Thermal wells were widely developed with the expansion of thermal enhanced oil recovery processes like SAGD, CSS or steamflood. These high temperature processes brought new challenges to the well design in term of well integrity and well performance. The use of vacuum insulated tubing (VIT) or vacuum insulated casing (VIC) has significant benefits on the well completion by two main aspects: mitigate the effect of high temperature on some part of the completion and reduce the heat loss from the injected steam.
This paper describes both design and economic considerations that lead to the selection of VIT or VIC for the completion of thermal wells. Vacuum insulated tubing design makes significant progress driven by its strength and weaknesses. VIC was developed as an alternate solution for some specific completion. The main well integrity failure modes are reviewed: casing expansion and resulting loads, cement integrity under thermal cycling, annular pressure build-up. A thermal well modeling providing casing and tubing temperature assesses the solution brought by VIT (or VIC) to avoid a well failure. On the well performance side, the heat loss will be presented for different VIT product to measure the impact on the efficiency of the process and the economic aspect.
The results shared in this paper are some of the parameters considered during thermal well design: temperature on the casing, tubing and heat loss. Knowing these parameters, the well integrity can be studied and the overall efficiency of the process estimated. Some simple cases between different completion using VIT or different VIT products are run as a comparison. More specifically, the thermal model will show how a non-thermal well can be converted to steam injection by using the proper VIT.
The wide range of thermal performance of VIT is to be understood when it comes to select the proper product for thermal well application.