FE 02-16F Collecting a Sample

Nội dung text: FE 02-16F Collecting a Sample

1. Sampling and Cuttings Analysis • Reasons for sample collection and shipping • Sample Intervals • Sample Types • Sample collection and preparation • Cuttings examination • Sample description
2. Sample Intervals • Set by the client • Common intervals: 5 feet to 30 feet • Regardless of the sampling interval, under no circumstances should the mudlogger neglect their other responsibilities • Other times that the sample interval should be shortened: – During coring – 1 ft or 0.5 meter intervals – Areas of geological interest – Changes in drilling parameters (drill breaks / reverse drill breaks, torque changes) – Changes in mud properties (viscosity, cut MW, chlorides, etc) – Changes in gas content
3. Sample Collection • Install a sample collection board at the base of the shaker • Try to collect from the shaker with the smallest mesh size • Samples are taken at regular intervals specified by the client • Samples should be taken when changes in ROP, background gas or any other parameter is noticed • Regularly check desander and desilter for samples • When sampling in smaller intervals than required, the sample bags should be progressively filled up • Clean the sample board after a sample is taken
4. Sample Preparation • In clayey areas, care must be taken to wash away as little of the clay as possible. • When determining the sample composition, take into account any clay that may have been washed away • Samples are washed through at least 2 sieves (80 or 120 mesh at the bottom and 8 mesh on top) • Cuttings left on the 8 mesh sieve are considered to be cavings • A sample of these cavings should be placed on the sample tray for observation
5. Importance of Cavings • An increase in the amount of cavings this could indicate an unstable hole • Cavings with splintery, concave appearance may indicate increasing formation pressure • If the cavings are of the same lithology, then by reviewing the mudlog, areas of washouts or hole problems can be pinpointed
6. Catching an Unwashed Sample 3. Clean the sample board to allow fresh samples to accumulate. 4. Hang the closed cloth bags to air dry. It is preferable that the site where the bags would be hanged is sheltered. 5. When the samples have been sufficiently dried, place them into a cardboard box. 6. When the box is full, write down the interval of the samples in the box. You can also write down the number
7. Preparing Samples Where Oil Based Mud Is Used
8. Preparing and Bagging a Wet and Dried Sample 3. Remove the No. 8 sieve; slightly rinse the accumulated sample in the fine sieve of excess mud. 4. Use a metal tray to scoop a sample. Fill the tray with sample. Leave some sample for lithological and hydrocarbon analyses. 5. Place a sample tag on the tray.
9. Preparing and Bagging a Wet and Dried Sample 8. Place the tray into the plastic mud cup or similar container. Scoop out the samples into the cup. 9. Place envelopes into marked brown Kraft clasp envelopes. 10. Place the envelopes into the corresponding white cardboard boxes.
10. Samples for Lithological Evaluation 2. Lean the tray against the wall or splashboard of the sink to let the excess water drain off 3. If there are cavings in the coarse sieve, include a representative sample in the metal tray 4. Place a tag on the sample tray
11. Geochemical Samples 4. Add four drops of bactericide to the can. ILO uses Zephiran Chloride. • If Zephiran Chloride is not available use: – Alkylbenzyldimethylammoniumchlorid: solid Alkylbenzyldimethylammoniumchlorid is to be liquefied in warm water and diluted with hot water to obtain a saturated solution (4 drops per can) – Any algaecide or bactericide used for swimming pools (4 drops per can) – Copper sulfate (saturated solution), 10 ml – Rubbing alcohol (isopropanol), 10 ml – Chloroform, 5 ml (last choice)
12. Metal Shavings Samples • Pull out the ditch magnets • Use a non-magnetic scraper (wood or plastic) to initially scrape the majority of the metal shavings from the magnet/s. Scrape the magnets clean by using one hand with extra protective equipment, rubber gloves and safety glasses. This should be done slowly so as not to cause hand injuries. Place the metal shavings in a bucket.
13. Cuttings Examination • Samples are examined under the microscope for: – Lithology – Oil staining – Porosity • Objective: – To depict changes of lithology and appearance of new formations
14. Cases Where Unrepresentative Samples Occur • Evaporite sections drilled with water-based muds • Drilling soft clays/shales • “Rock flour” due to high speed drilling • “Burning” of cuttings while drilling with diamond bits