| dc.description.abstract | When an oil & gas well proves not to be economically favourable anymore, or is technically inviable, the well has served its life and are due to be shut-down and sealed, also referred to as permanent plug & abandonment. Depending on the country one operates in, different local regulatory requirements have to be followed. Various guidelines, set by the regulatory authorities, refer to recognized industry standards. Within permanent plug & abandonment, four recognized industry standards concerning well integrity and barriers are covered; NORSOK D-010 well integrity in drilling and well operations, Oil & Gas United Kingdom well decommissioning guidelines, API wellbore plugging and abandonment and DNV risk based abandonment of wells.
Portland cements are the most common used barrier material in today’s permanent plug & abandonment operations. The use of Portland cements have faced excessive well integrity problems since it was first introduced, where common issues has been development of micro-annuli over time due to shrinkage, mechanical failure, and degradation at elevated temperatures. Use of Portland cement has historically been inexpensive and further satisfying fundamental barrier material requirements, despite its weaknesses. The oil & gas industry has researched substitutes in the last decade, but few alternatives have had commercial success.
Through a technical qualification process based on review and comparison of industry accepted standards, the rock-based geopolymer cement is proved to be acceptable as a barrier material in the oil & gas industry. Geopolymers naturally expanding properties together with a permeability similar to shale is advantageous to seal the wellbore against leakage to the external environment. Combined with an environmental footprint that is less than half of Portland cements, geopolymer-based cement shows many benefits compared to Portland cement and can thus be a viable barrier substitution material. | |
