In 2003 the mature gas field K12-B was selected as a demonstration site for offshore injection of CO2. The initial project was aimed at investigating the feasibility of CO2 injection and storage in depleted natural gas fields on the Dutch continental shelf, with the objective to realize a permanent CO2 injection facility. Over the years many different aspects related to CO2 storage at K12-B have been researched, most of them widely applicable to other CO2 storage sites as well. CO2 injection and related research projects involving K12-B have continued until 2017, completing a period of almost 15 years of CO2 injection. This paper presents an overview of the most relevant and memorable research topics, their related activities and results.

The K12-B gas field, is located in the Dutch sector of the North Sea, some 150 km northwest of Amsterdam. It was developed and operated by predecessors of the current operator, which since 2017, is Neptune Energy Netherlands B.V. K12-B has been producing natural gas from the Permian age, Upper Slochteren Member (Rotliegend) since 1987. The natural gas produced has a relatively high CO2 content (13%) and the CO2 is separated from the production stream on site, prior to gas transport to shore. The CO2 used to be vented into the atmosphere but from 2004 on it has been injected into the gas field above the gas-water contact; at a depth of approximately 4000 m. K12-B was the first site in the world where CO2 has been re-injected into the same reservoir from which it originated. The average CO2 injection rate could reach 30,000 Nm3 CO2 per day, which is approximately 20 kt per year.

This paper presents an overview of the results and lessons learned of the multiple measurements campaigns and numerous research projects related to the CO2 injection at K12-B since 2004, performed by the operator and TNO. The research ranged from the investigation of top side and well equipment to the behavior of the gas field to social, environmental and risk assessment aspects. This paper will take you through our journey where we encountered anomalous tubing thicknesses, abnormal downhole injection pressures and surprising chemical evaluations. The paper will present how we learned more and more about the reservoir itself through the analysis of tracer chemicals breaking through, continuous extensive reservoir modelling, geomechanical modelling and even the actual back production of re-injected CO2.

This paper shows what valuable knowledge and information the CO2 injection project at K12-B has produced over the years. CO2 injection at K12-B was stopped when end 2017 the separation of CO2 at K12-B itself came to a halt. Without the active separation of CO2 on site there was no supply of CO2 anymore, which could be injected into the reservoir.