First Use of Coagulant for Solids in the Drilling Fluid Crude Oil for Underbalanced Drilling in Russia

Oil-base drilling fluids provide considerable advantages, however they have a number of limitations mainly related to drilling fluid system contamination with drill solids and formation water. The primary objective is to remove solids from the drilling fluid during the first cycle of their entering into the system in the course of well lengthening. These solids are defined as the concentration of suspended particles. Current solids control equipment does not remove the generated drill cuttings due to the absence of the first stage of solids control – shale shakers; therefore the cuttings transform into fine solids and accumulate as colloidal particles causing the growth of the concentration of suspended particles and reducing reservoir drilling-in quality. To meet the requirement, i.e. quality reservoir drilling-in, it is necessary to ensure effective cuttings removal during the first cycle of their movement. In 2018 Surgutneftegaz planned and performed field tests of the AKROS coagulant for solids (hereinafter – Coagulant) at the Talakanneft Field Office. The test results enabled conclusions on specific features of the Coagulant use in the drilling fluid – crude oil (hereinafter – crude oil) and identification of the potential for reservoir drilling-in optimization that may expand its applicability. As part of the New Technological Solution Implementation Program at Surgutneftegaz fields, additional lab equipment was used to obtain extended data, enabling a new interpretation of multilateral well lengthening. A lengthened multilateral well was drilled at a Surgutneftegaz field using the Coagulant. Coagulant field test results enabled the following improvements in drilling performance indicators: –reduced torque;–reduced tool weight during pulling out;–improved transfer of load to drilling tool;–increased ROP;–reduced concentration of suspended particles;–removal of formation water from crude oil. Results achieved on the concentration of suspended particles allow the transfer of crude oil to the following well/interval upon the completion of well lengthening or its injection into an oil reservoir with the minimum concentration of suspended particles. Crude oil treatment with the Coagulant will mitigate risks of heating elements failure, reduce the crude oil volume used for well lengthening, and ensure its reuse without additional replacements and/or dilutions. The use of the Coagulant demonstrated the ability to reduce the swelling activity of anhydrite occurring in the producing formation when it comes in contact with water contained in the crude oil, making well lengthening operations more technological. Results of the Coagulant use enabled the development of field practices of its application and recommendations on crude oil properties control as well as performance of comparative analysis of the efficiency of solids content reduction and water phase de-emulsification in the crude oil.