论文部分内容阅读
Abstract: The development history of the inhibitors of drilling fluid reviewed in this paper. The advances of inhibitors commonly used at home and abroad were included. That the inhibitive ability was good enough whose inhibiting mechanisms and effects were introduced in the past 10 years.
Key Words: Wellbore Stability, Drilling Fluid, Inhibitors
1.Introduction
Wellbore instability is always a complex global problem in drilling engineering. It often makes huge problems: hole shrinkage, wellbore caving, drill pipe sticking, poor cementing quality, and so on. These drilling accidents not only extend the drilling cycles, but also improve the drilling costs.[1]~[2] Especially in recent years, the number of deep drillings increase year by year with the further development of resources exploration and development and extended reach wells also increase in the oilfield. Wellbore instability is quite outstanding problems due to the complex and changeable formation types during drilling, with the addition of the influence of high temperature and high pressure in deep well.[3]~[5]It would be more serious when there are some clay shale formations, like swelling because of physical factors and chemical factors, which would not be extend in this paper.[6]
According to the experience of engineers, this problem can be controlled through the following two aspects: drilling technology and drilling fluid.
Drilling technology, many people think, can play a role through the following aspects: 1)controlling trip speed to avoid too high swab pressure, 2) controlling the pump pressure to avoid too large annular velocity of drilling fluid to scour sidewall, 3) avoiding big changes of well orientation in the design of wellbore trajectory and in the process of drilling,4)avoiding severe mechanical touch attack when drilling, especially in the fragile formation,5)running casing to separate the formations when they are extremely easy to collapse or have strong ability of hydration expansion. In fact, unaware of the information underground or misunderstanding the actual situation, the operating personnel operate, which may cause greater harms. At the same time, even if all the facts are all considered, I think, as for deep well drilling , it does not make sense just though drilling technology to control wellbore instability.
Meanwhile, making use of drilling fluid to stabilize wellbore has the following advantages: 1)timeliness, 2) long effectiveness, 3)high efficiency, 4) other beneficial effect. Therefore, we pay more attention to drilling fluid in reality and it is a good technical measure to select well inhibitive drilling fluid whose main treating agents are inhibitors to control the problems mentioned above.
In conclusion, it is of great use to direct drilling, realize safe production and improve the economic benefit with reviewing past and present inhibitors.
Generally speaking, effective inhibitors should have the following characteristic: 1) powerful inhibitive, 2) a little sealing characteristic, 3) having seldom effect on drilling rate, 4) having seldom effect on the rheological properties of drilling fluid, 5) wide adaptability (it can be used in geological prospecting and in oil and gas).
2.Development History and Current Situation
During drilling well, drilling workers drived a herd of cattle through a pit filled with water at Spindletop, in Texas, in 1900. It became mud, which was sticky, slimy and water-soil mixture. Then, drilling workers put it into well with pump. From the category, it belonged to dispersed mud system. Then, drilling workers put inorganic treatment such as sodium carbonate into mud mentioned above which became early fine scattered drilling fluid. But this kind of mud just could be used in shadow wells. To improve the performance of controlling the wellbore instability, they mixed other inorganic treatments gropingly into it, which was, we called, inhibitor.
Now there are many commonly used inhibitors, which can be mainly divided into inorganic and organic ones[7].
Inorganic inhibitors are used early. Potassium chloride, calcium chloride and the like are commonly used. The main inhibiting mechanisms of potassium chloride are neutralization and mosaic effect. And that of calcium chloride are neutralization, common ion effect and penetration hydration effect.
Inorganic inhibitors also have some developments in recent decades, such as silicate[8]~[9],quaternary ammonium salt[10]~[11]and formate, acetate[12]~[16]and so on. Inhibiting mechanisms of silicate are membrane effect and plugging effect. That of quaternary ammonium salt are neutralization, mosaic effect and adsorption effect. That of formate and acetate are membrane effect and bonding effect of carboxylic root and water, and it is also a kind of environmental protection inhibitors. And new MMH[17]~[21](positive colloid) has more characteristic, which can solve the contradiction between wellbore stability and the yield of bentonite through neutralization and adsorption effect. What’s more, it has plugging effect in a degree. So ,it is a promising treatment.
Then, common organic inhibitors are anionic polymer inhibitors, cationic polymer inhibitors and zwitterion polymer inhibitors. Anionic polymer inhibitors include polyethylene acid, polyacrylamide, polyacrylonitrile[22] and humic acid[23].Among them, what used more are PAC, PAM, PHPA[24], KPAM, KPAN and humic acid potassium and so on. Inhibiting mechanisms of them are bridge league effect, flocculation effect and membrane effect. Cationic polymer inhibitors mainly include large and small cationic[25]~[27],secondary organic cationic polymerCSJ-1[28], cationic stabilizer CWD-1[29], high salt cationic polymer HWJ[30]. The effect of them are good but they have bad effect on environment and higher prices. Inhibiting mechanisms of them are neutralization, flocculation action and membrane effect. Zwitterion polymer inhibitors mainly include XY-27 and FA[31] series. Although this type of inhibitors have cation and anion for inhibition effect, the inhibition mechanisms and formation mechanisms are not very clear.
Inhibiting mechanisms of asphalt include adsorption effect and plugging effect. It is good sometimes but easily cause environmental pollution.
