3D-3C Multicomponent Seismic – A successful fracture characterization case study in Algeria

Abstract

Multi-component acquisition has been used in the industry for many years for fracture density and orientation studies with proven success. In the field under study, it has been observed from well information at target level that there is a relationship between gas production and natural fractures, faults, and changes in facies. The target horizon located at a depth of approximately 1950 m is composed of low-porosity gas-bearing Ordovician sandstones of 5 to 6% average porosity. The Ordovician is characterized by a highly heterogeneous matrix affected by natural fractures. This paper describes a 3D multi-component land seismic project conducted in Algeria, designed to perform a fracture characterization study. This pilot survey, acquired in 2010 over the Tin Fouye Tabankort West block, is the first land 3D-3C acquisition ever performed in Algeria. It covers an area of about 67 km² centered on a well location. The following project phases will be described hereafter: (1) 3D-3C survey design and field operations, (2) Main steps of the PP and PS-wave pre-processing sequences, (3) PP and PS-wave interpretation study at deep levels made possible by the cleaned and signalpreserved seismic data. The resulting PP seismic dataset from the 3D-3C survey provides a better resolution of subtle faults and lineaments than the conventional 3D acquired in 2003 and reprocessed in 2010, even though the noise level remains slightly high. Furthermore, PS seismic data shows evidence of azimuthal anisotropy in relation to the faults and lineaments interpreted on the PP dataset. Anisotropy analysis results tie reasonably well with FMI information available in the Ordovician, showing great potential for using this technology for fracture studies.