基于脉宽及脉位调制的钻井液压力MPSK信号的数学建模及信号特性分析
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摘要
钻井液压力信息遥测技术是随钻测量(MWD)中最常用的井下数据传输技术,采用钻井液压力多进制相移键控(MPSK)方式进行数据调制,是进一步提高井下信息传输速率的行之有效方法。
本文根据旋转阀式钻井液连续压力波信号发生器的逻辑控制分析,构建基于脉宽调制(PWM)及脉位调制(PPM)的钻井液压力MPSK信号的旋转阀控制逻辑脉冲序列函数,通过控制脉冲序列函数的数学分析得到相移函数表达式,根据相移函数的傅利叶正、逆变换及数字通信理论,构建出基于脉宽调制及脉位调制的钻井液压力MPSK信号时域数学模型。通过MPSK信号数学模型的短时傅利叶变换,对基于脉宽调制及脉位调制的钻井液压力MPSK信号的频域特性进行了分析。数值计算表明,基于脉位调制钻井液压力MPSK信号的平均功率谱优于脉宽调制,由于基于脉位调制的基带控制脉冲宽度窄,信号调制过程短,MPSK调制后常规频带内信号能量相对较大,信号能量集中,有利于信号的频带传输。相对于数据的二进制差分相移键控(BPSK)调制,基于脉宽和脉位调制的MPSK信号在相同带宽下,信息传输速率和频带利用率提高了一倍,但调制后常规频带内信号能量远小于BPSK信号,且对旋转阀转速的控制要求很高,这也是目前钻井液压力多进制相移键控调制方式没有采用基于脉宽调制及脉位调制的主要原因。通过对MPSK钻井液压力信号进行的数值仿真,从信号波形反映的调制规律上验证了所构建数学模型的正确性。
根据流体力学理论及理想气体状态方程,结合钻柱内的压力和温度分布,分析了钻井液含气率沿定向井井深长度的变化;通过信号在钻井液信道中的传输特性分析,采用数值分析方法研究了传播距离、钻柱内径、载波频率、钻井液粘度及体积含气率对钻井液压力MPSK信号传输的影响,数值分析表明,钻井液粘度和含气率对信号传输的影响最大。
通过对基于脉宽调制及脉位调制钻井液压力MPSK信号的数学建模及信号特性分析,从理论上解释了将其作为井下数据传输的局限性,对于采用更合理的多进制相移键控数据调制的井下信息遥测技术的探索性研究具有相对大的参考价值。
The drilling fluid pressure telemetry in MWD (Measurement While Drilling) is the most common down-hole tool that transmits data by drilling fluid pressure modulation technology, and the multiple phase shift keying (MPSK) modulation is the effective method to improve the data transmission rate.
In this paper, a transmission characteristics analysis of drilling fluid pressure MPSK signals based on PWM (Pulse Width Modulation) and PPM (Pulse Position Modulation) in a directional well is introduced. With the control logic analysis of a rotary valve in a drilling fluid pressure generator, a logical control signal is built and a phase-shift function is obtained from integral function of the logical control signal with Fourier and inverse transform operation along with numeric communication theory. A mathematic model of drilling fluid pressure MPSK signals based on PWM and PPM is built by acting the phase-shift function to a carrier wave. With short-term Fourier transform of MPSK signal’s mathematic model, the signal frequency spectrum is analyzed. The numerical calculation result shows that the average power spectra of MPSK signal based on PPM is better than that based on PWM, owning to the narrow width of baseband control pulse, the process of modulating signal is momentary, the signal’s power in routine bandwidth after the modulation of MPSK signals is better relatively and the power is concentrated, so PPM is in favor of the frequency-band transmission of the signals. Compared with BPSK (Binary Phase Shift Keying) signal, in the same bandwidth, the information transmission rate and utilization ratio of trequency-band of MPSK signals based on PWM and PPM is enhanced once, but the signal’s power in routine bandwidth after modulated is less than BPSK, in addition, the control demand for rotary wave is high. As the consequence, the modulation means of PWM and PPM is still not used in drilling fluid pressure MPSK. By means of numerical simulation of MPSK signal, the modulation rule reflected by signal wave verifies the exactitude of built mathematic model.
