Gravity surveys of subterranean formations may be based on the simultaneous measurement of gravity and its derivatives to produce a higher resolution formation map or wellbore log. For example, a method of performing a gravity survey may include positioning a matter wave interferometer relative to a subterranean formation; producing at least one cloud of atoms in the matter wave interferometer; producing a superposition of atoms in two different, spatially separated superimposed clouds from each of the at least one cloud of atoms; propagating the two different, spatially separated superimposed clouds along the matter wave interferometer as they with a gravitational field of the subterranean formation; combining the two different, spatially separated superimposed clouds with a Raman laser beam; measuring an interference produced by producing and combining the two different, spatially separated superimposed clouds; and calculating gravity for the gravitational field of the subterranean formation based on the interference.

The present invention discloses a MEMS gravimeter comprising: a spring-mass system, a displacement sensing structure, a displacement detecting circuit, a cavity body and a level adjustment base; the spring-mass system is disposed inside the cavity body and includes: a negative-stiffness spring, a positive-stiffness spring, a proof mass and an outer frame; the proof mass is connected to the outer frame by the negative-stiffness spring and the positive-stiffness spring, the negative-stiffness spring and the positive-stiffness spring are symmetrically disposed with respect to the proof mass, and the outer frame is fixedly connected to the cavity body; the displacement sensing structure is located on a surface of the proof mass, and the displacement detecting circuit is configured to detect a displacement signal from the displacement sensing structure; the spring-mass system realizes reduction in resonant frequency by matching of the positive and negative stiffness springs; and change in gravitational acceleration is detected by detecting a displacement of the proof mass. The MEMS gravimeter has high stability, small size and light weight, and thus can effectively reduce the production cost as well as the development difficulty of the signal detection unit and stable platform.

An atomic interferometric accelerometer comprises a laser that emits a pulsed beam at a first frequency, an electro-optic modulator that receives the beam, and a vacuum cell in communication with the electro-optic modulator. The electro-optic modulator outputs a first optical signal corresponding to the beam at the first frequency and a second optical signal having a second frequency different from the first frequency. The vacuum cell has a chamber for laser cooled atoms. The vacuum cell receives the optical signals such that they propagate in a direction that passes through the atoms. A piezo mirror retro-reflects the optical signals back through the vacuum cell in a counter-propagating direction. The piezo mirror is driven with substantially constant velocity during a beam pulse, thereby imparting a Doppler shift to the retro-reflected optical signals to create two non-symmetric counter-propagating lightwave pairs. One of the lightwave pairs supports interferometry while the other is non-resonant.

The general field of the invention is that of matter-wave gravimeters. The gravimeter according to the invention comprises at least: means for generating, for capturing and for cooling a cloud of ultra-cold atoms; means of transferring the atoms into a superposition, with equal weights, of a first internal electronic state called state |1>) and of a second internal electronic state called state |2> comprising the application of at least a first microwave field and of a radiofrequency field; means for separating the atoms into two wave packets for a given period of time under the effect of at least a second microwave field, the said separation leading to a phase-shift associated with the local gravitational field; calibration means allowing a “magic” magnetostatic field to be determined for which the difference in energy between the first internal electronic state and the second internal electronic state is independent, to a first order, of the fluctuations of the magnetostatic field.

The general field of the invention is that of matter-wave gravimeters. The gravimeter according to the invention comprises at least: means for generating, for capturing and for cooling a cloud of ultra-cold atoms; means of transferring the atoms into a superposition, with equal weights, of a first internal electronic state called state |1>) and of a second internal electronic state called state |2> comprising the application of at least a first microwave field and of a radiofrequency field; means for separating the atoms into two wave packets for a given period of time under the effect of at least a second microwave field, the said separation leading to a phase-shift associated with the local gravitational field; calibration means allowing a “magic” magnetostatic field to be determined for which the difference in energy between the first internal electronic state and the second internal electronic state is independent, to a first order, of the fluctuations of the magnetostatic field.

A gyroscope apparatus for a device including an accelerometer and a magnetic component has a gravity vector generator connected to the accelerometer and receptive to acceleration readings therefrom. A magnetic component output generator is connected to the magnetic component and receptive to magnetic component readings. A sensor fusion engine is connected to the gravity vector generator and to the magnetic component output generator, with a gravity vector value and a magnetic field vector value at a first time instance being combined to represent a first orientation value. The gravity vector value and the magnetic field vector value at a second time instance are combined to represent a second orientation value. An orientation rate of change is derived from a difference between the first orientation value and the second orientation value.

A gyroscope apparatus for a device including an accelerometer and a magnetic component has a gravity vector generator connected to the accelerometer and receptive to acceleration readings therefrom. A magnetic component output generator is connected to the magnetic component and receptive to magnetic component readings. A sensor fusion engine is connected to the gravity vector generator and to the magnetic component output generator, with a gravity vector value and a magnetic field vector value at a first time instance being combined to represent a first orientation value. The gravity vector value and the magnetic field vector value at a second time instance are combined to represent a second orientation value. An orientation rate of change is derived from a difference between the first orientation value and the second orientation value.

An acceleration measuring device is disclosed, for use as a gravimeter or gradiometer for example. The device has a support and a proof mass, connected to each other by at flexures allowing displacement of the proof mass relative to the support. The support defines a space for displacement of the proof mass. The device is configured so that the modulus of the gradient of the force-displacement curve of the proof mass decreases with increasing displacement, for at least part of the force-displacement curve. This is the so-called anti-spring effect. The resonant frequency of oscillation of the proof mass is determined at least in part by the orientation of the device relative to the direction of the force due to gravity. The proof mass is capable of oscillating with a resonant frequency of 10 Hz or less. The proof mass has a mass of less than 1 gram.

An acceleration measuring device is disclosed, for use as a gravimeter or gradiometer for example. The device has a support and a proof mass, connected to each other by at flexures allowing displacement of the proof mass relative to the support. The support defines a space for displacement of the proof mass. The device is configured so that the modulus of the gradient of the force-displacement curve of the proof mass decreases with increasing displacement, for at least part of the force-displacement curve. This is the so-called anti-spring effect. The resonant frequency of oscillation of the proof mass is determined at least in part by the orientation of the device relative to the direction of the force due to gravity. The proof mass is capable of oscillating with a resonant frequency of 10 Hz or less. The proof mass has a mass of less than 1 gram.

Aspects of the disclosure can relate to simulating expected sensor values associated with a drill tool (e.g., a drill assembly) before drilling to monitor the sensor. A planned trajectory for the drill assembly is received, where the planned trajectory is associated with a borehole to be drilled by the drill assembly along a geographic path. Next, an expected position for the drill assembly is determined along the geographic path. Then, an expected sensor value for a sensor associated with the drill assembly is simulated at the expected position. Next, an actual sensor value at an actual position corresponding to the expected position is determined. Then, the expected sensor value and the actual sensor value are dynamically displayed together at a user interface.