Perspectives of Unconventional Water Sources Implementation in Hydraulic Fracturing

Abstract Currently, Russia experienced a rapid growth in horizontal wells drilling. The most popular method of completion is hydraulic fracturing. About 99% of hydraulic fracturing fluids are prepared using water. This fact undoubtedly increases the importance of technology and practices of collecting and utilizing water from underground and surface sources. The current direction of development of multi-stage hydraulic fracturing is increasing the number of stages and the volume of the proppant. So the main task of fracturing companies in Russia is to optimize the process of collecting and preparing water without increasing the cost of hydraulic fracturing. The use of organometallic fluids fracturing is the most common solution for use of unconventional water sources. However, due to the high cost of organometallic liquids, borate fluids will be considered in this work. Existing quality control requirements applied to hydraulic fracturing fluids cannot be directly used to study the rheological properties of fluids based on alternative sources of water — produced water from artesian wells and low temperature water. In connection with the foregoing, in the framework of this work, a new approach to testing and quality control of hydraulic fracturing fluids is presented. In case of using water with low temperature (15 degC in summer, 25 degC in winter), it is crucial to maintain the required recovery rate of fluid viscosity after application of high shear rates when passing through perforations in the near wellbore zone. In the case of the use of artesian water, it will be crucial to maintain the necessary stability of the liquid in a highly mineralized medium. During the hydraulic fracturing campaign in 2017-2019, pilot works were carried out using low temperature water and water from artesian wells. Implementation of water with a lower temperature leads to a reduction in the time of preparation for hydraulic fracturing by 33-50% reduction in heating time for the fluid. As a result, this practice leads to an increase in the monthly amount of work and the production of hydraulic fracturing fleets. Extended laboratory studies revealed that, developed for low temperature conditions, the hydraulic fracturing fluid not only satisfies the parameters for transferring and holding the proppant in the NWB zone, but even surpasses the liquid prepared by the traditional method (25 degC in summer, 35 degC in winter). The main goal of optimization of hydraulic fracturing fluid prepared using artesian water was to reduce the negative impact of some ions, primarily iron ions and hydrocarbonate ions. The presence of these ions in the hydraulic fracturing fluid leads to deterioration of the thermal stability of the hydraulic fracturing fluid. However, following the recommendations developed for the preparation of a fracturing fluid based on artesian water, it is possible to significantly reduce the influence of both one and other ions. The use of artesian water in the area of pads located near artesian wells, has reduced the time of water transportation by 50%. Pilot treatments were successfully carried out, showing a satisfactory level of production after hydraulic fracturing, comparable to similar work using conventional surface water preparation techniques using the standard procedure. Reduction of preparation time, optimization of resources required for water treatment, and reduction of negative environmental impact confirm the significant economic benefits of the methodology described in this paper. This approach, using the environmentally safe "green" chemistry as part of a hydraulic fracturing fluid, allows operators to minimize the negative impact of production factors on the environment and confirm the effectiveness and environmental friendliness of hydraulic fracturing technology as a well workover.