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

Abstract

Summary Wellbore-temperature logs and associated field-history data from a high-pressure/high-temperature (HP/HT) condensate North Sea platform are presented that validate the accuracy of a transient model of the multiwell thermal interaction (MWTI). The model is an updated version of previous work by McSpadden and Coker (2010) that simulates transient thermal interaction or "cross heating" between closely spaced wells of a template. As discussed in the preceding work, the MWTI alters final wellbore temperatures as well as formation temperatures in the interwell zone and also farther 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 at a vertical depth range of more than 3,000 ft. The empirical data, including field history, represent a unique opportunity to study and understand this important topic. Before this current work, the authors’ experience found the industry discussion of the MWTI or "cross heating" to be 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. The modeling of wellbore and formation temperatures for closely spaced wells has not been widely examined in the industry literature, as observed by Bellarby (2009). The current work presents an improved methodology on the basis of standard-industry techniques. The method uses standard industry thermal/hydraulic modeling software for a single well and a fully transient finite-difference model for the formation in a loosely coupled, iterative analysis. The iteration scheme is achieved by the 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 the MWTI 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. For example, given nominal flowing wellhead temperatures (FWHTs) approaching 350°F for HP/HT platform developments, even small temperature increases may have a critical impact on the design and layout of surface receiving systems. Annular-pressure buildup (APB), wellhead movement, tubular-stress design, cement-slurry design, subsidence/compaction effects, and facilities health and safety issues can all be affected. If the MWTI is not taken into account, then load events such as APB, wellhead movement, and thermally induced stresses may be underestimated. Concurrent and batch-drilling operations, including cementation, will also be affected.