Considering the theory of fluid mechanics and ideal gas state equation, associated with drillingpipe pressure and drilling fluid temperature, the change of volume fraction of gas in drilling fluids along the directional drillpipe is analyzed. Through the transmission characteristics analysis of MPSK signal in drilling fluid channel and adoption of numerical simulation , the impact of propagation distance, drilling size, carrier frequency, drilling fluids viscosity and volume fraction of gas is studied. The numerical simulation result shows that the impact of drilling fluid viscosity and volume fraction of gas in drilling fluid on the signal transmission is more notable than the others.
According to the mathematical model and transmission characteristics analysis of drilling fluid pressure MPSK signals based on PWM and PPM, the limitation is theoretically explained of adopting those modulations as a method of down-hole data transmission. This research presents considerable reference merit in terms of down-hole information telemetry technology adopting more feasible modulation of MPSK.
本文根据旋转阀式钻井液连续压力波信号发生器的逻辑控制分析,构建基于脉宽调制(PWM)及脉位调制(PPM)的钻井液压力MPSK信号的旋转阀控制逻辑脉冲序列函数,通过控制脉冲序列函数的数学分析得到相移函数表达式,根据相移函数的傅利叶正、逆变换及数字通信理论,构建出基于脉宽调制及脉位调制的钻井液压力MPSK信号时域数学模型。通过MPSK信号数学模型的短时傅利叶变换,对基于脉宽调制及脉位调制的钻井液压力MPSK信号的频域特性进行了分析。数值计算表明,基于脉位调制钻井液压力MPSK信号的平均功率谱优于脉宽调制,由于基于脉位调制的基带控制脉冲宽度窄,信号调制过程短,MPSK调制后常规频带内信号能量相对较大,信号能量集中,有利于信号的频带传输。相对于数据的二进制差分相移键控(BPSK)调制,基于脉宽和脉位调制的MPSK信号在相同带宽下,信息传输速率和频带利用率提高了一倍,但调制后常规频带内信号能量远小于BPSK信号,且对旋转阀转速的控制要求很高,这也是目前钻井液压力多进制相移键控调制方式没有采用基于脉宽调制及脉位调制的主要原因。通过对MPSK钻井液压力信号进行的数值仿真,从信号波形反映的调制规律上验证了所构建数学模型的正确性。
根据流体力学理论及理想气体状态方程,结合钻柱内的压力和温度分布,分析了钻井液含气率沿定向井井深长度的变化;通过信号在钻井液信道中的传输特性分析,采用数值分析方法研究了传播距离、钻柱内径、载波频率、钻井液粘度及体积含气率对钻井液压力MPSK信号传输的影响,数值分析表明,钻井液粘度和含气率对信号传输的影响最大。
通过对基于脉宽调制及脉位调制钻井液压力MPSK信号的数学建模及信号特性分析,从理论上解释了将其作为井下数据传输的局限性,对于采用更合理的多进制相移键控数据调制的井下信息遥测技术的探索性研究具有相对大的参考价值。
The drilling fluid pressure telemetry in MWD (Measurement While Drilling) is the most common down-hole tool that transmits data by drilling fluid pressure modulation technology, and the multiple phase shift keying (MPSK) modulation is the effective method to improve the data transmission rate.
In this paper, a transmission characteristics analysis of drilling fluid pressure MPSK signals based on PWM (Pulse Width Modulation) and PPM (Pulse Position Modulation) in a directional well is introduced. With the control logic analysis of a rotary valve in a drilling fluid pressure generator, a logical control signal is built and a phase-shift function is obtained from integral function of the logical control signal with Fourier and inverse transform operation along with numeric communication theory. A mathematic model of drilling fluid pressure MPSK signals based on PWM and PPM is built by acting the phase-shift function to a carrier wave. With short-term Fourier transform of MPSK signal’s mathematic model, the signal frequency spectrum is analyzed. The numerical calculation result shows that the average power spectra of MPSK signal based on PPM is better than that based on PWM, owning to the narrow width of baseband control pulse, the process of modulating signal is momentary, the signal’s power in routine bandwidth after the modulation of MPSK signals is better relatively and the power is concentrated, so PPM is in favor of the frequency-band transmission of the signals. Compared with BPSK (Binary Phase Shift Keying) signal, in the same bandwidth, the information transmission rate and utilization ratio of trequency-band of MPSK signals based on PWM and PPM is enhanced once, but the signal’s power in routine bandwidth after modulated is less than BPSK, in addition, the control demand for rotary wave is high. As the consequence, the modulation means of PWM and PPM is still not used in drilling fluid pressure MPSK. By means of numerical simulation of MPSK signal, the modulation rule reflected by signal wave verifies the exactitude of built mathematic model.
