Africa (Sub-Sahara) ExxonMobil will drill its first exploratory well offshore Liberia this month, the company announced on 18 October. A deepwater well is planned on the Liberia-13 Block, which is about 50 miles off the coast of the West African country. Solo Oil plans to spud the Ntorya-2 appraisal well in Tanzania next month. The drilling pad is a mile southwest of the 2012 Ntorya-1 discovery well, which was tested at rates of 20.1 MMcf/D of gas and 139 B/D of condensate. An independent report estimated the discovery to hold 153 Bcf of gas in place, of which 70 Bcf is considered a gross best-estimate contingent resource. A gross best estimate of more than 1 Tcf of gas in place has been made for the Ntorya prospect as a whole, in which the company has a 25% interest. Asia Pacific BP has decided to abandon drilling plans in the Great Australian Bight offshore southern Australia, an area in which prospective drilling has long been contested by environmentalists.
Nolting, Andrea (The University of Texas at austin) | Zahm, Christopher (The University of Texas at austin) | Kerans, Charles (The University of Texas at austin) | Brooks, Donald (The University of Texas at austin)
We investigate the Pleistocene (<400 Ka) outcrop exposures on West Caicos Island, British West Indies to assess the factors that affect the mechanical behavior of young, recently deposited carbonate grainstone facies. West Caicos provides an ideal location to evaluate the factors that affect the porosity and unconfined compressive strength (UCS) of carbonate rocks that have undergone little (<10m) to no burial since deposition and because of the well-documented stratigraphic framework and constrained eustatic signal for the Pleistocene epoch. Schmidt hammer measurements taken on West Caicos were used to evaluate the variability in rock strength while hand samples were used to make thin sections and plugs to measure porosity, permeability, density, and UCS of collected samples. Field observations, in-situ measurements, and laboratory testing reveal there are three significant factors that control carbonate grainstone rock strength: (1) porosity and degree of cementation; (2) age and degree of exposure to meteoric fluids, and (3) degree of vadose zone weathering. Collected UCS data shows a strong relationship between degree of cementation associated with proximity to weathered horizons. There is an expected relationship between increased cementation, loss of porosity, and higher rock strength (UCS), but the new finding in this study is that these factors occur in the absence of burial or presence of overburden.
Within the rock mechanics literature, there is a notable lack of studies that characterize the physical and mechanical properties of carbonates by facies at the time of or soon after deposition. Without this knowledge our understanding of how the rock properties affect deformation of carbonates during the time when changes may be most dramatic is limited. Several studies document the acoustic and petrophysical properties of Pleistocene carbonates facies which address rocks that have undergone some degree of burial, but do not include information on rock strength. (e.g., Anselmetti and Eberli, 1993; Eberli et al., 2003; Incze, 1998; Longman, 1980; Lucia, 1968; Schmoker and Halley, 1982; Steinen, 1974). However, the link between porosity, cementation and age to rock strength has not been reported. This limits our understanding of the factors that affect changes in unconfined compressive strength (UCS) and potential fracture development.