Multiwell Thermal Interaction: Field Data Validation of Transient Model for Closely Spaced Wells

Abstract

Abstract Wellbore temperature logs and associated field history data from an HPHT condensate North Sea platform are presented which validate the accuracy of a transient model of multiwell thermal interaction. The model is an updated version of previous work which simulates transient thermal interaction or "cross-heating" between closely spaced wells of a template. Multiwell thermal interaction alters final wellbore temperatures as well as formation temperatures in the inter-well zone and also further out from the well template. The multiwell thermal model is shown to converge closely in very characteristic fashion to two different logged and measured temperature profiles over a vertical depth range of 3000 ft. The empirical data including field history represents a unique opportunity to study and understand this important topic. Prior to this current work, industry discussion of multiwell thermal interaction or "cross-heating" has been largely anecdotal. Model validation against field data is necessary to achieve a full understanding of the physical system and to provide confidence in the predictive capability. Modeling of wellbore and formation temperatures for closely spaced wells has not been widely examined in the industry literature. The current work presents an improved methodology based on standard industry techniques. The method employs standard industry thermal-hydraulic modeling software and a fully transient finite-difference time-domain (FDTD) model in a loosely-coupled, iterative analysis. The iteration scheme is achieved by coupling of the standard analytical solution for the isolated single-well temperature scenario with the solution in the formation for the cross-heating scenario. The effect of multiwell thermal interaction is important for closely-spaced wells such as offshore platforms or subsea and arctic developments. The multiwell disturbance on formation and wellbore temperatures may affect well design, facilities planning and operations. Annular pressure build-up (APB), wellhead movement, tubular stress design, cement slurry design, subsidence/compaction effects and facilities health and safety issues can all be affected. If multiwell thermal interaction is not taken into account, then load events such as APB, wellhead movement and thermal induced stresses may be underestimated. Concurrent and batch drilling operations including cementation will also be affected.