Isolated seafloor pockmarks linked to BSRs, fluid chimneys, polygonal faults and stacked Oligocene-Miocene turbiditic palaeochannels in the Lower Congo Basin

Based on high-resolution 3D seismic data sets, we document the subsurface reservoir architecture and organization of a portion of the Oligocene–Miocene stratigraphy within the Congo Basin, offshore southwestern Africa. Within the 3D seismic volume, we have identified four levels of turbiditic palaeochannels, which are separated by low-amplitude continuous reflectors interpreted as hemipelagic sediments. Geochemical analyses on sediment samples taken within overlying seafloor pockmarks reveal the presence of thermogenic gases and oils, suggesting that deep-seated fluids have migrated through both the channel deposits and the impermeable layers between them, forming a conduit to the surface. Deep thermogenic fluids produced within Cretaceous source rocks are preferentially entrapped within coarse-grained turbiditic Oligocene–Miocene palaeochannels. We show in this study that the vertical stacking pattern of turbiditic palaeochannels allows the best pathway for fluids migration. Once the fluids migrate to the upper layer (i.e., Upper Miocene) of palaeochannels, they can reach the seafloor via migration along a highly faulted interval composed of polygonal faults. They are temporarily inhibited below an interpreted 300-m-thick gas hydrate layer marked by a strong BSR on seismic profiles. Fluids accumulate under the hydrate stability zone to form a thick layer of free gas. The generation of excess pore fluid pressure in the free gas accumulation leads to the release of fluids along faults of the highly faulted interval forming pockmarks on the seafloor. Ultimately, we show in this study that fluids are progressively concentrated in the sedimentary column and aligned pockmarks on the seafloor may represent a focused fluid flow from stacked turbiditic palaeochannels

Evidences of early to late fluid migration from an Upper Miocene turbiditic channel revealed by 3D seismic coupled to geochemical sampling within seafloor pockmarks, Lower Congo Basin

Using high quality 3D seismic data within the Lower Congo Basin (LCB), we have identified pockmarks that are aligned above the sinuous belt of a buried turbiditic palaeo-channel, 1000 m beneath the seafloor. Geochemical analyses on cores (GC traces), taken in the centre of four of these pockmarks along this channel, show no clear evidence for migrated oil. But, some features of the GC traces, including elevated baselines (UCM>34 ?g/g) and a broad molecular weight range of n-alkanes with little odd–even preference, may be interpreted as indicating the presence of thermogenic hydrocarbons in the cores.Seismic profiles show that these pockmarks developed above two main features representative of pore fluid escape during early compaction: (1) closely spaced normal faults affecting the upper 0–800 ms TWT of the sedimentary column. This highly faulted interval (HFI) appears as a hexagonal network in plane view, which is characteristic of a volumetrical contraction of sediments in response to pore fluid escape. (2) Buried palaeo-pockmarks and their underlying chimneys seem to be rooted at the channel–levee interface. The chimneys developed during early stages of burial and are now connected to the HFI.This study shows that the buried turbiditic channel now concentrates thermogenic fluids that can migrate through early chimneys and polygonal faults to reach the seafloor within some pockmarks. Using a multidisciplinary approach within the Lower Congo Basin, combining 3D seismic data and geochemical analyses on cores, we trace the fluid history from early compaction expelling pore fluids to later migration of thermogenic hydrocarbons

FOLFIRINOX as induction treatment in rectal cancer patients with synchronous metastases: Results of the FFCD 1102 phase II trial

IF 7.191 (2017)International audienceAim of the studyThe optimal therapeutic strategy in patients with rectal cancer and synchronous unresectable metastases remains unknown. We evaluated the efficacy of FOLFIRINOX induction therapy in this setting.Patients and methodsChemotherapy-naïve patients received at least 8 cycles of FOLFIRINOX. The primary end-point was the 4-month disease control (4 m DC) rate. Tumour responses were centrally reviewed and assessed by computed tomography scan for metastases (Response Evaluation Criteria in Solid Tumours criteria) and magnetic resonance imaging for rectal tumorus. With a Simon 2-stage design and a targeted (H1) 4 m DC > 75%, 65 patients were enrolled from July 2012 to February 2015: male, 78%; median age, 61 years; performance status, 0–1, 98%; liver metastases, 92%; ≥2 metastatic sites, 63%.ResultsFifty-six (85%) of the 65 patients received the 8 planned FOLFIRINOX cycles. The primary objective was achieved (4 m DC rate: 94%; 95% confidence interval [CI], 86.3–97.8). Primary tumour symptoms decreased from 72% at baseline to 10% at 4 months. Response rate was 86%, and a >70% primary tumour volume decrease was seen in 63% of patients. Forty-four patients (68%) had at least one grade 3 side-effect; no toxic deaths occurred.Median follow-up was 35.0 months (95% CI, 31.3–43.7). Median progression-free survival and overall survival were 10.9 m (95% CI, 8.8–12.9) and 33.4 m (95% CI, 22.6–38.2), respectively.ConclusionUpfront FOLFIRINOX is feasible and allows good local and distant control. It therefore offers the opportunity to choose the best therapeutic strategy for each patient and to personalise treatment according to the local and distant efficacy results of this induction step.Trial registrationClinicaltrials.gov, NCT01674309