Development of a borehole gravimeter for mining applications

Nind, Chris; Seigel, Harold O.; Chouteau, Michel; Giroux, Bernard

doi:10.3997/1365-2397.25.1109.27514

Cited by 30 publications

(2 citation statements)

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“…However, the preliminary testing results show that the repeatability of 7000 μGal is far from meeting the practical application requirements. Recently, it has been reported that the measuring resolution of the instrument reaches 8 μGal in the laboratory (Nind et al, 2007(Nind et al, , 2013Nind & Niebauer, 2008). Through numerical simulations, Li (2013, 2015) illustrated that 3-C gravity was superior to vertical gravity in applications, such as locating and characterizing anomalous mass and in tracking the movement of fluid injection in reservoirs.…”

Section: Introductionmentioning

confidence: 99%

MEMS‐based 3‐C borehole gravimeter development

et al. 2023

Geophysical Prospecting

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A micro-electro-mechanical-based 3-C borehole gravimeter has been developed in China for mineral and hydrocarbon exploration. The 3-C borehole gravimeter is composed of a three-axis gravity sensor chip based on a deep silicon etching technique, high-precision capacitive displacement sensing and weak signal detection circuitry.The gravity-sensing chip is a silicon-based integrated spring-mass block system. Silicon wafer is etched by the micro-nanofabrication technique to form a high collimation groove. The size of the gravity-detecting mass block in the sensitive element plays a decisive role in the thermal noise level of the instrument. Deep silicon processing technique can produce a thicker silicon mass block (500 μm), which can obtain a larger mass block in the same area compared with the traditional silicon surface processing technique (10-100 μm). The out diameter of the final tool is 50 mm with 10,000 mGal measurement range, 155˚C temperature and 100 MPa pressure rating. Apart from the 3-C micro-electro-mechanical gravity sensor, a 3-C fluxgate magnetic sensor is also integrated into the downhole tool. This allows us to measure both 3-C gravity field and 3-C magnetic field downhole simultaneously and conduct joint inversion of both the downhole 3-C gravity and 3-C magnetic data during the data processing stage. The prototype tool was tested in a borehole up to 850 m depth, and the 3-C gravity sensor inside the tool can measure the vibration of the environment during the stationary measurement downhole. The first test data set shows repeatability near 800 m depth, which verifies the adaptability of the micro-electro-mechanical-based gravimeter to the down instrument environment.

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Section: Introductionmentioning

confidence: 99%

MEMS‐based 3‐C borehole gravimeter development

et al. 2023

Geophysical Prospecting

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“…Relative gravimeters are suitable for either spatial surveys or time-variable gravity, so they have been widely used in various areas, such as volcano observation, mineral and oil exploration, and many other fields [1][2][3][4][5]. In recent years, with the increasing demand for relative gravimeters, the requirements have become more and more stringent.…”

Section: Introductionmentioning

confidence: 99%

A novel ultra-simplified flexure-based spring-mass device for relative gravimeter

Kong

Liu²,

Diao

et al. 2023

Meas. Sci. Technol.

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This study presents the design and test of a novel ultra-simplified flexure-based spring-mass device (NUFSMD) with high sensitivity for relative gravimeters. The NUFSMD is mainly composed of a highly sensitive spring based on flexure hinges (SFH) and a cantilever beam. When the change of gravity causes SFH to rotate, an amplified displacement can be obtained on the tail of the cantilever beam. The displacement is measured by a capacitive displacement sensor. The change of gravitational acceleration can be calculated based on the output of the sensor. A theoretical analysis of the working principle of the NUFSMD is established. A prototype NUFSMD is machined from 304 stainless steel and a series of experiments are carried out. The effectiveness of gravity measurement is demonstrated by finite element simulations and experiments. The experimental results show that the sensitivity of the NUFSMD is about 15.27 μgal/nm, and the resolution is about 1.83 μgal. The designed NUFSMD shows outstanding performance. And the sensitivity and resolution of the NUFSMD can be further improved by increasing the number of flexible hinges connected in series. Compared with the existing spring-mass devices in high-precision relative gravimeters, the significant advantage of the NUFSMD is that it is simple in structure and easy to machine, which helps to greatly improve performance. Firstly, it is simple in structure, so it can be machined in one piece, which considerately contributes to stability and precision. Secondly, it is easy to machine, so it can be machined from high-performance but difficult-to-machine materials to improve its performance. Thirdly, there are a few parameters that need to be traded off for miniaturization because of the simple structure, so it is easy to be miniaturized to adapt to narrow measurement space. Therefore, it is expected to greatly improve the performance of the existing spring-mass device in relative gravimeters.

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