Comparative Performance Evaluation of Well Control Methods for Onshore Vertical Oil Wells: A Case Study of Exploration Well 6P2-59, Sirte Basin, Libya

Abstract

Well control operations represent the technical cornerstone for human safety, environmental integrity, and asset protection in oil and gas drilling operations. This research presents comprehensive hydraulic, geological, and operational evaluation comparing two primary well control techniques, The Driller’s Method (DM) and the Wait & Weight Method (W&W) for circulating out a kick and restoring the primary well barrier. The mathematical modeling and hydraulic simulations are applied to the onshore vertical exploration well 6P2-59 (E.6P1-59 Deep Pool Test), located in Concession 59A near the Harash field within the Sirte Basin, Libya.

Following shut-in procedures, stabilized surface readings recorded a Shut-In Drill Pipe Pressure (SIDPP) of 1,610 psi, a Shut-In Casing Pressure (SICP) of 1,920 psi, and a pit gain (influx volume) of 25 bbl at a Total Vertical Depth (TVD) of 10,000 ft. The required Kill Mud Weight (KMW) was calculated at 13.10 ppg (adjusted to 13.20 ppg with a 0.10 ppg operational safety margin), compared to the original mud weight of 10.0 ppg. Initial Circulating Pressure (ICP) and Final Circulating Pressure (FCP) were established at 1,950 psi and 449 psi, respectively, with a pressure step-down rate of 111 psi per 100 strokes.

This study provides a technical comparison regarding dynamic casing shoe stress, potential underground blowout risks, equipment exposure times, and operational complexities between both methods, serving as a critical reference for deep exploration drilling in high-pressure sedimentary regimes.