API Endorses Use of Portland Cement in Carbon Storage Wells

API provides engineers, operators, and regulatory agencies with a reference document for evaluating the performance of Portland cement in permanent carbon storage situations. By Joshua Falcon on November 19, 2025

The American Petroleum Institute (API) has released Bulletin 5100, a new technical document that supports the use of ordinary Portland cement (OPC) as an efficient and protective barrier in wells designed for carbon capture, utilization and storage (CCUS) projects.

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The implementation of Portland cement in CCUS projects

Portland cement has been the standard material in well construction for decades because of its sealing ability and durability. Now, with the rise of CCUS technologies, its prominence is becoming more significant. The API bulletin compiles up-to-date research that confirms the suitability of OPC for maintaining the integrity of wells where CO₂ is injected deep for safe storage.

This white paper brings together laboratory data and field experiences that demonstrate the chemical and mechanical stability of OPC under conditions typical of EPA-regulated Class VI wells. These wells require materials that can withstand prolonged exposure to CO₂ without degrading or compromising the safety of other subsurface formations.

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The publication of Bulletin 5100 is part of a larger effort to standardize practices associated with subsurface carbon storage. With more than 800 standards developed, API continues to expand the regulatory framework necessary for the energy industry to move toward more sustainable solutions, supported by technologies such as CCUS.

With this technical guide, API provides engineers, operators, and regulatory agencies with a reference document for evaluating the performance of Portland cement in permanent carbon storage situations. Permanent carbon storage. This is especially useful in the face of growing demand for Class VI well permits and infrastructure development associated with decarbonization.