ANSI API RP 10B-6-2010 pdf free download – Petroleum and natural gas industries — Cements and materials for well cementing — Part 6: Methods for determining the static gel strength of cement formulations.
6 Test method using rotating-type static gel strength apparatus
6.1Apparatus
The apparatus contains a pressure chamber that can be heated and pressurized according to a simulated cementjob schedule. The SGS is calculated from the torque required to rotate a paddle of known geometry at very lowspeed.The rotation speed of the paddle during the SGS measurement portion of the test is normally a continuous0,o00 009 2 rls (0,2°Imin). The initial stirring to simulate placement in the well is typically conducted at2,5 rls±0,25 rls (150 r/min±15 rlmin). The rotating-type static gel strength apparatus shall be calibratedaccording to the manufacturer’s instructions. During the test period, the temperature and pressure of the slurry inthe test cell is increased in accordance with the appropriate well-simulation test schedule (see 6.2.2). Determinethe temperature of the cement slurry by use of an ASTM E220 classification “special” type J thermocouple located inthe centre of the testing cell. The temperature-measuring system shall be calibrated to an accuracy of ±2°C(±4 °F).Calibration shall be performed no less frequently than every three months.
NOTE Changing the rotational speed of the apparatus can be required depending on slurry design. The permissiblerange of rotational speed for the apparatus is 0,000 006 9 rls (0,15 %/min) to 0,000 023 1 rls (0,5°/min).
6.2Test procedure
6.2.1lf there is a batch mixing time being used for the job, the test schedule should include this segment. Theslurry should be exposed to the anticipated temperature conditions during the batch mixing time. The pressure atthis time shall be atmospheric. The strring is typically maintained at 2,5 ris±0,25 rls (150 r/min ± 5 r/min). If thereis no batch mixing time, omit this step.
6.2.2 Calculate the expected time to bottom and the expected placement time required to displace the cementto the flow zone. Ramp the cement slurry to bottom-hole circulating temperature (Toac) and the bottom-holepressure (Ps) in the expected time to bottom.Then ramp to the circulating temperature and pressure at the flowzone. The time interval to ramp to the circulating temperature and pressure at the flow zone is the expectedplacement time to the flow zone, minus the expected time to bottom.After the circulating temperature at the flowzone is reached， hold at the specified temperature and pressure for 5 min ± 30 s to allow for temperaturestabilization. Maintain paddle rotation at 2,5 rls ± 0,25 rls (150 rlmin ± 15 rlmin). In cases when an extendedperiod of fluidity is expected, the test temperature may be increased to static temperature at the flow zone in 240min after reaching the circulating temperature at the flow zone plus 5 min for temperature stabilization. During theplacement simulation, the temperature and pressure shall be maintained within 3 °C(5 F) and 2 MPa (300 psi) ofthe appropriate elapsed time versus temperature and pressure targets.Within 10 min after the end of the ramp,the temperature and pressure shall be within±1 C(±2°F) and 0,7 MPa (100 psi) of the specified values.
NOTE During the time of stirring at APIISO rotational speeds [2,5 rls ±0,25 rls (150 r/min± 15 r/min),the test gives anindication of slurry consistency. It is not an exact slurry thickening time consistency since the paddle does not conform to therequired dimensions for determining thickening time.
6.2.3 For the SGS determination, at the end of the slurry placement simulation, the rotational speed is changedfrom the typical 2,5 r/s±0,25 rls (150 rlmin± 15 rlmin) to 0,0oo o09 2 rls (0,2 /min) or other permissible rotationalspeed.Maintain circulating temperature and pressure at the zone of interest. During sGs determination thetemperature and pressure shall be maintained within±1℃(±2°F) and ±0,7 MPa(±100 psi) of the target values.
6.2.4 Record the initial SGS and the elapsed time when the sample is placed in SGS determination mode fromthe previous placement simulation. Record the time to 50 Pa (100 lbf/100 f2)，100 Pa (200 lbf100 f2).150 Pa (300 lbf/100 ft2), 200 Pa (400 lbf100 f2) and 250 Pa (500 lbfl100 f2)sGS and, csGs. where applicable,determine the critical static gel strength period (CSGSP) by measuring the time required for the cement toprogress from the critical static gel strength (csGs) value (see Annex A) to a sGs of 250 Pa (500 lbf/100 f2).Themanufacturer, model and rotational speed of the apparatus used to make the SGS determination shall be reported.ANSI API RP 10B-6 pdf download.