AN INTEGRATED PRESSURE COMPATIBILITY FRAMEWORK FOR OPTIMIZING WELL DESIGN AND DRILLING PARAMETERS IN A MATURE OIL FIELD – CASE STUDY FROM THE VATYOGANSKOYE FIELD, RUSSIA

Well design in oil drilling requires a thorough analysis of geological conditions, formation pressures, and technical risks. The Vatyoganskoye field (Russia) features a complex sedimentary structure with potentially problematic carbonate intervals.

This study presents a systematic application of pressure compatibility analysis for integrated well design optimization in the Vatyoganskoye oil field. The contribution lies in combining geological characterization, pressure analysis, drilling-fluid design, casing selection, cementing planning, and drilling-parameter optimization within a unified engineering workflow.

The design is based on a combined coefficient plot (formation pressure anomaly coefficient k_a, lost circulation index k_loss, fracture pressure index k_frac, and mud relative density ρ_rel) to define compatibility zones. The novelty of this work lies in the integrated framework that links these dimensionless pressure coefficients directly to engineering decisions (casing depths, mud density, bit selection, cementing), providing a reproducible template for well design in mature fields. Casing and bit diameters are calculated from the bottom upward. Drilling parameters (weight on bit, rotary speed, flow rate) are determined per interval. Cementing operations are dimensioned with volume calculations, equipment count, and pressure estimates. The selected architecture comprises four strings: conductor (30 m), surface casing (1110 m), intermediate casing (1880 m), and production casing (2000 m). Bit diameters range from 558.8 mm to 187.3 mm. Roller-cone bits are selected according to rock categories (II to VII). Drilling fluids consist of a low-clay polymer mud (0–420 m) followed by a non-dispersed polymer mud (420–2000 m). Cementing requires two mixing units and two pumping units. The BU-2000/125 EBM rig is selected.

Fractured carbonate reservoirs, analyzed from experience in analogous fields (Yurubcheno-Tokhomskoye), present major risks of lost circulation and kicks. The proposed design incorporates safety margins but lacks specific features to manage such complications in real time. The coefficient-based compatibility analysis reveals a narrowing operational window with depth, justifying the selected casing depths. This study provides a reproducible framework for well design in similar geological settings and highlights the need to integrate risk anticipation for carbonate heterogeneities into conventional design workflows.