New Approach to Temperature Modelling using Bottom Hole Temperature Datasets in the Permian Basin
Ian Deighton¹, Erika Tibocha¹, Pete Dotsey¹, and Duncan Bate¹
¹TGS Geological Products and Services
Temperature data within a basin may be used to identify where favorable gas-to-oil ratios (GOR) exist for shale gas formations. However, a consistent and reliable dataset that covers an entire basin at all levels of interest is often not readily available. A new methodology for basin temperature modelling has been developed that utilizes large volumes (~10,000 points) of properly indexed and QC'd bottom-hole temperature (BHT) data for an onshore basin or area. It is important to honour the theory that borehole temperatures equilibrate, increasing towards formation temperature with elapsed time since fluid circulation. We thus use the maximum BHTs recorded in a layer (normalized for depth) or cell, rather than a corrected average or regression based model. Present day temperature volumes (cubes) have been constructed with two methodologies. In the MaxG cube, we first define a depth varying interval geothermal gradient (IGG) function that models the maximum envelope of the BHT cloud for each major lithostratigraphic unit. We then construct the cube by stacking the IGGs for all the units in the basin. With sufficiently dense data, in the second method (MaxBHT), we use the maximum BHT in each cell of the cube, with some background infill of the voids using MaxG.
For both methods, we can apply a unit related thermal conductivity shift to the cube to more closely approximate formation temperature, if appropriate.
The concept is illustrated with examples from the Midland and Delaware Basins.
AAPG Datapages/Search and Discovery Article #90190©AAPG Southwest Section Annual Convention, Midland, Texas, May 11-14, 2014