Geothermal anywhere is a concept getting much buzz among renewable energy sources. Oil and gas companies are showing more interest in geothermal drilling because their expertise in drilling operations can aid in expanding geothermal energy production to create reliable energy.
Traditional geothermal energy systems are located near natural reservoirs of high-temperature water in permeable rock close to the surface and limited to specific locations. Unconventional geothermal systems use engineered reservoirs to produce geothermal energy and can access geothermal power from resources traditionally considered unrecoverable due to rock type, location, or lack of water. Categories of geothermal energy systems include:
- Enhanced or Engineered Geothermal Systems (EGS) improve the permeability of geothermal systems through hydraulic, chemical, and thermal stimulation to geologic formations with high subsurface temperatures and low rock permeability that lack a natural water source. Using an injection well drilled into a fracture zone, injection fluid is heated and then brought to the surface.
- Advanced Geothermal Systems (AGS) drill wells into hot rock and circulate fluid through a closed-loop system. The fluid is circulated and heated without making direct contact with the hot rock. The heat is brought to the surface and can be used for direct heating or transferred to electricity systems.
- Geothermal Oil and Gas Hybrid Systems use geothermal fluids from existing wells to extend the life of the well, deliver energy savings and reduce greenhouse gas emissions.
- Sedimentary Geothermal Systems take advantage of hot sedimentary basins, usually in oil and gas basins, and can provide heat for direct use and electricity.
Drilling Geothermal Wells
Tapping into geothermal energy as a reliable renewable energy source means utilizing the experience and expertise of drilling companies. Oil and gas drilling knowledge provides insight into geothermal drilling projects, but the objectives and risks associated with each are not the same.
Drilling at the increased depths necessary for establishing geothermal energy systems causes high temperatures, which brings another set of challenges. While experienced oil and gas operators can address technical challenges, it is important to note what to expect from geothermal drilling projects and be prepared to address issues as they arise.
High-Temperature Drilling
Drilling geothermal wells means increased temperatures. Wells are estimated to be 7- to 10-km in order to reach fluid at the high temperature required to produce electricity. Drilling to these depths requires drilling at faster rates of penetration (ROP). Specific issues arise when drilling under these conditions, like drill bit damage and lost circulation. Operators must utilize drill bits composed of materials that can withstand the heat and speed at which geothermal drilling requires. Hybrid drill bits yield optimal results in high temperatures and at faster speeds needed in geothermal drilling.
Lost Circulation
Due to the fracture systems encountered in geothermal drilling, lost circulation is often an issue. In sedimentary formations, lost circulation is easier to remedy than in the high-temperature volcanic formations that are more desirable for geothermal energy production. Understanding the potential for loss circulation and how to mitigate it with proper loss control materials helps minimize downtime and maximize returns on drilling projects.
Geothermal Drilling Fluids
Optimal geothermal drilling fluids include thinners and filtration control additives, like synthetic polymers to improve filtration control and thinners to increase stability and tolerance to contaminants. Water-based mud is advantageous in geothermal drilling due to its stability at elevated temperatures and its ability to mitigate corrosion. Oil-based mud is not the most practical for geothermal applications due to the substantial risk of loss and the high temperatures that increase the risk of corrosion.
Geothermal drilling fluids require features such as:
- Controlled Viscosity at circulating temperatures
- Minimal thickening during static periods
- Cement tolerance
- Elevated pH to prevent corrosion and acid gases
Successful geothermal energy systems require the proper application of fluid programs to maintain hole conditions and equipment longevity. Comprehensive fluid programs and well-site fluid experts, like those provided by Panther Fluids, ensure timely and incident-free completion of your geothermal drilling project.
Cutting Transport and Solids Control
Quality fluids management includes haul-off and disposal to effectively transport cuttings to the surface for efficient separation and removal. Proper on-site equipment for cutting transport and control streamlines efficiency and guarantees compliance with local, state, and federal regulations.
Comprehensive Geothermal Drilling Plan
The drilling operations of a geothermal well can account for almost 70% of the overall cost of a geothermal energy project. Lost circulation, drill bit damage, and longer drilling times from slower ROPs often add to initial project costs. Anticipating and addressing issues that may arise when drilling for geothermal energy systems is imperative to planning any geothermal drilling project. Using experts with proven experience in drilling will help cut time and costs.
Plan for success in your geothermal drilling project by partnering with Panther Fluids. We offer a comprehensive fluids management plan that includes:
- Drilling fluids
- Solids control
- Haul-off and disposal
- Equipment rentals
Our knowledgeable onsite drilling fluids experts predict problems before they arise and provide proven solutions for drilling geothermal wells. Contact us today to plan your next geothermal drilling project.