Study context

Fractures in sedimentary rocks have a large influence on the development of underground reservoirs, and especially in the case of carbonate rocks. About 85% of carbonate reservoirs are naturally fractured (Naturally Fractured Reservoirs, NRF) and 30% of the world's hydrocarbon reserves is stored in NFR. Indeed, any reservoir should be considered fractured in a geologic meaning, because no one reservoir is not fractured. However, fractures are often a priori ignored in reservoir exploitation because fractures are highly heterogeneous and below the seismic resolution. The quantification of fractures is a posteriori done with well data imaging and cores. This provides 1D data in a very heterogeneous 3D area which makes it difficult to provide good predictions in 3D. Therefore, NFR are studied on reservoirs analogues, providing good 2D to 3D exposures for quantitative analysis what provides data for simulations of Discrete Fracture Networks (DFN) applied to reservoir simulations.

Among fractures, Fracture Corridors (FC) are anomalous structures as they are made of perennial fracture clusters. FC have a profound effect on multi-phase fluid flow in the subsurface. While mechanical and geological conditions for diffuse fractures generation are well constrained, FC genetic conditions remains a matter of questioning. FC corridors can be localized in larger structures such as folds and faults zones but recent studies suggest that a large amount of fractures and FC arise as diffuse in the host rock and formed in tabular layers during burial with early rock mechanical differentiation. In addition, while the mechanical stratigraphy is of prime importance for fracture stratigraphy, it is still unknown which factor prevails on FC genesis among the local versus regional stress-state, the host rock mechanical stratigraphy and the litho-stratonomic facies.

Expected work

This project aims at understanding the 3D geometry and the genetic factors for FC development. Several geological and geomechanical factors will be investigated. FC will be fully characterized in carbonate layered rocks of various stratonomy and compared to clastic layers. The geometric characterization in the field includes a structural analysis in 1D (scan lines), 2D (Digifrac, Hardebol & Bertotti, 2013) and 3D (Lidar). It will be compared to underground reservoirs in 1D (well data), 2D and 3D (seismics) The tectonic context will be constrained with regional structural analysis and burial-uplift curves. The host rock mechanical control will be quantified with mechanical ( ; ) and petrophysical (K, , Vp) measurements constrained in the geological history with a sedimento-diagenetic analysis on host-rock samples. The genetic conditions deduced from these analysis will be tested with mechanical simulations (ENS Paris, Univ. Cergy-Pontoise) while the geometric rules will be tested with DFN simulations (GoFrac, Kidova).

Conditions

The PhD is planned to last for 3 years as a full time position. It occurs in the frame of a TOTAL S.A. - Aix-Marseille Univ. research cooperation. The host laboratory is the Sedimentary and Reservoir Systems Team of the CEREGE (http://www.cerege.fr/). The PhD student will mostly work in Marseille laboratory and in the field. In a lesser proportion some work will be achieved in Pau Total research center, ENS Paris and Cergy Pontoise University, as well as in Kidova (close de Paris).

Supervisors:

Juliette Lamarche (Sedimentary and Reservoir Systems Team of the CEREGE)
Bertrand Gauthier (Naturally Fractured Reservoir advisor, Total S.A.)

Involved team

Yves Guglielmi, Philippe Léonide (Sedimentary and Reservoir Systems Team of the CEREGE); Giovani Bertotti (Delft University); Yves Leroy (Geomechanician advisor for geosciences, Total S.A.); Pauline Souloumiac (Cergy-Pontoise Université); Jérôme Fortin (ENS Paris); Michel Garcia (KIDOVA).

PhD start: January 2014

The candidate (m/f) must have a Master in Geology, specialized in structural geology, in sedimentary rocks and preferably in brittle tectonics. He/she should have some good basis in geomechanics. We look for someone able to enlarge his primary skills, especially with petrophysics, diagenesis and rock mechanics. We seek for candidates keen on hardly working in the field, with good english and french skills. We will pay attention to the expressed whish of the candidates to work in the oil and gas domain.

Application

Dead Line for application: 18^th September, 2013.

Interviews for selected candidates: 30^th September - 4^th October, 2013.

Applications should include at least your CV, diploma, motivation, reference letters and master thesis and be send to Cerege13071@earthworks-jobs.com