Undersea Hydrate Well Layout for Faster Depressurization Extraction
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Solution Overview
Problem
Conventional offshore drilling methods for natural gas hydrates are costly due to long drilling cycles and high platform operating costs, and are inefficient due to low permeability and shallow burial of hydrate reservoirs, leading to slow heat transfer and low production rates.
Innovation Solution
An undersea in-situ exploitation method involving a well pattern layout based on simulation models, using a vessel to deploy equipment for drilling, completion, and depressurization to decompose hydrates, without a drilling platform, employing casing drilling and remote operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional offshore drilling methods are used for natural gas hydrate exploitation, then drilling can be performed using existing technology, but the drilling cycle is long and operating costs are high
Solution Approach 1:
The system divides the drilling operation into modular components: a drilling device with multiple drill bits, a completion device with completion pipe string, and a wellhead device, all deployable from a single vessel. This segmentation enables parallel operations and reduces the overall drilling cycle while maintaining reliability through standardized modular units.
Solution Approach 2:
The drilling device is equipped with pre-installed drill bits and the completion device has pre-assembled completion pipe strings ready for deployment. The wellhead device is pre-positioned on the seabed before drilling commences, allowing immediate drilling operations without setup delays, thus shortening the drilling cycle.
2Reliability
If conventional offshore platforms are used for hydrate exploitation, then stable operation can be achieved, but platform operating costs are huge
Solution Approach 1:
The invention extracts the essential drilling and completion functions from the expensive conventional offshore platform structure. The drilling device, completion device, and wellhead device are deployed as separate modular units from a vessel, eliminating the need for a permanent platform while maintaining operational stability through controlled deployment and retrieval mechanisms.
Solution Approach 2:
The system uses temporary, deployable drilling and completion devices that can be rapidly deployed and retrieved from a vessel, replacing expensive permanent platform infrastructure. These modular devices are designed for specific operational campaigns rather than permanent installation, significantly reducing capital and operating costs while maintaining reliability during active exploitation.
3Productivity
If well spacing is reduced to compensate for low permeability, then commercial production can be achieved, but the number of wells increases dramatically
Solution Approach 1:
The drilling device is designed as a universal platform capable of drilling multiple wells with different configurations (vertical, inclined, horizontal) using the same equipment. The completion device can be adapted to various well types and the wellhead device serves multiple wells, allowing dense well patterns to be implemented without proportionally increasing overall system complexity.
Solution Approach 2:
The system employs dynamic well pattern optimization where the drilling device can adjust drill bit orientation and trajectory in real-time based on reservoir characteristics. The completion device can be reconfigured for different well types, and the wellhead device can accommodate varying production rates, allowing the system to adapt to dense well patterns without fixed complexity constraints.
4Productivity
If heat transfer rate is increased to improve decomposition rate, then gas production rate increases, but the effective mining radius remains limited by low permeability
Solution Approach 1:
The system transitions from vertical drilling to multi-dimensional well patterns including inclined and horizontal wells. This dimensional change allows the drilling device to access reservoir areas that would be unreachable with vertical wells alone, expanding the effective mining radius by utilizing lateral and inclined trajectories to reach distant hydrate deposits while maintaining high gas production rates through enhanced heat transfer.
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
Reduces exploitation costs and increases efficiency by transferring drilling equipment to the sea, allowing denser well patterns and faster well construction, improving output and reducing risks.
Implementation Method 1
start a depressurization exploitation process to reduce the pressure at the reservoir depth to decompose natural gas hydrates in the reservoir into gas and water
Implementation Method 2
decompose natural gas hydrates in the reservoir into gas and water
Data Source
AI summary
A method for undersea in-situ exploitation of natural gas hydrates is provided. The method includes: obtaining a well pattern layout diagram of a natural gas hydrate exploitation block based on a natural gas hydrate simulation exploitation model; carrying an undersea in-situ exploitation system to a target sea area using a ship configured to deploy deep-water equipment, selecting the well location according to the well pattern layout diagram; lowering a drilling device using a casing drilling technique; lowering a completion device, lowering a completion pipe string into the well, and connecting the completion device to an undersea wellhead to perform completion operation; and lowering the wellhead device, connecting the wellhead device to the completion pipe string, connecting the wellhead device to a production pipeline, and starting a depressurization exploitation process to reduce the pressure at a reservoir to make gas and water flow into the production pipeline to be extracted.