Successful Implementation of Zirconate Borate Based Dual Crosslinked Gel and Continuous Mixing System During Proppant Fracturing Treatment in a Complex High Temperature and High Pressure Sandstone Gas Reservoir in Saudi Arabia that Exceeded the Well Objective and Showed Substantial Increase in Operational Efficiency - A Case Study

Abstract

Abstract The success in a proppant fracture treatment depends on achieved effective fracture half-length and vertical proppant distribution. The desired fracture geometry can be challenging to achieve in deep and heterogeneous sandstone reservoirs in Saudi Arabia where temperature (up to 350 °F) and pressure are very high. Conventional borate based cross-linked polymer guar gel as a fracturing fluid — for high pressure high temperature (HPHT) reservoir in KSA — is outside of the optimum envelope as far as required rheology is concerned and exhibits extreme sensitivity to brine quality at bottom hole static temperature (BHST). A new fracturing fluid consisting of Carboxymethyl-Hydroxypropyl Guar (CMHPG) crosslinked with dual-crosslinker (Borate and Zirconate) has been found to be a more suitable fluid — than only borate based crosslinked fluid — for HPHT gas wells. This new fracturing fluid provides stable rheology under bottom-hole conditions, is compatible with reservoir fluids, and has excellent proppant-suspending and leak-off properties, while providing improved retained proppant permeability. Most sandstone gas completed with cased-hole or Multi-Stage-Frac completions in Saudi Arabia require large size proppant fracture treatments. The base potassium chloride (KCl) brine and linear gel are batch-mixed prior to fracturing treatment. This batch mixing process is time consuming and takes up to 3 days per stage fracture treatment. A significant increase in operational efficiency and fracturing fluid quality was observed when all fracturing additives, including: solid polymer and liquid Organic Clay Stabilizer (OCS), a KCl substitute; were used on-the-fly in a HPHT gas well during proppant fracturing treatment, utilizing an advanced continuous mixing system. The advanced continuous mixer was a pumping and blending system that provided linear gel to the blender. The system continuously metered and simultaneously mixed dry polymer powder to produce a gel at desired concentration that was completely free from oil-based material. A total of eight additives were added on-the-fly, utilizing solids and liquid additive system mounted on advanced continuous mixing and blender units. This paper provides details on lab testing, treatment design, field implementation, and treatment evaluation of a complex HPHT gas well in Saudi Arabia using the novel fracturing fluid system and state-of-art Continuous Mixing System.