Thermochemical Re-Pressurization to Mitigate Fracture Hits and Enhance Productivity in Tight Formation Infill Drillings

Infill drilling in unconventional reservoirs often leads to stress redistribution and pressure depletion around the parent well. This well interference results in fracture hits between parent and child wells, reducing stimulation effectiveness and production from both wells. This work presents an in-situ thermochemical re-pressurization treatment to increase pressure in the depleted region near the parent well prior to child well treatment, with the objective of protecting the parent well while improving reservoir access for the child well. A reactive fluid system is injected into the parent well to trigger a controlled exothermic reaction that generates in-situ heat and pressure, increasing the local state of stress to recharge the pressure in the well drainage zone. The treatment is conducted in multiple stages in the parent well, while the child well remains shut-in. Once adequate re-pressurization levels are achieved, the child well can be stimulated. The elevated stress field near the parent well will redirect fractures in the child well(s) towards less-depleted and undisturbed regions of the reservoir, where higher pore pressure and intact rock support more effective fracture propagation. In addition to evaluating critical engineering controls required for downhole implementation, candidate chemical systems are evaluated, and competing thermodynamic reaction pathways are analyzed. A process simulation methodology was developed to model the heat and mass balance of the primary candidate reaction, Ammonium Chloride and Sodium Nitrite, under representative unconventional reservoir conditions. The simulation results confirm that the system can generate considerable heat and a gas phase composed of Nitrogen and steam, resulting in the thermal expansion of fluids and the formation, thus re-pressurizing the parent well. This approach makes it possible to avoid fracture overlaps with existing stimulated volumes and facilitates the development of new drainage pathways, which in turn improves overall stimulation coverage and reservoir contact efficiency.