Magnetofluid Heating for Gas Hydrate Wellbore Blockage
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Solution Overview
Problem
Current methods for natural gas hydrate exploitation, such as the depressurization method, face challenges with reservoir instability, sand production, subsidence, and 'ice blockage' due to secondary hydrate formation, which reduces gas production efficiency and requires ineffective remote heating solutions.
Innovation Solution
A magnetofluid enhanced electromagnetic heating device and method using a coil assembly outside the casing pipe and a high-frequency alternating current generator to generate an alternating electromagnetic field, combined with ferromagnetic nanoparticles in the fracturing fluid, to prevent and treat secondary hydrates by directly heating the reservoir sediment around the well.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If depressurization method is used for hydrate exploitation, then exploitation efficiency is improved, but secondary hydrate formation occurs causing ice blockage
Solution Approach 1:
Ferromagnetic nanoparticles are injected into the reservoir before exploitation to prepare the heating system in advance. When secondary hydrates form, the pre-positioned nanoparticles can immediately be activated by electromagnetic fields to generate heat and prevent blockage, rather than waiting to deploy heating equipment.
Solution Approach 2:
Ferromagnetic nanoparticles serve as an intermediary substance that converts electromagnetic energy into thermal energy in situ. The nanoparticles are injected into the reservoir and remain dormant until needed, then act as a mediator to transfer energy from the electromagnetic field to the surrounding sediment and hydrates, preventing secondary hydrate formation without requiring direct contact heating equipment.
2Reliability
If electric heating or microwave heating is used inside wellbore, then wellbore hydrates are prevented, but heat cannot reach reservoir sediment outside wellbore
Solution Approach 1:
Ferromagnetic nanoparticles act as an energy transfer intermediary that can be distributed throughout the reservoir sediment beyond the wellbore. When exposed to electromagnetic fields, these nanoparticles generate heat locally within the reservoir, extending the heating coverage area without requiring physical heating equipment to be positioned outside the wellbore.
Solution Approach 2:
The patent replaces conventional mechanical or electrical heating systems (which are confined to the wellbore) with an electromagnetic field-based heating system using ferromagnetic nanoparticles. This substitution allows thermal energy to be generated distributed throughout the reservoir sediment, significantly expanding the effective heating area beyond the wellbore constraints.
3Reliability
If inhibitor is injected to prevent secondary hydrates, then wellbore hydrate inhibition is improved, but inhibitor cannot reach reservoir outside wellbore due to pressure differential
Solution Approach 1:
Ferromagnetic nanoparticles serve as a thermal mediator that can be easily transported into the reservoir with fracturing fluid, overcoming the pressure differential barrier that prevents inhibitor injection. Once in place, these nanoparticles provide thermal management by generating heat through electromagnetic excitation, extending the effective coverage area to the entire reservoir zone without requiring high-pressure inhibitor injection.
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 solution effectively prevents secondary hydrate formation, maintaining open pore channels and enhancing gas hydrate exploitation efficiency by directly heating the sediment, reducing the risk of 'ice blockage' and improving continuous production.
Implementation Method 1
a coil assembly and a high-frequency alternating current generator outside the casing pipe are used to generate an alternating electromagnetic field
Implementation Method 2
the alternating electromagnetic field directly acts on ferromagnetic nanoparticles to heat the sediment around the well
Implementation Method 3
magnetofluid enhanced electromagnetic heating device... ferromagnetic nanoparticles in the fracturing fluid... directly heating the reservoir sediment around the well
Data Source
AI summary
A magnetofluid enhanced electromagnetic heating device and method for preventing and treating secondary hydrates around a well are provided. When exploiting natural gas hydrates by depressurization, secondary hydrates or ice can form due to the decreasing temperature around the well, so that gas migration in sediment is blocked, and the gas production is reduced. According to this disclosure, a coil is arranged outside a casing pipe to generate an alternating electromagnetic field radiated to sediment. As a result, magnetite nanoparticles naturally contained in the sediment generate magnetothermal effect to heat the sediment. Additionally, the magnetofluid containing the ferromagnetic nanoparticles can be injected together with fracturing fluid during hydraulic fracturing of the reservoir, so that the magnetothermal effect of the sediment is further enhanced. Thus, secondary hydrates or ice can be prevented from forming around the well so that the exploitation efficiency of natural gas hydrates is improved.