深层环境气井压裂工艺技术研究
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摘要
大庆油田深层火山岩储层致密,孔隙度(一般为3%～20%)和渗透率(0.01×10~(-3)～10×10~(-3)μm~2)极低,非均质性强。大多数井自然产能较低,必须经过压裂才能达到工业产能。但是,由于火山岩气藏埋藏深(一般为3000～4500m),地温梯度高(一般为4～4.5℃/100m),岩性复杂坚硬,破裂压力最高可达80MPa以上,在火山岩压裂中采用以往的深井压裂管柱会出现压裂工具耐温耐压指标低、压裂规模低、不能实施分层改造、深层气井压裂管柱的循环问题等诸多难题。为解决深层天然气储层压裂面临的实际问题,本课题开展了180℃、100MPa深层气井压裂工艺技术研究。通过理论研究和室内及现场试验,在国内首次研制出180℃、100MPa插入式分层压裂管柱和单压下层管柱。解决了深层致密气藏的分层压裂问题。对现有压裂管柱进行了力学模型简化,对压裂下部层段,上部层段两种工况下的管柱进行了应力、应变和z向位移的分析,得出了不同工况下水力锚位置的轴向力,最后校核了管柱强度,对现有管柱进行了结构优化,研制了大砂量条件下的井下工具,深层气井压裂超过100m~3规模。同时配套研制了适应深井井身特点的封隔器、反循环阀等工具,解决了封隔器中途坐封、有效循环压井等问题,提高了深层气井压裂施工的安全性和可靠性。深层气井压裂工艺管柱现场应用共111井次,压裂121层段,施工成功率为97.6%,压裂施工最高压力达到97.95MPa,最大施工排量6.0m~3/min,单井最大加砂130m~3。试验表明:深层气井压裂工艺管柱在耐温耐压指标、分层压裂工艺、加砂规模及安全可靠性等方面完全满足深层火山岩储层压裂改造工艺需要。
The deep volcanic reservoirs in Daqing Oilfield is dense, its porosity (usually 3% to 20%) and permeability (0.01×10~3～10×10~3μm~2) are very low, and its non-homogeneous is strong. Since natural productivities of most wells are low, they must be fractured in order to achieve industrial production capacity. However, because gas reservoir of volcanic rocks are deep buried (usually 3000～4500m), geothermal gradient is high (usually 4～4.5℃/100m), lithology is complex and hard, fracture pressure is up to 80MPa or more, However, because of deep buried gas reservoir of volcanic rocks (usually 3000～4500m) and high geothermal gradient (usually 4～4.5℃/100m), as well as complex, hard lithology and up to 80MPa or more fracture pressure, the following questions will be appeared when traditional deep well fracturing is used in volcanic rock fracturing. (1) Temperature and pressure resistant indexes of fracturing tool are low. The domestic technical indexes of high temperature and high pressure fracturing tool are generally temperature resistant 150℃, working pressure 80MPa. They can meet the needs for general technologies of deep well fracturing. However, volcanic reservoirs can not be fractured when its temperature exceeds 150℃and formation fracture pressure is above 80MPa. And it limits further development of volcanic reservoirs. High-performance packer rubber is the core of fracturing packer's temperature and pressure resistant indexes. Packer rubbers both at home and abroad are made from HNBR, but the maximum allowable temperature which HNBR supports is only 160℃. This limits further performance improvement of packer rubber's technical indexes. Therefore, rubber materials with better performance are needed to be found and they are needed to be studied from such areas as formulation design, vulcanization technology, structure optimization of packer rubber and protection measures. (2) Fracturing scale is low. Deep volcanic rock wells could achieve higher production capacity after large-scale fracturing. But due to large-scale and long time construction, there are some serious wear and tear problems when fracturing tool are eroded in high-strength proppant, resulting in lower casing strength, especially high deformation in prone position and some accidents which happen while drawing. Therefore, string abrasion mechanism in large-scale fracturing is needed to be studied to determine the reason and position of the abrasion occurrence in order to develop high abrasion resistance well tools. (3) Hierarchical transformation can not be implemented. Volcanic reservoir has multiple vertical layers, and is non-homogeneous and strong, the formation fracture pressure of which is high. For the volcanic reservoir with 40～50MPa formation fracture pressure, its pressure of the ground construction is more than 80MPa. When the pressure of the ground construction is 80MPa , the axial tension F which actions on the string can be achieved 919.5kN. But the tubing in general card form isΦ76mm, and its threadlock anti-slip strength is only 846kN. When axial tension exceeds anti-slip strength connecting threadlock, the slip accident will appear for card form tubing. Therefore, deep well generally use test gas method by fracturing layer by layer. However, the method has some problems such as long time construction, high formation damage by many times killing, and low construction efficiency. (4) Existing cycle instruments are not adapted to deep gas well fracturing. At the end of the test gas, gas well fracturing string must be full cycled before killing. Therefore, the cycle instruments need to be designed in fracturing string device. There are two kinds of conventional cycle instruments: shear pin mode and hydraulic switch mode. But when they are implemented in deep gas well, there are some problems such as low temperature and pressure resistant indexes, poor wear resistance, low reliability. Therefore, new cycle instruments adapted to deep gas well fracturing need to be studied.
