Page 309 - Practical Well Planning and Drilling Manual

Section 2 revised 11/00/bc 1/17/01 12:04 PM Page 285

Formation Evaluation [ ]
2.8.2

area that the bit has to cut, improves ROP, and minimizes the likeli-
hood of the core jamming.
Planning considerations. To give the best chance of a success-
ful coring job, all phases have to be carefully planned. If this is not
done then the required information may not be obtained and more
cores may have to be taken on future wells at high cost. Planning
actions include:

Producing specific action plans and checklists
Reviewing the plans with all concerned personnel
Assigning responsibilities to specific personnel

Points to cover during the planning stages that may need answer-
ing before the program can be finalized include:

Objectives and justification

1. Which formations should be cored?
2. Has a list been created of the client departments requiring infor-
mation from the core, as well as the information each client wants?
(Do not forget to include drilling. It may be that a core includes
nonreservoir material such as shales, and analyzing it could bene-
ficial.)
3. Can the required information be obtained through cheaper alter-
natives rather than full-hole coring? (e.g., wireline logging, side-
wall coring [rotary or explosive], cuttings analysis)
4. What are the criteria for coring? (e.g., on shows, after penetrating
a particular marker)

Methods of coring

1. Is the core likely to be unconsolidated, fractured, or otherwise dif-
ficult to core?
2. What type of coring system will give the best chance of obtaining
all the information needed?
3. If special techniques are called for (e.g., pressurized coring, orient-
ed), is the equipment available in this country and at what cost?
4. Are there any special requirements for the bit, core catcher,

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