New organic inhibitorsincludepolyamine[32]~[35],polyalcohol[36]~[37],carbohydrate derivatives[38]~[39], organic positive colloid[40]~[41], organic aluminum[42], anti-sloughing lubricant FSF[43], low molecule inhibitors FTy[44], synthesis of natural polymer and olefins monomers QYJ[45], UL TRA HIB[46]in ULTRADRILTM water-based drilling fluid system, KHIs[47] (active hydrate inhibitors raised by Malcolm A. Kelland). Small amine and NH+ of polyamine have similar diameter with potassium ion, so inhibiting mechanisms of them are neutralization and mosaic effect. Polyalcohol is from marine drilling and is an environment friendly inhibitor, whose effect is not so good. Carbohydrate derivatives (such as MEG) is surface active material and it has membrane effect. In the meantime, it is a kind of higher price but environmental friendly inhibitors. New organic positive colloid has more positive charge, so it has strong inhibition, but it is a high price inhibitors. Due to good effect in the dissolve and crystallization state, Organic aluminum, being anew inhibitor, has strong inhibition. FSF is anti-sloughing lubricant. QYJ has good temperature resistance, and it can keep stable effect in 150 ℃. And it has good resistance to salt. ULTRA HIB can step in and narrow the distance between the clay electrode to prevent water molecule penetrating and inhibiting shale inflation. KHIs is a kind of inhibitors in deep drilling.
3.Inhibiting Mechanisms and Effects of Some Inhibitors
3.1 Inorganic Inhibitors
3.1.1 Potassium Chloride: inhibiting mechanisms mainly are neutralization and mosaic effect. Potassium ion can partly counteract negatively charged clay from lattice substitution. Meanwhile, due to the right size, potassium ion embeds six ring which consist of oxygen atoms between adjacent crystal layer. Therefore, the effect is better than other inorganic Inhibitors. It is shown in figure 3-1.
Figure 3-1Mosaic effect of potassium ion
3.1.2 Formate: because filtrate of formate drilling fluid has high mineralization and formic acid root has good compatibility with formation water, it can get out of some defects which other drilling fluid with inorganic salts bring to maintain wellbore stability and provide appropriate density and strong inhibitive ability for drilling fluid. Simultaneously, surface of shale is similar to selective semipermeable membrane and water activity of formate drilling fluid is smaller than water activity of formation. Then, infiltration pressure will come and it will keep a trend of formation water flowing into drilling fluid. And HCOO- of formate can form hydrogen bonding with water molecule to restraint free water. According to all of the above mentioned, it can reduce the hydration expansion of clay, stabilize wellbore and protect the reservoir.
3.1.3 Quaternary ammonium salt: it is proved that potassium ion and ammonium ion have the same diameter in the standard pH of drilling fluid.[48]So, typically, many people think that the two kinds of inhibitors should have the same mechanism and effect.
3.1.4 MMH(positive colloid): inhibiting mechanisms have the following aspects: 1) forming a "static membrane" in low shear rate near wellbore, which can make drilling fluid scour wellbore less and stabilize wellbore effectively, 2) “fighting against formation for water”. In this king of drilling fluid, to form drilling fluid system, water molecule is an important part of the complex structure. MMH has a better affinity for water than formation. Then, water will flow from formation to drilling fluid, 3)”stabilizing formation water activity”. After MMH and clay mineral forms complex, it can push a great deal of exchangeable ion out. So it can make ion activity of clay mineral and infiltration hydration reduce. And after MMH-clay complex forms, a layer of positive charge potential barrier forms around charged clay particles, which can obstruct the exchange of exchangeable positive ion and stabilize wellbore.
Table 3-1The readings of CST with different additive amount(MMH)
In the experiment (CST), the reading is smaller, the inhibitive ability is better. The reading was 80(s) in the same drilling fluid with5% potassium chloride. According to what mentioned above, we know that MMH had better effect at small amount than potassium chloride.
3.2 Organic Inhibitors
3.2.1Large and small cationic: large cationic mainly is regarded as flocculant and small cationic clay stabilizer. Due to positive charges of large cationic, it has better adsorption with clay than anion inhibitors. It can neutralize part of negative charges of clay, so its flocculation effect and inhibitory effect is good. Small cationic also has neutralization, at the same time, because of its small ionic diameter, so it can enter the crystal layer and has good inhibitory effect.
Table 3-2 Shale roll recovery of cationic and potassium chloride with different additive amount In the same drilling fluid system
For the test of shale rolling recovery, the higher the recovery is, the better the inhibitory effect is. From the table above, the recovery of cationic inhibitor can reach more than 90% with little added amount.
3.2.2Anionic polymer inhibitors(KPAM):there are many kinds of anionic polymer inhibitor, and PAM , PHPA and their derivatives are used widely and an ideal category. Because of the adsorption and hydration groups of its molecular chain, the former form" anchor point" on shale surface and macromolecules suture tiny cracks transversely, and, for the latter, due to the electrostatic repulsion leading the stretching of molecular chain, which increases its effective length and improves the ability of encapsulation effect for shale particles, then, it stabilizes wellbore and reduces the hydration expansion of clay.
Table 3-3 Shale roll recovery of KPAM with different additive amountIn the same drilling fluid system
From the table above, the recovery of KPAM can reach more than 60% in basic mud.
3.2.3 Polyalcohol: firstly, due to its high viscosity, the flow velocity of filtrate is low and the rate of filtrate intruding into formation is low. Secondly, it can form complex on the surface of clay, row off part of the free water, prevent the water molecules from entering into formation and reduces the hydration expansion of clay. Thirdly, turbidity point effect: when the temperature in the well is higher than its turbidity point temperature, it can separate from drilling fluid and form oil film underground, which can block cake and effectively reduce the filtrate of drilling fluid intruding into formation.