Considering the theory of fluid mechanics and ideal gas state equation, associated with drillingpipe pressure and drilling fluid temperature, the change of volume fraction of gas in drilling fluids along the directional drillpipe is analyzed. Through the transmission characteristics analysis of MPSK signal in drilling fluid channel and adoption of numerical simulation , the impact of propagation distance, drilling size, carrier frequency, drilling fluids viscosity and volume fraction of gas is studied. The numerical simulation result shows that the impact of drilling fluid viscosity and volume fraction of gas in drilling fluid on the signal transmission is more notable than the others.
According to the mathematical model and transmission characteristics analysis of drilling fluid pressure MPSK signals based on PWM and PPM, the limitation is theoretically explained of adopting those modulations as a method of down-hole data transmission. This research presents considerable reference merit in terms of down-hole information telemetry technology adopting more feasible modulation of MPSK.
引文
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[2]曹来勇,王振升,何炳振.随钻测量与井筒油气评价技术[M].东营:石油大学出版社,1997:10-77
[3]张绍槐,张洁.21世纪中国石油钻井技术发展战略研究[J].探矿工程(岩土钻掘工程),2001,4:1-5
[4] Inglis T.A.(苏义脑等译).定向钻井[M].北京:石油工业出版社,1995:120-153
[5]石在虹,刘修善.井筒中钻井信息的传输动态分析[J].天然气工业,2002,22(5):68-71
[6]张文波,孙志刚.MWD(无线随钻测量)系统在钻井工程中的应用[J].新疆石油科技,1996,6(2):1-5
[7]李军,马哲,杨锦舟.一种新型的MWD无线随钻测量系统[J].石油仪器,2006,20(2):30-32
[8]苏义脑,窦修荣.随钻测量、随钻测井与录井工具[J].石油钻采工艺,2005,27(1):74-78
[9]马哲,杨锦舟,赵金海.无线随钻测量技术的应用现状与发展趋势[J].石油钻探技术,2007,35 (6):112-115
[10]赖信坚.随钻测量技术与传感器原理探讨[J].石油钻采工艺,1991,13(4):9-17
[11]谢学明,梁定火.有线随钻和无线随钻测量技术在水平井中的推广应用[J].江汉石油科技,2004,14(2):54-70
[12] Martin C.A., Philo R.M., Decker D.P., et al. Innovative advances in MWD[R]. SPE 27516, 1994
[13]刘广志.中国钻探科学技术史[M].北京:地质出版社,1998:47
[14]刘修善,苏义脑.泥浆脉冲信号的传输速度研究[J].石油钻探技术,2000,28(5):4-26
[15]张绍槐.智能油井管在石油勘探开发中的应用于发展前景[J].石油钻探技术,2004, 32(4):1-4
[16]肖仕红,梁政.旋转导向钻井技术发展现状及展望[J].石油机械,2006,34(4):66-70
[17]骆康雄.井下随钻测量系统连续压力波BPSK信号传输特性的研究[D].东营:中国石油大学(华东),2008:1-46
[18] Roden M.S.. Analog and Digital Communication Systems[J]. (Third Edition) rentice-Hall International Edition, 1991
[19] Lubinski A.. A Study of Buckling of Rotary Drilling String, Drilling and Production Practice[M]. 1950: 178-214
[20]樊昌信.通信原理(第6版)[M].北京:国防工业出版社,2008:180-234
[21]杨西侠,柯晶.信号分析与处理[M].北京:机械工业出版社,2007:175-180
[22]刘聪锋.高效数字调制技术及其应用[M].北京:人民邮电出版社,2006:2-34
[23]王秉鈞,冯玉珉,田宝玉.通信原理[M].北京:清华大学出版社,2006:180-252
[24]李文海.数字通信技术[M].北京:人民邮电出版社,1998:87-95
[25]杨尔滨,赵玲.信号处理原理与应用[M].北京:清华大学出版社,2008:140-171
[26]南利平,李学华.通信原理简明教程[M]].北京:清华大学出版社,2007:228-273
[27]沈海娟.现代通信原理[M].武汉:武汉理工大学出版社,2006:58-79
[28]王海燕.信号与线性系统分析基础[M].北京:北京邮电大学出版社,2005:55-58
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