Borehole gravity gradiometry

Nekut, A. G.

doi:10.1190/1.1442646

Cited by 16 publications

(3 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These benefits have led to gravity surveys being used in a number of environments to detect features of interest [ 3 ], including below the surface in boreholes. Borehole gravity sensing is used for a number of applications, including: remote sensing of gas and oil zones behind casing [ 4 ]; vertical density profiling for gravity map interpretation and for seismic modelling and analysis [ 5 ]; detection of geologic structures [ 6 , 7 ]; determination of reservoir porosity for reserve estimates [ 8 ]; monitoring of reservoir fluid conditions for production evaluation, and rock-type change mapping for groundwater and engineering studies [ 9 , 10 ]; Carbon Capture and Storage (CCS) monitoring [ 11 , 12 ]; as well as tests of fundamental physics [ 13 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

Magneto-optical trapping in a near-suface borehole

et al. 2023

View full text Add to dashboard Cite

Borehole gravity sensing can be used in a number of applications to measure features around a well, including rock-type change mapping and determination of reservoir porosity. Quantum technology gravity sensors, based on atom interferometry, have the ability to offer increased survey speeds and reduced need for calibration. While surface sensors have been demonstrated in real world environments, significant improvements in robustness and reductions to radial size, weight, and power consumption are required for such devices to be deployed in boreholes. To realise the first step towards the deployment of cold atom-based sensors down boreholes, we demonstrate a borehole-deployable magneto-optical trap, the core package of many cold atom-based systems. The enclosure containing the magneto-optical trap itself had an outer radius of (60 ± 0.1) mm at its widest point and a length of (890 ± 5) mm. This system was used to generate atom clouds at 1 m intervals in a 14 cm wide, 50 m deep borehole, to simulate how in-borehole gravity surveys are performed. During the survey, the system generated, on average, clouds of (3.0 ± 0.1) × 105 87Rb atoms with the standard deviation in atom number across the survey observed to be as low as 8.9 × 104.

show abstract

Section: Introductionmentioning

confidence: 99%

Magneto-optical trapping in a near-suface borehole

et al. 2023

View full text Add to dashboard Cite

show abstract

“…Applications range beyond this simple description to include detection of oil‐ and gas‐filled porosity, detection and definition of remote structures, such as salt domes, faults and reefs. BHGMs are used to measure gravity differences along the borehole trajectory (Nekut, 1989). One of the primary aspects of the borehole gravity measurements that makes it such an attractive logging tool in the petroleum industry is its ability to make a direct measurement of in situ bulk density and porosity of the formation and to characterize pore content.…”

Section: Introductionmentioning

confidence: 99%

MEMS‐based 3‐C borehole gravimeter development

et al. 2023

Geophysical Prospecting

View full text Add to dashboard Cite

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.

show abstract

“…The gravitational potential U due to a 2-D body of density p is Recent progress in gravity gradient instrumentation (Nevrekar, 1988) and current research in borehole-gravity gradiometry (Nekut, 1989) suggest the need for improved methods to compute higher-order derivatives of the gravity potential due to geologically realistic density models (Beyer L.A., 1988, Pers. commun.).…”

Section: Introductionmentioning

confidence: 99%

Conjugate complex variables method for the computation of gravity anomalies

Kwok

1989

GEOPHYSICS

View full text Add to dashboard Cite

Using conjugate complex variables, a generalized method is presented to derive formulas to calculate first-and higher-order derivatives of the gravity potential due to selected mass models. Double integrals in the computation of gravity-gradient anomalies are transformed into complex contour integrals. Analytical expressions for higher-order derivatives of the gravitational potential in arbitrary directions due to two-dimensional (2-D) polygonal mass models are derived. The method is extended to 2-D polygonal bodies whose density contrasts vary with depth and horizontal distance and can be generalized to deal with 2-D bodies of any shape. The vertical gravity field and its first derivatives due to a homogeneous radially symmetric body are also computed using conjugate complex variables. Derivation of gravity and gravity gradient formulas generally is greatly simplified by the use of complex variables.Complex variables have been an effective mathematical tool in geophysical gravimetry research for Soviet geophysicists (Antonov, 1975; Devitsyn, 1981a,b;Sretensky, 1946;Strakhov, 1974; Tsirulsky, 1963;Zhdanov, 1980). My paper presents a unified method using conjugate complex variables to compute first-and higher-order derivatives of the gravity potential for 2-D polygonal bodies. The spatial variables x and z are replaced by the conjugate complex variables w = x + iz and w = x -iz. Using complex-variables theory, double integrals in the computation of gravity anomalies are transformed into complex contour integrals. The method is then extended to 2-D polygonal bodies whose density contrasts vary with depth and lateral distance; the technique can be generalized to deal with 2-D bodies of any shape. I also compute, using conjugate complex variables, the vertical gravity field and its first-order derivatives due to homogeneous, radially symmetric bodies. This formulation significantly simplifies the procedures for the derivation of the computational formulas for gravity anomalies.

show abstract

Borehole gravity gradiometry

Cited by 16 publications

References 1 publication

Magneto-optical trapping in a near-suface borehole

Magneto-optical trapping in a near-suface borehole

MEMS‐based 3‐C borehole gravimeter development

Conjugate complex variables method for the computation of gravity anomalies

Contact Info

Product

Resources

About