INTEGRATION OF PASSIVE-SOURCE METHODS IN SHELL’S EXPLORATION OF ALBANIA’S FOLD-THRUST BELT

Earthquakes and ocean noise are natural sources of energy that can be used to image the subsurface. In Shell’s first large-scale experiment, data from these natural sources were collected between August and December, 2016, in the fold-thrust belt of central Albania. Three hundred three-component 5-Hz Fairfield nodes and one hundred one-component 5-Hz Innoseis nodes were distributed over a 500 km² area for a period of three months. The Fairfield nodes were then redeployed for two weeks along the trace of a legacy seismic dip line. The data from both deployments, which was managed by Schlumberger’s Integrated EM group, have been processed by Sisprobe (Grenoble, France) and Shell personnel. The logistics of these deployments and some results of the analyses will be presented in this talk.

Magnetotelluric (MT and AMT) and time-domain EM (TDEM) data were collected in the same area, most of which were acquired along and around the same legacy 2D seismic line used in the passive-source seismic survey. The EM data were obtained to map out the very resistive carbonate thrust sheets within the more conductive flysch. The quality of the data is very good due in part to the solar winds having been very energized during much of the acquisition period. The data have been analyzed by the Schlumberger’s EM group (Milan, Italy) and Shell’s EM personnel. Some results of these surveys will be presented in this talk.

The results of this study combined with pre-existing information on the surface geology, sparse well data, and legacy 2D active-source seismic lines have improved our understanding of the subsurface geology in the area. Even though numerous questions remain regarding the subsurface, the value of the passive-source methods in our exploration efforts is evident especially in light of the methods’ relatively low costs, the rapidity and ease of their deployment, significant reduction of HSSE risks, and extremely low environmental impact.

Acknowledgements: Many other people inside Shell have helped this project; we very much appreciate their concerted support and efforts and recognize this has been a jointly owned project among many. We also appreciate the numerous people involved in the project from Sisprobe (Grenoble, France) and Schlumberger’s Integrated EM Center of Excellence (Milan, Italy).