During a twelve year period, seven companies conducted 118 iodine surveys over previously undrilled prospects or field extensions. These surveys consisting Of 72,000 samples were conducted in many different types of environments throughout the world. These are surveys that ATOKA collected and have permission to release. However, these do not include samples collected by the clients and their subsequent results.
Of the 55 wells drilled in areas with positive geochemical anomalies, 50 wells (90.9%) had significant hydrocarbon shows and 5 wells (9.1%) were dry with minor shows. By incorporating iodine surface geochemistry into your company’s exploration program, the risk of drilling dry holes is significantly reduced while increasing the company’s overall exploration success rate.
Seismic was involved in siting 125 drill sites, results in 33 successful (26.4%) and 92 (73.6%) dry holes. The iodine surface geochemistry correctly predicted the 92 dry holes defined by seismic. If the iodine surface geochemistry had been included in the decision to drill or not drill, this would have resulted in substantial economic savings.
Crosstab plots for all surveys in the study. (a) iodine results. The numbers were obtained by summing the numbers in each survey’s iodine crosstab plot by quadrant. (b) Random case for all areas. The numbers were obtained by summing the numbers in each survey’s random case crosstab plot by quadrant. This technique compensates for any differing areas that calculate as positive between each individual survey.
Individually, no survey had a sufficient number of drill sites to achieve a good level of confidence about the soil-iodine technique. But taken together, they represent 32 producers and 57 dry holes. With these numbers, a meaningful assessment can be made of the relationship between high concentrations of iodine in the soil and underlying hydrocarbon accumulations.
Figure 25a and 25b shows crosstab plots for all case-study areas (not including the Eland field areas medium-threshold case or the Springfield East area’s detailed survey). Of the 32 producers in the four cases, the iodine method correctly predicted 27 where it should have predicted only 9.0 if the technique were random. A chi-square test on these numbers suggests that it can be said, with a greater than 99.5% confidence level, that soil iodine is not a random technique. Of the 57 dry holes in these four cases, the iodine method correctly predicted 53, where it should have predicted 47.3 if it were random. A chi-square test on these numbers suggests that it can be said, with about a 95% confidence limit, that the iodine method is not random. Although these numbers are based on only four surveys, it can be concluded that there is an association between apical soil-iodine anomalies and hydrocarbon accumulations in the variety of settings similar to those presented here.
This leads to an examination of Figure 25a on a different axis. If drill sites had been selected based on the iodine technique alone, five producers would not have been drilled, but 53 dry holes would have been avoided. In addition, 27 producers would have been drilled, along with four dry holes. This success rate is good, but it includes both wildcat and development wells.