Removal of polymeric filter cake in petroleum wells: A study of commercial amylase stability

• Published in: Journal of petroleum science & engineering Vol. 59; no. 3; pp. 263 - 270
• Main Authors: Kameda, Etel, de Queiroz Neto, João C., Langone, Marta A.P., Coelho, Maria Alice Z.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-11-2007; Elsevier Science
• Subjects: Amylase; Applied sciences; Completion equipments and methods. Casing. Cementing. Tests and measurements in wells; Crude oil, natural gas and petroleum products; Drilling fluid; Drilling fluids; Drilling methods and equipments. Rocks mechanics. Directional and horizontal drilling; Drilling. Casing. Preparing wells for production; Energy; Exact sciences and technology; Fuels; Openhole conditions; Petroleum wells; Prospecting and production of crude oil, natural gas, oil shales and tar sands; Starch filter-cake removal; Openhole conditions; Starch filter-cake removal; Petroleum wells; Amylase; Drilling fluid; Drilling; Enzyme; Brine; Xanthan gum; Polymer; Borehole; Petroleum; Salt; Completion; Pressure effect; Acids; Hydrostatic pressure; Horizontal well; Filter cake
• ISSN: 0920-4105; 1873-4715
• DOI: 10.1016/j.petrol.2007.04.005

The drilling fluid contact with the productive zone of drilling wells, with horizontal or complex configurations, can reduce its productivity by fluid invasion in the borehole wall. Drilling fluids usually comprise natural polymers as starch and xanthan gum. These polymers are deposited as a filter cake on the wellbore wall. A common approach to remove this filter cake is the application of acids or strong oxidative solutions. However, these are non-specific species and a possible alternative lies in enzymatic preparations that are able to hydrolyze such polymers. The enzymes catalyze specific substrates, are environmentally friendly and the enzymatic degradation rate is slower than that achieved by the oxidative species, permitting to produce uniform degradation of the filter cake. Openhole operations require thermo and pressure stability of these enzymatic products. The results herein reported deals with the technical viability analysis of a commercial α-amylase as a new catalyst for filter cake removal. The effects of process parameters, like temperature (65, 80 and 95 °C), enzyme concentration (1, 5.5 and 10% v/v), calcium concentration (5, 70 and 135 ppm), and pressure (100, 500, 100 and 6000 psi), on amylase stability under openhole operations were investigated. Temperature demonstrated to be the most important parameter for the enzyme stability. The enzyme thermostability behavior in high salt (NaCl) concentration (completion fluid) was not significantly different from the control solution in distillated water. The pressure effect on enzyme stability did not affect the enzyme stability as temperature. Hydrostatic pressure (6000 psi) did not impact the amylolytic activity in brine solution. Combined pressure–temperature assays showed that temperature is the key factor in enzyme stability for application in polymeric filter cake removal in petroleum wells.