INVESTIGATION OF ADMIXTURES EFFECT ON DEGRADATION OF CEMENT PASTE IN SAGD AND CCS WELLS

In recent years, Steam Assisted Gravity Drainage (SAGD) and Carbon dioxide Capture and Storage (CCS) projects are being developed in oil and gas fields. SAGD is a heavy oil recovery technology to reduce heavy oil viscosity and extract it from underground. CCS is a technology to inject CO2, emitted from plants, into a couple of 1000m deep ground through well. The deterioration of well in SAGD and CCS projects may cause leakage of deleterious gas. In this study, mechanical and chemical degradation of hardened cement paste made of Oil Well Cement (OWC) and Geothermal Well Cement (GWC) containing silica flour in the wells was studied experimentally. In order to imitate the underground condition of SAGD, the cement paste was exposed to the drying and moist sealed condition at 200°C. In addition, the cement paste was exposed to supercritical CO2 to reproduce the condition to inject CO2 gas in CCS well. The compressive strength tests after exposure to 200°C and thermal analysis to study carbonation after exposure to supercritical CO2 suggested that the replacement of silica flour to cement is effective to be applied to both SAGD and CCS injection wells

SHEAR CRACKING BEHAVIOR OF ULTRA-HIGH-STRENGTH PRESTRESSED REINFORCED CONCRETE BEAMS

ABSTRACT An experimental program was conducted to investigate the shear cracking behavior of both normal strength concrete and ultra-high-strength concrete I-shaped beams. All beams were tested by focusing on the influence of prestressing force and compressive strength of the concrete on the shear crack width. It was found that there is a linear relationship between shear crack width and stirrup strain in the both normal strength and ultra-high-strength concrete beams. Shear crack widths are smaller in ultra-high strength PRC beams

Well Integrity: Modeling of Thermo-Mechanical Behavior and Gas Migration along Wells-Application to Ketzin Injection Well

AbstractWell integrity plays a key role in the overall performance of oil and gas projects, including Carbon Capture and Storage (CCS) projects. Well integrity has to be demonstrated over the well life-cycle, during operations (production, injection and/or monitoring), abandonment and few hundreds of years after closure, particularly to ensure effective CO2 confinement into the reservoir.To contribute to the development of CCS technologies at a commercial scale, a CO2 injection experiment was developed in Ketzin, Germany. The project included drilling three wells: one for CO2 injection, and two for CO2 monitoring. The COSMOS 2 R&D project included wellbore integrity evaluation through extensive modeling at a meso-scale (well components scale) and a macro scale (well scale). The modeling activities focused on the fluids migration from the reservoir along the wellbore taking into account ageing mechanisms (e.g. casing corrosion and cement leaching) and micro-annulus opening at cement/casing/rock interfaces due to thermo-mechanical stresses.Such modeling results have to be integrated in a pro-active risk-based management of well integrity in order to optimize design, define monitoring and maintenance action plan or demonstrate safety to authorities. The benefits are a good knowledge of the risks (causes and impacts), the assurance these are under control and, as a consequence, insurance of a secured investment

The Cover Depth Effect on Corrosion-Induced Deterioration of Reinforced Concrete Focusing on Water Penetration: Field Survey and Laboratory Study

Reinforced concrete bridges were visually surveyed in Japan, Thailand, and Vietnam to study the deterioration caused by internal steel corrosion under different climates, focusing on the concrete cover depth. Spalling or cracking arising from corrosion is likely where water is supplied. According to prior studies and our surveys, a concrete cover depth of more than 40 mm was found to prevent spalling, regardless of environmental conditions and structure age. Because water supply at steel is a key corrosion factor, it was hypothesised that under natural conditions, the water penetration in concrete would remain at a depth of approximately 40 mm. Our laboratory study examined water penetration under drying and wetting conditions. The results also suggested that under periodic rainfall conditions, the threshold of water penetration was not exceeded. The numerical study indicated maximum moisture evaporation to facilitate oxygen diffusion occurred at a depth of approximately 30–40 mm unless the concrete was exposed to continuous drying for more than one month. It was experimentally and numerically concluded that an adequate cover depth of greater than 40 mm could inhibit moisture and oxygen penetration at the steel, which supported the survey findings of cover depth effect on a high resistance to corrosion-induced deterioration despite an increase in service life

Influence of Reinforcing Rebar on Expansion due to Delayed Ettringite Formation along the Bonding Length – Part I: The Role of Bond on Expansive Behavior of Concrete

International audienceThis paper explores the effects of rebar as an internal restraint on the expansion of delayed ettringite formation (DEF) in concrete. Concrete specimens embedded with steel bars without end plates are subjected to heat treatment followed by immersion in water. The effect of stirrups on expansion is also investigated. The results show that the longitudinal expansion of specimens without stirrups differs depending on the longitudinal position, owing to the different degrees of restraint resulting from stress in the steel bar. The final transverse expansions of the specimens without stirrups are close to those measured for stress-free specimens. Conversely, longitudinal and transverse expansions are significantly reduced in the specimens with stirrups. This indicates that the combination of a longitudinal steel bar and stirrups induces three-dimensional confinement stresses that help to limit DEF expansion in both the longitudinal and transverse directions. Furthermore, possible debonding along the longitudinal bar is observed in specimens without stirrups when the transverse expansion of the prismatic specimens is 0.4 to 0.6%. This behavior is not observed in the specimens with stirrups, which demonstrates the effectiveness of three-dimensional restraints in significantly mitigating the risk of debonding, as well as DEF expansion

Influence of Reinforcing Rebar on Expansion due to Delayed Ettringite Formation along the Bonding Length – Part II: Bond Performance of Reinforced Concrete Affected by DEF Expansion

International audienceThe purpose of this study is to clarify the bond behavior between rebar and concrete during DEF expansion and pullout testing. The details of the expansion test and the influence of reinforcing bar on DEF expansion have been precisely described in Part I. In Part II, the data related to the bond test is described. The change in bond behavior due to DEF expansion is investigated via the one-end pullout test and the influence of DEF expansion on the bond behavior is discussed. The local bond behavior (slip and bond stress) during the pullout test of the specimens without stirrups is observed to be dramatically changed by DEF expansion. Regarding the specimens with stirrups, failure did not occur during the pullout test and the local bond behavior slightly changed as in the case without stirrups. From the experimental results, a conceptual diagram is proposed to explain the bond behavior during DEF expansion and the pullout test based on the general conceptual understanding of the bond. It can be considered that the direction of local slip and local bond stress during the pullout test is opposite to that during the expansion process. This results in the observed complex local bond behavior during DEF expansion and the pullout test and the effect of stirrups on DEF expansion

Standardized models for cracking due to restraint of imposed strains - the state of the art

Crack control throughout the service life of a structure has always been a challenging task for engineers and asset owners, particularly those who are involved with the design and construction of structures with increased durability requirements, such as liquid retaining structures, nuclear containment buildings or structures in direct contact with ground, but also other externally restrained structures. For these reasons, several standardized methods exist throughout the global engineering community which encompass differences between them. This work is a state-of-the-art review of the methods for crack width control due to imposed strains recommended by different regulatory documents from Europe, USA, Australia and Japan, and provide a reasonable degree of guidance with respect to the assumptions, possibilities and restrictions of each method. This work resonates with the scope of the RILEM TC 287-CCS: Early age and long-term crack width analysis in RC structures.Arup; Fundação para a Ciência e a Tecnologia, Grant/Award Number: UIDB/ 04029/2020; Politechnika Sląska, Grant/Award Number: BK-225/RB6/202