Wellbore Casing in Salt Formation Creep
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Solution Overview
Problem
Salt formations exhibit viscoelastic creep behavior, leading to wellbore closure issues during drilling due to continuous deformation under pressure, which conventional mud methods fail to prevent, necessitating frequent casing setting operations.
Innovation Solution
A method combining in-situ stress measurements, laboratory experiments, and creep model calibration to estimate a time window for setting wellbore casings by calculating overburden stress and integrating multiple analytical models with laboratory data to determine the optimal mud weight and casing setting time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mud methods are used to maintain wellbore stability, then the mud pressure can initially support the wellbore, but the wellbore diameter gradually reduces due to salt formation creep
Solution Approach 1:
The patent applies preliminary action by calculating the creep rate and time window before drilling operations begin. The method determines the optimal casing setting time window in advance based on predicted salt formation creep behavior, allowing operators to plan and execute casing setting within the stable period before wellbore closure occurs
Solution Approach 2:
The patent implements feedback by continuously monitoring wellbore diameter changes and comparing actual creep rates with predicted values. This feedback mechanism allows operators to adjust drilling parameters and casing setting timing based on real-time observations of salt formation deformation behavior
2Productivity
If drilling operations continue in salt formations without predicting creep behavior, then drilling can proceed, but additional drilling operations are necessary due to wellbore closure
Solution Approach 1:
The patent calculates the time window for safe drilling operations and casing setting before drilling begins. By predicting the creep rate and determining when wellbore closure will occur, operators can complete all necessary operations within the calculated time window, avoiding the need for additional drilling operations to restore wellbore diameter
3Loss of time
If accurate time window estimation is implemented, then casing setting can be timed optimally, but complex calculations and model calibration are required
Solution Approach 1:
The patent introduces creep rate as an intermediary parameter that simplifies the complex relationship between salt formation properties and wellbore closure. By measuring creep rate in the laboratory and using it as a key input parameter, the method avoids the need for complex numerical simulations while still achieving accurate time window prediction
Solution Approach 2:
The patent transforms the complex multi-parameter creep problem into a simplified model by identifying and focusing on the most critical parameters: creep rate, wellbore diameter, and time window. This parameter reduction allows for practical field applications without requiring complex computational resources
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 provides an accurate time window for casing setting, reducing the need for additional drilling operations and maintaining wellbore stability by correlating creep behavior with quantitative analysis, thus enhancing drilling efficiency and reducing costs.
Implementation Method 1
Salt formations exhibit viscoelastic behavior making them continuously deform under pressure even if they are initially stable. This deformation is called creep and occurs over time once the salt has been disturbed into a non-hydrostatic stress state.
Implementation Method 2
Salt formations exhibit viscoelastic behavior making them continuously deform under pressure even if they are initially stable.
Implementation Method 3
The overburden stress can be calculated based a density profile of the overlying layers.
Data Source
AI summary
A method for setting a wellbore casing in a subterranean formation is described. The method includes: drilling a test wellbore in the subterranean formation; generating a density profile of a plurality of geological layers above a salt formation in the subterranean formation based on observations from the test wellbore; calculating an overburden stress imposed on the salt formation by weight of overlying formation based on the density profile of the plurality of geological layers; performing creep mechanical behavior tests on core samples from the salt formation to generate a strain-time curve for the salt formation; calibrating multiple analytical creep models with mechanical properties of the salt data generated by the creep mechanical behavior tests; implementing a wellbore closure model based on a best-fit analytical model and mechanical properties of the multiple analytical creep models; drilling a well; and setting a casing through the salt formation.