Utilizing Extremely High Salinity Waters for Unconventional Hydraulic Fracturing in the UAE - A Chemistry Oriented Solution
Authors: Elazab S. A. , de Melo A. B. , Nechakh A. , Mendez A. , Illa X. 
Published: March 2024

Hydrocarbon production from unconventional resources, such as tight oil and gas, has witnessed a remarkable global growth in the past two decades. This growth is largely attributed to the development and application of horizontal drilling and hydraulic fracturing technologies, which enable the extraction of hydrocarbons from low-permeability reservoirs that were previously considered uneconomical or inaccessible. Hydraulic fracturing is a stimulation technique that involves pumping a fluid, usually water-based, mixed with proppant and additives, into the target formation at high pressure to create and propagate fractures that enhance the flow capacity of the reservoir. However, hydraulic fracturing also poses significant environmental and operational challenges, such as water sourcing, water disposal, water consumption, and water quality.

In the UAE, unconventional hydrocarbon resources are located mainly in the onshore Western Region, where water availability and quality are critical issues. The region is characterized by an extremely arid climate, with scarce and saline groundwater resources, and a high dependency on desalinated seawater for domestic and industrial use. Therefore, relying on fresh or potable water for hydraulic fracturing operations is neither feasible nor sustainable in the long term, especially as the unconventional resource development progresses from exploration to appraisal and production phases, requiring more wells and larger fracturing volumes. Hence, there is a need to identify and utilize alternative water sources that can meet the demand for fracturing fluids while minimizing the environmental impact and operational cost. Some of the potential alternative water sources include produced water, flowback water, recycled water, seawater, and brackish water. However, using alternative water sources for hydraulic fracturing also entails modifying the fracturing fluid chemistry to cope with the varying water quality and salinity. High salinity can affect the performance and compatibility of the fracturing fluid additives, such as friction reducers, scale inhibitors, biocides, surfactants, clay stabilizers, and crosslinkers. For instance, high salinity can reduce the friction reduction efficiency, increase the viscosity and drag, interfere with the crosslinking reaction, promote scale precipitation, and enhance microbial growth. Therefore, selecting and testing the appropriate additives that can function effectively and reliably under extreme salinity conditions is essential for the success of hydraulic fracturing operations. Moreover, evaluating the impact of the fracturing fluid chemistry on the formation damage, proppant transport, fracture conductivity, and hydrocarbon recovery is also important to optimize the fracturing design and execution.

In this paper, we present the results of a comprehensive laboratory study that investigated the feasibility and suitability of using extremely high salinity waters for unconventional hydraulic fracturing in the UAE. The study focused on two key aspects of the fracturing fluid chemistry: friction reduction and scale inhibition. We evaluated the performance and compatibility of different friction reducers and scale inhibitors with various water qualities, including seawater, extremely high TDS brine, and mixtures of both. We also assessed the rheological properties, proppant suspension, and thermal stability of the fracturing fluids. The paper discusses the challenges, solutions, and lessons learned from this study, and provides recommendations and best practices for using extremely high salinity waters for hydraulic fracturing in the UAE.

A careful set of over 200 tests were performed to prepare for the job executions. With this investigation, the aim was to improve the sustainability and efficiency of hydraulic fracturing operations in very high-salinity environments, reducing water use and environmental impact. This study offers useful insights and data, possibly transforming the industry's approach to water resource management in the context of completion operations for the region.

The scale inhibition additives package, selected after thorough evaluation across 18 simulated scenarios, is presented as a solution that effectively precludes scale formation within both ambient and bottomhole static temperature of 300˚F environments. This inhibitor exhibits remarkable thermal stability exceeding 300˚F and complete compatibility with extreme high Total Dissolved Solids (TDS) brines. Two friction reducers were selected to cover the majority of the waters to be used with results focused on friction reduction, full sweep rheology and proppant suspension. Significantly, it exerts no discernible impact on rheological measurements or fracturing fluid formulations, as substantiated by the test results contained within this study. In essence, the study investigated the effectiveness of salt-tolerant products, specifically formulated to endure, and perform optimally under extreme salinity conditions.