Abstract
The control of the formation, accumulation, and precipitation of downhole solids is critical to the efficient operation of placed equipment. Downhole solids formation can lead to premature sucker rod lift pump failure and subsequent lost production. Control of these solids is often complicated by the speciation, location and treatment availability. Well conditions, such as temperature and pressure, commonly have varying effects on the individual components of these complex solids mixtures thereby complicating the control of their formation, maturation and precipitation. Removal of these solids is generally accomplished by the application of batch treatment programs or continuous application of scale inhibitors, surfactants or iron chelators. However, there is another mode of control that is not common practice in the oil field, control of the particle size. In this paper, we seek to demonstrate the control of the particle size of a complex mixture of solids by the use of a highly surface active dispersant that is specific for FeS. In this study, removal and control of a complex scale mixture, which included FeS, FeCO3, ZnS and CaCO3 in several oil wells in North Dakota, was studied by applying the FeS dispersant and a FeCO3/CaCO3 scale inhibitor. Action against these solids present at the downhole interfacial pad, as well as those that are newly formed are inferred from observation of the suspended solids, as collected from Millipore filtration, pump friction, pump loading, and residual oil in water. Correlation of this data showed that control of the particle size, as well as, the removal of the downhole interfacial pad was achieved within a month of treatment with this highly surface active dispersant and scale inhibitor. After approximately 14 months of treatment, the long term analysis of this treatment has revealed that this approach has increased SRL pump life and decreased operational costs due to treater upsets, pump longevity and reduction of the instances of bad oil.
