Well Integrity Estimation of Salt Cements with Application to Long Term Underground Storage Systems

Abstract

The new quest for unconventional resources as well as underground storage sector (CO2, air and natural gas) is the achievement of well integrity which is highlighted by the inadequacy of conventional cementing procedures to provide zonal isolation. Knowledge of the mechanism of fatigue in cement and factors that affect it such as the magnitude of the load, strength and composition of the cement, mechanical properties of the cement and pattern of load cycles are important to achieve a realistic design of a cement system subjected to fatigue loading. Finite element investigations help engineers to assess the stress magnitude and evolution for a given well configuration, but when structural calculations for casing-cement system are required, missing input parameters reduce the quality of the results. In order to obtain reliable data, extensive experimental work using Class G cement with and without salt addition has been performed in order to measure the principal parameters for mechanical structural calculations: compressive and tensile strength, Young modulus, Poison Ratio. The data was measured under room conditions and elevated temperature and pressure. The results were also extrapolated for a time period beyond 60 days. The obtained data is also compared with published values. Several SPE papers showed that excellent data inventory for well cement is needed when mechanical studies on cement, like finite element studies, are required. This paper will focus on various cement properties required to succsesfull cement an underground storage well by showing the effects of salt concentration on class G cements used as a reference. The results will help fill gaps in the knowledge about the behavior and reliability of NaCl salt cement slurry in cementing jobs by providing extensive data to perform mechanical and rheological calculations. It will similarly aid in the optimization of cement design and represents a source of input data for numerical simulations of well cement performance. We were able to establish/prove a relationship between salt content and permeability and, moreover, to show that fresh water in contact with set cement may massively change the porosity of the cement. For the first time, public reliable cement properties are systematically collated and compared.

Integrity Experiments for Geological Carbon Storage (GCS) in Depleted Hydrocarbon Reservoirs: Wellbore Components under Cyclic CO2 Injection Conditions

“…However, the literature reports a sparse permeability range for class G cement. Nevertheless, it is commonly accepted that a typical value for low permeability in cement is 1 × 10 −18 m 2 or even less, as suggested by studies conducted by Reinicke et al [29], Müller-Hoeppe et al [59], Czaikowski et al [60], Teodoriu et al [61], and Le-Minous et al [62]. Some researchers have reported permeabilities reaching up to 1 × 10 −17 m 2 for a standard class G cement, as indicated by studies conducted by Goode [63], Nelson and Guillot [64], and Lund et al [65].…”

Casing structural integrity and failure modes in a range of well types - A review

“…Figure 6 presents well logs signatures of a section in the well where the casing has buckled (highlighted in red ellipse as shown). Teodoriu et al (2016) established that casing eccentricity could increase the local stress distribution in the well and makes the cement most likely to fail and causes subsequent casing failure in the process. In addition, McDaniel et al (2014) in a study on cement sheath durability in Marcellus shale show that sustained casing pressure is the main reason behind cement damage.…”

Numerical Simulation of Hydrogen Diffusion in Cement Sheath of Wells Used for Underground Hydrogen Storage

“…Finally, the economics of injecting and producing hydrogen from depleted oil and gas diffusion decreases with increasing relative humidity. Teodoriu et al [31] studied the effects of salt concentration on class G cement for wells used in underground gas storage sites. The study analyzed the thickening time, compressive strength, elastic modulus, and set cement permeability of class G cement at different salt concentrations.…”