Abstract: The apparatus for evaluating a wellbore while drilling includes a logging toolheld on a drill string and is adapted to obtain data from the wellbore while moving the drill string including the logging tool uphole and out of the wellbore. The logging tool includes a memory for storing obtained data and an on-board power supply battery. A computer being positioned at a surface level of the wellbore is adapted to obtain the data from the memory when the logging tool is also positioned at the surface level. The logging tool is adapted to perform a minimum power-consuming sleep mode with a data obtaining and storing function being disabled and the computer is adapted to transmit a wake-up signal downhole to enable the data obtaining and storing function of the logging tool just prior to tripping out the drill string from the wellbore. The wake-up signal preferably is a mud pulse signal sent through the drilling fluid used when drilling the wellbore.

Abstract: A centralizer includes a centralizer body to be situated at the outer surface of a pipe string in the form of casing, liner, or the like used while drilling, the centralizer body being formed with a plurality of outer centralizer blades arranged in an inclined manner to the longitudinal axis thereof, wherein the centralizer body has an separate split inner tube secured to the pipe string by means of a press fit, and low friction inner surface of the centralizer body and separate center tube facing each other are made from low friction material.

Abstract: A centralizer includes a centralizer body to be situated at the outer surface of a pipe string in the form of casing, liner, or the like used while drilling, the centralizer body being formed with a plurality of outer centralizer blades arranged in an inclined manner to the longitudinal axis thereof, wherein the centralizer body has an separate split inner tube secured to the pipe string by means of a press fit, and low friction inner surface of the centralizer body and separate center tube facing each other are made from low friction material.

Abstract: A centralizer includes a centralizer body to be situated at the outer surface of a pipe string in the form of casing, liner, or the like used while drilling, the centralizer body being formed with a plurality of outer centralizer blades arranged in an inclined manner to the longitudinal axis thereof, wherein the centralizer body has an separate split inner tube secured to the pipe string by means of a press fit, and low friction inner surface of the centralizer body and separate center tube facing each other are made from low friction material.

Abstract: A centralizer includes a centralizer body to be situated at the outer surface of a pipe string in the form of casing, liner, or the like used while drilling, the centralizer body being formed with a plurality of outer centralizer blades arranged in an inclined manner to the longitudinal axis thereof, wherein the centralizer body has an separate split inner tube secured to the pipe string by means of a press fit, and low friction inner surface of the centralizer body and separate center tube facing each other are made from low friction material.

Abstract: The apparatus for evaluating a wellbore while drilling includes a logging toolheld on a drill string and is adapted to obtain data from the wellbore while moving the drill string including the logging tool uphole and out of the wellbore. The logging tool includes a memory for storing obtained data and an on-board power supply battery. A computer being positioned at a surface level of the wellbore is adapted to obtain the data from the memory when the logging tool is also positioned at the surface level. The logging tool is adapted to perform a minimum power-consuming sleep mode with a data obtaining and storing function being disabled and the computer is adapted to transmit a wake-up signal downhole to enable the data obtaining and storing function of the logging tool just prior to tripping out the drill string from the wellbore. The wake-up signal preferably is a mud pulse signal sent through the drilling fluid used when drilling the wellbore.