Abstract
This paper presents analytical and semi-analytical solutions based on a coupled wellbore/reservoir thermal model to investigate the information content of transient temperature measurement made within an inclined wellbore across from the producing horizon or at a gauge depth above it. The models are capable of simulating bottomhole transient temperatures from multi-rate production tests including buildups. We provide interpretation/analysis methodology based on temperature-derivative and straight line methods for estimating near wellbore and far field formation parameters from temperature transient data. Slightly compressible, single-phase, and homogeneous infinite-acting single-layer reservoir system is considered. The reservoir and wellbore models account for Joule-Thomson heating/cooling, adiabatic fluid expansion, conduction and convection as well as heat losses to strata and formation. Wellbore temperatures at a certain gauge depth are evaluated through a wellbore thermal energy equation coupling the reservoir temperature equation. Sandface temperature data during production and buildup periods may exhibit two semilog straight lines; one at early-times reflecting the effects of adiabatic fluid expansion in the in the skin zone near the wellbore, whereas the late-time semilog straight line reflecting the Joule-Thomson effects and exhibiting the nonskin zone properties. For temperature measurements made at locations above the producing horizon, wellbore transient temperature is dependent upon the flowrate, distance above the producing horizon, geothermal gradient, and radial heat losses from the wellbore fluid to the formation on the way to gauge. Depending upon these parameters, transient temperature response at early times may be almost solely reflective of the wellbore/thermal storage effects, and the flow regimes that are exhibited by the sandface temperatures are distorted due to heat losses effects between the wellbore and the formation adjacent to the wellbore. Synthetic test examples demonstrate the use of the models and methods proposed to interpret and analyze bottomhole temperature transient data.