Table 3-4The readings of shale inflation experiment (1%polyalcohol)
For the test, the smaller the linear expansion ratio is, the better the inhibitor is. So it can be seen from the table above that it can effectively improve the inhibitory effect of drilling fluid.
3.2.4 Methylglucoside (MEG): through a lipophilic group and four hydrophilic groups, MEG can reduce the hydration expansion of clay. Hydrophilic group adsorb on shale, makes lipophilic group outwards and form water-in-oil adsorption film on the wall, which can separate water from formation and reduce the loss of filtration. Meanwhile, the hydrophilicity of hydrophilic group is extremely strong, so the time it intrudes into the formation, it will separate water from shale.
Table 3-5Shale roll recovery of MEG with different aperture
4. Conclusion
1）Now, the conventional inorganic inhibitors can actually have certain inhibition with large additive amount, and which can not be good enough.. In recent years, the effect of inorganic inhibitors has been improved and they can meet the environmental requirements. However, compared with organic inhibitors, they still below the mark.
2) The effects of conventional organic inhibitors are good, but whose adaptability is not good enough, and great majority inhibitors can't meet the environmental requirements. The effect and adaptability of new organic inhibitors have improved in recent years, and are more environmental protection which inferior to inorganic inhibitors.
3) The author thought that, in later years, when drilling we should consider organic and inorganic inhibitors at the same time, namely, synergistic effect. Meanwhile, either organic or inorganic inhibitors should strive to achieve better inhibition effect and be more environmental protection.
4)The derivatives of new inhibitors (polyamine derivative UID[49]), nanoscale inhibitors (positive colloid nano-emulsion[50]) and super polymer[51] may be good development directions.
References：
[1] Chen Xiurong. Study on shale wellbore stability [D]. Hubei: China University of
Geosciences.2009.5,1.
[2] R.L. Anderson, et al. Clay swelling — A challenge in the oilfield[J].Earth-Science
Reviews,2010,98:201~216.
[3] Yan Jienian. Drilling fluid process principle [M]. Shandong: Petroleum University Publishing
House.2001.5,24.
[4] Wu Xiaoming, Hu Yule, et al. Drilling fluid and geotechnical slurry[M]. Hubei: China
University of Geosciences.2002,4.
[5] Chen Tinggen, Guan Zhichuan, Liu Xisheng. Drilling engineering theory and technology [M]. Beijing: China's oil university press.2006,207~211.
[6] Van Oort E. On the physical and chemical stability of shales. J. Petrol. Sci. Eng 38：
[7] Wang Quanping. Drilling fluid and its function principle [M]. Beijing：Petroleum University
Publishing House,2003.9,2~4.
[8] Tu Yunzhong, et al. A research on silicate drilling fluid of marine natural gas hydrate drilling
[J].Modern Geology,2009.4,23（2）:224~228.
[9] Yang Yong, et al. High inhibition and HSE advantages of WDX silicate drilling
fluid[J].Drilling Fluid & Completion Fluid,2010.9,27（5）：38~40.
[10] Zhong Hanyi, et al. Development and features of amine shale inhibitors [J].Petroleum
Drilling Techniques, 2010.1,28（1）：104.
[11] R. Schlemmer, et al. Progression of Water-Based Fluids Based on Amine Chemistry– Can
[12] the Road Lead to True Oil Mud Replacements?.AADE-03-NTCE-36,1~12.
[13] Dai Yongjin, et al. Application of non-dispersed formate/polymer drilling fluid in Hongze Area of Jiangsu Province[J]. Drilling Fluid & Completion Fluid,2004.11,21（6）：67~69.
[14] Li Yishou, et al. Application of non-dispersed formate/polymer drilling fluid in Tuba oilfield[J]. Drilling Fluid & Completion Fluid,2006.11,23(6):5~9.
[15] Yi Shaojin, et al. Study on Environment Acceptable Formate Brines for Drilling and Completion[J].Environmental Protection of Oil and Gas Fields,2000.9,10（3）：40~42.
[16] Meng Xiaomin, et al. Application of formate base drilling fluid technology [J].Drilling Fluid & Completion Fluid ,2003,20（5）：62~64.
[17] Li Zhiyong, et al.ANovelFormate/Positive-ChargedPolyglycolDrillingFluid[J].Petroleum Drilling Techniques ,2006.9,34（5）：34~37.
[18] Yin da, et al. Using MMH system for lost circulation prevention and plugging [J]. Drilling Fluid & Completion Fluid,2000,17（1）：46~48.
[19] Wang Fuhua, et al. Study on Inorganic Positive Gel/Polyol/Polymer Drilling and Completion Fluid[J].Petroleum Drilling Techniques ,2001,33（1）：24~27.
[20] Huang Hefu. Application of MMH polyol drilling fluid in Linpan area[J].Drilling Fluid &Completion Fluid,2002,19(4):44~45.
[21] Zhang Qinfu. Study on the performance of MMH drilling fluid system[J].Journal of Oil and Gas Technology,2005.4,27（2）：251~253.
[22] Liu Guichuan, GuoCaixuan. Application of MMH drilling fluid system[J].Geology and Prospecting,2000.3，36(2)：76~78.
