Probing the use of electrochemical cells in downhole conditions to reduce the environmental footprint of Oil & Gas well Plug & Abandonment.

It is projected that Equinor will have to permanently P&A (Plug and Abandon) over 1,200 wells within the next 40 years. The standard for well integrity requires that for permanently abandoning a well, barriers shall extend across the full cross section of the well. The purpose of the cross-sectional plug is to guarantee the isolation of reservoirs and other sources of inflow that could, among others, contaminate water reservoirs or leak hydrocarbons to the surface. To provide full access to the cross section of the well, a window in the present metal tubing has to be cut, milled or in some cases the metal tubing would have to be entirely pulled out of the well. Most of the technology currently available to open this window requires the use of a drilling rig and all the environmental footprint associated with it. It is estimated that the emission related to plugging these wells may exceed 260K Tons of CO2 per year or 10M Tons over the next 40 years. Fortunately, there is considerable industry focus on developing new technology that will enable the many operations involved in P&A to be performed without the use of a rig. Upcoming rig-less P&A technology such as the dSolve project, would complement each other and, together, enable a rig-less P&A operation, substantially reducing the CO2 emissions. The dSolve project is based on fundamental research performed and published by Equinor and SINTEF. It demonstrated that electrochemical cells could be used to accelerate the corrosion of the casing in order to open cross-sectional windows in tubing, without using a rig or coil tubing. It was also demonstrated that the window could be opened competitively and in a variety of casing string designs. The results of the project have confirmed that the electrochemical cell can successfully operate under high downhole pressures and temperatures in vertical to horizontal wells. Furthermore, the models based on empirical data that were created, will provide the operation with valuable information for job planning and execution. Studies also confirmed the non-hazardous characteristics of the by-products when opening cross-sectional windows in both casing steel and 13Cr-Steel.

A successful development of the dSolve technology together with other upcoming technology, will results in a rig-less P&A operation. The biggest contribution from a successful realization of this project is the impact to the environment. It is estimated that opening a window using a rig, would release between 2,5K and 3.3K tons of CO2. On the other hand, experiments showed that CO2 emission when using the dSolve to open a 10-meter window are estimated to be 1.3 tons or under 10 minutes of emissions from a rig. The cost related to opening windows in casing could be reduced by 65%. With over 1,200 wells to be P&A, it is estimated that Equinor could save over 25,000 MNOK over the next 40 years. This cost reduction will improve the life-time of the fields, since the current high cost of P&A is factored into the economic assessment of an asset. Lowered costs of P&A will help extending the brownfield life of assets. This will result in better utilization of the national resources.

It is projected that Equinor will have to permanently P&A (Plug and Abandon) over 1,200 wells within the next 40 years. The standard for well integrity requires that for permanently abandoning a well, barriers shall extend across the full cross section of the well. The purpose of the cross-sectional plug is to guarantee the isolation of reservoirs and other sources of inflow that could, among others, contaminate water reservoirs or leak hydrocarbons to the surface. To provide full access to the cross section of the well, a window in the present metal tubing has to be cut, milled or in some cases the metal tubing would have to be entirely pulled out of the well. Most of the technology currently available to open this window requires the use of a drilling rig and all the environmental footprint associated with it. It is estimated that the emission related to plugging these wells may exceed 260K Tons of CO2 per year or 10M Tons over the next 40 years. Fortunately, there is considerable industry focus on developing new technology that will enable the many operations involved in P&A to be performed without the use of a rig. Upcoming rig-less P&A technology such as the dSolve project, would complement each other and, together, enable a rig-less P&A operation, substantially reducing the CO2 emissions. The dSolve project is based on a fundamental research performed and published by Equinor and SINTEF. It demonstrated that electrochemical cells could be used to accelerate the corrosion of the casing in order to open cross-sectional windows in tubing, without using a rig or coil tubing. It was also demonstrated that the window could be opened competitively, in a variety of casing string designs while producing environmentally friendly by-products. The objective of this project is to learn how the electrochemical cells operate under downhole conditions and how the by-products from the corrosion process affects the well and the operation.