Exploring Channel Reservoirs in a Frontier Area Using Regional 3D CSEM and 2D Seismic

Abstract

Summary In this paper we explore the West Africa-South America analogue proven by the Jubilee and Zaedyus discoveries in Ghana and French Guiana, respectively. Instead of the Turonian turbidite fan reservoirs, we consider younger unproven deep water channel systems in Foz do Amazonas Basin in Brazil which could be analogous to the Campanian pay found in the Teak field in Ghana. We present a geological overview of the basin together with acquisition details and imaging results of a regional 3D CSEM survey in the area. Using CSEM as a fluid indicator, we calculate the Net Rock Volume (NRV) from a channel-shaped EM anomaly and with conservative parameterization we obtain a P10/P90 ratio of 14.7 and an average NRV of ~23000hm3. Introduction In September 2011 Tullow Oil announced a significant oil discovery in the Zaedyus prospect in French Guiana that established the Turonian aged Jubilee play from Ghana, West Africa. Following the Zaedyus discovery, a 2012–2013 drilling program of 4 exploration wells targeting nearby turbidites resulted in disappointing commercial success. We will discuss the potential of the younger channel play in the lower Tertiary and upper Cretaceous in Foz do Amazonas basin rather than the Turonian turbidite fans. Continuing the West Africa/South America analogue, the channel systems could resemble the Campanian pay of the Teak-1 exploration well in Ghana (Kosmos Energy, 2011). First, we will give an overview of the geology providing potential reservoir and trapping mechanisms. Second, we will use results of a regional multi-client 3D CSEM survey as a fluid indicator. Acquired in 2013, the survey is bordering French Guiana towards west within 15km of the last exploration well of the drilling program, GM-ES-5, and within 50km of the Zaedyus discovery. Third, we will use the method introduced by Baltar and Roth (2013) to estimate the Net Rock Volume in a sub-region of the CSEM coverage. Geological overview The present day shelf margin region of the Foz do Amazonas Basin has undergone significant modification from mass wasting events and debris flows. The basin provides analogous examples for deep water depositional systems in the underlying Tertiary and Cretaceous sections. Based on seismic observations, the shelf is shaped by the orientation of shallow basement that is interpreted as continental crust from potential field data. The basement extends outward from the coastline for approximately 130 kilometers before rapidly dropping off in a series of complex fault systems that are related to older rift stage graben systems.