Temperature corrections for bore hole data as part of thermal state, source and maturation investigations of basins

Abstract

Subsurface temperature data are vital for many aspects of petroleum exploration (and development), especially maturation and basin thermal history. However, much of the older temperature data that have been obtained in Australian petroleum exploration are of limited usefulness, mainly because of restricted information concerning circulation times and time(s) of logging. Only very occasionally during petroleum exploration are temperature data obtained after the perturbing (mainly cooling) effects of drilling have subsided. Hence corrections need to be applied by using circulation time and time since circulation for correcting the original temperature measurements for a logging suite. Provided several logging runs have been made, and the data obtained are reasonably accurate, then it is generally accepted that a good approximation to the true formation temperature can be obtained if "corrections" are applied. For older wells for which only limited temperature and time data are available a simple procedure has been established to correct temperature data ? by adding 15% or 10% to measured temperatures (first to last in a logging suite). If that procedure is applied to fuller data sets, it is found that there is good agreement between the various correction techniques. Accurate temperature data can provide the basis for determining temperature gradients and heat flow and thence can be useful for correlation (between wells and with other data) and for maturation studies, including burial history. Useful temperature data ? for analysis and for prediction ? in petroleum exploration is necessary for a full understanding of the thermal setting of a sedimentary basin. Temperature studies can also be useful in exploration for and studies of groundwater, metallic mineral deposits and coal.