Oil well cement slurries are used to protect casing from damage from surrounding Water; gives strength & prevents fluid migration (See fig illustration)
Quality Requirements of Oil Well cement (Class- G-HSR) Vs Ordinary Portland/Pozzolana cements (OPC/PPC)
| Oil Well cement Class G | OPC/ PPC | |||
|---|---|---|---|---|
| Specification Code | IS-8223:1986 API- 10 A Class G HSR* |
BIS- 269:2015- OPC BIS- 1489 (Part I):PPC |
||
| Physical Parameters | Unit | Requirement | ||
| Mix Water | % bwoc | 44 | Based on Consistency | |
| Free Fluid Content | % by vol. | 5.9 (max) | Not Applicable | |
| Compressive Strength after 8 hrs. