Formation Sampling


ORIENTATION enhances sample recovery and data quality


The TOOL TAXI orientates and centralises the logging tool-string, it’s sensors & probes 

The TOOL TAXI completely supports the sampling tool on wheels, minimising the risk of differential sticking.


The sampling TOOL TAXI  turns the sampling tool on its “back”.  This permits sampling from the undamaged high side of the wellbore.


In deviated wells the weight of the drill pipe is borne on the low side of the wellbore.  Suspended cuttings are ground into the pore spaces by the rotating drill-string.  Further damage is done as the drill pipe scours the sealing mudcake from the wellbore wall, thereby allowing repeated invasion of drilling fluids.
Sampling from the high side of the wellbore results in faster clean-up due to improved permeability and less invasion.


FIELD EXAMPLE – pressure testing


In a recent operation in a high angle well, formation pressures were recorded from both the high-side and low-side of the wellbore. High-side permeabilities were proven to be 20x higher and valid fluid gradients were obtained.


This technique has been used successfully on large  sampling strings (50m long, 5000lbs)


Field experience proves that the logging tool will achieve the desired orientation in deviations as little as 1deg.



The TOOL TAXI carries the logging tool off centre.  The weight of the tool string causes the whole assembly to rotate in the wellbore until the system achieves the lowest centre of gravity. In this stable orientation, the TOOL TAXI is sitting squarely on its wheels and the sampling probe is aligned to the high side, perpendicular to the wellbore wall. 




 FIELD EXAMPLE – side wall cores

Using the TOOL TAXI to achieve near perfect centralisation and orientation – recovery on jobs to date >90%  

The TOOL TAXI centres the sampling tool-string and orientates the core drill perpendicular to the wellbore wall. This ensures optimal core recovery.

Stephen McCormick | Managing Director | Petromac Limited
Auckland, New Zealand Mob +64(0)210549158 Tel +64(0)95366621 Email