Zero-Flaring Mudcake Removal: New Techniques for Efficient Natural Cleanup of Horizontal/Multilateral Open-Hole Wells

Abstract

Effective mudcake removal is essential to restore the optimal well productivity/injectivity after different drilling operations. Typically, this objective is achieved by using harsh chemical treatments such as hydrochloric acid (HCl), organic acids and oxidizers. However, these methods have been limited due to associated high corrosion rates, high operation cost, and un-even mudcake removal. This task becomes even more difficult and very challenging in horizontal/multilateral wells. Organic acids and acid precursors have been also used to clean long horizontal wells following drilling operations. However, in long multilateral horizontal wells, fluid placement is considered one of the main challenges with chemical mudcake removal treatments due to accessibility to each lateral and reaching its TD. Additionally, the use of these treatments has poor health, safety and environmental (HSE) footprints. This work provides a workflow and illustrates the use of an in-house designed zero-flaring flowback system to clean up recently drilled multilateral horizontal wells with water-based mud. The system consists of two upstream solid management systems, namely de-sander (cyclone), and sand catcher (filter). Downstream, the choke manifold, 4-phase separator, a downstream solid management equipment, and 3-phase separator are also included. Additionally, there is also a surge tank, as a backup flowback vessel to be used if needed to revive the well and offload any heavy fluids. This tank is used to initially help the well to gain the pressure momentum to naturally flow and offload heavy fluid present in production tubular. The cleanup campaign was successfully and safely completed for effective cleanup of more than 30 openhole horizontal multilateral wells without the use of any chemical treatments. The duration of cleanup operations was optimized using several techniques to effectively and efficiently remove existing mudcake. This paper provides the operational criteria to achieve effective and adequate mudcake removal for horizontal/multilateral wells and restore its optimal performance. Different design parameters and tailored flowback programs will be discussed, which led to effective drawdown pressure to reach optimized natural cleanup of each well. The well simulated flow model was also considered and used as input to design each well specific flowback program and minimize the risks of erosion, solids settlement in pipeline and downstream facilities. As a result, each well cleanup duration was reduced to an average of 1-2 day, while achieving the maximum potential production rate of each treated well.