No abstract

The thermodynamic solubility product for baryte, determined at standard conditions, from data in commonly used compilations, was compared with published experimental solubility products for baryte and with the solubility products from databases used by the PHREEQC geochemical speciation code and MultiScale, which is often used by oil companies to predict or describe baryte scaling. The values in the various databases agree well with experimental data (10 À10.05 À10 À9.96 ;Melcher, 1910;Neuman, 1933;Templeton, 1960;Davis and Collins, 1971; Blount, 1977;Felmy et al., 1990), which agree within uncertainty with the values presented in the compilations of Robie et al. (1979), Wagman et al. (1982), Lide (2005), Raju and Atkinson (1988), as well as Nordstrom and Munoz (1994), whose values have the least uncertainty. In solutions of 50% seawater mixed with 50% reservoir formation waters, the data predict baryte supersaturation, both at standard temperature and at the temperatures expected in the reservoir, completely consistent with field observations. This provides confidence that the Pitzer approach for activity correction and the database is valid for investigations of baryte precipitation rates in high ionic strength solutions.

Consideration of the risk associated with operations at the earliest possible stage is a key factor for effective chemical HSE risk management. This paper describes the operational and strategic decisions behind the design and implementation of a method developed for Maersk Oil, where the responsibility for chemical risk assessment is transferred to the earliest possible point in the chemical handling chain -the procurement process.Separate HSE risk assessment procedures conducted solely by specialists may lead to decoupling of the HSE considerations from the operational requirements. The objective was to integrate chemical HSE risk assessment into the overall consideration of chemical suitability (technical and cost) for a particular operation. When extending HSE risk assessment responsibility to operational staff with procurement responsibilities from HSE specialists, certain criteria must be met. The developed methodology was to meet the following targets:1. Give consistent answers without applying HSE expertise; 2. Be easy and fast to use; 3. Take into account regulative demands; and 4. Allow linking chemical HSE risk to management actions and corporate policy The developed methodology provides the assessor with a simple yet plausible and understandable result of the associated level of HSE risk. The assessment is based on linking data supplied by the vendors to chemical usage scenarios supplied by the actual operative personnel. Implementation of the methodology for easy user interface is based on an IT-solution tailored to the operators existing processes. This paper summarises the definition of the objectives and the main considerations taken when developing the methodology and presents an overview of the supporting tool developed.