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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractPrevious work has derived an analytical model for simultaneous flow of incompatible waters in porous media with sulphate salt precipitation, determined typical values of kinetics reaction coefficient from corefloods and what the impact would be on productivity impairment during sulphate scaling.This paper extends the previous work, by modelling the injectivity impairment during simultaneous injection of incompatible waters, i.e. cation-rich produced water (PWRI) and seawater with sulphate anions. An analytical model with explicit expressions for deposited concentration and injectivity decline was developed.The location of scale deposition and the resulting injectivity impairment are calculated for a range of sensitivities, including reaction kinetics (ranging from minimum to maximum values as obtained from coreflood and field data), fraction of produced water in the injected mixture and barium concentration in produced/re-injected water.The theoretical parameter of the size of formationdamaged zone was introduced. It was found out that almost all deposition takes place in 2-4 well radii neighbourhood. Calculations show that simultaneous injection of seawater with produced water containing even decimal fractions of ppm of barium would results in significant injectivity decline.

In the process of physical annealing, a solid is heated until all particles randomly arrange themselves forming the liquid state. A slow cooling process is then used to crystallize the liquid. This process is known as simulated annealing. Simulated annealing is stochastic computational technique that searches for global optimum solutions in optimization problems. The main goal here is to give the algorithm more time in the search space exploration by accepting moves, which may degrade the solution quality, with some probability depending on a parameter called temperature. In this discussion the simulated annealing algorithm is implemented in pest and weather data set for feature selection and it reduces the dimension of the attributes through specified iterations.

Scale build-up in petroleum production systems is a major impediment to efficient oil and gas production. Calcium carbonate is one of the most commonly occurring sources of scale, but the formation of gas hydrate is also a challenge, especially in offshore and subsea deep water production. Thermodynamic inhibitors like monoethylene glycol (MEG) are frequently used to prevent hydrate formation. This paper describes the influence of MEG on the calcium carbonate scaling time by using a Dynamic Scale Loop System (DSL). The study also examines the influence of temperature, pressure and salt concentration on the scaling time. Experiments were performed using a 25-1 fractional factorial experiment design. The experiments showed that as MEG content increases, the expected calcium carbonate scale decreases. In contrast, an increase in temperature, will increase the calcium carbornate scale, while pressure and salt concentration did not have a significant influence on their own. Furthermore, the paper describes the interaction between the variables under review. The interaction between pressure, temperature and MEG content results in an overall decrease in MEG performance to avoid scale build-up by changes in the system's viscosity. Finally, we determine that the increase of MEG content increases the time to reach full-scale blocking; thus, the results indicate that an inhibition of the calcium carbonate deposition occurs as the MEG content increases.

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