WELL-KILLING FLUID INFLUENCE ON DECLINE OF PERMEABILITY DURING WELL COMPLETION IN CARBONATE RESERVOIRS

Abstract

Link for citation: Sentemov A.A., Dorfman M.B. Well-killing fluid influence on decline of permeability during well completion in carbonate reservoirs. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 6, рр.35-46. In Rus. Relevance. Carrying out repair operations in production and injection wells with improperly selected well-killing fluid can lead to significant decrease in the permeability of the bottomhole formation zone. The important problem of well operations is the preservation of reservoir filtration properties. The main aim of this work is to study the effect of various additives in the well-killing fluid compositions on the reservoir properties and to identify approaches to prevent complications during workover and well servicing. Methods: empirical and analytical methods. Under laboratory conditions, the chemical composition, optical density and light transmission coefficient of well-killing fluids and formation water were determined. Modeling of formation fluids filtration was performed on a core study unit. Results. The main bottomhole zone permeability decrease reason during well-killing operations in the Timan-Pechora oil and gas province is the high iron ions content in formation waters. Formation waters of the Famennian horizon contain 60–70 mg/l of iron. To solve the problem of bottomhole zone filtration characteristics decline, it is necessary to significantly reduce the iron content in the well-killing fluids or prevent precipitation of iron compounds. Analysis of the solutions optical density results show effectiveness of the oxyethylene diphosphonic acid and AKSIS-KS for clarification and stabilization of well-killing fluids with the content of hydrated iron ions up to 70 mg/l. Based on the conducted filtration experiments, in order to reduce the negative effect of iron compounds on the permeability, it is recommend the use an iron stabilizer oxyethylene diphosphonic acid 2,0 % (with an iron ion content up to 70 mg/l) and a hydrophobiser Neftenol-K 1 %.

Keywords

• Well-killing fluid
• permeability
• bottomhole formation zone
• carbonate reservoirs
• iron compounds