Determination of the formation temperature from shut-in logs: Estimation of the radius of thermal influence

As a consequence of drilling and completion operations most wells have reduced permeability near the borehole (skin zone). This may result in a corresponding change of thermal conductivity of formations near the borehole. At the same time the mathematical models, which describe the process of thermal recovery of formations are based on the assumption that the thickness of the radius of heated zone (during circulation of the drilling mud) is significantly larger than the well radius (or skin zone). It is shown below that the radius of the heated zone (radius of investigation or radius of thermal influence) can be approximated by simple formulas. It is shown that for six field bottom-hole temperature surveys the radius of thermal influence (RTI) is too small, and for this reason, the duration of the drilling mud circulation period should increased.