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Drilling with real time pore pressure data

Thursday, June 5, 2014

Pore pressure data is a critical parameter for drilling, and it could be more useful if it was updated during the drilling process, making more use of the large amounts of data generated. Eamonn Doyle of Ikon GeoPressure explained how it works

Knowledge of pore pressure is critical during drilling of a well, to help drill safely and cost-effectively..

Drillers are given a pore pressure estimation, or estimation range, before they start, based on the seismic data or data from nearby ('offset') wells. This information is used to plan mud weight and the casing plan.

But the pore pressure estimate will always contain uncertainties - the rock properties can be different to the offset wells, stratigraphic uncertainties are always present, and the seismic data might not have been processed with pore pressure calculations in mind.

'Pore pressure prediction estimation is considered a black art,' said Eamonn Doyle, vice president of real time operations with Ikon GeoPressure, a UK company specialising in helping companies understand rock's physical properties, speaking at Digital Energy Journal's February 20 Aberdeen conference, 'using data to improve well integrity'.

The more complex the geological environment the less certain your pore pressure and fracture gradient predictions are, he said.

But there is a lot of data generated during the drilling process which could be used to update the estimate of pore pressure, and it makes sense to use it.

Expertise

To get better pore pressure estimate while drilling, gather as much relevant data as possible from the drilling process and make it available in realtime to a team of geoscience and rock physics experts, he said. 'You have to bring the whole team in to make sure all sides of the problem are looked at.'

Ikon GeoPressure, Mr Doyle's company, offers a service to provide experts who can look at real time data during the drilling process and provide frequent updates of the pore pressure estimate and prediction ahead of the drillbitneeds to be changed.

Useful information includesdrilling parameters,, gas and gas peak data, , mud logs, analysis of rate of penetration, logging while drilling (LWD) and wireline data such as gamma ray, resitivity and sonic, , and information about the well condition and how it changes during drilling.


'All these things are valuable information that needs to be made use of,' he said. 'You end up with a cloud of data, resulting from the various quantitative calculations, that can be calibrated using the other pieces of information.'

One main obstacle to more pore pressure services is that pore pressure experts are often in the geoscience part of the company, and the drilling budget is held by the drillers. So geoscientists need to make an argument to the drillers as to why they should pay for having a better pore pressure estimate.

To do pore pressure monitoring properly, you might also want to put geoscientists on the wellsite, which adds to the upfront expense.

Benefits

Having a good understanding of pore pressure is extremely valuable. Studies of Gulf of Mexico data have estimated that pore pressure related problems can cost an average of $2m-3m per well, he said.

In another example, the Operator of a North Sea deepwater well estimated that it had saved $7m from updating pore pressure data during drilling, mainly because it avoided having to run a contingency liner.

Having better information about pore pressure of the rock you are about to drill into can prevent kicks, which means that the pressure of fluids in the formation (pushing into the well) is greater than the pressure of the drilling mud pushing outwards from the well, causing the fluids to enter the wellbore and creating potentially dangerous situations.

Pore pressure problems can cause the drill pipe to get stuck, or even to twist off. With better pore pressure knowledge, you are better equipped to avoid, or deal with, drilling problems. ,. You can also avoid using time for checking the relationship between the drilling mud weight and the pore pressure (the amount of 'overbalance' in the wellbore). A typical offshore operation costs$40-50,000 per hour and therefore a saving of just a few hours over the course of a well can pay for the realtime monitoring service

Having better pore pressure information can help you make decisions about when you should set intermediate casing and start drilling again at a narrower diameter. The more complex the well is, the more critical it is to get this decision right. There are also only so many stages of narrower diameter casing you can use, and you have to make sure you don't use them all up before you reach the target.

With better pore pressure data, you are less reliant on logging while drilling data - so if there is a failure with a sensor it isn't so much of a problem - you may be able to drill ahead thus avoiding an expensive 'trip' to change out the failed equipment.

When monitoring both depth- and time-based data you have the chance to predict, and thus avoid, impending drilling problems such as drillstring washouts and poor borehole cleaning, which can lead to costly downtime and in the worst case loss of the borehole.


Many well experts believe that all well control events are predictable and avoidable with use of the right data at the right time, Mr Doyle said.

You can watch Eamonn Doyle's talk on video and download slides at
http://www.digitalenergyjournal.com/video/918.aspx




Associated Companies
» Ikon GeoPressure
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