Determining Physical and Chemical Behavior of Cement Barriers Used in Ultra-Deepwater Systems

3-D renderings of a 10.4 mm3 digital subsection of 10% foam quality cement sample. (A) Opaque grayscale cement cube. (B) Orthoslices of solid cube with largest bubbles. (C) Largest bubbles in data set that sum to 10% of the total void space in the sample. (D) The next largest bubbles, summing again to 10% of the total void volume. (E) The mean bubbles, between the largest and the smallest in the sample set. (F) The smallest half of the bubbles.

Because cement stability is critical to ensure that gas (hydrocarbons) will not break out of the slurry, cement must be tested under conditions that simulate placement in the well and situations that exist in post placement. The objective of this task is to determine lightweight cement stability at various depths in the well and correlate those test results with current of atmospheric testing as outlined in the API Recommended Practice (RP).

This project is focused on improving the science base for wellbore integrity as it relates to the near term and long term efficacy of lightweight cements. Lightweight cements are used in many wells. However, they are increasingly used in deepwater wells and are the system of choice for high stress environments and shallow flow conditions such as those prevalent in the Gulf of Mexico (GOM). Currently, there is little, if any, information regarding the stability of lightweight cement systems under wellbore conditions. Operators and regulators do not have the information to predict or understand the properties of lightweight cement as it is placed in the well and at bottom hole conditions. In addition, the state of knowledge about the integrity and longevity of wellbore cements over decadal is poor, with little or no data or tools available for researching the situation. As wells are increasingly repurposed for secondary and tertiary purposes, ensuring that cement remains a barrier to subsurface flow is key. Research in this project seeks to address these challenges.