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Theoretical and experimental study of the pulling force of jet bits in radial drilling technology

Theoretical and experimental study of the pulling force of jet bits in radial drilling technology Pet.Sci.(2009)6:395-399 395 395 DOI 10.1007/s12182-009-0060-6 Theoretical and experimental study of the pulling force of jet bits in radial drilling technology Guo Ruichang, Li Gensheng , Huang Zhongwei, Tian Shouceng, Zhang Xiaoning and Wu Wei State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China Abstract: Radial drilling technology, of which the jet bit is the key device, is a research focus in the fi eld of oil drilling and production. This paper establishes mechanical equations for jet bits and analyzes the hydroseal of backward jets in bottom holes. Meanwhile this paper establishes a mechanical equation for a high pressure hose and analyzes the axial force distribution. Laboratory experiments indicate that the fl ow rate, the angle between the backward nozzle axis and the jet bit axis, and the hole diameter are the major infl uencing factors; the generation of the pulling force is mainly due to the inlet pressure of the jet bit; the backward jets can signifi cantly increase not only the pulling force but also the stability of jet bits. The pulling force would reach 8,376 N under experimental conditions, which can steadily pull the high-pressure hose forward. Key words: Radial drilling, water jet, jet bit, depression effect, pulling force 1 Introduction Radial drilling technology, which is also called ultra-short Whipstock radius radial drilling technology, was developed over the Overlying formation last two decades. It is mainly applied to depleted reservoirs, fault block oil reservoirs, margin reservoirs and heavy oil Casing reservoirs and has become a research focus in the fi eld of oil drilling and production. High pressure hose Jet bit Reservoir Ultra-short radius radial drilling technology is much different from conventional drilling technology. The key equipment of this technology mainly includes a jet bit, a high pressure hose, and a whipstock, as shown in Fig. 1. This technology completely depends on hydraulic energy to break rock. The fl exible high pressure hose, which is strengthened by reinforcing layer in which steel cord is used as braided material, is used as the drilling pipe. The whipstock is small enough so that it can enter the main hole smoothly, avoiding Fig. 1 Ultra-short radius radial drilling underreaming. The high pressure hose is flexible enough to get through the whipstock, which has a track whose axis hole trajectory, which has greatly hindered the development changes from vertical to horizontal in the ultra-short radius. of this technology. Further research on the pulling force of This technology can drill several horizontal wells within the the jet bit is important in resolving the diffi culty how to make same pay zone up to one hundred meters long. the high pressure hose move ahead smoothly. However, little At present this technology has been used with good research has been done on the generation of the pulling force results in different places around the world, such as of jet bit. Buset et al (2001) made a preliminary study and Argentina, Bolivia, and Russia (Cirigliano and Talavera drew the conclusion that the complex bottom hole fl ow fi eld Blacutt, 2007; Bruni et al, 2007; Ursegov et al, 2008). But can enhance the pulling force of the jet bit. The generation there are still many difficulties in making the high pressure mechanism of the pulling force of the jet bit remains unclear. hose and jet bit move ahead smoothly, and controlling the The authors established mechanical equations for the jet bit and high pressure hose, and analyzed the generation mechanism of the pulling force and the infl uence of the main factors. The theory was experimentally validated. *Corresponding author. email: ligs@cup.edu.cn Received January 10, 2009 θ 396 Pet.Sci.