Novel Smart Shape Memory Polymers for Rapid Mitigation of Lost Circulation in High-Temperature EGS Formations

Geothermal drilling is highly affected by mud losses. This adverse event is the leading cause of non-productive time in geothermal well construction. Mud losses account for 20% of total drilling costs in geothermal drilling. If not adequately addressed, mud losses can lead to costly drilling problems such as stuck pipe, kicks, and well control events. Circulating lost circulation materials (LCMs) is the first step to cure mud losses. However, the highly fractured geothermal environment presents a challenge for LCM bridging and sealing action. Indeed, the success rate of curing lost circulation using LCM is around 25%. Besides, conventional fibrous and flaky LCMs exhibit thermal degradation at high temperatures, which affects their performance to tackle lost circulation events. Shape memory polymers (SMPs) are new programmable smart LCMs that can be activated by temperature. During programming, a combination of heat and load is applied to temporarily deform SMP. The material has a smaller volume once it is programmed, allowing it to circulate without plugging drilling assembly restrictions (such as measuring while drilling tools) or drill bit nozzles. The SMP is programmed to activate at the desired temperature. When the temperature is equal to or above the programing temperature, the SMP returns to its original shape. It is necessary to adjust the activation temperature to the formation temperature so that the SMP can return to its original size and shape inside the fractures for the purpose of curing mud losses. In this study, different experiments were performed to evaluate the sealing capabilities of SMP at high temperatures (above 300ºF). SMP performance at high temperatures is investigated experimentally through filtration, rheology, and flow loop studies. The low cost, increased flexibility, and easy programming of SMPs make them an ideal material for geothermal drilling. They can also withstand high temperatures.