[23] Fu Meilong, Hu Xingqi. An Investigation into Shale Stability by Utilizing Copolymer of
Acrylamide and Acrylonitrile and Its Derivatives [J]. Journal of Jianghan Petroleum Institute,1997.3，19(1):70~74.
[24] Shi Yongli, ShenQinchang. Application of humic acid in the oil drilling fluid [J].HumicAcid,1996,4:1~5.
[25] Guerrero, X., et al. Use of amine/PHPA system to drill high reactive shales in the Orito field in Colombia. SPE Paper 104010, First International Oil Conference and Exhibition. Cancun, Mexico, 31 August–2 September.
[26] Beihoffer, T.W, et al. The Development of an inhibitive Cationic Drilling Fluid for Slim Hole CoringApplication.SPE19953
[27] Retz, R.,Friedheim, et al. An environmentally acceptable and Field-Practical, Cationic Polymer Mud System, SPE 23064.
[28] Wang Junying. Research and application of cationic drilling fluid in Tuha Oilfield[J].Drilling Fluid & Completion Fluid,2008.5,25(3):39~42.
[29] Lin Zhipeng, Yang chengzhi. Secondary organic cationic Polymer drilling fluid technology[J].Drilling Fluid & Completion Fluid ,2003,20(5):1~3.
[30] Ye Guanghui, Zhang Xiaojun. Application of CWD一l in drilling fluid[J].Inner Mongolian Petrochemical,2008,18:120~121.
[31] Wang Jian, et al. Lab study on hyperhaline cationic polymer drilling fluid for deep water drilling[J]. China Offshore Oil and Gas，2007.12,19（6）：405~408.
[32] Liu Feng, Chen Feng, LI Lei. Application of zwitterionic polymer drilling fluid in Shanbei Area[J].Petroleum Drilling Techniques ,1998.12,26(4):22~23.
[33] Su Xiuchun, et al. Research on organic amine inhibitor BZ-AN1 used in high inhibitive drilling fluid.[J].Drilling Fluid & Completion Fluid,2011.3,28(2):32~35.
[34] Mei Hong, et al. Synthesis and evaluation of new polyamine inhibitor [J].Xinjiang Oil and Gas，2010.6,6（2）：47~49.
[35] Wang Jian, et al. A laboratory study on strongly inhibitive polyamine drilling fluid[J]. Oilfield Chemistry，2007.12,24（4）：296~300.
[36] Arvind Patel, Emanuel Stamatakis, James E. Highly Inhibitive Water-Based Fluid System Provides Superior Chemical Stabilization of Reactive Shale Formations [J]. AADE 01-NC-HO-55.
[37] Li Wanqing, Yu Jian, et al. Application of Inhibitive Polyglycol drilling fluid in Da'an area [J].Drilling Fluid & Completion Fluid,2006.5,23(3):77~78.
[38] Liu Tianle, Jiang Guosheng, TuYunzhong, et al. Research on the polyolcol drilling fluids for offshore hydrate drilling [J]. Oil Drilling & Production Technology，2009.10,31（5）：52~55.
[39] Lv Kaihe, Qiu Zhengsong, Sun Mingbo. Study on anti-sloughing mechanism of methylglucoside [J]. Natural Gas Industry,2007.2,27（2）：70~72.
[40] Zhang Jie, GuoGang. An evaluation of high temperature inhibition behavior of heteropolysaccharide drilling fluids [J].Natural Gas Industry,2010.1,30(1):80~82.
[41] Wang Xueying, Wei Jun, Li Kaiqi. Study and applicationof newly organic cationic GEL drilling fluid [J]. Oil Drilling and Production Technology，2005.12,27(6):30~33.
[42] Wang Fuhua, Wu Mingqiang. Preparation and application of organic positive polymer drilling fluid [J]. Acta Petrolei Sinica,2004.9,25(5):93~98.
[43] Yan Daobing, et al. Research and application of organic aluminum complex-potassium drilling fluid system [J].Drilling Fluid & Completion Fluid, 2005.17.
[44] Mei Jie, et al. The Application of FSF Anti - collapse Lubricating Drilling Liquid in North Shanxi[J]. Shanxi Science and Technology, 2005.5,5: 106~107.
[45] Ding Tongwei, Yan Jienian. Experimental study of new water-based drilling fluid: FT y, of [J].Drilling Fluid & Completion Fluid, 2005.11, 22(6):13~15.
[46] Qian Mengzhan, et al. Development and application of anti-sloughing agent QYJ.[J]. Oil Drilling and Production Technology，2006.12,28（6）：27-30.
[47] Kong Qinming, et al. Application of ULTRADRILTM Water Base Mud in Well Zhanghai 502FH [J].Drilling Fluid & Completion Fluid, 2006.11,23（6）：71~76.
[48] Malcolm A. Kelland, et al. Feasibility Study for the Use of Kinetic Hydrate Inhibitors in Deep-Water Drilling Fluids[J].Energy & Fuels,2008,22:2405~2410.
[49] Grim, R.E.: Clay Minerology, First Edition; McGraw- Hill (1953) 148.
[50] Wang Jian, et al. Lab Research on the Novel Inhibitive Drilling Mud : UID.[J].Drilling Fluid & Completion Fluid,2007.9,24:72~75.
[51] Wang Peiping, et al. Application of Positive Colloid Nano-emulsion Drilling Fluid in Shengli Oilfield[J]. Journal of Jianghan Petroleum University of Staff and Workers,2006.7,19(4):38~40.