(2009)6:395-399 where the term on the left side of Eq. (1) represents the rate 2 Working principle of the jet bit of momentum change ' M in the control volume in the x The working principle of the jet bit of the ultra-short direction; the fi rst term on the right side of Eq. (1) represents radius radial drilling system is shown in Fig. 2. Compared the stress on the boundary of the control volume; and the with the commonly-used jet bit, the jet bit of the radial second term is the weight component in the x direction. drilling system specially contains several backward nozzles. The x direction represents the horizontal, and the weight Therefore, the new type of jet bit can generate both forward component in this direction is zero. By integrating, Eq. (1) and backward jets. The forward jets from the forward nozzles can be written as follows (Hu, 2005): may be swirling or multiple jets, the main function of which is to break rock and make a hole with a diameter of several PA P A F U Q v v in in out out drag front front in feet. The function of the backward jets is to increase the (2) pulling force of the jet bit, and they also can enlarge the hole unQUT  v co s v back back in by scouring the hole wall while simultaneously removing cuttings. Then the pulling force can be represented as FP A P A U Q v v drag in in out out front front in (3) unQUT v cos  v back back in where P and P are the inlet and outlet pressures in out respectively of the jet bit, A and A are the inner and outer in out sectional areas of the jet bit, respectively; Q and Q are front back the fl ow rates of the forward and backward jets, respectively; v and v are the flow velocities of the forward and front back backward jets, respectively; v is the fl ow rate in the hose; θ in is the angle between the axis of the backward nozzle and the jet bit. Fig. 2 Schematic diagram of working principle of the jet bit back drag The backward jets produce reverse thrusts, whose out horizontal components are part of the pulling force, while the component forces in the radial direction are in balance (i.e. their resultant force is zero), in the ideal case that the jet in v v front in bit is in the hole center, due to their symmetrical distribution around the circumference. However, when the jet bit is close out drag to the lower side of hole wall, the radial component forces of reverse thrust produced by the lower side jets will increase, back and then push the jet bit to the hole center until the resultant Forces on the jet bit Fig. 3 force of the radial component forces, gravity, and buoyancy of the jet bit becomes zero and the jet bit reaches a balanced state again. So the jet bit is usually suspended in the jetted The fi rst two terms on the right side of Eq. (3) represent hole when drilling, which makes hole trajectory control less the forces generated by the inlet and outlet pressures of the diffi cult, and assures that a relatively straight, horizontal hole jet bit. The last two terms are the rate of momentum change. is drilled (Sunet al, 2006). According to Eq. (3), the pulling force increases when the angle θ decreases. When the angle θ is 0, the pulling 3 Theory analysis of pulling force force reaches its maximum. Considering the limitation of manufacturing capability, the angle θ is generally 30º-60º. The pulling force also increases with an increase in the fl ow 3.1 Pulling force analysis of drilling nozzle rate of the backward jet. However, the whole fl ow rate of the According to the momentum theorem, the rate of jet bit is limited and a part of it has to be enough to ensure momentum change in control volume is equal to the sum of rock breaking, so the flow rate of backward jets cannot all the external force applied to the control volume. As shown increase infi nitely, so the pulling force due to the momentum in Fig. 3, the momentum equation of the control volume in change cannot be very large. In order to obtain a high speed the x direction is jet, the jet bit pressure drop should be increased. When the pressure drop reaches 30-50 MPa, the produced the pulling (1) UV uudd A  A FdV xx x i force reaches 3,000-5,000 N. So the pulling force of the jet AA A A cv in 1 2 z Totall bit is mainly generated by the high inner pressure. ³³³ ³³ ³³ Pet.Sci.