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Annular Pressure Buildup Mitigation using Glass–Ceramic Materials having Negative Thermal Expansion Coefficient

IP.com Disclosure Number: IPCOM000239641D
Publication Date: 2014-Nov-20
Document File: 5 page(s) / 140K

Publishing Venue

The IP.com Prior Art Database

Abstract

Annular pressure build up (APB) is caused by thermal expansion of wellbore fluid enclosed in an annulus experiencing cyclic thermal loads due to production and injection. This may lead to significant damage to the cement sheath causing zonal isolation issues and may also cause casing collapse/burst. Most existing solutions to mitigate APB are either expensive or cannot be reused. The present invention aims at providing a solution that will not only be inexpensive but also can be reused. The present solution involves adding Glass–ceramic materials having a negative coefficient of thermal expansion inside the displaced fluids which will prevent APB by giving the heated fluid room to expand. It has been reported that these materials which are made from industrial waste such as Blast Furnace Slag show Negative Thermal Expansion of more than 10-7/K over a wide range of temperature.

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Annular Pressure Buildup Mitigation using Glass-Ceramic Materials having Negative Thermal Expansion Coefficient

Abstract

Annular pressure build up (APB) is caused by thermal expansion of wellbore fluid enclosed in an annulus experiencing cyclic thermal loads due to production and injection. This may lead to significant damage to the cement sheath causing zonal isolation issues and may also cause casing collapse/burst. Most existing solutions to mitigate APB are either expensive or cannot be reused. The present invention aims at providing a solution that will not only be inexpensive but also can be reused. The present solution involves adding Glass-ceramic materials having a negative coefficient of thermal expansion inside the displaced fluids which will prevent APB by giving the heated fluid room to expand. It has been reported that these materials which are made from industrial waste such as Blast Furnace Slag show Negative Thermal Expansion of more than 10-7/K over a wide range of temperature.

Introduction

Annular Pressure Buildup (APB) is one of the major issues concerning casing integrity today. In the oil and gas wells it is not un-common that a section of the formation must be isolated from the rest of the well. This is typically achieved by bringing the top of the cement column from the subsequent string up inside the annulus above the previous casing shoe. While this isolates the formations, bringing the cement up inside the casing shoe effectively blocks the safety valve provided by the nature's fracture gradient. Instead of leaking off the shoe, any pressure buildup will be exerted on the casing, unless it can be bled-off at the surface. Most land wells and many offshore platforms are equipped with wellheads that provide access to every casing annulus and an observed pressure increase can be quickly bled off. Unfortunately most subsea wellhead installations do not have access to each casing annulus and often a sealed annulus is created. Because the annulus is sealed, the internal pressure can increase significantly in reaction to increase in temperature.

Most casing strings and displacement fluids are installed at near-static temperature. The production fluids are drawn from the hot formations that dissipate and heat the displaced fluids as the production fluids are drawn near the surface. When the displaced fluid is heated, it expands and substantial pressure increase can result. This condition is present in all producing wells, but is most evident in deep water wells. Deep water wells are likely to be vulnerable to annular pressure buildup because of the cold temperature of the displaced fluid, in contrast to elevated temperature of the production fluid during the production. Also, subsea well head does not provide access to all the annulus and any pressure increase in the annulus cannot be bled off. Sometimes the pressure can become so great as to collapse the inner string or even rupture the outer string, thereby de...