In order to solve the practical problems faced by deep gas reservoir fracturing, the research of this thesis focus on 180℃, 100MPa deep gas well fracturing technologies including the following four main aspects:
1. Plug-in hierarchical fracturing string is developed, and thus providing technical means for fracturing transformation of deep volcanic rocks. Plug-in hierarchical fracturing string takes drillable packer as layered plugging packer, and achieves hierarchical fracturing combined with plug-in fracturing string. Its characteristics include high construction efficiency, small formation damage, and it solves the problems that hierarchical fracturing string for two-card string of packer will be slipped when deep well is fractured. A non-linear static model of fractured string is established by using finite element method, which takes full account of the structure of fractured string, boundary conditions and various loads. And it correctly describes collision contact state between fractured string and the casing inner wall, constructs the conditions of contacting state. The results got by iterative calculation show that the deformation of fracturing siring in high temperature and high pressure working conditions meets strength requirements.
2. Deep well fracturing packers Y344-115 and Y443-108 are developed, which are 180℃and 100MPa resistant. The closure issues during placing packer Y443 are solved through structural design and material selection. 180℃, 100MPa packer rubbers are developed from such areas as preferred selection of plastic materials, formulation design, curing process, structural design and plastic tube's protection, which significantly improve technical indexes of packer. And the performance indexes of packer achieve international advanced level.
3. Fluent software is used to establish the internal flow field model of fracturing string. Fluid flow of different traffic, sand-ratio fracturing fluid in string is numerical simulated. And streamlines, velocity field, pressure field and solid-liquid phase distribution are obtained. Abrasive wear mechanism and the main abrasive positions while fracturing are determined. According to the theoretical research results, technical methods for solving abrasive problems of fracturing string with large volume of sand are proposed.
4. Reverse circulation valve used in deep wells is studied, which has the characteristics including high technical indexes (180℃, 100MPa), sand and wear resistant, high reliability. It can be repeated used in high temperature and high pressure deep wells. It establishes an effective channel circle of killing to ensure safe construction of fracturing string in deep gas wells.
Deep gas well fracturing techniques are used 111 times in field, fractures 121 layers, and the success rate of construction is 97.6%, maximum pressure of fracturing construction reaches 97.95MPa, the largest construction displacement is 6.0m~3/min, the largest volume of sand in single well is 130m~3. Theoretical studies and the indoor and field tests demonstrate that the 180℃, 100MPa plug-in hierarchical fracturing string and single-layer pressure pipe string which were developed at the first time in domestic satisfies deep volcanic reservoir fracturing technology needs from the aspects such as indexes of temperature and pressure resistant, hierarchical fracturing process, sand size, security and reliability, and achieves domestic advanced level.
