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Mechanical Concepts for protecting LWD Geophone from Damage While Drilling

IP.com Disclosure Number: IPCOM000236316D
Publication Date: 2014-Apr-18

Publishing Venue

The IP.com Prior Art Database

Abstract

A geophone is a type of seismic sensor required in the seismic while drilling tool for seismic data collection. In the normal drilling operation, the geophone in the seismic while drilling tool, together with the rest of the bottom hole assembly (BHA), are subjected to high vibration condition (e.g. high pressure shock when the drill bit crushes through the formation). The 2D leaf spring within the geophone geometry design, which are attached to the moving coil assembly, may be damaged (e.g. creep or crack) due to high vibration. In order reduce the unnecessary damage caused by the shock and vibrations of the drilling tool, there are three solutions that can be applied onto the geophone design: (1) external side locking mechanism, (2) internal pin locking mechanism, and (3) a passive vibration isolator mechanism within the geophone structure design.

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Title: Mechanical Concepts for protecting LWD Geophone from Damage While Drilling

Abstract:

A geophone is a type of seismic sensor required in the seismic while drilling tool for seismic data collection. In the normal drilling operation, the geophone in the  seismic while drilling tool, together with the rest of the bottom hole assembly (BHA), are subjected  to high vibration condition (e.g. high pressure shock when the drill bit crushes through the formation). The 2D leaf spring within the geophone geometry design, which are attached to the moving coil assembly, may be damaged (e.g. creep or crack) due to high vibration. In order reduce the unnecessary damage caused by the shock and vibrations of the drilling tool, there are three solutions that can be applied onto the geophone design: (1) external side locking mechanism, (2) internal pin locking mechanism, and (3) a passive vibration isolator mechanism within the geophone structure design.

Seismic sensor such as geophone is required in the seismic while drilling tool for seismic data collection. In the normal drilling operation, seismic sensor in the  seismic while drilling tool together with the rest of the bottom hole assembly (BHA) are subjected  to high vibration condition (i.e. high pressure shock when the drill bit crushes through the formation). The seismic data are collected in the period of temporarily suspending the rotation and mud circulation of the drilling process.  Therefore, it is important to reduce the unnecessary damage causes by the shock and vibrations of the drilling tool while seismic sensors are not in operating mode

The general geophone design is comprised of a coil assembly (moving mass) suspended by 2D leaf springs via a magnetic field produced by a static magnet assembly as per figure 1. The signal capturing operation of the geophone is activated by upward and downward motion of the moving which supported by 2D leaf spring as per figure 2.

Figure 1:

Figure 2:

The 2D leaf springs which are attached to the moving coil assembly may be damaged (e.g. creep or crack) due to high vibration as per figure 3.

Figure 3:

In order to reduce the high stress generated by the impact of the moving mass and housing, there are two solutions can be applied onto the geophone design which are secure the moving mass while the geophone is not in its operating mode or include the passive vibration isolator mechanism into the geophone structure design in order to absorb the shock and significantly lower the maximum stress or attenuate the vibration of the moving mass during high vibration.

The moving mass of the geophone can be secured by external sidewall locking mechanism and internal locking mechanism through the static magnet assembly. 

The external sidewall locking mechanism of the geophone which proposed here is using a side wall holder to secure the moving mass of the geophone during vibration condition. There are three types of holder are as follow.

(1) Piston-based Locking...