Showing papers by "Abu Dhabi Company for Onshore Oil Operations published in 2010"

Dolomite formation within microbial mats in the coastal sabkha of Abu Dhabi (United Arab Emirates)

Abstract: Microbial mediation is the only demonstrated mechanism to precipitate dolomite under Earth surface conditions. A link between microbial activity and dolomite formation in the sabkha of Abu Dhabi has, until now, not been evaluated, even though this environment is cited frequently as the type analogue for many ancient evaporitic sequences. Such an evaluation is the purpose of this study, which is based on a geochemical and petrographic investigation of three sites located on the coastal sabkha of Abu Dhabi, along a transect from the intertidal to the supratidal zone. This investigation revealed a close association between microbial mats and dolomite, suggesting that microbes are involved in the mineralization process. Observations using scanning electron microscopy equipped with a cryotransfer system indicate that authigenic dolomite precipitates within the exopolymeric substances constituting the microbial mats. In current models, microbial dolomite precipitation is linked to an active microbial activity that sustains high pH and alkalinity and decreased sulphate concentrations in pore waters. Such models can be applied to the sabkha environment to explain dolomite formation within microbial mats present at the surface of the intertidal zone. By contrast, these models cannot be applied to the supratidal zone, where abundant dolomite is present within buried mats that no longer show signs of intensive microbial activity. As no abiotic mechanism is known to form dolomite at Earth surface conditions, two different hypotheses can reconcile this result. In a first scenario, all of the dolomite present in the supratidal zone formed in the past, when the mats were active at the surface. In a second scenario, dolomite formation continues within the buried and inactive mats. In order to explain dolomite formation in the absence of active microbial metabolisms, a revised microbial model is proposed in which the mineral-template properties of exopolymeric substances play a crucial role.

Micro-environmental fine-tuning of electronic and kinetic properties of photochromic dyes

Abstract: Despite the recognition of the importance of Spiropyran (SP)–Merocyanine (MC) photochromic materials in molecular switching, the majority of studies have been reported in solution with relatively few in the solid-state as required in modern displays and other devices. In contrast, the present work bridges solution, condensed phase and solid-phase media and is to our knowledge the first micro-environmental study on electronic and kinetic effects for the SP–MC system. Expanding on our previous work we have investigated the photochromic properties of an SP molecule (1b) attached to a 100 μm commercially available polystyrene micro-particle (Wang Resin). The thermal MC → SP reversion kinetics (5a,b → 4a,b and 2a,b → 1a,b) which reflect the critical lifetime of the open MC form were measured. Reduction in kobs of thermal reversion, MC → SP, up to two orders of magnitude, and a blue-shift up to 58 nm was observed with the potential for tailoring or fine tuning. The use of polymeric micro-particles in controlling both electronic and kinetic properties of photochromic molecular switches has been highlighted.

3D VSP technology now a standard high-resolution reservoir-imaging technique: Part 1, acquisition and processing

Abstract: Abu Dhabi Company for Onshore Oil Operations (ADCO) undertook a two-well 3D VSP pilot project in 2007. Because it was acquired concurrently with a high-resolution wide-azimuth surface seismic survey, it was at the time the largest 3D VSP ever recorded. The project consisted of four main parts: acquisition, processing, interpretation, and quantifying value. In part 1 of this paper the acquisition and processing of the 3D VSP is described with an emphasis on the lessons learned. Significant advances in processing are described that demonstrate how larger 3D VSP images with better amplitudes and structural preservation can be produced. In part 2, the results of the 3D VSP interpretation and economic evaluation effort are described and illustrate different ways that a VSP image can help characterize a hydrocarbon reservoir.

Preliminary experiments to evaluate the Gassmann equation in carbonate rocks: calcite and dolomite

Abstract: Fluid substitution is used to predict potential changes in seismic data due to production in oil reservoirs. The fluid changes in clastic rocks are often predicted by the Gassmann equation. However, the applicability of Gassmann's equation in carbonates is not well understood. Apparently, part of this failure is due to the violation of the assumption of a constant shear modulus for different fluids (Baechle et al., 2005; Adam et al., 2006), but it is not clear yet.

3D VSP technology now a standard high-resolution reservoir-imaging technique: Part 2, interpretation and value

Abstract: This second part of an article about a large 3D VSP survey in Abu Dhabi describes the interpretation effort which quantifies the value that a 3D VSP seismic image can bring when supplementing even a 640-fold, high-resolution surface seismic volume.

An overview on ADCO crude oil storage tanks

Abstract: Purpose – The purpose of this paper is to present an overview of storage tank incidents and the causes of the incidents. The paper also seeks to present a brief overview on Abu Dhabi Company for Onshore Oil Operations (ADCO) experience of Jebel Dhanna (JD) export terminal.Design/methodology/approach – Major hazard installations (MHIs) store large quantities of flammable material in storage tanks. Storage tanks represent important capital assets and are often critical operational items. The failure of a tank can have several undesirable effects such as endangering personnel, affecting the environment and interrupting the operator's business. The storage tank incidents and ADCO's experience on operating of an export terminal are collected from several sources such as technical articles, text books, internet web sites, and internal reports. The incidents and the causes of the incidents are reviewed and summarised. The ADCO's experience in operation of a crude oil tank farm are outlined.Findings – The world h...