【摘要】：隨著測井技術(shù)的發(fā)展,三維聲波測井已經(jīng)成為一種重要的測井方法,其測量原理是利用聲波在不同介質(zhì)中傳播,它的幅度和頻率等物理特性會產(chǎn)生不同變化的特點(diǎn)來研究鉆井的地質(zhì)剖面,判斷固井質(zhì)量。在實(shí)際的測井過程中,井下高溫環(huán)境非常復(fù)雜,噪聲干擾嚴(yán)重,待測量的聲波信號很微弱而難以被檢測解析,因此研發(fā)出高精度的井下測量電路十分必要,這樣才能適應(yīng)未來測井對精度要求越來越高的發(fā)展趨勢。三維聲波測井儀能夠同時測量井周多個方位的聲波信號,從而提供地層徑向、軸向及周向三維立體地質(zhì)構(gòu)造信息。本文首先介紹了三維聲波測井儀的總體結(jié)構(gòu)、測井原理及測井過程;然后根據(jù)測井的需求設(shè)計了高精度測量電路,主要包含前置調(diào)理電路和模數(shù)轉(zhuǎn)換電路。三維聲波測井儀高精度測量電路是以“ADC+FPGA”為硬件架構(gòu),低噪聲的前置調(diào)理電路實(shí)現(xiàn)對地層反射回來的微弱聲波信號的放大、濾波等預(yù)處理功能,主要涉及的內(nèi)容有電荷放大電路設(shè)計、程控增益設(shè)計、高通濾波電路設(shè)計;sigma-delta型高精度模數(shù)轉(zhuǎn)換器利用高采樣速率換取高采樣精度的原理,把輸入的模擬信號轉(zhuǎn)換為易于存儲和傳輸?shù)臄?shù)字信號;串行數(shù)據(jù)的高速傳輸技術(shù)實(shí)現(xiàn)測井?dāng)?shù)據(jù)的實(shí)時傳輸,其采用的低電壓差分傳輸技術(shù)能有效地減小數(shù)據(jù)傳輸過程中共模噪聲的干擾。本電路使用基于Verilog的硬件描述語言來實(shí)現(xiàn)FPGA的基本功能,包括ADC采樣流程的控制、測井?dāng)?shù)據(jù)的存儲和傳輸。最后,本文通過一系列的實(shí)驗(yàn)驗(yàn)證了高精度測量電路設(shè)計的正確性和測井儀工作的穩(wěn)定性,其中水槽實(shí)驗(yàn)驗(yàn)證了三維聲波測井儀功能的正確性,高溫實(shí)驗(yàn)驗(yàn)證了系統(tǒng)的高溫穩(wěn)定性。此外,通過導(dǎo)出模數(shù)轉(zhuǎn)換器輸出的大量樣本數(shù)據(jù),對其進(jìn)行處理計算,得到模數(shù)轉(zhuǎn)換器的有效位數(shù),從而驗(yàn)證了所設(shè)計的高精度測量電路達(dá)到預(yù)期的精度目標(biāo)。
[Abstract]:With the development of logging technology, 3D acoustic logging has become an important logging method. Its physical characteristics such as amplitude and frequency will produce different characteristics to study the geological profile of drilling and to judge the cementing quality. In the actual logging process, the underground high temperature environment is very complex, the noise interference is serious, the acoustic signal to be measured is very weak and difficult to be detected and analyzed, so it is necessary to develop a high precision downhole measurement circuit. Only in this way can we adapt to the developing trend of higher and higher precision of logging in the future. The 3D acoustic logging tool can simultaneously measure the acoustic signals in several directions around the well, thus providing the three-dimensional geological structure information of radial, axial and circumferential directions. This paper first introduces the overall structure, logging principle and logging process of 3D acoustic logging tool, and then designs a high-precision measuring circuit according to the requirements of logging, which mainly includes preconditioning circuit and analog-to-digital conversion circuit. The high precision measuring circuit of 3D acoustic logging tool is based on "ADC FPGA" as hardware structure. The preconditioning circuit with low noise realizes the preprocessing functions such as amplifying and filtering weak acoustic signals reflected from formation, etc. The main contents involved include the design of charge amplifier circuit, the design of program-controlled gain, the design of high-pass filter circuit and the principle of using high sampling rate to exchange high sampling precision for high precision ADC. The input analog signal is converted into a digital signal which is easy to store and transmit, and the high-speed transmission technology of serial data realizes the real-time transmission of logging data. The low voltage differential transmission technique can effectively reduce the common-mode noise interference during data transmission. This circuit uses the hardware description language based on Verilog to realize the basic functions of FPGA, including the control of ADC sampling flow, the storage and transmission of logging data. Finally, a series of experiments are carried out to verify the correctness of the design of the high-precision measuring circuit and the stability of the logging tool, and the validity of the function of the three-dimensional acoustic logging tool is verified by the flume experiment. The high temperature stability of the system is verified by high temperature experiment. In addition, a large number of sample data are derived from the analog-to-digital converter and processed and calculated, and the effective bits of the ADC are obtained, which verifies that the designed high-precision measuring circuit achieves the desired accuracy target.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P631.83

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本文編號：2260105