(2009)6:395-399 397 Due to the symmetrical distribution of the backward jets, won’t decrease too much with the length of the high pressure the resultant force of the force generated by the backward jets hose and even will increase if the pressure drop gradient is in the radial direction is zero when the jet bit is located in the large enough, which keeps the high pressure hose always in hole center. If there are no backward jets like the traditional tension. The hose will still extend smoothly ahead in a steady jet bit, the jet bit is also subjected to a contact force except for straight state, even in an irregular hole. gravity and buoyancy. The existence of the force generated by 3.3 Depression effect of backward jets the backward jets changes this state. So the stability of the jet bit and high pressure hose is greatly enhanced. The high-speed water jets ejecting from the backward nozzles mixes with fl uids in the annulus, carries them fl owing 3.2 Force analysis of the high pressure hose backwards, and produces a steady low pressure zone acting The radial hole drilled by an ultra-short radius radial as a “seal”, which: 1) can reduce the chip hold-down effect drilling system is horizontal, i.e. with a deviation angle of 90 to enhance penetration rate; and 2) can reduce backward degrees (Wang et al, 1999), so the forces on the high pressure pushing force generated by down hole pressure, resulting in hose, only when it is in the horizontal hole, are necessary an increase in the relative pulling force of the jet bit (Shen, to be analyzed (Fig. 4). The x direction is horizontal. The 1998; Huang et al, 2008). governing equation is In order to calculate the pulling force, a differential pressure coeffi cient β was introduced, which can be defi ned PAF PA F F (4) as follows 11 pull 2 2 drag f where F and F are the forces in the forward and pull drag PP ' P oout backward directions, respectively; P and P are the pressures (7) E f QD , 1 2 QQ in the forward and backward directions respectively; A and A are the fl ow cross sectional areas at the inlet and outlet of the high pressure hose, respectively. where P is the annular pressure behind the jet bit; Q is the total fl ow rate; D is the diameter of the hole. The differential pressure coefficient β is a function of the flow rate Q and the hole diameter D, which represents F F drag pull the ability to generate a low pressure zone. Because the downhole flow fields are very complex, the differential P 2 in pressure coefficient β is difficult to calculate and has to be drag experimentally determined. pull So the pressure in front of the jet bit can be represented as P PQ E (8) Fig. 4 Forces on a high pressure hose in a horizontal hole out o The pulling force of the jet bit can be calculated by In the x direction, the pressure drop is mainly due to hydraulic friction along the high pressure hose, so Eq. (4) can be expressed as F  PAPQEUu A Q v v drag in in o out front front in (9) 2 f U vL unQ U v v back back in (5) FF F PA P A F F drag pullff 1 1 2 2 pull 4 Test equipment and method where f is the frictional coeffi cient; v is the fl ow velocity in the high pressure hose; L is the length of the high pressure A jet bit with a single forward jet was used in the hose; d is the inner diameter of the high pressure hose. experiment. The pulling force was measured under The frictional drag F between the high pressure hose and experimental conditions: flow rate 0.1-2.0 L/s, ambient the hole wall can be calculated by pressure 0 MPa, and hole diameter 30, 40, 50 mm. The schematic equipment, as shown in Fig. 5, mainly includes a FK P qL (6) f bp power and circulating system, experimental device, and a data acquisition system. where μ is the frictional coeffi cient between the high pressure hose and the hole wall; K is the buoyancy factor; q is the b p 5 Analysis of test results hose weight per unit length. The hose weight per unit length is very small, varying 5.1 Pressure drop at the jet bit from 0.4 to 0.5 kg/m, so that the frictional drag F between the high pressure hose and the hole wall is small too. Meanwhile A parabolic relationship between pressure drop and fl ow the thrust generated by the pressure drop along the high rate is shown in Fig. 6. High fl ow rate indicates a big pressure pressure hose is positive in the x direction, so the force F , drop. Test results are basically identical with calculated drag which is equal to the pulling force of the next hose segment, results. When the fl ow rate was 1.0 L/s, the pressure drop of 398 Pet.Sci.