TY - THES

T1 - Numerical Modelling to Estimate the Amount of Formation Deformation and its Effect on Cement Integrity

AU - Atkin, Timothy

N1 - no embargo

PY - 2019

Y1 - 2019

N2 - In drilling, thus far, there have been several issues that may have significant impact on cement integrity that have not been fully understood. One of these issues is borehole ballooning. Borehole ballooning is sometimes referred to as breathing and is an expression used to describe the small volumetric change of the active fluid system, which might occur during the circulation of drilling fluids. At the present time, there has been limited research and inclusion of cementing to the bore hole ballooning challenge. With the increased amount of focus that comes with well integrity issues, accurate prediction of borehole ballooning while performing primary cement jobs becomes increasingly necessary to assure that the volumetric change and its effect on the cement/formation bond that this causes is correctly accounted for. In the context of the above challenges this thesis project aims to explore the utilisation of a numerical software model to study the effects of borehole ballooning that occurs while cementing on the cement integrity in terms of volumetric change, several scenarios are studied with three different types of cement and 3 different types of surrounding formation. Based on the results recommendations will be proposed, which may help to reduce risks and improve the cement operation. This thesis suggests that a somewhat small volume change over a relatively moderate section length, as indicated by the results, could mean that problems with the integrity of wells might not be as considerable as originally proposed. This small volume would be taken into account by existing quantities of cement or by changing the cement properties in a minor way to reduce the degree of deformation. The strength of the surrounding formations also provides support and limits the amount of deformation. The displacement velocity has the largest impact on the level of deformation, the marginal difference increases as the velocity increases but is still comparatively small.

AB - In drilling, thus far, there have been several issues that may have significant impact on cement integrity that have not been fully understood. One of these issues is borehole ballooning. Borehole ballooning is sometimes referred to as breathing and is an expression used to describe the small volumetric change of the active fluid system, which might occur during the circulation of drilling fluids. At the present time, there has been limited research and inclusion of cementing to the bore hole ballooning challenge. With the increased amount of focus that comes with well integrity issues, accurate prediction of borehole ballooning while performing primary cement jobs becomes increasingly necessary to assure that the volumetric change and its effect on the cement/formation bond that this causes is correctly accounted for. In the context of the above challenges this thesis project aims to explore the utilisation of a numerical software model to study the effects of borehole ballooning that occurs while cementing on the cement integrity in terms of volumetric change, several scenarios are studied with three different types of cement and 3 different types of surrounding formation. Based on the results recommendations will be proposed, which may help to reduce risks and improve the cement operation. This thesis suggests that a somewhat small volume change over a relatively moderate section length, as indicated by the results, could mean that problems with the integrity of wells might not be as considerable as originally proposed. This small volume would be taken into account by existing quantities of cement or by changing the cement properties in a minor way to reduce the degree of deformation. The strength of the surrounding formations also provides support and limits the amount of deformation. The displacement velocity has the largest impact on the level of deformation, the marginal difference increases as the velocity increases but is still comparatively small.

KW - Casing

KW - Cementing

KW - Borehole Ballooning

KW - Cement Job

KW - Volumetric changes

KW - Well Integrity

KW - Well control

KW - Cement

KW - Casing

KW - Cementing

KW - Borehole Ballooning

KW - Cement Job

KW - Volumetric changes

KW - Well Integrity

KW - Well control

KW - Cement

M3 - Master's Thesis

ER -