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Wellbore Stability and Sanding Potential Laboratory Method

IP.com Disclosure Number: IPCOM000238387D
Publication Date: 2014-Aug-21
Document File: 5 page(s) / 239K

Publishing Venue

The IP.com Prior Art Database

Abstract

Wellbore instability while drilling and sand production during hydrocarbon production are caused by failure to maintain reservoir material around the wellbore in the subsurface. One of the ways of quantifying this failure is to learn more about the formations through a thick-walled (or hollow) cylinder test. Current methods for measuring/monitoring material failure in tests such as these are quantified simply by pre- and post-test sample comparison. Useful benefits, such as improved sanding predictions, gravel pack treatments, filter sizing, modeling, and chemical formulations can be gained from adding real-time solid particle measurements as they are produced from stimulating a reservoir core, outcrop, or a synthetic cement/sand/proppant sample for sanding and wellbore stability studies.

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        Wellbore Stability and Sanding Potential Laboratory Method Abstract

Wellbore instability while drilling and sand production during hydrocarbon production are caused by failure to maintain reservoir material around the wellbore in the subsurface. One of the ways of quantifying this failure is to learn more about the formations through a thick-walled (or hollow) cylinder test. Current methods for measuring/monitoring material failure in tests such as these are quantified simply by pre- and post-test sample comparison. Useful benefits, such as improved sanding predictions, gravel pack treatments, filter sizing, modeling, and chemical formulations can be gained from adding real-time solid particle measurements as they are produced from stimulating a reservoir core, outcrop, or a synthetic cement/sand/proppant sample for sanding and wellbore stability studies.

Introduction

Rocks are composed of grains of varying shapes, sizes, orientations and textures. Due to burial and compaction of these grains and cementing in the pore spaces, they become consolidated. The consolidation leads to an increase in strength and stiffness. However, in the absence of consolidation, the material strength is much lower and leads to wellbore stability problems while drilling. Compressive or tensile failure occurs when the stresses in the material exceed its strength. The tensile strength of a rock is much smaller than the compressive strength, usually in the order of 10% of the compressive strength.

Wellbore stability problems can be classified into two categories. The first category is the instability of the well during drilling causing breakouts and/or tensile fractures. The second category is the production of solid particles during the production of reservoir fluids. The decision of a well completion solution, such as open holes, perforated liners, screens, or gravel packs, also depends on the likelihood of sand (or solid) production from a well.

During drilling, the objective is to drill a stable well by utilizing a safe mud weight window. Safe mud weight window refers to the difference between the minimum and maximum mud density to be used while drilling at a particular depth. A stable well need not be one with zero mechanical failure but usually one where the breakout width stays below 60 degrees, so that the wellbore does not collapse.

The presence of a borehole changes the natural state of stress in the sub-surface around the drilled hole and causes stress concentration of the far-field stresses. The stress concentration can manifest itself as compressive and/or tensile failure of the borehole wall. In addition to rock mechanical properties such as stiffness, compressive strength and tensile strength; mud pressure as well as azimuth and inclination of borehole also contribute in whether a borehole will fail. Borehole failures may also occur during the production of hydrocarbon from a well. The depletion of pore pressure during production increases...