(2009)6:395-399 Fig. 6 Relationship between the pressure drop and the fl ow rate 5.3 Pulling force of the jet bit in holes of different diameters 5.2 Downhole differential pressure Figs. 8-10 show the relationships between the pulling Fig. 7 shows the relationship between the differential force of the jet bit and the flow rate in holes of different pressure coeffi cient β and the fl ow rate in holes of different diameters. The red and the blue lines represent theoretical diameters. Test results showed that β value increased and experimental values respectively. The difference between approximately linearly with fl ow rate, and the larger the hole theoretical and experimental values was within 3%. When the diameter, the smaller the rate of increase of the fl ow rate. So fl ow rate was under 0.5 L/s, the pulling force remained small. the higher the fl ow rate and the smaller the hole diameter, the When the fl ow rate was more than 1.0 L/s, the pulling force larger the pressure differential between the zone in front of increased signifi cantly. It would reach 8,000 N at a fl ow rate and behind the jet bit. Under experimental conditions, the β of 2.0 L/s. Because the high pressure fl exible hose could only value would reach 3.75×10 , while the pressure differential bear small axial force, the pulling force was the main factor would reach 0.75 MPa. in keeping the hose steady. Pet.Sci.(2009)6:395-399 399 2) The pressure drop of the jet bit is the main factor in Experimental value producing pulling force. The relationship between pressure Theoretical value drop and fl ow rate is parabolic. 3) The pressure differential coefficient β, characterizing the ability of the backward jets to produce depression region, increases linearly with the flow rate. The smaller the hole diameter, the greater the rate of increase of the flow rate. Under experimental conditions, β value reaches 3.75×10 at a 0.00.4 0.81.2 1.62.0 fl ow rate of 2.0 L/s. Flow rate, L/s 4) Calculated and experimental results show that the pulling force reaches 8,000 N at a fl ow rate of 2.0 L/s. Fig. 8 Relationship between pulling force and fl ow rate, D= 30 mm Acknowledgements This work was financially supported by High-tech Experimental value Research and Development Program of China (No. Theoretical value 2007AA09Z315) and Doctoral Foundation of Ministry of Education of China (No. 20070425006). The authors are grateful for approval to publish. 2000 References Bru ni M, Biassotti H and Salomone G. Radial drilling in Argentina. 0.0 0.4 0.8 1.2 1.6 2.0 SPE Latin American and Caribbean Petroleum Engineering held in Buenos Aires, Argentina, April 15-18, 2007 (SPE paper 107382) Flow rate, L/s Bus et P, Riiber M and Eek A. Jet drilling tool: cost-effective lateral Fig. 9 Relationship between pulling force and fl ow rate, D= 40 mm drilling technology for enhanced oil recovery. SPE/ICoTA Coiled Tubing Roundtable held in Houston, Texas, March 7-8, 2001 (SPE paper 68504) Cir igliano R and Talavera Blacutt J F. First experience in the application of radial perforation technology in deep wells. SPE Latin American Experimental value and Caribbean Petroleum Engineering held in Buenos Aires, Theoretical value Argentina, April 15-18, 2007 (SPE paper 107182) Hua ng Z W, Li G S,Tian S C, et al. Mechanism and numerical simulation of pressure stagnation during water jetting perforation. Petroleum Science. 2008. 5(1): 52-55 Hu Q F . Analysis of jet pipe feeding in hydraulic deep penetrating operation. China Petroleum Machinery. 2005. 33(5): 7-9 (in Chinese) 0.0 0.4 0.8 1.2 1.6 2.0 She n Z H. Water Jet Theory and Technology. Dongying: China Flow rate, L/s University of Petroleum Press. 1998. 84-95 (in Chinese) Sun N, Su Y N and Li G S. Progress in Drilling Engineering Technology. Relationship between pulling force and fl ow rate, D= 50 mm Fig. 10 Beijing: Petroleum Industry Press. 2006. 120-122 (in Chinese) Urs egov S, Bazylev A and Taraskin E. First results of cyclic steam stimulations of vertical wells with radial horizontal bores in heavy 6 Conclusions oil carbonates. SPE Russian Oil & Gas Technical Conference and Exhibition held in Moscow, Russia, October 28-30, 2008 (SPE paper 1) The newly-designed jet bit can be used to break rock, 115125) remove cuttings, enlarge the drill-holes, and to produce Wang K S, Teng Q, Sun J H, et al. Theoretical analysis of lance pulling force. The depression effect of its backward jets from propelling in coiled tubing water jet drilling. Journal of Beijing the backward nozzles reduces the chip hold-down effect, Institute of Machinery. 1999. 14(3): 21-24 (in Chinese) which helps enhance the penetration rate. (Edited by Sun Yanhua) Pulling force, N Pulling force, N Pulling force, N http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Petroleum Science Springer Journals

