Multiwell Thermal Interaction: Predicting Wellbore and Formation Temperatures for Closely Spaced Wells

Abstract

Summary A method is presented to predict wellbore and formation temperatures for a template of closely spaced wells. Multiwell thermal interaction will alter the wellbore temperatures as well as formation temperatures in the interwell zones and also farther out from the well template. The change in temperature profile relative to a single well can be significant. For producing wells in close proximity, wellbore and formation temperatures will converge to a significantly hotter condition than in the isolated-single-well case. The modeling of wellbore and formation temperatures for closely spaced wells has not been widely examined to date. This problem has been approached only by using theoretical formulations based on simplified assumptions. The current work presents for the first time a methodology based on standard industry tools and models that yield results consistent with field experience. The method employs standard industry thermal/hydraulic-modeling software and a finite-element model (FEM) in a loosely coupled, iterative analysis that assumes steady-state conditions. Other numerical approaches including finite-difference (FD) and boundary-element-method (BEM) techniques are also considered. The far-field thermal-flux behavior of a single well is also considered as an important baseline for comparison. The effect of multiwell thermal interaction is important for closely spaced wells such as offshore platforms or subsea and Arctic developments. A case study is presented for a high-pressure/high-temperature offshore field development. The multiwell disturbance on formation and wellbore temperatures affects well design, facilities planning, and operations. Annular-pressure buildup, wellhead movement, tubular-stress design, cement-slurry design, subsidence/compaction effects, and facilities health and safety issues can all be affected. In some cases, unexpectedly high wellbore temperatures can be catastrophic. If multiwell thermal interaction is not taken into account, then load events such as annular-pressure buildup, wellhead movement, and thermal-induced stresses may be underestimated. For high-rate production wells, the increase in produced-fluid temperatures may be small, but even a small change may be critical. In all cases, the effect on outer wellbore strings/annuli and on the formation is significant. This also impacts the planning of offshore fields to be developed in phases with batch drilling.