Transition Time of Cement Slurries, Definitions and Misconceptions, Related to Annular Fluid Migration

Abstract

Transition time of cement slurries is a term that has been used throughout the oil industry for many years. During this time, the term has been defined, redefined and misused to cover a wide range of cementing topics. This has led to numerous misconceptions and confusion as to what transition time really means. For many years, this term has been directly tied to the term right-angle-set, which relates to the speed in which slurries undergoing continuous shear go from a pumpable to a non-pumpable state. Once pumping is stopped, the profile of how cement transition from a liquid, to a gel, to a set cement changes. These changes can directly affect the performance of cement slurries to control fluid migration. With the advent of the Ultrasonic Cement Analyzer (UCA), the term "transition time" of cement slurries was redefined. UCA's have developed into an essential piece of equipment. Not only can they achieve compressive strength information, but the apparatus can also provide a continuous measurement of how cement sets in static state. This information has shortened wait on cement (WOC) time, and provides an excellent profile on how fast cement develops strength. However, the transducers in a standard UCA only provide information after the cement develops a compressive strength set. With improvement in computerization and transducers, a more sensitive evaluation of gel strength development can be studied. Another definition for transition time is the use of a static gel strength (SGS) analyzer to measure the time from which cement goes from 100 lbf/100 sq. ft (48 Pa) to 500 lbf/100 sq.ft (240 Pa). It has become an industry standard that once cement slurries reach an SGS of 500 lbf/100 sq. ft (240 Pa)., gas or other fluids cannot be transmitted through the cement. The faster that you achieve this optimum SGS, the less likely that the cement will transmit gas. This paper will establish a definition for cement transition time and discuss the misconception of only using gel strength development to control gas migration. Test data that exhibits gas tight slurries with long transition and those with short transition that allowed gas influx will be shown. Also discussed in the paper will be the advantages of cements with a short transition in controlling high-pressure water flows. Introduction The control of annular gas migration after cementing has been the subject of many studies and papers1–6. These include practical approaches, theoretical approaches, mathematical modeling and physical modeling, each concentrating on one or two specific causes of gas migration. The one thing that all these studies have in common is the fact that they all present valid conclusions, and although beneficial, have all failed in field applications at one time or another. These failures illustrate that although we have learned a great deal about the causes and prevention of gas migration, there is still a lot to learn. However, before we can progress, we need to make sure that we understand and are using the preferred nomenclature.

Designing Cement Slurries for Preventing Formation Fluid Influx After Placement

“…The results also demonstrate that accomplishment of the above three main slurry characteristics to resist fluid flow invasion will ensure a right-angle set behavior by default. As previously reported, 12 designing cement slurries primarily for their right-angle set behavior may not guarantee resistance to fluid migration through cement slurries.…”

“…Creating a cement sheath that provides proper zonal isolation under any circumstance should be a primary objective [1][2][3][4][5][6][7][8][9][10][11][12] in every well construction project to (1) protect fresh water from contamination, (2) provide effective interzonal isolation, and (3) provide mechanical support to the casing string. All these objectives will facilitate the production of oil and gas safely and economically over the well's lifetime.…”

New Slurry Design Concepts Using Multifunctional Additives to Improve Quality and Sustainability of Cementing Systems for Zonal Isolation

“…The ability of a cement slurry to provide gas control was tested in a gas flow model at BHCT, and results were evaluated with a pass/fail analysis as described by Rogers et al (2004). The cement slurries were conditioned to BHCT of 146°F within 41 minutes and then maintained at that temperature for 20 additional minutes.…”

Wpływ nanotlenków glinu i cynku na parametry świeżego i stwardniałego zaczynu cementowego

“…czas przejścia, czyli czas od rozpoczę-cia budowy statycznej wytrzymałości strukturalnej (SGS -50 Pa) do uzyskania wartości granicznej SGS -250 Pa, któ-rej osiągnięcie oznacza, że gaz nie powinien migrować przez wiążący zaczyn. Im krótszy czas przejścia, tym mniejsze prawdopodobieństwo zjawiska migracji gazu [16].…”