Results of Frequency Based Interpretations of Deep Water Passive EM Survey Data

Abstract

Abstract Airborne 3D high resolution EM survey data were collected by eField in thenorthern Norwegian Sea. Survey areas included a producing field, a drystructure and other deep water areas. We confirmed with newly developedfrequency-based algorithms that:The 3D passive airborne system recognized areas with and without largehydrocarbon deposits,Relative depth information was obtained from a parallel interpretation withgeophysical data,Multiple hydrocarbon bearing strata were identified,Consistent survey results were found in 1200 meters of water. Data interpretations supporting these claims are included. We used the results for basin evaluations in support of a license applicationbecause the survey method allows us to optimize existing data (such asgeological and seismic data) interpretations with independent EM datainterpretations. Such combined interpretations can reduce the explorationrisk. Introduction The purpose of a high resolution electric and magnetic (EM) airborne surveyoffshore is to provide an economic basin evaluation for the presence of largedeposits of hydrocarbons. The resolution of this evaluation can go down to thedevelopment field level. We developed a novel survey system and a datainterpretation procedure to conduct such surveys and obtain interpretationsthat can be mapped. This paper describes the survey system and the validationresults. Commercial capabilities exist to conduct aerial EM surveys. However, thecommercially available data interpretation capabilities are very limited. Wecompleted a three-year R&D project to develop a new frequency-basedinterpretation for the non-stationary 3D EM signals. We also defined the tunedE and M sensor, receiver and compatible interpretation systems speciallyadapted to the software development. The EM interpretations can be used for independentbasin evaluations,prospect evaluations anddrilling site selections. In the ideal case independent EM survey results should be integrated with otherinterpretations based on geological, geophysical and other data sources, suchas Fig. 1 depicts.