The deep volcanic reservoirs in Daqing Oilfield is dense, its porosity (usually 3% to 20%) and permeability (0.01×10~3～10×10~3μm~2) are very low, and its non-homogeneous is strong. Since natural productivities of most wells are low, they must be fractured in order to achieve industrial production capacity. However, because gas reservoir of volcanic rocks are deep buried (usually 3000～4500m), geothermal gradient is high (usually 4～4.5℃/100m), lithology is complex and hard, fracture pressure is up to 80MPa or more, However, because of deep buried gas reservoir of volcanic rocks (usually 3000～4500m) and high geothermal gradient (usually 4～4.5℃/100m), as well as complex, hard lithology and up to 80MPa or more fracture pressure, the following questions will be appeared when traditional deep well fracturing is used in volcanic rock fracturing. (1) Temperature and pressure resistant indexes of fracturing tool are low. The domestic technical indexes of high temperature and high pressure fracturing tool are generally temperature resistant 150℃, working pressure 80MPa. They can meet the needs for general technologies of deep well fracturing. However, volcanic reservoirs can not be fractured when its temperature exceeds 150℃and formation fracture pressure is above 80MPa. And it limits further development of volcanic reservoirs. High-performance packer rubber is the core of fracturing packer's temperature and pressure resistant indexes. Packer rubbers both at home and abroad are made from HNBR, but the maximum allowable temperature which HNBR supports is only 160℃. This limits further performance improvement of packer rubber's technical indexes. Therefore, rubber materials with better performance are needed to be found and they are needed to be studied from such areas as formulation design, vulcanization technology, structure optimization of packer rubber and protection measures. (2) Fracturing scale is low. Deep volcanic rock wells could achieve higher production capacity after large-scale fracturing. But due to large-scale and long time construction, there are some serious wear and tear problems when fracturing tool are eroded in high-strength proppant, resulting in lower casing strength, especially high deformation in prone position and some accidents which happen while drawing. Therefore, string abrasion mechanism in large-scale fracturing is needed to be studied to determine the reason and position of the abrasion occurrence in order to develop high abrasion resistance well tools. (3) Hierarchical transformation can not be implemented. Volcanic reservoir has multiple vertical layers, and is non-homogeneous and strong, the formation fracture pressure of which is high. For the volcanic reservoir with 40～50MPa formation fracture pressure, its pressure of the ground construction is more than 80MPa. When the pressure of the ground construction is 80MPa , the axial tension F which actions on the string can be achieved 919.5kN. But the tubing in general card form isΦ76mm, and its threadlock anti-slip strength is only 846kN. When axial tension exceeds anti-slip strength connecting threadlock, the slip accident will appear for card form tubing. Therefore, deep well generally use test gas method by fracturing layer by layer. However, the method has some problems such as long time construction, high formation damage by many times killing, and low construction efficiency. (4) Existing cycle instruments are not adapted to deep gas well fracturing. At the end of the test gas, gas well fracturing string must be full cycled before killing. Therefore, the cycle instruments need to be designed in fracturing string device. There are two kinds of conventional cycle instruments: shear pin mode and hydraulic switch mode. But when they are implemented in deep gas well, there are some problems such as low temperature and pressure resistant indexes, poor wear resistance, low reliability. Therefore, new cycle instruments adapted to deep gas well fracturing need to be studied.
In order to solve the practical problems faced by deep gas reservoir fracturing, the research of this thesis focus on 180℃, 100MPa deep gas well fracturing technologies including the following four main aspects:
1. Plug-in hierarchical fracturing string is developed, and thus providing technical means for fracturing transformation of deep volcanic rocks. Plug-in hierarchical fracturing string takes drillable packer as layered plugging packer, and achieves hierarchical fracturing combined with plug-in fracturing string. Its characteristics include high construction efficiency, small formation damage, and it solves the problems that hierarchical fracturing string for two-card string of packer will be slipped when deep well is fractured. A non-linear static model of fractured string is established by using finite element method, which takes full account of the structure of fractured string, boundary conditions and various loads. And it correctly describes collision contact state between fractured string and the casing inner wall, constructs the conditions of contacting state. The results got by iterative calculation show that the deformation of fracturing siring in high temperature and high pressure working conditions meets strength requirements.
2. Deep well fracturing packers Y344-115 and Y443-108 are developed, which are 180℃and 100MPa resistant. The closure issues during placing packer Y443 are solved through structural design and material selection. 180℃, 100MPa packer rubbers are developed from such areas as preferred selection of plastic materials, formulation design, curing process, structural design and plastic tube's protection, which significantly improve technical indexes of packer. And the performance indexes of packer achieve international advanced level.
3. Fluent software is used to establish the internal flow field model of fracturing string. Fluid flow of different traffic, sand-ratio fracturing fluid in string is numerical simulated. And streamlines, velocity field, pressure field and solid-liquid phase distribution are obtained. Abrasive wear mechanism and the main abrasive positions while fracturing are determined. According to the theoretical research results, technical methods for solving abrasive problems of fracturing string with large volume of sand are proposed.
4. Reverse circulation valve used in deep wells is studied, which has the characteristics including high technical indexes (180℃, 100MPa), sand and wear resistant, high reliability. It can be repeated used in high temperature and high pressure deep wells. It establishes an effective channel circle of killing to ensure safe construction of fracturing string in deep gas wells.
