Abstract
Abstract
While depleted oil and gas fields can provide important storage capacity for Carbon Capture and Storage (CCS), injection of carbon dioxide into extremely pressure depleted hydrocarbon fields can be problematic due to the phase change of CO2 that can cause flow instability and result in adverse physical phenomena, such as the cooling associated with the latent heat of vaporization and Joule-Thomson cooling which could damage the completion equipment, reduce the hydrostatic head of CO2 and make it difficult to inject carbon dioxide.
Thus far, most completion solutions to this problem have focused on multi-string designs, either parallel or concentric, using flow conduit friction to maintain sufficient back pressure to prevent CO2 flashing. These methods can restrict the amount of carbon dioxide which can be injected and/or are costly or technically prohibitive. An alternative solution is proposed using variable, autonomous or surface-controlled, flow control devices strategically placed in the injection tubing string to provide stepwise pressure drops with depth.
This paper builds on the CCS simulator examined in SPE-209705 (Petitt and Konopczynski, 2022) by comparing three case studies modelled by altering the aperture of the wellhead choke and the inline control devices to maintain the CO2 in liquid form. These real-life scenarios were modelled with a variety of injection and reservoir pressures thus mimicking the varying conditions over the life of a well.
Using a purpose-designed CCS wellbore flow simulator that honors the thermodynamics and heat transfer of CO2 injection, we have modelled the flow performance of CCS well completions with multiple downhole flow control devices placed at strategic depths, the size and number of devices chosen to achieve the desired pressure distribution and CO2 injection rate.
The modelling shows that the multi-flow control device concept can maintain the carbon dioxide in a dense phase over anticipated operating conditions and provides a greater injection rate capacity and turndown range than multi-string solutions inside the same casing size. Depleted reservoirs and restricted CO2 injection rates require the greatest number of flow control devices, while maximum injection rates at maximum reservoir pressures require the fewest number of devices, introducing the potential for completion designs that permit retrieval of the in-line devices with minimal intervention as the reservoir is charged through project life.