Theoretical and experimental study of the pulling force of jet bits in radial drilling technology

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Publisher
Springer Journals
Copyright
Copyright © 2009 by China University of Petroleum (Beijing) and Springer Berlin Heidelberg
Subject
Earth Sciences; Mineral Resources; Industrial Chemistry/Chemical Engineering; Industrial and Production Engineering; Energy Economics
ISSN
1672-5107
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1995-8226
DOI
10.1007/s12182-009-0060-6
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Abstract

Pet.Sci.(2009)6:395-399 395 395 DOI 10.1007/s12182-009-0060-6 Theoretical and experimental study of the pulling force of jet bits in radial drilling technology Guo Ruichang, Li Gensheng , Huang Zhongwei, Tian Shouceng, Zhang Xiaoning and Wu Wei State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China Abstract: Radial drilling technology, of which the jet bit is the key device, is a research focus in the fi eld of oil drilling and production. This paper establishes mechanical equations for jet bits and analyzes the hydroseal of backward jets in bottom holes. Meanwhile this paper establishes a mechanical equation for a high pressure hose and analyzes the axial force distribution. Laboratory experiments indicate that the fl ow rate, the angle between the backward nozzle axis and the jet bit axis, and the hole diameter are the major infl uencing factors; the generation of the pulling force is mainly due to the inlet pressure of the jet bit; the backward jets can signifi cantly increase not only the pulling force but also the stability of jet bits. The pulling force would reach 8,376 N under experimental conditions, which can steadily pull the high-pressure hose forward. Key words: Radial drilling, water jet, jet bit, depression effect, pulling force 1 Introduction Radial drilling technology, which is also called ultra-short Whipstock radius radial drilling technology, was developed over the Overlying formation last two decades. It is mainly applied to depleted reservoirs, fault block oil reservoirs, margin reservoirs and heavy oil Casing reservoirs and has become a research focus in the fi eld of oil drilling and production. High pressure hose Jet bit Reservoir Ultra-short radius radial drilling technology is much different from conventional drilling technology. The key equipment of this technology mainly includes a jet bit, a high pressure hose, and a whipstock, as shown in Fig. 1. This technology completely depends on hydraulic energy to break rock. The fl exible high pressure hose, which is strengthened by reinforcing layer in which steel cord is used as braided material, is used as the drilling pipe. The whipstock is small enough so that it can enter the main hole smoothly, avoiding Fig. 1 Ultra-short radius radial drilling underreaming. The high pressure hose is flexible enough to get through the whipstock, which has a track whose axis hole trajectory, which has greatly hindered the development changes from vertical to horizontal in the ultra-short radius. of this technology. Further research on the pulling force of This technology can drill several horizontal wells within the the jet bit is important in resolving the diffi culty how to make same pay zone up to one hundred meters long. the high pressure hose move ahead smoothly. However, little At present this technology has been used with good research has been done on the generation of the pulling force results in different places around the world, such as of jet bit. Buset et al (2001) made a preliminary study and Argentina, Bolivia, and Russia (Cirigliano and Talavera drew the conclusion that the complex bottom hole fl ow fi eld Blacutt, 2007; Bruni et al, 2007; Ursegov et al, 2008). But can enhance the pulling force of the jet bit. The generation there are still many difficulties in making the high pressure mechanism of the pulling force of the jet bit remains unclear. hose and jet bit move ahead smoothly, and controlling the The authors established mechanical equations for the jet bit and high pressure hose, and analyzed the generation mechanism of the pulling force and the infl uence of the main factors. The theory was experimentally validated. *Corresponding author. email: ligs@cup.edu.cn Received January 10, 2009 θ 396 Pet.Sci.