In most of the Gulf of Mexico operations, hydrates and wax depositions are considered to be the primary flow assurance issues. However, as the fields become more mature and water flooded, other non-wax/hydrate deposition may affect flow assurance in multi-phase pipelines. One of these is scale deposition.
Conditions that can cause scales to form, such as temperature or pressure drop or mixing of incompatible water will be presented. The characteristics of the important groups of scales will be discussed. For example, sulfates tend to form quickly in supersaturated solutions while carbonate precipitation takes longer.
Techniques for brine sampling and analysis, predicting the conditions for potential for scaling problems will be presented. These include proper techniques for on and off-site analysis of waters, geochemical modeling of water systems as well as physical testing of scaling water systems. An example of the effect of quality control on geochemical modeling will be given.
Prevention and remediation techniques for scale will also be presented. The most important of these entails the use of scale inhibitors. Conventional scale inhibitors function as threshold inhibitors. They increase the time required for the onset of scale precipitation and/or slow the growth of scale once started, but are used in such small amounts they do not actually change the thermodynamic driving force for scale precipitation. In conventional operations the time delay in scaling is sufficient to dispose of scaling water after separation. In extended multi-phase flowlines the delay may not be sufficient to prevent scaling. Emerging technologies such as multifunctional scale inhibitors and barite dissolvers will also be discussed.