Well fossilization for P&A

Formation of mineral scale is a common problem in tubing pipes in petroleum wells. Over the years, scientists have learnt a lot about scale formation - more specifically how to minimize or avoid it. In this project, we turn everything upside down, and we aim to maximize scale formation. The idea is to simplify permanent well plugging and abandonment (P&A) operations by forming thick mineral layers outside unsupported well pipes (to form annular barriers between the steel casing and formation wall), and inside them (to form well plugs). When wells are no longer operational as petroleum producers or CO2 injectors, they must be permanently sealed across the entire formation-cement-casing section. If this groundbreaking concept works, it opens for completely rig-less P&A of all well types (also those damaged by subsidence), and it offers a possibility to repair leaking, previously P&A'ed wells. The project will build upon the vast knowledge base we have from prior scale science projects, and it will focus on testing the applicability of promising ways of enhancing scale formation on pipes. Examples are: making use of biomineralization, applying voltage on the pipe and/or tailoring well fluids for scale formation. If this "scale-as-a-barrier" concept works, it can give savings in the range of ten-hundred million NOK per well, and it will greatly enhance the safety on the Norwegian Continental Shelf, both for oil & gas activities and for CO2 storage. We tested electrochemical precipitation of minerals from Gyda, Smeaheia, Ekofisk, Troll, Statfjord and Sleipner reservoir waters with different compositions. Precipitation was provoked in reservoir water with and without purging with CO2. The amount of precipitated material was proportional to the concentration of calcium in the water. More mineral was deposited when CO2 was purged through solution. Gyda water, that was richest in calcium, gave the greatest precipitation. It was also shown that by using anodic polarization mineral deposition can be prevented. These findings are of great importance for mineral scale prevention and maximization. Based on our experiments, we have proposed the design of new well intervention equipment that can be used to provoke mineral formation inside the well. We hane also formulated a workflow to evaluate the potential for the technique in various fields/wells based on knowledge on geology, oceanography, drilling and completion fluids, and the wells.

- Fått klarhet i de viktigste mekanismene som styrer dannelse av scale rundt foringsrør i en P&A-setting - Publisert en rekke (5) fagfellevurderte artikler - Presentert resultatene for brukergrupper (konferanse med industrideltakelse)

Formation of mineral scale is a common problem in tubing pipes in petroleum wells. Over the years, scientists have learnt a lot about scale formation, and the idea of this proposal is to make use of this knowledge in a groundbreaking new way. Instead of trying to minimize scale formation, which has been the goal so far, we aim to maximize scale formation. The goal is to simplify permanent well plugging and abandonment (P&A) by forming thick mineral layers outside unsupported well pipes (to form annular barriers), and inside them (to form well plugs). The project will focus on testing the applicability of promising ways of enhancing scale formations in/on pipes, such as applying voltage on the pipe and tailoring well fluids for scale formation. If the method works, it opens for completely rig-less P&A of all well types (also those damaged by subsidence), and it offers a possibility to repair previously P&A'ed wells if the upper part of the well pipes can be accessed. Potentially, this can give savings in the range of ten-hundred million NOK per well, and it will greatly enhance the safety on the Norwegian Continental Shelf, both for oil & gas activities and for CO2 storage.