Development and Successful Field Application of a Novel Low Solids, Brine-Based, HTHP Well Testing Fluid

Abstract

Deep and ultradeep reservoirs are commonly characterized by high temperature and high pressure (HTHP), which poses a severe challenge to well testing operations. The requirement for high-density clear brine drives the overall cost of the well testing operations. There are only a few alternative high-density (>14.5ppg) clear brines in the market that can deliver the hydrostatic pressure requirements for HTHP wells. Zinc-based brines pose health, safety and environment (HSE) concerns, and can show high general corrosion rates as well as issues with elastomer compatibility. There are other alternative high density brine systems that are more benign, but they may have limits with respect to density and crystallization temperature, and/or they may have an extremely high cost per barrel. Considering the challenges of minimizing HSE risks and costs, a high-temperature divalent brine-based completion fluid was designed, utilizing novel synthetic polymer technology. This paper presents the laboratory work and field performance of this newly developed low-solids, brine-based, clay-free fluid system designed for HTHP well testing. 14.2ppg calcium bromide (CaBr2) brine was selected as the base fluid to provide density and minimize the total amount of acid-soluble solids in the fluids (as well as a very low crystallization temperature). Lab studies were conducted for rheological stability across a range of temperatures and for long-term stability under high temperature conditions. Return permeability tests were conducted on the final formulations to validate their suitability for use in the reservoir. The synthetic polymer technology provided excellent rheology and suspension in the fluid systems designed in the laboratory and proven in the field applications. The fluid was re-utilized multiple times in multiple wells and adjusted as per well requirement of density to control downhole pressure. This reusable well testing fluid resulted in a significant cost reduction to the operator.