1. According to formation characteristics, reservoir characteristics, cementing technology and quality requirements of cementing, scientifically and reasonably prepare cementing construction design.
2. Aiming at the special features and difficulties of natural gas well cementing, select cementing tools and string accessories with superior performance and reliable quality to ensure normal, smooth and safe on-site construction.
3. Requirements for the preparation of borehole and drilling fluid before cementing: a. Plugging and water treatment for the easy-to-leakage and water out of the formation to improve the bearing capacity of the formation and ensure the quality of cementing. b. Requirements for the drilling fluid before the completion of cementing are low viscosity, low dynamic-plasticity ratio, and thin and tough mudcake, which can satisfy the requirements of cementing. c. Requirements for the preparation of drilling fluid before the completion of cementing are as follows
4. According to the quality of the borehole and the downhole condition, control the circulation time appropriately, and do not circulate for a long time to ensure the safety of the well.
5. Select the best cement paste system and tubing string accessories, optimize the performance of cement paste, tubing string structure and field construction parameters, strengthen the borehole preparation and borehole purification before lowering casing, and adopt reasonable jacking technology to improve the jacking efficiency, so as to ensure the smooth lowering of the casing and the quality of cementing.
6. Before lowering casing, the well must be passed carefully and meticulously to ensure the safety of the well and the smoothness of the borehole, and the well should be passed with large joints or undersized stabilizers to prevent obstruction of casing and stuck drilling, and the gas layer section should be paddled repeatedly in order to remove the mud cake on the wall of the well, circulate the diluted slurry sufficiently, and wash the well in large volume to ensure the smoothness of the borehole without leakage, well collapse, and the bottom of the well without sand sinking.
7. Floating shoes, floating hoops and grading hoops used should be carefully checked before lowering the casing to ensure the normal use of the accessories, and the grading hoops are strictly prohibited from collision when buckling with the casing tongs. Should borrow the last casing to transfer torque, to achieve the standard torque value and torque diagram on the buckle. Shall not bite the body of grading hoop with casing pliers. 8.
8. Conduct casing operation in strict accordance with the casing operation procedures, carefully check the cementing tools and string accessories, and reasonably put the correcting device to ensure that the casing centering degree is ≥67%. Principles of placing the correcting device: a. Add a set of correcting device below the floating hoop; b. Add a correcting device for each section from the floating hoop to the bottom of the lowest gas layer; c. Add a correcting device for each section at the top of the lowest gas layer and the bottom of the uppermost gas layer avoiding the gas layer; d. Add a correcting device for each section from 0 to 50 meters, and add a group of correcting devices for each section from 50 to 150 meters, and add a group of correcting devices for every section from 150 to 300. e. Place correcting devices before and after grading hoops, and ensure that the centering of the casing is ≥67%; e. Add 5 groups before and after the grading hoop, add one group of rigid correctors at the wellhead, and add one group of correctors for every five casing in other sections, paying special attention to the elastic correctors that must be added at the connecting hoop.
9. The lower casing must be smooth. If there is a leakage to strictly control the speed of lowering below 30 seconds / root, in general, in 15 ~ 20 seconds / root, not allowed to lift, put, brake, should ensure the stability of the borehole, no well surge, blowout, well leakage and well collapse.
10. Pass the inner diameter of casing in the well site, it is strictly prohibited to pass the inner diameter of casing in the drilling platform, clean the casing threads with detergent and check whether there is any damage to the sealing surface, the casing pliers with torque meter must be used to tighten the threads, and the torque of threads must be in accordance with the standard, and the thread torque is printed and reported to the Party. Casing thread sealing grease must be used to ensure the sealing of the fillet.
11. After the casing has been lowered, the technician shall install the casing head according to the Calculate the coupling length. After the wellhead is installed with a good hanger, after filling with mud, the drilling fluid can only be circulated in large displacement to avoid well leakage after the pump is topped off with a single vanadium open pump.
12. According to the working condition of the well and the rheological property of the fluid inside and outside the pipe, carry out rheological calculation, apply the jacking technology scientifically and reasonably, and improve the jacking efficiency and the cement ring cementing quality of the first and second interfaces.
13. Carry out the comprehensive evaluation and prediction of gas intrusion and gas runoff scientifically and comprehensively, so as to provide theoretical basis for the optimization of cement injection construction parameters.
14. Strictly follow the operation procedures and construction requirements of two-stage cementing to ensure the cementing quality of 51/2″ production casing.
15. Before cementing, equipment and tools such as drilling rig, pump, circulating system and cementing head should be carefully checked to ensure that the cementing construction is continuous and smooth.
16. Calculate the quantity of cement slurry according to the electric measurement of well diameter and on-site experience, and adopt dry mixing process to ensure that the cement, external mixing materials and additives are mixed evenly.
17. Take samples from vertical tanks and ash tankers, simulate downhole working conditions, and conduct a full set of performance review tests on water samples, cement samples and admixtures to ensure the safety of cementing construction.
18. When mixing cement slurry, injecting replacement and touching pressure, according to the downhole situation, adjust the displacement and flow rate of injection replacement in time, reduce the “U” tube effect, reduce the resistance of flow in the annulus, and reduce the pressure agitation, so as to ensure that the well is normal.
19. Refine the on-site construction measures, strengthen the continuity of construction, and enhance the responsibility of construction personnel to ensure the normal operation of equipment, uniform density of cement slurry, and continuous and safe on-site construction.
20. After 48 hours of cementing, drilling and grading hoop (rubber plug, inner sleeve), through the well to the end of the cementing quality inspection and pressure test, the pressure test requires 25 MPa, pressure drop within 30 minutes ≤ 0.5 MPa.
21. Recommended torque value of N80 long round button casing thread: A. Steel grade N80, Φ51/2”, δ9.17mm long round button casing recommended optimum tightening torque value: 5800 N-M; maximum torque value of 7250 N-M, minimum torque of 4350 N-M. B. Casing spinning position, the tolerance of machine tightening position ± 2 buckles. The best position, the male buckle disappearance point (tail buckle) completely into the hoop and hoop end face flush. c. When the actual torque when the casing screwed together to 7250 N-M, and the remaining buckle is greater than 2 buckles, it is considered that there are problems with the casing thread fit.
