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Rotary coring device and method for acquiring downhole stiffness measurement real-time during sidewall coring from an earth formation

IP.com Disclosure Number: IPCOM000246972D
Publication Date: 2016-Jul-19
Document File: 2 page(s) / 396K

Publishing Venue

The IP.com Prior Art Database

Abstract

A method for estimating the stiffness of a rock formation from sidewall coring is disclosed. A rotary coring device is conveyed down hole and before rotating the coring bit to obtain sidewall cores, the coring bit is advanced to deform the borehole wall at a constant specified pressure throughout the wellbore at depth intervals where sidewall cores are to be obtained. One such device is with a rotary coring device which is a device fitted with coring bit that is lowered to a desired depth in a well and the coring bit advanced to deform the borehole formation in order to measure the bit displacement into the wellbore on a wireline tool string. This is done before rotating the coring bit at a predetermined auxiliary bit pressure at all depth interval of interest before coring after predrilling the wellbore face for a constant engagement area.

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Title:  Rotary coring device and method for acquiring downhole stiffness measurement real-time during sidewall coring from an earth formation

Abstract:   A method for estimating the stiffness of a rock formation from sidewall coring is disclosed. A rotary coring device is conveyed down hole and before rotating the coring bit to obtain sidewall cores, the coring bit is advanced to deform the borehole wall at a constant specified pressure throughout the wellbore at depth intervals where sidewall cores are to be obtained. One such device is with a rotary coring device which is a device fitted with coring bit that is lowered to a desired depth in a well and the coring bit advanced to deform the borehole formation in order to measure the bit displacement into the wellbore on a wireline tool string. This is done before rotating the coring bit at a predetermined auxiliary bit pressure at all depth interval of interest before coring after predrilling the wellbore face for a constant engagement area.

Description:   The relative rock stiffness profile of the rock formation is then calculated since we are monitoring the bit advancement length at a constant auxiliary bit pressure at all depth interval and we know how much the material is deforming based on the bit penetration into the wellbore. We can estimate the stiffness caused by the deformation from the bit penetrating into the wellbore at different depth because we are measuring the bit advancement at the same auxiliary bit pressure, we can then in real-time estimate the relative stiffness of the rock at those depth based on the displacement and the known stress, hence we can obtain measurements of stiffness throughout the wellbore wherever the rotary coring device is deployed. In order to monitor the displacement required at each depth due to the applied auxiliary pressure (medium or high pressure), the wellbore face is first predrilled slightly to create an engagement face and remove the influence of the mud cake especially in permeable formation such as sandstone where mud cake can build up an...