In order for hydrocarbon exploration and production - wells have to be drilled.
In exploration and appraisal phase well locations are decided by interpreting seismic, gravity, and magnetic data. This interpretation helps build initial estimate of the subsurface geological model -Structural framework plus rock properties.
In development phase well locations are decided by using geological model derived from continuously increasing data plus reservoir simulation which uses the geological model and production history data.
Once the location of well has been decided then first step is to come up with drilling plan for the well. And wellbore stability analysis is key component of well drilling plan.
There is no acquired well data at the well location to be drilled. But there are some estimates from the geological model. So to do wellbore stability analysis for proposed well location -following is done:
- Do post drill wellbore stability analysis at nearby well locations.
- Using Geological model derive some guestimate of relevant log data onto proposed well location
- Do predrill wellbore stability analysis at proposed well location
- As the well is drilled and actual data starts becoming available - refine the wellbore stability analysis using data from drilled section to improve the analysis for undrilled section
Below are the steps involved in postdrill wellbore stability analysis for a single well:
- Data Loading, validation, editing and QC
- Overburden Stress computation
- Pore pressure computation
- Rock properties computation
- Horizontal stress computation
- Fracture Gradient computation
- Vertical effective stress computation
- Wellbore stability analysis
- Wellbore stability sensitivity analysis
Next post will be about Step 1. Stay Tuned.
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