Convective SAGD Well Pair with Variable Annular Resistance
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Solution Overview
Problem
Conventional Steam Assisted Gravity Drainage (SAGD) processes face challenges in achieving uniform fluid distribution and heat transfer due to non-condensing gases and pressure differences along wellbores, leading to inefficiencies in hydrocarbon recovery from viscous reservoirs like oil sands.
Innovation Solution
The implementation of a well pair configuration with complementary axial fluid resistance profiles in the injection and production wellbores, utilizing telescoping tubing and varying annular resistance to fluid flow, which enhances both gravity drainage and convective displacement, effectively managing fluid distribution and non-condensing gas removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If steam is injected into the overlying horizontal well to heat and mobilize bitumen, then hydrocarbon recovery is improved, but non-condensing gases interfere with heat transfer between steam and bitumen
Solution Approach 1:
The patent extracts and removes non-condensing gases from the reservoir through vent wells before implementing SAGD. This extraction eliminates the harmful interference of non-condensing gases with steam-bitumen heat transfer, allowing efficient thermal recovery to proceed without gas blockage.
Solution Approach 2:
The patent performs preliminary gas removal through vent wells prior to the main SAGD operation. By removing non-condensing gases in advance, the subsequent steam injection can proceed efficiently without encountering gas interference that would impede heat transfer.
2Productivity
If horizontal wells are made long (700 to 1000 meters) to restrict flux and achieve commercial rates, then productivity is improved, but pressure differences along the wellbore cause non-uniform fluid distribution and hot spots
Solution Approach 1:
The patent applies local quality by varying the annular cross-sectional area at different locations along the horizontal wellbore. The annulus is designed with different flow characteristics at the heel, toe, and intermediate sections to compensate for pressure differences and achieve uniform fluid distribution throughout the entire well length.
Solution Approach 2:
The patent changes the geometric parameter of the annular cross-sectional area along the wellbore length. By progressively varying this parameter, the system compensates for axial pressure gradients and ensures uniform steam-bitumen contact and heat transfer throughout the well.
3Use of energy by moving object
If the annular cross-sectional area is varied along the wellbore to achieve uniform fluid distribution, then heat transfer efficiency is improved, but the wellbore configuration becomes more complex
Solution Approach 1:
The patent employs a telescoping tubing arrangement that allows the annular cross-sectional area to vary dynamically along the wellbore. The telescoping mechanism enables progressive expansion or contraction of the annulus at different locations, providing uniform flow distribution while maintaining a relatively simple overall wellbore structure.
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 improves hydrocarbon recovery rates and energy efficiency by ensuring uniform fluid distribution, reducing hot spots, and effectively removing non-condensing gases, resulting in a superior cumulative steam-oil ratio and oil production compared to conventional SAGD methods.
Implementation Method 1
steam is injected into the overlying horizontal well on an ongoing basis. Due to density difference, the steam tends to rise and heat the oil sand, and thereby mobilizes the resident bitumen.
Implementation Method 2
The mobilized bitumen is denser than the steam, and tends to move downward towards the underlying horizontal well from which it is then produced.
Implementation Method 3
The operation of a well pair thus configured results in a recovery process that includes the benefit of a gravity drainage mechanism, while also including a significant component of convective displacement.
Data Source
AI summary
The present disclosure describes a recovery process using injector and producer wells, each well having means for varying the axial resistance to fluid flow to provide a complementary first and second annular axial fluid flow resistance profile. The recovery mechanism includes a gravity drainage component and also includes a convective flow mechanism which operate concurrently.