- What is GDN? -
United Surveys’ Gamma Ray/Density/Neutron (GDN) cased hole logging service is unique in the oil and gas industry. The GDN system has developed from years of research and field testing. Over 2000 wells, with depths ranging from 200 feet to 17,000 feet, have been successfully logged and evaluated. The GDN service was originally developed to find gas zoned behind pipe in existing wells to aid operators in their recompletion evaluations. Later the GDN service was adapted to evaluate abandoned wells for possible re-entry. When used in conjunction with any available open hole logs, the GDN has proven to be extremely accurate in predicting production. As refinements have been made, the GDN service has proven to be a valuable aid to determine depleted zones and moved water contacts within producing zones. In some cases oil productive zones have been recognized. The GND tool responses are qualitative in nature and are not calibrated to show effective porosity. However, in the presence of producible hydrocarbons, especially natural gas, the density curve responds as an excursion towards the depth track and the neutron curve count rate increases shown as an excursion away from the depth track, resulting in the Density/Neutron crossover. In many cases this crossover exactly mirrors the responses of open hole Density/Neutron logs. United Surveys’ staff, with over 100 years combined experience in log interpretation, is available to aid in the evaluation of your next well.
Tool Specifications
Tool OD(in)
Minimum Pipe ID(in)
Depth of Investigation
Decentralized
21/8"
2.5"
Maximum
No
111/16"
2.0"
Limited
