A logging-while-drilling (LWD) caliper is a tool used for the real-time measurement of a borehole diameter in oil drilling engineering. This study introduces the mechanical structure and working principle of a new LWD caliper based on ultrasonic distance measurement (UDM). The detection range is a major performance index of a UDM system. This index is determined by the blind zone length and remote reflecting interface detection capability of the system. To reduce the blind zone length and detect near the reflecting interface, a full bridge acoustic emission technique based on bootstrap gate driver (BGD) and metal-oxide-semiconductor field effect transistor (MOSFET) is designed by analyzing the working principle and impedance characteristics of a given piezoelectric transducer. To detect the remote reflecting interface and reduce the dynamic range of the received echo signals, the relationships between the echo amplitude and propagation distance of ultrasonic waves are determined. A signal compensation technique based on time-varying amplification theory, which can automatically change the gain according to the echo arrival time is designed. Lastly, the aforementioned techniques and corresponding circuits are experimentally verified. Results show that the blind zone length in the UDM system of the LWD caliper is significantly reduced and the capability to detect the remote reflecting interface is considerably improved.

Laboratory testing is a pre-requisite for the practical application of new methods and techniques, and it is crucial in the research and development of acoustic well-logging tools. Various tools have been developed based on different acoustic logging theories and methods. Thus, these tools are equipped with different acoustic sonde structures. To meet the test requirements of different tools in a laboratory environment, we designed a general experimental system that includes hardware platform, software platform, and model wells according to the common structure of actual logging tools. Similar to the internal electrical structure of downhole tools, the hardware platform consists of several main parts, such as power supply, control and telemetering, acoustic emission, and data acquisition. The functions of this hardware platform include controlling the working sequence of the experiment, exciting the transmitter sonde, and collecting the acoustic signals received by the receiver sonde. The software platform installed in the host computer provides a human–computer interface for the experimental system to complete the data transmission between the host computer and the hardware platform, store measured data, and process the data in real time. The model wells approximate the actual engineering environment and stratum condition for system testing. A series of practical laboratory experiments is conducted in the model wells by using this experimental system. The process proves that the hardware and software of the experimental system can work in coordination, and the experimental system meets the basic testing requirements of conventional acoustic logging tools.

As a widely used technology in the field of test and measurement, virtual instrument (VI) combines high-performance modular hardware with flexible software to perform a variety of experimental tasks. In order to perform the sound field test in laboratory, we build an specialized platform of VI, whose hardware system mainly consists of multi-channel data acquisition boards, independence analyzer, mechanical positioning device, and industrial personal computer equipped with PXI, GPIB, and Ethernet bus interface. Also, a graphical VI programming language (LabVIEW) is adopted to develop the corresponding software system. With this VI platform, we measure the impedance property of transducers and the sound field of a phased array composed of them. The results show that the transducers are positioned correctly by the mechanical positioning device, the excitation time of every transducer of the phased array is controlled accurately, and finally a set of high-quality waveforms are acquired.

<p>In this paper, the test-bench for sonic logging tool is proposed and designed to realize automatic calibration and testing of the sonic logging tool. The test-bench System consists of Host Computer, Embedded Controlling Board, and functional boards. The Host Computer serves as the Human Machine Interface (HMI) and processes uploaded data. The software running on Host Computer is designed on VC++, which is developed based on multithreading, Dynamic Linkable Library (DLL) and Multiple Document Interface (MDI) techniques. The Embedded Controlling Board uses ARM7 as the microcontroller and communicates with Host Computer via Ethernet. The Embedded Controlling Board software is realized based on embedded uclinux operating system with a layered architecture. The functional boards are designed based on Field Programmable Gate Array (FPGA) and provide test interfaces for the logging tool. The functional board software is divided into independent sub-modules that can repeatedly be used by various functional boards and then integrated those sub-modules in the top layer. With the layered architecture and modularized design, the software system is highly reliable and extensible. With the help of designed system, a test has been conducted quickly and successfully on the electronic receiving cabin of the sonic logging tool. It demonstrated that the system could greatly improve the production efficiency of the sonic logging tool.</p>

Continuous-wave pulse generator plays an important role in generating high-quality pulse signals in measurement while drilling systems. However, the generator affects the quality of pressure wave signals due to erosion on the continuous wave generator rotary valve caused by drilling fluid during operation. In this paper, the computational fluid dynamics (CFD) model of a rotary valve was established by ANSYS finite element method, and a series of three dimensional flow field simulation experiments were conducted to analyze the influence of factors, such as drilling fluid density, viscosity, inclusion particle diameter, and particle mass flow on the erosion of the rotary valve. Experiments show that the rotor erosion increases with increasing drilling fluid density, viscosity, diameter, and mass flow of particles in the drilling fluid. Moreover, the rotor erosion exponentially increases with increasing viscosity of the drilling fluid. The results provide necessary data for drilling fluid system improvement, rotor material selection, and surface structure treatment.