average mechanical drilling speed of the neighboring Jingnan 70-6H1 well at the same level; after using CAPG in Wen209 side 7 well, the average well diameter expansion rate of the applied section is only 11.4%, which is 44.63% lower than that of the neighboring Wen209 -After using CAPG on Wen209 side 7 well, the average well diameter enlargement rate of the applied section is only 11.4%, which is 44.63% lower than that of the neighboring well Wen209.
2.4 Polyetheramine based alkyl glycosides
Through molecular design, Si Xiqiang et al. developed polyether amine alkyl glycosides based on alkyl glycosides for the first time. The product has a strong inhibitory effect on the hydration dispersion of rock chips with a small content. 0.1% NAPG aqueous solution has a primary shale recovery rate of 96.8%, an EC50 value of 528,800×10-6 and a temperature resistance of 160°C. Compared with CAPG, the NAPG product has a better inhibitory performance and good compatibility with conventional water-based drilling fluids.
At present, the product is being tested in the field in more than 20 wells, including Jingyue 4-3 well and Cele 1 well. In response to a series of problems in the field, such as blocking when changing the drill bit and drilling to a depth of 4960 m, repeatedly scribing the hole but still difficult to lift the lowering, and returning to the pump and dropping more blocks, adding 0.5% NAPG product to the well slurry in the field, the blocking phenomenon disappeared after circulating the drilling fluid for a period of time, and the block dropping was obviously reduced, and in the later drilling process, keeping the amount of NAPG in the drilling fluid at 2%, there was no block dropping in the well, and the electric test and lower In the later stage of drilling, the NAPG dosage of 2% in the drilling fluid was maintained, and there was no block drop in the well.
The alkyl glycoside derivative high-performance water-based drilling fluid with NAPG, CAPG and APG as the core was tested in three wells including YS108H8-5 in Zhaotong Shale Gas Demonstration Area, and the application results showed that the alkyl glycoside derivative high-performance water-based drilling fluid has stable performance, strong inhibition and plugging, good lubricity, extreme pressure lubrication coefficient of 0.09, viscosity The coefficient of extreme pressure lubrication is 0.09, the viscosity coefficient is 0.04, the start-up and downhole drilling is smooth, the casing operation is successful once, and no downhole complications occur. At the same time, compared with the high-performance water-based drilling fluids used in CNPC and overseas, the mechanical drilling speed is higher, the drilling cycle is shorter, and the cost is 15% to 20% lower compared with neighboring wells.
The oil-based drilling fluid formed by NAPG as the main agent was tested on site in the YunHPing 6 well in the Yanchang Shale Gas Demonstration Area. Under the condition that the soft mudstone in the second-opening slope section was as high as 70%, the average friction of starting and drilling in this section was 2-4t, and the average well diameter expansion rate was only 4.89%; while the average well diameter expansion rate in the neighboring YunHPing 3 well was 20.2%. The test results show that NAPG-type oil-based drilling fluid can effectively solve the problems of well wall instability and bit mud pack in highly reactive mud shale formations.
3 Conclusions and recommendations
1) Alkyl glycosides, as a composite functional treatment agent, can be selected and used for different needs of drilling fluids. In addition to the main functions of anti-collapse inhibition, lubrication and environmental protection, alkyl glycosides of different structures in drilling fluids can also improve the solid phase capacity of drilling fluids and the temperature resistance of polymers in drilling fluids, and can be used as viscosity and filtration loss reducing agents for conventional drilling fluids, dispersing agents and retarders for cement slurries, emulsifiers for oil-in-water drilling fluids and foaming agents for microfoaming systems.
(2) Alkyl glycoside derivatives, sulfomethylethyl glycoside, have been substantially improved in terms of temperature resistance while the dosage in drilling fluids has been reduced and the inhibition has been improved; alkyl glycoside derivatives, CAPG and NAPG, have been substantially improved in terms of inhibition and anti-collapse ability in mud shale formations with less dosage and lower cost in drilling fluids, and have been produced on a large scale and applied to more than 60 wells in the field with remarkable effects.
(3) Based on the high performance water-based drilling fluid of alkyl glycoside derivatives and oil-based drilling fluid of NAPG type, we are exploring the formation of alkyl glycoside derivatives based on NAPG and other alkyl glycoside derivatives with strong inhibition, high lubrication and green features, which will bring the research and application of domestic high performance water-based drilling fluid to another stage.