Deep gas well fracturing techniques are used 111 times in field, fractures 121 layers, and the success rate of construction is 97.6%, maximum pressure of fracturing construction reaches 97.95MPa, the largest construction displacement is 6.0m~3/min, the largest volume of sand in single well is 130m~3. Theoretical studies and the indoor and field tests demonstrate that the 180℃, 100MPa plug-in hierarchical fracturing string and single-layer pressure pipe string which were developed at the first time in domestic satisfies deep volcanic reservoir fracturing technology needs from the aspects such as indexes of temperature and pressure resistant, hierarchical fracturing process, sand size, security and reliability, and achieves domestic advanced level.
引文
[1]戴平生,李建波,杨东.大庆探区低孔低渗油气层压裂改造增产工艺技术[J].中国石油勘探,2003,8(1):67-83.
[2]周望,谢朝阳.大庆油田水力压裂技术的发展[J].大庆石油地质与开发,1998,17(2):34-37.
[3]张传胜,冯敬红,程云甫,何志勇.高温高压低渗透油气藏压裂改造技术[R].大庆:大港油田集团钻采工艺研究院,2000.
[4]马新仿,张士诚.水力压裂技术的发展现状[J].河南石油,2002,16(1):44-48.
[5]陈养龙,王新来,何树栋.套管悬挂载荷的现场计算[J].石油钻探技术,2000,(6):11-14.
[6]郝俊芳,龚伟安.套管强度计算与设计[M].北京:石油工业出版社,1987.
[7]Bathe K J.Finite Element Procedures in Engineering Analysis[M].Englewood Cliffs,N.J:Prentice-Hall Inc,1986.
[8]巴斯.工程分析中的有限元法[M].北京:机械工业出版社,1991.
[9]Sheldon I.Sheldon's ANSYS Tips and Tricks:Understanding Lagrange Multipliers[EB/OL].[2001-11-4].http://ansys.net/ansys/tips_sheldon/STI07_Lag range_Multipliers.pdf.
[10]Sheldon I.Sheldon's ANSYS Tips and Tricks:PSD Postprocessing[EB/OL].[2004-4-20].http://ansys.net/ansys.
[11]Bathe K J,Ramm E,Wilson E.Finite Element Formulation for Large Deformation Dynamics Analysis[J].International Journal for Numerical Methods in Engineering,1975,9:353-386.
[12]Alessandri C,Tralli A.Sensitivity Analysis for Unilateral Contact Problems:Boundary Variational Formulations and BEM Distributions[J].Comp.Mech,1995,15.
[13]Panagiotopolus P D,Lazanidis P P.Boundary Minimum Principles for the Unilateral Contact Problems[J].International Journal of Solids and Structures.1987,23(11):1100-1123.
[14]Oden J T,Pires E B.Nonlocal and Nonlinear friction Laws and Variational Principles for Contact Problems in Elasticity[J].Journal of Application Mechanical of ASME.1983,50:67-76.
[15]署恒木.工程有限元法[M].北京:石油大学出版社,2003.
[16]刘巨保.石油设备有限元分析[M].北京:石油工业出版社,1996.
[17]易日.使用ANYSY6.1进行结构力学分析[M].北京:北京大学出版社,2003.
[18]李皓.ANSYS工程计算应用教程[M].北京:中国铁道出版社,2003.
[19]王艳伟.超深井酸压工艺技术在塔河油田的应用[J].新疆石油地质,2000,21(6):518-520.
[20]苏益仁,赵惠忠,李克敏.井下石油专用管硫化物应力腐蚀开裂失效分析[J].石油钻采机械,1983,(6):14-17.
[21]Maradudin A P,Drill Pipe.Casing Tubing Sucker Rods-Corrosion failures and methods of combating corrosion[J].Material Protection,1965,4(12):45-51.
[22]Barton J P,Caliper.Surveys Monitor Down hole Corrosion in Production Tubing Petrol Eng Int[J],1993,3:44-47.
[23]雷群,慕立俊,陆红军.长庆上古生界低压低渗透砂岩气藏压裂工艺技术[J].天然气工业,2003,23(5):66-69.
[24]李遇昌,王本德.工程材料[M].成都:成都科技大学出版社,1998.
[25]申峰,周伟勤,王琴,刘作江.深层气井试油压裂技术研究与应用[J].断块油气田,2002,3:60-64.
[26]陈淘平,胡靖帮.采油工程[M].北京:石油工业出版社,2000.
[27]刘鸿文.材料力学[M].北京:高等教育出版社,1992.
[28]罗英俊,万仁溥.采油技术手册[M].北京:石油化学工业出版社,1977.
