Best Practices—Direct Emulsion-Based Drilling Solution as a New Approach to Drilling in Mature Fields with Low Reservoir Pressure

Abstract

Abstract Currently, most fields in Western Siberia are classified as mature with significant reductions in reservoir pressure. This fact greatly complicates the drilling of horizontal wells in these fields. The role of quality and the requirements for drilling fluids increase significantly under such circumstances. Standard drilling fluids often fall short in achieving the drilling objectives because of significant overburdening of formations. To resolve this issue, the geological information provided by an operator drilling in Western Siberia was used as the basis for developing an oil-in-water direct emulsion fluid system that reduces the likelihood of formation damage and allows trouble-free drilling under abnormally low reservoir pressure (ALRP) conditions. Filtration studies were carried out, and the impact on the restoration of the core's natural permeability was evaluated before this fluid system was used in the field. Active use of this drilling mud system began in Western Siberia in 2002, with the drilling of horizontal wells. In their development, all wells showed much higher completion quality: an easy transition of the well into production mode without additional measures (swabbing, stimulation, etc.) and obtained production rates above those planned. The use of this type of drilling mud under ALRP conditions was accompanied by a substantial reduction in the risk of differential sticking, which in turn reduced the likelihood of losing expensive downhole equipment used in logging while drilling (LWD), measurement while drilling (MWD), and annular pressure while drilling (APWD), etc. Additionally, by aiding the maintenance of a minimum overburdening of formations, this fluid allows the use of conventional drilling equipment that does not require the time and cost of rig reconstruction, as is required in the case of oil-based mud (OBM). Based on the analysis of drilling efficiency and completion quality conducted after testing the use of the emulsion fluid to drill horizontal wells in reservoirs with ALRP, the research institute of the field operator has recommended this technology for regular use, especially for reservoirs with low porosity and permeability properties. The use of oil-in-water direct emulsion fluid is not intended as a replacement for the conventional water-based solutions used for reservoir completion in the cases of normal reservoir pressure values and in partially depleted reservoirs. However, where the reservoir conditions are such that the use of conventional water-based mud (WBM) is inefficient, the use of oil-in-water emulsion-based mud can substantially enhance drilling efficiency and completion quality.