Closed-Loop Geothermal Well Layout for Lower Drilling Cost
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current geothermal energy extraction methods from Hot Dry Rock (HDR) formations face challenges such as high drilling costs, difficulty in controlling fracturing and heat transfer, and inefficient water flow, leading to impractical plant designs and high costs.
Innovation Solution
A geothermal energy plant design that combines supply and return holes, with production holes drilled either vertically or horizontally depending on thermal gradients, forming a closed loop with an insulated pipe to optimize energy output and reduce drilling costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple separate supply and return holes are drilled widely separated to allow reasonable heat output, then energy output is improved, but plant design becomes impractical and drilling costs increase
Solution Approach 1:
The patent combines multiple supply holes and return holes into a single integrated well structure. The well contains multiple supply holes drilled from the surface to different depths, and multiple return holes that converge and connect to a common production zone underground. This merging approach maintains the ability to extract sufficient heat from widely separated rock volumes while consolidating the surface infrastructure into a single well location, making the plant design practical and reducing drilling costs.
Solution Approach 2:
The patent transitions from a two-dimensional surface layout with multiple widely separated wells to a three-dimensional subsurface structure. By drilling supply holes to different depths and having return holes converge at different levels underground before connecting to the production zone, the system utilizes vertical and radial dimensions to achieve heat extraction from extended rock volumes while maintaining a compact surface footprint.
2Temperature
If rock fracturing is performed to establish heat exchanger circuit, then heat transfer efficiency is improved, but control of fracturing process and maintenance of fractures becomes difficult
Solution Approach 1:
The patent performs rock fracturing as a preliminary action during the well construction phase, before the heat exchanger system is fully operational. By creating the fracture network and establishing the heat exchanger circuits during drilling and completion operations, the system ensures adequate heat transfer pathways are in place before production begins. This preliminary fracturing approach allows better control over the fracture development compared to attempting to fracture already-operational production zones.
3Quantity of substance
If water flow follows path of least hydraulic resistance, then flow rate is improved, but heat production optimization becomes difficult
Solution Approach 1:
The patent creates different hydraulic properties in different zones of the heat exchanger system. By controlling the fracture characteristics and permeability in various regions of the rock formation, the system guides water flow through pathways that optimize heat extraction. The local variation in rock properties and fracture density ensures that water follows paths that maximize thermal energy transfer from the rock to the circulating fluid, rather than simply following the path of least resistance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly reduces drilling costs and risks while optimizing energy output, allowing for efficient heat transfer and plant expansion, with the flexibility to adapt to varying thermal gradients.
Implementation Method 1
The wells consist of single a hole with an internal pipe separating water flow downward and upward water flow. The water is injected in the outer annulus and is gradually heated until reaching the lower end of the pipe where it returns in the inner pipe
Implementation Method 2
Hot Dry Rock (HDR) is rock formations with low porosity and with no natural aquifers. In such rocks heat transfer takes place mainly through conduction. Given the very low conductivity of most types of rock, heat transfer must be expected to be low in the rock.
Implementation Method 3
Several methods for exploiting the significant thermal energy stored in HDR formations have been proposed and tested. The most common method consists of drilling one or more water injection holes and a production hole at a different location. By fracturing the rock between the injection and production holes, a closed circuit for water flow can be established in the rock.
Data Source
AI summary
A plant for exploiting geothermal energy by circulating water or another fluid through a non-porous geological formation at a substantial depth below the earth surface, comprising multiple heat absorbing/production holes penetrating the said formation, with a total length of several kilometers and spaced more than 50 m apart. The production holes are connected to the surface by one single combined supply and return hole in which upward and downward flow is separated by a pipe comprising an insulating material and a seal. At the given positions of the common supply and return hole manifold zone designs connect the hole to the multiple production holes. The supply and return holes and production holes are closed circuits for transport of a fluid such as water through the said formation. A method for designing and establishing the plant is also disclosed.