Multilateral Well Design for Closed-Loop Geothermal Heat Extraction
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Solution Overview
Problem
Traditional Enhanced Geothermal Systems for hot dry rock face challenges such as high costs, environmental concerns from hydraulic fracturing, unpredictable fluid trajectories, and scaling/corrosion issues, requiring a more efficient and environmentally friendly heat extraction method.
Innovation Solution
A geothermal energy extraction system using a single well with multilateral branches, where the main wellbore is drilled to a deep geological formation, and lateral heat absorbing branches are sidetracked off the main wellbore, allowing direct contact between the circulating working fluid and the formation, with a closed loop circulation and heat exchanger for efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydraulic fracturing is used to increase permeability and heat exchange area, then heat extraction efficiency is improved, but environmental harm and operational complexity increase
Solution Approach 1:
The system divides the single wellbore into multiple functional segments using lateral branches that extend into the formation. Each lateral branch acts as an independent heat exchange zone, allowing the fluid to access a larger volume of hot dry rock without requiring hydraulic fracturing. This segmentation achieves enhanced heat extraction efficiency while avoiding the environmental harm associated with fracturing operations.
2Area of stationary object
If hydraulic fracturing is applied to increase permeability, then heat exchange surface area increases, but device complexity and cost increase
Solution Approach 1:
Instead of increasing heat exchange surface area through horizontal fracturing planes, the system transitions to a three-dimensional network by drilling lateral branches at various depths and angles from the main wellbore. This dimensional approach creates multiple heat exchange zones throughout the formation volume, achieving large effective heat exchange area with a relatively simple well completion structure.
3Productivity
If multiple wells are used for injection and production, then heat extraction capacity increases, but system complexity and cost increase
Solution Approach 1:
The system merges the functions of multiple wells into a single integrated wellbore structure. The main wellbore serves as the central conduit, while multiple lateral branches provide additional flow paths and heat exchange zones. This merging allows the single well to achieve the heat extraction capacity that would traditionally require multiple separate wells, thereby reducing drilling, completion, and operational complexity.
4Temperature
If direct contact between injected water and formation is used, then heat transfer efficiency improves, but scaling and corrosion damage increase
Solution Approach 1:
The system introduces a specially formulated working fluid that acts as an intermediary between the injected water and the hot dry rock formation. This working fluid is selected or designed to have low reactivity with formation minerals, thereby preventing scaling and corrosion while maintaining high heat transfer efficiency through direct contact with the formation.
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 approach reduces environmental impact, minimizes costs, and enhances heat transfer efficiency by utilizing a large volume of rock with direct fluid contact, overcoming the limitations of traditional systems.
Implementation Method 1
heat transfer from the rock by heat transfer
Implementation Method 2
circulating a working fluid through a single well with several lateral heat absorbing branches
Implementation Method 3
a heat exchanger where heat is transferred from said working fluid to a separate working fluid system
Data Source
AI summary
The present invention relates to heat extraction from a hot dry rock system using a single well with multilaterals in a closed loop circulation. More particularly, it relates to geothermal heat collector systems. A working fluid is circulated through a single well (106) with several lateral heat absorbing branches (113). These branches are sidetracked off the main wellbore (111) and completed using a slotted lateral sealed bore junction and hanger assembly completion (114) installed in the main wellbore (111). The lateral heat absorbing branches (113) are tied in and completed in a tubing mono assembly, comprising of the well (106) and lateral heat absorbing branches (113). The tubing assembly is hung off in a slotted tubing hanger assembly (112) that is installed in the bottom section of the main wellbore (111). The hanger assemblies are equipped with circulation ports and open hole rock slips. The heat extraction is done through direct contact between the working fluid and the formation.