[52] Young, S., Maas, Ton Maas, Noviant, B.V., Nijmegen, 2001. Novel polymer chemistry increases shale stability. AADE National Drilling Technical Conference, AADE 01-NC-HO-41.
Key Words: Wellbore Stability, Drilling Fluid, Inhibitors
1.Introduction
Wellbore instability is always a complex global problem in drilling engineering. It often makes huge problems: hole shrinkage, wellbore caving, drill pipe sticking, poor cementing quality, and so on. These drilling accidents not only extend the drilling cycles, but also improve the drilling costs.[1]~[2] Especially in recent years, the number of deep drillings increase year by year with the further development of resources exploration and development and extended reach wells also increase in the oilfield. Wellbore instability is quite outstanding problems due to the complex and changeable formation types during drilling, with the addition of the influence of high temperature and high pressure in deep well.[3]~[5]It would be more serious when there are some clay shale formations, like swelling because of physical factors and chemical factors, which would not be extend in this paper.[6]
According to the experience of engineers, this problem can be controlled through the following two aspects: drilling technology and drilling fluid.
Drilling technology, many people think, can play a role through the following aspects: 1)controlling trip speed to avoid too high swab pressure, 2) controlling the pump pressure to avoid too large annular velocity of drilling fluid to scour sidewall, 3) avoiding big changes of well orientation in the design of wellbore trajectory and in the process of drilling,4)avoiding severe mechanical touch attack when drilling, especially in the fragile formation,5)running casing to separate the formations when they are extremely easy to collapse or have strong ability of hydration expansion. In fact, unaware of the information underground or misunderstanding the actual situation, the operating personnel operate, which may cause greater harms. At the same time, even if all the facts are all considered, I think, as for deep well drilling , it does not make sense just though drilling technology to control wellbore instability.
Meanwhile, making use of drilling fluid to stabilize wellbore has the following advantages: 1)timeliness, 2) long effectiveness, 3)high efficiency, 4) other beneficial effect. Therefore, we pay more attention to drilling fluid in reality and it is a good technical measure to select well inhibitive drilling fluid whose main treating agents are inhibitors to control the problems mentioned above.
In conclusion, it is of great use to direct drilling, realize safe production and improve the economic benefit with reviewing past and present inhibitors.
Generally speaking, effective inhibitors should have the following characteristic: 1) powerful inhibitive, 2) a little sealing characteristic, 3) having seldom effect on drilling rate, 4) having seldom effect on the rheological properties of drilling fluid, 5) wide adaptability (it can be used in geological prospecting and in oil and gas).
2.Development History and Current Situation
During drilling well, drilling workers drived a herd of cattle through a pit filled with water at Spindletop, in Texas, in 1900. It became mud, which was sticky, slimy and water-soil mixture. Then, drilling workers put it into well with pump. From the category, it belonged to dispersed mud system. Then, drilling workers put inorganic treatment such as sodium carbonate into mud mentioned above which became early fine scattered drilling fluid. But this kind of mud just could be used in shadow wells. To improve the performance of controlling the wellbore instability, they mixed other inorganic treatments gropingly into it, which was, we called, inhibitor.
Now there are many commonly used inhibitors, which can be mainly divided into inorganic and organic ones[7].
Inorganic inhibitors are used early. Potassium chloride, calcium chloride and the like are commonly used. The main inhibiting mechanisms of potassium chloride are neutralization and mosaic effect. And that of calcium chloride are neutralization, common ion effect and penetration hydration effect.
Inorganic inhibitors also have some developments in recent decades, such as silicate[8]~[9],quaternary ammonium salt[10]~[11]and formate, acetate[12]~[16]and so on. Inhibiting mechanisms of silicate are membrane effect and plugging effect. That of quaternary ammonium salt are neutralization, mosaic effect and adsorption effect. That of formate and acetate are membrane effect and bonding effect of carboxylic root and water, and it is also a kind of environmental protection inhibitors. And new MMH[17]~[21](positive colloid) has more characteristic, which can solve the contradiction between wellbore stability and the yield of bentonite through neutralization and adsorption effect. What’s more, it has plugging effect in a degree. So ,it is a promising treatment.
Then, common organic inhibitors are anionic polymer inhibitors, cationic polymer inhibitors and zwitterion polymer inhibitors. Anionic polymer inhibitors include polyethylene acid, polyacrylamide, polyacrylonitrile[22] and humic acid[23].Among them, what used more are PAC, PAM, PHPA[24], KPAM, KPAN and humic acid potassium and so on. Inhibiting mechanisms of them are bridge league effect, flocculation effect and membrane effect. Cationic polymer inhibitors mainly include large and small cationic[25]~[27],secondary organic cationic polymerCSJ-1[28], cationic stabilizer CWD-1[29], high salt cationic polymer HWJ[30]. The effect of them are good but they have bad effect on environment and higher prices. Inhibiting mechanisms of them are neutralization, flocculation action and membrane effect. Zwitterion polymer inhibitors mainly include XY-27 and FA[31] series. Although this type of inhibitors have cation and anion for inhibition effect, the inhibition mechanisms and formation mechanisms are not very clear.
Inhibiting mechanisms of asphalt include adsorption effect and plugging effect. It is good sometimes but easily cause environmental pollution.
