Unconventional Clay Control Alternative to Inorganic Compounds that Can Prevent Swelling and Reduce Friction in Underbalanced Drilling
Authors: Altammar Mohammed A. , Almubarak Tariq , Elhajj Hicham , Suzart Walter , Alhulail Ibrahim 
Published: March 2019

An unconventional clay-control substitute was introduced in the Middle East and North Africa (MENA) region, where a total of twenty-nine wells have been completed successfully. This paper presents a homogenous, on-the-fly clay stabilizer, which renders clay insensitive to fresh water, preventing swelling and migration while leaving formation/fluid properties unchanged.

Formation damage and drilling difficulties are very commonly associated with clay problems. Clay-control additives are crucial in any drilling operation, particularly in Saudi Arabian gas wells where drilling activities use underbalanced coiled tubing drilling (UBCTD). UBCTD optimizes this on-the-fly alternative and achieves multiple objectives. The primary objective of UBCTD is to minimize fresh water contact time with the formation through flowing back; however, having to change the bottom hole assembly (BHA) because of wear halts circulation and production and increases fresh water contact with the formation, which could lead to clay swelling in the near wellbore area and result in damage. This new fluid system has proven to provide superior protection even at higher rates of penetration. In addition, inorganic compound quality and inconsistency could lead to deposits on equipment and affect instrumentation performance with UBCTD at the production/treatment systems when flowing back while drilling. These issues can be avoided with this treatment, and the costs associated with equipment rental can be reduced. Additionally, concentrations can be changed on-the-fly as needed depending on the formation.

This clay stabilization fluid helps control clay swelling, fines migration, and decreases hydrostatic pressure and friction pressure when exposed to a freshwater-based fluid system. It fundamentally adheres to the clay mineral surface and prevents ion exchange, therefore providing pore throat protection and deterring damage to the formation matrix.

The treatment was used during underbalanced drilling projects where each well/project had two to three laterals of low permeability. It was successfully used in nine pilot projects with excellent results, awarding distinctive advantages compared to typically used inorganic-based clay and shale stabilizers This development could increase the efficiency of downhole motors and drill bits as a result of low friction pressure and minimal deposits left behind. No additional equipment or manpower is necessary compared to other inorganic compound treatments. In addition, it reduces mixing time (on-the-fly) and is added at a lower concentration, which helps reduce logistical challenges and makes the treatment more efficient at a lower cost and with a reduced footprint.

Original permeability is not affected by the addition of this fluid system, and permanent clay stabilization is provided. Data are presented and cross-checked with adjacent wells/candidates that used conventional clay protection such as inorganic compounds. Gamma-ray logs, the rate of penetration (ROP), productivity index (PI), and associated depth are also presented. Wells drilled with this fluid exhibited excellent protection throughout laterals and open-hole sections.