(2009)6:395-399 where the term on the left side of Eq. (1) represents the rate 2 Working principle of the jet bit of momentum change ' M in the control volume in the x The working principle of the jet bit of the ultra-short direction; the fi rst term on the right side of Eq. (1) represents radius radial drilling system is shown in Fig. 2. Compared the stress on the boundary of the control volume; and the with the commonly-used jet bit, the jet bit of the radial second term is the weight component in the x direction. drilling system specially contains several backward nozzles. The x direction represents the horizontal, and the weight Therefore, the new type of jet bit can generate both forward component in this direction is zero. By integrating, Eq. (1) and backward jets. The forward jets from the forward nozzles can be written as follows (Hu, 2005): may be swirling or multiple jets, the main function of which is to break rock and make a hole with a diameter of several PA P A F U Q v v in in out out drag front front in feet. The function of the backward jets is to increase the (2) pulling force of the jet bit, and they also can enlarge the hole unQUT  v co s v back back in by scouring the hole wall while simultaneously removing cuttings. Then the pulling force can be represented as FP A P A U Q v v drag in in out out front front in (3) unQUT v cos  v back back in where P and P are the inlet and outlet pressures in out respectively of the jet bit, A and A are the inner and outer in out sectional areas of the jet bit, respectively; Q and Q are front back the fl ow rates of the forward and backward jets, respectively; v and v are the flow velocities of the forward and front back backward jets, respectively; v is the fl ow rate in the hose; θ in is the angle between the axis of the backward nozzle and the jet bit. Fig. 2 Schematic diagram of working principle of the jet bit back drag The backward jets produce reverse thrusts, whose out horizontal components are part of the pulling force, while the component forces in the radial direction are in balance (i.e. their resultant force is zero), in the ideal case that the jet in v v front in bit is in the hole center, due to their symmetrical distribution around the circumference. However, when the jet bit is close out drag to the lower side of hole wall, the radial component forces of reverse thrust produced by the lower side jets will increase, back and then push the jet bit to the hole center until the resultant Forces on the jet bit Fig. 3 force of the radial component forces, gravity, and buoyancy of the jet bit becomes zero and the jet bit reaches a balanced state again. So the jet bit is usually suspended in the jetted The fi rst two terms on the right side of Eq. (3) represent hole when drilling, which makes hole trajectory control less the forces generated by the inlet and outlet pressures of the diffi cult, and assures that a relatively straight, horizontal hole jet bit. The last two terms are the rate of momentum change. is drilled (Sunet al, 2006). According to Eq. (3), the pulling force increases when the angle θ decreases. When the angle θ is 0, the pulling 3 Theory analysis of pulling force force reaches its maximum. Considering the limitation of manufacturing capability, the angle θ is generally 30º-60º. The pulling force also increases with an increase in the fl ow 3.1 Pulling force analysis of drilling nozzle rate of the backward jet. However, the whole fl ow rate of the According to the momentum theorem, the rate of jet bit is limited and a part of it has to be enough to ensure momentum change in control volume is equal to the sum of rock breaking, so the flow rate of backward jets cannot all the external force applied to the control volume. As shown increase infi nitely, so the pulling force due to the momentum in Fig. 3, the momentum equation of the control volume in change cannot be very large. In order to obtain a high speed the x direction is jet, the jet bit pressure drop should be increased. When the pressure drop reaches 30-50 MPa, the produced the pulling (1) UV uudd A  A FdV xx x i force reaches 3,000-5,000 N. So the pulling force of the jet AA A A cv in 1 2 z Totall bit is mainly generated by the high inner pressure. ³³³ ³³ ³³ Pet.Sci.