Well Control and Management: Killing Fluids for Oil Fields of JSOC Bashneft

摘要

Today well killing operations form an integral part of routine well control and management. Therefore the essential task is to select an optimum killing fluid for the given conditions which would secure safety of well operations by preventing any entry of formation fluid into the wellbore with no risks of formation damage in the near wellbore zone. At the same time killing fluids should be available on the market, easy to use and readily producible at a wellsite. The use of water-based killing fluids may result in a very long well stabilization time after the operation and reduced well productivity. The most important factors which affect an oil reservoir are the invasion volumes of a killing fluid, its compatibility with formation waters and hydrophilic minerals in the formation rock. Most fields operated by JSOC Bashneft are characterized by the presence of highly mineralized water bearing beds in the section with density up to 1.18 g/cc. This water is used as a killing fluid and if necessary can be mixed with fresh water to get a mixture of a certain density for the required back pressure on the formation. The paper discusses risks of scaling when a killing fluid is prepared and mixed with formation waters from various horizons. Within the scope of this study laboratory tests were performed on core to assess the risks of formation damage and reduced permeability in the result of killing fluid invasion into a reservoir. Given such geological and engineering conditions the design of killing operations should integrate optimization of killing fluid properties with the use of various chemical agents which would prevent any formation damage and protect well equipment.