Improved Science-Base for Materials & Wellbore Integrity

Studying performance & integrity of key offshore materials for which data in extreme environments are limited including metallic tubulars and borehole cements

Characterization of Metal-Based Systems Used in Control Devices Subject to Extreme Environmental Conditions: NETL is evaluating failure mechanisms and rates for critical components based in part on observed/reported behavior in the field augmented with experimental studies on materials behavior under simulated extreme conditions. At present, publically available data about the performance of these materials under extreme offshore conditions is limited. To date this study has successfully evaluated strength/corrosion potential of the most common alloys used in extreme offshore drilling at in situ conditions (pressure, temperature, H2S, etc). Ongoing work will result in a pit/fatigue model tool to allow for the assessment of catastrophic failure potential of these metallic components. NETL is also evaluating new alloys and surface treatments (e.g. hammer peening) for ultra-deep well environments to constrain their behavior under extreme borehole conditions. A recent Technical Report Series (TRS) publication presents findings on Fatigue Crack Growth Rate of UD-165 in Sour Environments, which can be found on NETL’s website.

 
Metal corrosion studies evaluate most commonly used offshore alloys

 

Determining Physical and Chemical Behavior of Cement Barriers Used in Ultra-Deepwater Systems: NETL is researching the physical and chemical behavior of typical wellbore cements to better understand how various cement formulations perform, with a particular emphasis on potential failure pathways and remediation technologies. Currently, there is no information on how foam cements, commonly used in extreme offshore settings, perform and persist under in situ conditions. NETL researchers initiated laboratory characterization studies of commonly used industry standard formulations of foam cements and have obtained the first CT images of foamed cement systems. The CT characterization of the samples allows for the quantitative analysis of physical properties and structures within the cement (particularly bubble sizes and distributions). NETL researchers have also developed a reliable methodology to probe the microstructure of foamed cements under in situ conditions. Going forward, the team will use this methodology to determine stability of foamed cement systems at various “depths” in the subsurface and correlate those properties with the current method of atmospheric testing. Phase 1 findings from this project were released in An Assessment of Research Needs Related to Improving Primary Cement Isolation of Formations in Deep Offshore Wells TRS publication. Initial results from this study's atmospheric foamed cement experiments are summarized in the recently released Computed Tomography and Statistical Analysis of Bubble Size Distributions in Atmospheric-Generated Foamed Cement TRS publication on NETL’s website.

Example 3D CT video highlighting bubble size distribution (color coded by size fraction) of borehole cement sample analyzed by NETL ORD researchers.

 

Characterization and Analysis of Formation, Cement, and Casing Barrier Integrity: A new project initiated by NETL researchers focuses on determining the physical, chemical, and temporal integrity of the formation of cement and cement casing systems used in extreme offshore settings. The project leverages NETL materials and natural systems expertise to evaluate short and long-term integrity of the seal/bond between the formation, cement, and casing at in situ conditions representative of the range of subsurface conditions associated with deep offshore drilling. Initially this project will focus on shallow subsurface conditions (up to 2,000 feet below the seafloor) and will incorporate experimental techniques with analysis of field datasets such as borehole geophysical logs.