New organic inhibitorsincludepolyamine[32]~[35],polyalcohol[36]~[37],carbohydrate derivatives[38]~[39], organic positive colloid[40]~[41], organic aluminum[42], anti-sloughing lubricant FSF[43], low molecule inhibitors FTy[44], synthesis of natural polymer and olefins monomers QYJ[45], UL TRA HIB[46]in ULTRADRILTM water-based drilling fluid system, KHIs[47] (active hydrate inhibitors raised by Malcolm A. Kelland). Small amine and NH+ of polyamine have similar diameter with potassium ion, so inhibiting mechanisms of them are neutralization and mosaic effect. Polyalcohol is from marine drilling and is an environment friendly inhibitor, whose effect is not so good. Carbohydrate derivatives (such as MEG) is surface active material and it has membrane effect. In the meantime, it is a kind of higher price but environmental friendly inhibitors. New organic positive colloid has more positive charge, so it has strong inhibition, but it is a high price inhibitors. Due to good effect in the dissolve and crystallization state, Organic aluminum, being anew inhibitor, has strong inhibition. FSF is anti-sloughing lubricant. QYJ has good temperature resistance, and it can keep stable effect in 150 ℃. And it has good resistance to salt. ULTRA HIB can step in and narrow the distance between the clay electrode to prevent water molecule penetrating and inhibiting shale inflation. KHIs is a kind of inhibitors in deep drilling.
3.Inhibiting Mechanisms and Effects of Some Inhibitors
3.1 Inorganic Inhibitors
3.1.1 Potassium Chloride: inhibiting mechanisms mainly are neutralization and mosaic effect. Potassium ion can partly counteract negatively charged clay from lattice substitution. Meanwhile, due to the right size, potassium ion embeds six ring which consist of oxygen atoms between adjacent crystal layer. Therefore, the effect is better than other inorganic Inhibitors. It is shown in figure 3-1.
Figure 3-1Mosaic effect of potassium ion
3.1.2 Formate: because filtrate of formate drilling fluid has high mineralization and formic acid root has good compatibility with formation water, it can get out of some defects which other drilling fluid with inorganic salts bring to maintain wellbore stability and provide appropriate density and strong inhibitive ability for drilling fluid. Simultaneously, surface of shale is similar to selective semipermeable membrane and water activity of formate drilling fluid is smaller than water activity of formation. Then, infiltration pressure will come and it will keep a trend of formation water flowing into drilling fluid. And HCOO- of formate can form hydrogen bonding with water molecule to restraint free water. According to all of the above mentioned, it can reduce the hydration expansion of clay, stabilize wellbore and protect the reservoir.
3.1.3 Quaternary ammonium salt: it is proved that potassium ion and ammonium ion have the same diameter in the standard pH of drilling fluid.[48]So, typically, many people think that the two kinds of inhibitors should have the same mechanism and effect.
3.1.4 MMH(positive colloid): inhibiting mechanisms have the following aspects: 1) forming a "static membrane" in low shear rate near wellbore, which can make drilling fluid scour wellbore less and stabilize wellbore effectively, 2) “fighting against formation for water”. In this king of drilling fluid, to form drilling fluid system, water molecule is an important part of the complex structure. MMH has a better affinity for water than formation. Then, water will flow from formation to drilling fluid, 3)”stabilizing formation water activity”. After MMH and clay mineral forms complex, it can push a great deal of exchangeable ion out. So it can make ion activity of clay mineral and infiltration hydration reduce. And after MMH-clay complex forms, a layer of positive charge potential barrier forms around charged clay particles, which can obstruct the exchange of exchangeable positive ion and stabilize wellbore.
Table 3-1The readings of CST with different additive amount(MMH)
In the experiment (CST), the reading is smaller, the inhibitive ability is better. The reading was 80(s) in the same drilling fluid with5% potassium chloride. According to what mentioned above, we know that MMH had better effect at small amount than potassium chloride.
3.2 Organic Inhibitors
3.2.1Large and small cationic: large cationic mainly is regarded as flocculant and small cationic clay stabilizer. Due to positive charges of large cationic, it has better adsorption with clay than anion inhibitors. It can neutralize part of negative charges of clay, so its flocculation effect and inhibitory effect is good. Small cationic also has neutralization, at the same time, because of its small ionic diameter, so it can enter the crystal layer and has good inhibitory effect.
Table 3-2 Shale roll recovery of cationic and potassium chloride with different additive amount In the same drilling fluid system
For the test of shale rolling recovery, the higher the recovery is, the better the inhibitory effect is. From the table above, the recovery of cationic inhibitor can reach more than 90% with little added amount.
3.2.2Anionic polymer inhibitors(KPAM):there are many kinds of anionic polymer inhibitor, and PAM , PHPA and their derivatives are used widely and an ideal category. Because of the adsorption and hydration groups of its molecular chain, the former form" anchor point" on shale surface and macromolecules suture tiny cracks transversely, and, for the latter, due to the electrostatic repulsion leading the stretching of molecular chain, which increases its effective length and improves the ability of encapsulation effect for shale particles, then, it stabilizes wellbore and reduces the hydration expansion of clay.
Table 3-3 Shale roll recovery of KPAM with different additive amountIn the same drilling fluid system
From the table above, the recovery of KPAM can reach more than 60% in basic mud.
3.2.3 Polyalcohol: firstly, due to its high viscosity, the flow velocity of filtrate is low and the rate of filtrate intruding into formation is low. Secondly, it can form complex on the surface of clay, row off part of the free water, prevent the water molecules from entering into formation and reduces the hydration expansion of clay. Thirdly, turbidity point effect: when the temperature in the well is higher than its turbidity point temperature, it can separate from drilling fluid and form oil film underground, which can block cake and effectively reduce the filtrate of drilling fluid intruding into formation.
