This document provides the outline of coring standards and practices. It identifies the company’s minimum standards and specifies general practices that enable the planning, safe and successful execution of coring operations.
1. Coring operations shall only be carried out if well conditions are good enough to contemplate coring. The COMPANY Well Operations Supervisor and Superintendent shall have authority to make this decision.
2. The COMPANY Well Operations Supervisor shall be in overall charge of all coring operations.
3. The Well-site Geologist shall have the authority to choose the depth where coring operations commence.
4. Instructions to commence coring operations that are additional to those provided in the Well Programme shall only be issued by the Well Operations department.
5. The COMPANY Well Operations Supervisor must ensure that the drill string has been drifted to allow the core ball and circulating sub ball to drop through freely.
6. When the presence of H2S is suspected, the personnel shall be equipped with breathing apparatus and H2S detectors before the core arrives on surface.
7. Core barrels equipped with gas relief devices must be used when coring gas reservoirs especially in HP/HT conditions.
8. Intermediate circulations shall be detailed in the coring programme.
9. The use of a compatible flapper valve is compulsory and should be positioned as close as possible to the core barrel.
10. Note: These flapper valves has to allow passage for the core ball.
11. On/off bottom circulation pressures and pick up/slack off weights will be recorded prior to coring. SCR's will be recorded prior to commencing to core, both prior to and after the ball is seated.
12. For HP/HT wells, special coring procedures have to be detailed in a specific programme. They shall cover:
a. Temperature effect on coring equipment
b. Tripping speeds to avoid swab/surge effects
c. Tripping speed for allowing the gas to bleed from the core.