(2009)6:395-399 397 Due to the symmetrical distribution of the backward jets, won’t decrease too much with the length of the high pressure the resultant force of the force generated by the backward jets hose and even will increase if the pressure drop gradient is in the radial direction is zero when the jet bit is located in the large enough, which keeps the high pressure hose always in hole center. If there are no backward jets like the traditional tension. The hose will still extend smoothly ahead in a steady jet bit, the jet bit is also subjected to a contact force except for straight state, even in an irregular hole. gravity and buoyancy. The existence of the force generated by 3.3 Depression effect of backward jets the backward jets changes this state. So the stability of the jet bit and high pressure hose is greatly enhanced. The high-speed water jets ejecting from the backward nozzles mixes with fl uids in the annulus, carries them fl owing 3.2 Force analysis of the high pressure hose backwards, and produces a steady low pressure zone acting The radial hole drilled by an ultra-short radius radial as a “seal”, which: 1) can reduce the chip hold-down effect drilling system is horizontal, i.e. with a deviation angle of 90 to enhance penetration rate; and 2) can reduce backward degrees (Wang et al, 1999), so the forces on the high pressure pushing force generated by down hole pressure, resulting in hose, only when it is in the horizontal hole, are necessary an increase in the relative pulling force of the jet bit (Shen, to be analyzed (Fig. 4). The x direction is horizontal. The 1998; Huang et al, 2008). governing equation is In order to calculate the pulling force, a differential pressure coeffi cient β was introduced, which can be defi ned PAF PA F F (4) as follows 11 pull 2 2 drag f where F and F are the forces in the forward and pull drag PP ' P oout backward directions, respectively; P and P are the pressures (7) E f QD , 1 2 QQ in the forward and backward directions respectively; A and A are the fl ow cross sectional areas at the inlet and outlet of the high pressure hose, respectively. where P is the annular pressure behind the jet bit; Q is the total fl ow rate; D is the diameter of the hole. The differential pressure coefficient β is a function of the flow rate Q and the hole diameter D, which represents F F drag pull the ability to generate a low pressure zone. Because the downhole flow fields are very complex, the differential P 2 in pressure coefficient β is difficult to calculate and has to be drag experimentally determined. pull So the pressure in front of the jet bit can be represented as P PQ E (8) Fig. 4 Forces on a high pressure hose in a horizontal hole out o The pulling force of the jet bit can be calculated by In the x direction, the pressure drop is mainly due to hydraulic friction along the high pressure hose, so Eq. (4) can be expressed as F  PAPQEUu A Q v v drag in in o out front front in (9) 2 f U vL unQ U v v back back in (5) FF F PA P A F F drag pullff 1 1 2 2 pull 4 Test equipment and method where f is the frictional coeffi cient; v is the fl ow velocity in the high pressure hose; L is the length of the high pressure A jet bit with a single forward jet was used in the hose; d is the inner diameter of the high pressure hose. experiment. The pulling force was measured under The frictional drag F between the high pressure hose and experimental conditions: flow rate 0.1-2.0 L/s, ambient the hole wall can be calculated by pressure 0 MPa, and hole diameter 30, 40, 50 mm. The schematic equipment, as shown in Fig. 5, mainly includes a FK P qL (6) f bp power and circulating system, experimental device, and a data acquisition system. where μ is the frictional coeffi cient between the high pressure hose and the hole wall; K is the buoyancy factor; q is the b p 5 Analysis of test results hose weight per unit length. The hose weight per unit length is very small, varying 5.1 Pressure drop at the jet bit from 0.4 to 0.5 kg/m, so that the frictional drag F between the high pressure hose and the hole wall is small too. Meanwhile A parabolic relationship between pressure drop and fl ow the thrust generated by the pressure drop along the high rate is shown in Fig. 6. High fl ow rate indicates a big pressure pressure hose is positive in the x direction, so the force F , drop. Test results are basically identical with calculated drag which is equal to the pulling force of the next hose segment, results. When the fl ow rate was 1.0 L/s, the pressure drop of 398 Pet.Sci.