Table 3-4The readings of shale inflation experiment (1%polyalcohol)
For the test, the smaller the linear expansion ratio is, the better the inhibitor is. So it can be seen from the table above that it can effectively improve the inhibitory effect of drilling fluid.
3.2.4 Methylglucoside (MEG): through a lipophilic group and four hydrophilic groups, MEG can reduce the hydration expansion of clay. Hydrophilic group adsorb on shale, makes lipophilic group outwards and form water-in-oil adsorption film on the wall, which can separate water from formation and reduce the loss of filtration. Meanwhile, the hydrophilicity of hydrophilic group is extremely strong, so the time it intrudes into the formation, it will separate water from shale.
Table 3-5Shale roll recovery of MEG with different aperture
4. Conclusion
1）Now, the conventional inorganic inhibitors can actually have certain inhibition with large additive amount, and which can not be good enough.. In recent years, the effect of inorganic inhibitors has been improved and they can meet the environmental requirements. However, compared with organic inhibitors, they still below the mark.
2) The effects of conventional organic inhibitors are good, but whose adaptability is not good enough, and great majority inhibitors can't meet the environmental requirements. The effect and adaptability of new organic inhibitors have improved in recent years, and are more environmental protection which inferior to inorganic inhibitors.
3) The author thought that, in later years, when drilling we should consider organic and inorganic inhibitors at the same time, namely, synergistic effect. Meanwhile, either organic or inorganic inhibitors should strive to achieve better inhibition effect and be more environmental protection.
4)The derivatives of new inhibitors (polyamine derivative UID[49]), nanoscale inhibitors (positive colloid nano-emulsion[50]) and super polymer[51] may be good development directions.
References：
[1] Chen Xiurong. Study on shale wellbore stability [D]. Hubei: China University of
Geosciences.2009.5,1.
[2] R.L. Anderson, et al. Clay swelling — A challenge in the oilfield[J].Earth-Science
Reviews,2010,98:201~216.
[3] Yan Jienian. Drilling fluid process principle [M]. Shandong: Petroleum University Publishing
House.2001.5,24.
[4] Wu Xiaoming, Hu Yule, et al. Drilling fluid and geotechnical slurry[M]. Hubei: China
University of Geosciences.2002,4.
[5] Chen Tinggen, Guan Zhichuan, Liu Xisheng. Drilling engineering theory and technology [M]. Beijing: China's oil university press.2006,207~211.
[6] Van Oort E. On the physical and chemical stability of shales. J. Petrol. Sci. Eng 38：
[7] Wang Quanping. Drilling fluid and its function principle [M]. Beijing：Petroleum University
Publishing House,2003.9,2~4.
[8] Tu Yunzhong, et al. A research on silicate drilling fluid of marine natural gas hydrate drilling
[J].Modern Geology,2009.4,23（2）:224~228.
[9] Yang Yong, et al. High inhibition and HSE advantages of WDX silicate drilling
fluid[J].Drilling Fluid & Completion Fluid,2010.9,27（5）：38~40.
[10] Zhong Hanyi, et al. Development and features of amine shale inhibitors [J].Petroleum
Drilling Techniques, 2010.1,28（1）：104.
[11] R. Schlemmer, et al. Progression of Water-Based Fluids Based on Amine Chemistry– Can
[12] the Road Lead to True Oil Mud Replacements?.AADE-03-NTCE-36,1~12.
[13] Dai Yongjin, et al. Application of non-dispersed formate/polymer drilling fluid in Hongze Area of Jiangsu Province[J]. Drilling Fluid & Completion Fluid,2004.11,21（6）：67~69.
[14] Li Yishou, et al. Application of non-dispersed formate/polymer drilling fluid in Tuba oilfield[J]. Drilling Fluid & Completion Fluid,2006.11,23(6):5~9.
[15] Yi Shaojin, et al. Study on Environment Acceptable Formate Brines for Drilling and Completion[J].Environmental Protection of Oil and Gas Fields,2000.9,10（3）：40~42.
[16] Meng Xiaomin, et al. Application of formate base drilling fluid technology [J].Drilling Fluid & Completion Fluid ,2003,20（5）：62~64.
[17] Li Zhiyong, et al.ANovelFormate/Positive-ChargedPolyglycolDrillingFluid[J].Petroleum Drilling Techniques ,2006.9,34（5）：34~37.
[18] Yin da, et al. Using MMH system for lost circulation prevention and plugging [J]. Drilling Fluid & Completion Fluid,2000,17（1）：46~48.
[19] Wang Fuhua, et al. Study on Inorganic Positive Gel/Polyol/Polymer Drilling and Completion Fluid[J].Petroleum Drilling Techniques ,2001,33（1）：24~27.
[20] Huang Hefu. Application of MMH polyol drilling fluid in Linpan area[J].Drilling Fluid &Completion Fluid,2002,19(4):44~45.
[21] Zhang Qinfu. Study on the performance of MMH drilling fluid system[J].Journal of Oil and Gas Technology,2005.4,27（2）：251~253.
[22] Liu Guichuan, GuoCaixuan. Application of MMH drilling fluid system[J].Geology and Prospecting,2000.3，36(2)：76~78.
[23] Fu Meilong, Hu Xingqi. An Investigation into Shale Stability by Utilizing Copolymer of
Acrylamide and Acrylonitrile and Its Derivatives [J]. Journal of Jianghan Petroleum Institute,1997.3，19(1):70~74.