[29]《井下作业技术数据手册》编写组.井下作业技术数据手册[M].北京:石油工业出版社,2001.
[30]Tailby R J,Yonker J H,Pearce J L.A New Technique for Servicing Horizontal Wells[C].Society of Petroleum Engineers,Annual Technical Conference and Exhibition,1991:43-58.
[2]周望,谢朝阳.大庆油田水力压裂技术的发展[J].大庆石油地质与开发,1998,17(2):34-37.
[3]张传胜,冯敬红,程云甫,何志勇.高温高压低渗透油气藏压裂改造技术[R].大庆:大港油田集团钻采工艺研究院,2000.
[4]马新仿,张士诚.水力压裂技术的发展现状[J].河南石油,2002,16(1):44-48.
[5]陈养龙,王新来,何树栋.套管悬挂载荷的现场计算[J].石油钻探技术,2000,(6):11-14.
[6]郝俊芳,龚伟安.套管强度计算与设计[M].北京:石油工业出版社,1987.
[7]Bathe K J.Finite Element Procedures in Engineering Analysis[M].Englewood Cliffs,N.J:Prentice-Hall Inc,1986.
[8]巴斯.工程分析中的有限元法[M].北京:机械工业出版社,1991.
[9]Sheldon I.Sheldon's ANSYS Tips and Tricks:Understanding Lagrange Multipliers[EB/OL].[2001-11-4].http://ansys.net/ansys/tips_sheldon/STI07_Lag range_Multipliers.pdf.
[10]Sheldon I.Sheldon's ANSYS Tips and Tricks:PSD Postprocessing[EB/OL].[2004-4-20].http://ansys.net/ansys.
[11]Bathe K J,Ramm E,Wilson E.Finite Element Formulation for Large Deformation Dynamics Analysis[J].International Journal for Numerical Methods in Engineering,1975,9:353-386.
[12]Alessandri C,Tralli A.Sensitivity Analysis for Unilateral Contact Problems:Boundary Variational Formulations and BEM Distributions[J].Comp.Mech,1995,15.
[13]Panagiotopolus P D,Lazanidis P P.Boundary Minimum Principles for the Unilateral Contact Problems[J].International Journal of Solids and Structures.1987,23(11):1100-1123.
[14]Oden J T,Pires E B.Nonlocal and Nonlinear friction Laws and Variational Principles for Contact Problems in Elasticity[J].Journal of Application Mechanical of ASME.1983,50:67-76.
[15]署恒木.工程有限元法[M].北京:石油大学出版社,2003.
[16]刘巨保.石油设备有限元分析[M].北京:石油工业出版社,1996.
[17]易日.使用ANYSY6.1进行结构力学分析[M].北京:北京大学出版社,2003.
[18]李皓.ANSYS工程计算应用教程[M].北京:中国铁道出版社,2003.
[19]王艳伟.超深井酸压工艺技术在塔河油田的应用[J].新疆石油地质,2000,21(6):518-520.
[20]苏益仁,赵惠忠,李克敏.井下石油专用管硫化物应力腐蚀开裂失效分析[J].石油钻采机械,1983,(6):14-17.
[21]Maradudin A P,Drill Pipe.Casing Tubing Sucker Rods-Corrosion failures and methods of combating corrosion[J].Material Protection,1965,4(12):45-51.
[22]Barton J P,Caliper.Surveys Monitor Down hole Corrosion in Production Tubing Petrol Eng Int[J],1993,3:44-47.
[23]雷群,慕立俊,陆红军.长庆上古生界低压低渗透砂岩气藏压裂工艺技术[J].天然气工业,2003,23(5):66-69.
[24]李遇昌,王本德.工程材料[M].成都:成都科技大学出版社,1998.
[25]申峰,周伟勤,王琴,刘作江.深层气井试油压裂技术研究与应用[J].断块油气田,2002,3:60-64.
[26]陈淘平,胡靖帮.采油工程[M].北京:石油工业出版社,2000.
[27]刘鸿文.材料力学[M].北京:高等教育出版社,1992.
[28]罗英俊,万仁溥.采油技术手册[M].北京:石油化学工业出版社,1977.
[29]《井下作业技术数据手册》编写组.井下作业技术数据手册[M].北京:石油工业出版社,2001.
[30]Tailby R J,Yonker J H,Pearce J L.A New Technique for Servicing Horizontal Wells[C].Society of Petroleum Engineers,Annual Technical Conference and Exhibition,1991:43-58.