(2009)6:395-399 Fig. 6 Relationship between the pressure drop and the fl ow rate 5.3 Pulling force of the jet bit in holes of different diameters 5.2 Downhole differential pressure Figs. 8-10 show the relationships between the pulling Fig. 7 shows the relationship between the differential force of the jet bit and the flow rate in holes of different pressure coeffi cient β and the fl ow rate in holes of different diameters. The red and the blue lines represent theoretical diameters. Test results showed that β value increased and experimental values respectively. The difference between approximately linearly with fl ow rate, and the larger the hole theoretical and experimental values was within 3%. When the diameter, the smaller the rate of increase of the fl ow rate. So fl ow rate was under 0.5 L/s, the pulling force remained small. the higher the fl ow rate and the smaller the hole diameter, the When the fl ow rate was more than 1.0 L/s, the pulling force larger the pressure differential between the zone in front of increased signifi cantly. It would reach 8,000 N at a fl ow rate and behind the jet bit. Under experimental conditions, the β of 2.0 L/s. Because the high pressure fl exible hose could only value would reach 3.75×10 , while the pressure differential bear small axial force, the pulling force was the main factor would reach 0.75 MPa. in keeping the hose steady. Pet.Sci.(2009)6:395-399 399 2) The pressure drop of the jet bit is the main factor in Experimental value producing pulling force. The relationship between pressure Theoretical value drop and fl ow rate is parabolic. 3) The pressure differential coefficient β, characterizing the ability of the backward jets to produce depression region, increases linearly with the flow rate. The smaller the hole diameter, the greater the rate of increase of the flow rate. Under experimental conditions, β value reaches 3.75×10 at a 0.00.4 0.81.2 1.62.0 fl ow rate of 2.0 L/s. Flow rate, L/s 4) Calculated and experimental results show that the pulling force reaches 8,000 N at a fl ow rate of 2.0 L/s. Fig. 8 Relationship between pulling force and fl ow rate, D= 30 mm Acknowledgements This work was financially supported by High-tech Experimental value Research and Development Program of China (No. Theoretical value 2007AA09Z315) and Doctoral Foundation of Ministry of Education of China (No. 20070425006). The authors are grateful for approval to publish. 2000 References Bru ni M, Biassotti H and Salomone G. Radial drilling in Argentina. 0.0 0.4 0.8 1.2 1.6 2.0 SPE Latin American and Caribbean Petroleum Engineering held in Buenos Aires, Argentina, April 15-18, 2007 (SPE paper 107382) Flow rate, L/s Bus et P, Riiber M and Eek A. Jet drilling tool: cost-effective lateral Fig. 9 Relationship between pulling force and fl ow rate, D= 40 mm drilling technology for enhanced oil recovery. SPE/ICoTA Coiled Tubing Roundtable held in Houston, Texas, March 7-8, 2001 (SPE paper 68504) Cir igliano R and Talavera Blacutt J F. First experience in the application of radial perforation technology in deep wells. SPE Latin American Experimental value and Caribbean Petroleum Engineering held in Buenos Aires, Theoretical value Argentina, April 15-18, 2007 (SPE paper 107182) Hua ng Z W, Li G S,Tian S C, et al. Mechanism and numerical simulation of pressure stagnation during water jetting perforation. Petroleum Science. 2008. 5(1): 52-55 Hu Q F . Analysis of jet pipe feeding in hydraulic deep penetrating operation. China Petroleum Machinery. 2005. 33(5): 7-9 (in Chinese) 0.0 0.4 0.8 1.2 1.6 2.0 She n Z H. Water Jet Theory and Technology. Dongying: China Flow rate, L/s University of Petroleum Press. 1998. 84-95 (in Chinese) Sun N, Su Y N and Li G S. Progress in Drilling Engineering Technology. Relationship between pulling force and fl ow rate, D= 50 mm Fig. 10 Beijing: Petroleum Industry Press. 2006. 120-122 (in Chinese) Urs egov S, Bazylev A and Taraskin E. First results of cyclic steam stimulations of vertical wells with radial horizontal bores in heavy 6 Conclusions oil carbonates. SPE Russian Oil & Gas Technical Conference and Exhibition held in Moscow, Russia, October 28-30, 2008 (SPE paper 1) The newly-designed jet bit can be used to break rock, 115125) remove cuttings, enlarge the drill-holes, and to produce Wang K S, Teng Q, Sun J H, et al. Theoretical analysis of lance pulling force. 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Petroleum Science – Springer Journals

Published: Nov 26, 2009

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