Using polygonal layer-bound faults as tools to delimit clastic reservoirs in the Levant Basin offshore Lebanon

Abstract

The Levant Basin offshore Lebanon contains an array of layer-bound normal faults in the Oligocene–Miocene units. The faults are believed to have nucleated in fine-grained sedimentary rocks similar to polygonal fault systems worldwide, and as a result, they may be influenced by lithological heterogeneities in the host-rock unit. Three-dimensional seismic data and amplitude extraction from offshore Lebanon were used to map deep-water channels and fan lobes, demonstrating that the distribution, geometry, and growth of the layer-bound normal faults are affected by these sedimentary bodies, which are impacting fault propagation. Three fault types are identified, differentiated by their growth models and overall geometry. Type I faults in the deep basin indicate that a competent unit is present in the lower Miocene and is affecting their growth. Type II and III faults in the Latakia ridge and the margin, respectively, are smaller because of restriction by upper Miocene and lower Oligocene basin-floor fans. Based on their seismic expression and on analogy with other basins containing similar faults, it is very likely that the overlying and underlying units causing restriction consist of coarse-grained clastic intervals. Therefore, reservoirs offshore Lebanon are probably lower Miocene in the deep basin, whereas in the Latakia ridge and the Levant margin, reservoirs are in upper Miocene and in lower Oligocene units. This study provides an additional evidence that layer-bound, or polygonal faults, can have practical industrial application during exploration of hydrocarbons, even in the absence of well data.