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Well's offset data analysis
27 January 2014
Now into a 4th project attempt to best collate and analyse a project's offset well's data. That is then used and applied to add value through the detailed well planning, design and operational phases of forthcoming well's.

I would be interested to discuss with others in this forum
- How/where offset data value is/can be added
- Do's and don'ts 
- Structure and content
- What else of value, benefits etc.

It's been interesting to note that the template we evolved in the 90's continues to improve, so all further knowledge and experience in this subject area to continue this evolvement is welcomed.
6 answer(s)
Augusto
Consultant [retired Shell staff]
SPREADAssociates
Total Posts: 244
Join Date: 02/09/05
I´m very partial to an audit of the old well design i.e. an in-depth "post mortem" comparing plan with actual and act on the "DELTA".

I like to do that on a Time x Depth chart of a reasonable dimension (like the size of your desk...) to be able to note the relevant details. As suggested, we should use data from the Daily Drilling Report - the data closer to the truth.
(In my almost 50 years of Oilwell drilling experience, only Esso/Exxon included copies of the Daily Drilling Reports in their end of well reports. All other Operators opt for summaries of summaries missing valuable information...)

Whenever practical, try to interview some of the players involved both in planning and in executing the plan.

The G&G people are the key to learn the lessons which can be applied to the next location.

Some operators design the wells too geometrically for may taste: "Drill to 2000 ft. Set casing" instead of "drill to geological marker "X" - expected around 2000 ft - and set the casing.
Scott_McNeil
Consultant
SPREADAssociates
Total Posts: 108
Join Date: 05/03/08

Hi Peter,

A lot depends on just how much offset info you have - I'm more used to 'frontier' drilling where offset info can be very limited, but the basics always boil down to:

A) Talk with the G&G people to find out which are the most valid offsets for the geological setting you are going to be in - this may not be the nearest well geographically.

B) A good mud log is worth it's weight in gold (incidentally, I've never seen a mud log tabulated by date instead of depth).

C) The Daily Drilling Reports need to be read by an experienced person, not a TA - "they round tripped from 2,000m to change the bit, but why did it take 12 hrs?". Also, if it's a more recent well where the time breakdown was coded - don't go by the codes, always go back to the original DDR as all too often the coding has been haphazardly applied. Software analysis can be very useful, but crud in = crud out.

D) While the more recent the well, the more complete and valid the data set, 'old' wells should not be ignored (I've gone back as far as a well drilled in the 1930's to get valuable information) as they can also provide valid insight into problems encountered and even things like seeing how casing designs have changed over time if there are several wells in the area.

E) Already mentioned, but worth repeating - try and validate the survey data, ESPECIALLY the actual surface location (including co-ordinate reference used) as in older Wells they may not actually be where you think they are (case in point, had to find a well in the Southern North Sea to P&A it. Drilled in the mid 1960's, we eventually found it about 1 1/2 miles from the posted location).

F) Already mentioned, but again worth repeating, if G&G haven't re-processed and analysed old seismic and E-Log data, they should do so.

Finally, if you have a lot of offset info, it can be easy to get drowned in information - make sure that the basics are focused on.

Thanks and Regards

Scott

Adebowale
Performance Drilling Superintendent
Maersk Drilling
Total Posts: 7
Join Date: 15/12/05
Some very good responses so far. It is good practice to validate your design with offset data.
I would like to add that having a record of the "lessons learnt" on offset well operations can be beneficial. Other offset data to consider are things like drilling parameters, casing, cement types, mud etc. You want to find out things like:
Casing: How were the casing setting depths selected? What grade of casing was used and why? Would the same be optimal for your application?
Cement: Type of cement slurries, What additives were used and why, Cementing problems, Cement height/tops (and why)
Mud: Mud properties per hole section, Loss rates, frequency and depths, type of LCM used etc

Ade
Ross.Bremner
Survey Focal Point
Enquest
Total Posts: 3
Join Date: 12/05/13
Hi Peter,
This is something that is vital for understanding your field.

From my perspective and background I would suggest that having the directional survey data QC'd. This will then allow you to import correctly into the various applications (COMPASS, Petrel, Kingdom etc) that you organization use is of paramount importance. All datasets will rely on this data as their starting point.
Two very import learning swill come out of havign a fully QC'd definitive survey dataset.
  • You will understand the trends across the field for directional limitations; top hole build, achiveable dog legs etc
  • For infil field wellplanning,  anti collision scaning is saftey critical.
This is just from the survey side of the project, but it is very important to get correct. Check out ISCWSA.net for further information.

Hope this helps

Ross
Ahmaid
senior drilling engineer
Kuwait Energy
Total Posts: 14
Join Date: 29/11/13
Dears,
Analysis of offset data is valuable for the following :
1. collecting electric logging data and perform the necessary computation, (Pore, Frac ) from Bulk density, sonic, resistivity will be helpful in interpretation of the problem occured like well control, losses, stuck due to shale problems.
2. Collecting Drilling data ( mud log, bit and BHA reports, directional reports) will be helpful in optmizing drilling performance.
3. revision of the DDRs will give insight of the well costs, well days, expected drilling problems.

a lot of data is available, but most of times we did not pay attention to more than 30% of this data. for me, I like to deal and handle the necessary calculations on electric log data for quantitative analysis.

Do's : you must perform quantitative approach.
Donot : Do not depend on what happened in the offset as solution is the only way to solve the problem.

Structure : Electric logging, mud loggin, IADC, Drilling reports, EOWR, Service company reports, keep archive.


Regards
Ahmed
Paul.Choate
Managing Director
SPREADAssociates
Total Posts: 8
Join Date: 17/08/13
Greater consistency of information provided by different contractors in offset well files would be helpful. Mud logs, for example, are very often tabulated according to date and not depth, so cross referencing mud weights with other contractor reports, such as BHA reports and logs etc, can be tedious and potentially introduce interpretation errors. Use of software applications that record and display all the information consistently is to be encouraged in my view.
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