[24] Shi Yongli, ShenQinchang. Application of humic acid in the oil drilling fluid [J].HumicAcid,1996,4:1~5.
[25] Guerrero, X., et al. Use of amine/PHPA system to drill high reactive shales in the Orito field in Colombia. SPE Paper 104010, First International Oil Conference and Exhibition. Cancun, Mexico, 31 August–2 September.
[26] Beihoffer, T.W, et al. The Development of an inhibitive Cationic Drilling Fluid for Slim Hole CoringApplication.SPE19953
[27] Retz, R.,Friedheim, et al. An environmentally acceptable and Field-Practical, Cationic Polymer Mud System, SPE 23064.
[28] Wang Junying. Research and application of cationic drilling fluid in Tuha Oilfield[J].Drilling Fluid & Completion Fluid,2008.5,25(3):39~42.
[29] Lin Zhipeng, Yang chengzhi. Secondary organic cationic Polymer drilling fluid technology[J].Drilling Fluid & Completion Fluid ,2003,20(5):1~3.
[30] Ye Guanghui, Zhang Xiaojun. Application of CWD一l in drilling fluid[J].Inner Mongolian Petrochemical,2008,18:120~121.
[31] Wang Jian, et al. Lab study on hyperhaline cationic polymer drilling fluid for deep water drilling[J]. China Offshore Oil and Gas，2007.12,19（6）：405~408.
[32] Liu Feng, Chen Feng, LI Lei. Application of zwitterionic polymer drilling fluid in Shanbei Area[J].Petroleum Drilling Techniques ,1998.12,26(4):22~23.
[33] Su Xiuchun, et al. Research on organic amine inhibitor BZ-AN1 used in high inhibitive drilling fluid.[J].Drilling Fluid & Completion Fluid,2011.3,28(2):32~35.
[34] Mei Hong, et al. Synthesis and evaluation of new polyamine inhibitor [J].Xinjiang Oil and Gas，2010.6,6（2）：47~49.
[35] Wang Jian, et al. A laboratory study on strongly inhibitive polyamine drilling fluid[J]. Oilfield Chemistry，2007.12,24（4）：296~300.
[36] Arvind Patel, Emanuel Stamatakis, James E. Highly Inhibitive Water-Based Fluid System Provides Superior Chemical Stabilization of Reactive Shale Formations [J]. AADE 01-NC-HO-55.
[37] Li Wanqing, Yu Jian, et al. Application of Inhibitive Polyglycol drilling fluid in Da'an area [J].Drilling Fluid & Completion Fluid,2006.5,23(3):77~78.
[38] Liu Tianle, Jiang Guosheng, TuYunzhong, et al. Research on the polyolcol drilling fluids for offshore hydrate drilling [J]. Oil Drilling & Production Technology，2009.10,31（5）：52~55.
[39] Lv Kaihe, Qiu Zhengsong, Sun Mingbo. Study on anti-sloughing mechanism of methylglucoside [J]. Natural Gas Industry,2007.2,27（2）：70~72.
[40] Zhang Jie, GuoGang. An evaluation of high temperature inhibition behavior of heteropolysaccharide drilling fluids [J].Natural Gas Industry,2010.1,30(1):80~82.
[41] Wang Xueying, Wei Jun, Li Kaiqi. Study and applicationof newly organic cationic GEL drilling fluid [J]. Oil Drilling and Production Technology，2005.12,27(6):30~33.
[42] Wang Fuhua, Wu Mingqiang. Preparation and application of organic positive polymer drilling fluid [J]. Acta Petrolei Sinica,2004.9,25(5):93~98.
[43] Yan Daobing, et al. Research and application of organic aluminum complex-potassium drilling fluid system [J].Drilling Fluid & Completion Fluid, 2005.17.
[44] Mei Jie, et al. The Application of FSF Anti - collapse Lubricating Drilling Liquid in North Shanxi[J]. Shanxi Science and Technology, 2005.5,5: 106~107.
[45] Ding Tongwei, Yan Jienian. Experimental study of new water-based drilling fluid: FT y, of [J].Drilling Fluid & Completion Fluid, 2005.11, 22(6):13~15.
[46] Qian Mengzhan, et al. Development and application of anti-sloughing agent QYJ.[J]. Oil Drilling and Production Technology，2006.12,28（6）：27-30.
[47] Kong Qinming, et al. Application of ULTRADRILTM Water Base Mud in Well Zhanghai 502FH [J].Drilling Fluid & Completion Fluid, 2006.11,23（6）：71~76.
[48] Malcolm A. Kelland, et al. Feasibility Study for the Use of Kinetic Hydrate Inhibitors in Deep-Water Drilling Fluids[J].Energy & Fuels,2008,22:2405~2410.
[49] Grim, R.E.: Clay Minerology, First Edition; McGraw- Hill (1953) 148.
[50] Wang Jian, et al. Lab Research on the Novel Inhibitive Drilling Mud : UID.[J].Drilling Fluid & Completion Fluid,2007.9,24:72~75.
[51] Wang Peiping, et al. Application of Positive Colloid Nano-emulsion Drilling Fluid in Shengli Oilfield[J]. Journal of Jianghan Petroleum University of Staff and Workers,2006.7,19(4):38~40.
[52] Young, S., Maas, Ton Maas, Noviant, B.V., Nijmegen, 2001. Novel polymer chemistry increases shale stability. AADE National Drilling Technical Conference, AADE 01-NC-HO-41.