Reduce Fresh Water Usage While Mitigating Scale

Abstract

Current seawater fluid systems were designed to reduce the usage of fresh water and the number of trips needed to transport the water. The composition of such fluids needed gel stabilizers to reduce the negative effects high salinity waters have on fluid performance. However, in solving one problem, another potential problem may have been overlooked. Sea water when met with the formation waters can cause scale production and formation damage. The damage is often worse when wells are shut in for extended periods of time. This paper will discuss the evaluation of a scale inhibitor package for immediate and long-term scale protection that can be delivered in the seawater fracturing operation without detrimental effects to fluid performance. Traditional and nontraditional screening methods were used to demonstrate the longevity of the scale inhibitor additive. Evaluation studies consisted of inhibitor compatibility studies, static bottle testing, and fluid rheology compatibility testing. Inhibitor compatibility studies were conducted to determine the inhibitors efficacy in high calcium environments at the pH of the fracturing fluid. Static bottle longevity testing was completed over 6 weeks using various inhibitor concentrations to optimize the scale inhibitor loading across varying seawater to formation water ratios. Fluid rheology studies were performed to determine compatibility with the inhibitor. Various loadings of the scale inhibitor were evaluated to determine the best loading across varying ratios of seawater to formation water. The scale inhibitor demonstrated that it could effectively inhibit calcium and barium scale formation for at least 6 weeks. Results were confirmed with ICP testing showing more than 80% of the cations in solution as per industry standard. The scale inhibitor had no determinantal effects to the fracturing fluid stability compared to the baseline. The data clearly shows the potential of using a scale inhibitor package with a seawater based fracturing fluid to fracture the formation while simultaneously inhibiting any scale formation. The inhibition was shown to last a minimum of 6 weeks at temperature to simulate shut in. The novelty of this scale package is to decrease use of fresh water and carbon footprint while providing long term prevention of scale through scale control additives. The optimized fluid and additives can provide enhanced management and protection from damaging scale deposition in HTHP wells later in the life of the well.