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Pumping alignment for Formation Integrity Test
05 August 2016
Hi all, 
What are the positives and negatives to perform formation integrity test pumping thru both drill pipe and annular, if the line up allow you to do so?? What is the benefit against pumping only thru the drill pipe-BHA. 
Thanks


2 answer(s)
Dennis_in_Oman
Ops Coordinator
SPREADAssociates
Total Posts: 5
Join Date: 16/03/16

I do not see the name of the person asking the question here in this posting - but using simpler logic than Peter used above I will say:

Normally when we clean out a well or Drill a Shoe track or hmmmmm what else can we be doing before we need to do a LOT/FIT or what was it Peter XFIT?

I would say in nearly all cases we pump down our DP or Tbg or what ever we have for a Work String to do the cleaning of the well bore prior to an FIT

We would also want to have the Fluid In  SG/PPG and Fluid Out a very similar Value - We will be able to measure & know very well the Fluid SG  we put into the well and be able to calculate the Hydrostatic pressure this Fluid will create.

So I would think that the practical method would be:

1) Circulate the Work String & Annulus until they are close to same weight of Fluid.

2) SI the BOP on the Work string & begin a Physically measured volume, low rate of  pressure build up pumping down the Work String (some areas & Rigs     have a Special Pump about the size of your Triplex Accumulator pump so to assure a small & consistent volume per minute) - this pressure up will be monitored on a freshly Calibrated or Dead Weight tested Chart recorder.

3) Monitor the Pressure BU on the Annulus (with a Second Chart Recorder if available) to be able to compare (in the end) Clean Fluid with Dirty Fluid effect on the Hydrostatic - (at least 1 DWTested Chart Recorder or Pre-calibrated Pressure Gauge double checking the Main Chart Recorder & pressure gauges on the Pump/Work String.

 My mind goes to the usually smaller volume of the Work String & the normally cleaner (more pure) Fluid leaving surface right from the Rig Tanks to pump to standpipe to pipe in the well - which normally will have been happening for some time (maybe even several hours). I would think we should feel more comfortable that we have a cleaner environment by using the Work string for the LOT volume wise on the whole well it should be very much the same forward or reverse (RH or LH).

The cleaner Fluid should also give a more pure answer than Annular Fluid being pumped towards the Formation of interest.

Depending on the area and the formations needing the FIT we could also be looking at displacing the work string to water & over displacing the heavier fluid on the back side to ensure cleanest possible fluid into the Formation of interest - but this would be more complicated & not necessary in most cases one would think. . .

Best Regards & Wishes

Dennis_in_Oman





Companyrep
Drilling Specialist/Well Engineer/Training Consultant
Kingdom Drilling
Total Posts: 360
Join Date: 10/01/05
note: I have seen company documents ranging from 1page to 20pages w.r.t supporting best practice methods to performing leak off tests. For this reason every case should be reviewed on its merits and often should not be treated as same as! There is only one way, i.e. the right way! Engineers surely having to assess what this is.

I suggest one first draws a schematic of the system in use illustrating all the physical and evident factors present. 
Then review each case on its needs, merits and requirements. 

Is a FIT / LOT / or XLOT required?.

What is the rig standpipe and cement pump configurations.
note: This at times drives the preferred and/or only method that can be used.

Casing shoe depth and size, volume to be compressed?
How many barrels are you expecting to pump to the desired expected value? These pre-calcs are important to assess

What is the Mud weight in use, expected fracture gradient and operating margins present?

Consider Pumping down the string only (for float fitted or not)
Is there a PWD in string?

Then pump down both string and annulus (surface BOP/subsea BOP)

Water based / oil based system?

Company policy is hesitation, continuous or extended leak off method?

Testing clay? sand or limestone formations? 

In summary too often we see 'same as' with few of the above factors given enough due consideration or MOC change process by engineers to assure we "do the right things to get it right first time."

Sometimes based on all of the above we pump down the string.
Other times e.g. offshore, deepwater, the safest, most effective and efficient method is to pump down through the string and choke and/or kill lines.

Why we may do it one way or another

If hestitation method is required? pumping down the string (with a float) will not work.

Water based mud, small casing volume, pressurisation to leak off only a few barrels? In this case pumping both ways gives us a bigger volume to compress where event at a low pump rate (cement equipment dependent) one may only get a few points on our graph before leak off occurs.

Validating a cement plug via a cementing string (down the string only agains a closed BOP( often suffices.

So its horses for courses I'm afraid, where I am sure other will add more valid best practice 'physical evidence' points of value.  









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