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New Techniques to Characterize and Remove Water-Based Drilling Fluids Filter Cake
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Filter cake characterization is very important in drilling and completion operations. Heterogeneity of the filter cake plays a key role in the design of chemical treatments needed to remove the filter cake. The objectives of this study are to characterize the filter cake under static and dynamic conditions, evaluate the using of polylactic acid and chelating agents to remove calcium carbonate-based filter cake, assess glycolic acid to remove Mn3O4-based filter cake, and evaluate ilmenite as a weighting material for water-based drilling fluid. In order to characterize the filter cake, computer tomography (CT) was used in combination with the scanning electronic microscopy (SEM) to analyze the filter cake. A modified HPHT filter cell was developed to perform the filtration tests. A see-through-cell was used to check the compatibility of different chemicals that were used to remove the filter cake. The results obtained from the CT scan showed that the filter cake was heterogeneous and contained two layers with different properties under static and dynamic conditions. Under static conditions, the formation of filter cake changed from compression to buildup; while under dynamic conditions, the filter cake was formed under continuous buildup. Polylactic acid was used as a component of the drilling fluid components and the results obtained showed that the drill-in fluid had stable rheological properties up to 250˚F over 24 hrs. The removal efficiency of the filter cake was nearly 100% and the return permeability was about 100% for Indiana limestone and Berea sandstone cores, when using a weight ratio of polylactic acid to calcium carbonate 3 to 1. GLDA (pH 3.3) and HEDTA (pH 4) can be used to remove the filter cake in one step without using α-amylase enzyme solutions. GLDA (20 wt% in a 200 g solution and pH of 3.3) and HEDTA (20 wt% in a 200 g solution and pH 4) had 100% removal efficiency of the filter cake using Indiana limestone and Berea sandstone cores. Chelate solutions, GLDA (pH of 3.3 - 13) and HEDTA (pH of 4 and 7) were incompatible with α-amylase enzyme solutions over a wide range of temperatures. CT results showed that no formation damage was observed when using chelating agents as a breaker to remove the calcium carbonate filter cake. Manganese tetraoxide-based filter cake had a removal efficiency of 85% after 20 hrs soaking with glycolic acid (5 wt%) after soaking with α-amylase for 24 hrs, and 89% after reaction with acid mixture (1 wt% HCl and 7 wt% glycolic acid) for 16 hrs. for both methods, the retained permeability was 100% for Indiana limestone cores and 120% for Berea sandstone cores, which indication maximum productivity of these formations. Ilmenite-based filter cake was ideal for HPHT applications, 0.2 in. thickness and 12 cm3 filtrate under dynamic conditions. The filtrate volume was reduced by adding a minor amount of CaCO3 solids that improved the particles packing. No sag problem was observed when using the micronized ilmenite in water-based drilling fluids. Ilmenite has a negative zeta potential in alkaline media and had a stable dispersion in water at pH > 7.
Elkatatny, Salaheldin Mahmoud (2013). New Techniques to Characterize and Remove Water-Based Drilling Fluids Filter Cake. Doctoral dissertation, Texas A&M University. Available electronically from