The Çınarcık Basin is a transtensional basin located along the northern branch of the northern North Anatolian Fault (NAF) in the Sea of Marmara, the eastern half of which has been identified as a seismic gap. During the SEISMARMARA (2001) experiment, a dense grid of multichannel seismic reflection profiles was shot, covering the whole Çınarcık Basin and its margins. The new seismic images provide a nearly three‐dimensional view of the architecture of the basin (fault system at depth and sedimentary infill) and provide insight into its tectonic evolution. Along both northern and southern margins of the basin, seismic reflection data show deep‐penetrating faults, hence long‐lived features, which have accommodated a large amount of extension. There is no indication in the data for a single throughgoing strike‐slip fault, neither a cross‐basin fault nor a pure strike‐slip fault running along the northern margin. Faster opening is presently observed in the eastern part of the basin. The Çınarcık Basin seems to have developed as a transtensional basin across strike‐slip segments of the northern NAF for the last few million years.

[1] Before being disrupted by a magmatic event in 1999, the vent temperatures and salinities along the axis of the Main Endeavour Field on the Juan de Fuca Ridge exhibited a quasi-steady spatial gradient in which the southern vent fluids were hotter and less saline than the northern vent fluids. We present 2-D numerical models of two phase flow in a NaCl-H 2 O system to understand these gradients. We consider homogenous permeability models with a range of bottom boundary temperature distributions and heterogeneous permeability models by imposing layer 2A extrusives with a constant bottom boundary temperature distribution. The aim is to understand the impact of both bottom boundary temperature and layer 2A permeability on hydrothermal fluids and to determine what combination of these controlling factors could cause the observed trend. We find that variations in bottom boundary temperature alone cannot explain the span of surface temperatures and salinities measured at the Main Endeavour Field. Heterogeneous permeability within layer 2A that has higher overall permeability in the northern part of the vent field than the southern part can reproduce the observed north to south temperature gradient, but such a permeability distribution cannot reproduce the observed salinity gradient. We conclude that both deep-seated heterogeneous permeability, perhaps localized by a fault zone, and a heterogeneous layer 2A are required to produce the trend of temperatures and salinities in vent fluids at the Main Endeavour Field prior to the 1999 event.

a b s t r a c tMid-ocean ridges are subject to episodic disturbances in the form of magmatic intrusions and earthquakes. Following these events, the temperature of associated hydrothermal vent fluids is observed to increase within a few days. In this paper, we aim to understand the rapid thermal response of hydrothermal systems to such disturbances. We construct a classic single-pass numerical model and use the examples of the 1995 and 1999 non-eruptive events at East Pacific Rise (EPR) 9150 0 N and Main Endeavour Field (MEF), respectively. We model both the thermal effects of dikes and permeability changes that might be attributed to diking and/or earthquake swarms. We find that the rapid response of vent temperatures results from steep thermal gradients close to the surface. When the perturbations are accompanied by an increase in permeability, the response on the surface is further enhanced. For EPR9150 0 N, the observed $ 7 1C rise can be obtained for a $ 50% increase in permeability in the diking zone. The mass flow rate increases as a result of change in permeability deeper in the system, and, therefore, the amount of hot fluid in the diffused flow also increases. Using a thermal energy balance, we show that the $ 10 1C increase in diffuse flow temperatures recorded for MEF after the 1999 event may result from a 3-4 times increase in permeability. The rapid thermal response of the system resulting from a change in permeability also occurs for cases in which there is no additional heat input, indicating that hydrothermal systems may respond similarly to purely seismic and non-eruptive magmatic events.

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Reservoir permeability is an integral parameter in the prediction of gas well and reservoir performance which is critical in operating a business built on gas deliverability. In the absence of dynamic performance data; core calibrated log permeability is typically used to estimate well deliverability. Historically actual permeability derived via pressure transient analysis indicated the need for further upscaling to the core calibrated log permeability. Two new permeability transforms are proposed for the bp Trinidad and Tobago LLC fields in the Columbus basin in Trinidad. This provides the ability to incorporate upscaling heterogeneities that would not be represented at a core or log scale. The updated transforms replace a single legacy transform which is no longer applicable since the underlying log calculated permeability method has undergone a refresh and the pressure transient analysis database has also been revised. The updated pressure transient derived permeability-thickness encompassed forty-plus wells from across the basin and was utilized in tuning well models to replicate actual performance and hence provide assurance against forecasted gas rate deliverability. The transforms have been developed for conventional sands in the Basin and are regional. Since they have been deployed, they have been blind tested with additional pressure transient analysis tests that have so far proven their robustness. This updated transform has proven to be a valuable tool to the business as wells have been designed as primarily big-bore high rate wells with the aim of delivering gas to market with minimal well count.