Halliburton Energy Services, Inc.

Pedro R Segura

Preston N Weintraub

Gregory N Gilbert

Mark Anthony Sitka

John Ransford Hardin, Jr

Kristopher V Sherrill

James E Stone

David Welshans

Tony T Vu

Mark Anton Proett

An apparatus including a drill collar having an outer surface, an assembly for interaction with an earth formation coupled to the drill collar, the assembly including a first member to extend beyond the drill collar outer surface and a second member to extend beyond the first member and toward the earth formation to receive formation fluids. An apparatus including an MWD tool having an outer surface, a formation testing assembly coupled to the MWD tool, the formation testing assembly recessed beneath the outer surface in a first position and including a piston to extend beyond the outer surface to a second position and an inner sampling member to extend beyond the piston to a third position.

MWD formation tester

A formation testing tool is described herein, including a formation probe assembly having an extendable sampling probe surrounded by a cylindrical sleeve. The sleeve is configured to engage a metal skirt having an elastomeric seal pad coupled thereto. The skirt and seal are configured to be field replaceable. The elastomeric pad has a non-planar outer surface which engages a borehole wall in preparation for formation testing. The seal pad may be donut-shaped, having an aperture through the middle of the seal pad. The seal pad and its surface may include numerous different embodiments, including having a curved profile. The seal pad may also include numerous different embodiments of means for coupling the seal pad to the metal skirt. The formation testing tool also includes formation probe assembly anti-rotation means, a deviated non-circular flowbore, and at least one closed hydraulic fluid chamber for balancing fluid pressures.

The present invention is directed to methods and apparatus for using a formation tester to perform a pretest, in a formation having low permeability, by intermittently collecting a portion of fluid at a constant drawdown rate. The drawdown pressure is monitored until a maximum differential pressure is reached between the formation and the tester. Then the piston is stopped until the differential pressure increases to a set value, at which time the piston is restarted. The controlled intermittent operation of the piston continues until a set pretest volume is reached. The modulated drawdown allows for an accurate collection of pressure versus time data that is then used to calculate the formation pressure and permeability. The present invention also finds applicability in logging-while-drilling and measurement-while drilling applications where power conservation is critical.

Formation tester pretest using pulsed flow rate control

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Houston, TX, United States of America

Pedro R Segura