Ways to Identify Bypassed Pay From DST Data
16 Ways To Identify Bypassed Pay From DST Data
2 Day Workshop
INSTRUCTOR: Hugh W. Reid, P.Geol.
This course arose out of the demand from past students at Hugh Reid's courses for a "quick refresher" on DSTs, plus a detailed focus on the many different ways to identify bypassed pay.
Most people believe that when potential pay is missed or bypassed because of pessimistic DST results, it is due to formation damage. However, there are numerous other reasons for overlooking pay from DST results and sixteen of these are detailed below. Students will learn how to prospect for these using case histories and field examples.
16 Specific Reasons Why Potential Pay is Overlooked From DST Results:
1. Mud only produced on test, so formation content unknown. This can be due to either:
2. Water produced from below test interval in straddle test (lower packer failure not recognized).
3. Simple "skin" damage.
4. Deep Damage (zone mistakenly identified as tight).
5. Filtrate invasion in zones - resulting in large volumes of "water" recovered mistaken as formation water.
6. Gas block in low kh oil zones or rocks with certain pore geometry ("s" curves).
7. Test tool off depth (fill is problem in conventional straddles).
8. Tool plugging obscuring zone content or reducing flow rate.
9. False depletion (wrongly abandoned).
10. Misruns not tested.
11. Misleading recoveries from DSTs with several tests carried out on a single trip in the hole (Multiple Resets).
12. "Tight Hole" tests run in the fifties/sixties for security, where the tight chamber volume was sized too small to recover anything but rat hole mud.
13. Incorrect positioning of tool perfs far below or above porosity, so only mud recovered.
14. Water cushions obscuring low rate gas in deep hot wells.
15. Imbibition and resulting water block in deep basin type reservoirs with large gas columns, identified as "filtrate flow back" signature on DSTs (first recognized by Murray Grigg).
16. Incorrect Reservoir Analysis. Erroneous interpretation of Horner Plots, eg. linear flow wrongly interpreted as depletion.
Course Outline / Schedule
Brief Review - The course will open with an hour's review of basic DST chart interpretation. "Refresher" topics include permeability types, well bore damage and depletion.
Prospecting for Bypassed Pay - This will be followed by a detailed focus on each of the reasons why potential pay may be overlooked, including field examples and a case history for each.
As usual a detailed manual is provided with numerous annotated DST charts and associated well data. In cases where wells have been re-drilled or twinned, the completions and production histories are provided to compare to the old DST.
Some DST Experience Required
It is a requirement that all registrants to this course have attended Hugh's basic week-long DST course or similar seminar. For each method of identifying bypassed pay covered there will be a brief 'refresher' of the appropriate DST skills necessary. This will ensure those who are 'rusty' in the subject are brought up to speed; however, this is not enough for those who are new to the subject. This course is not a substitute for Hugh's fundamental DST interpretation seminar.
Comments from Past Participants
"Great course. Well worth my time. Giving example bypassed DSTs that led to significant discoveries was eye opening."
Martin Buscheau, Exploitation
"Excellent course. I will recommend this to my colleagues - very useful in looking at the many DSTs in my area."
Scott Doyle, Geologist
"Best course I have ever taken, very worthwhile. I learned more than I could have hoped."
Mathew Cugenet, Geologist
December 2001 Course Brisbane, Australia (Host Pesa - Petroleum Exploration Society of Australia) (1/4 of this class travelled from Papua, New Guinea)
© 2009 Hugh W. Reid & Associates Ltd.