Determination of Permafrost Thawing Around Oil Wells

Abstract

Abstract A practical procedure is presented for determining the radius of the thawed-permafrost region around a well and finding the temperature distribution in that region. Such information is important in drilling, completion, and production operations in Arctic regions. A new numerical method was developed and used in a computer model to generate solutions for radial thawing of permafrost with axial symmetry, which was shown to be a function of three dimensionless parameters plus dimensionless radius and time. The model generated solutions for the range of values of the three parameters for conditions in Alaska's North Slope. The dimensionless radius of the thawed-permafrost region was related to dimensionless time through a simple power-law equation containing two constants. Results generated by the computer model were used to develop correlations giving the relationships between the two constants and the three parameters. The correlations can be used to find the thawed-permafrost radius, and once this information is available, the temperature distribution in the thawed region can also be calculated. For the correlations, the temperature at the well was assumed to be constant. In more realistic situations in which well temperature varies with time, we also describe a simple method of calculating the amount of thawing.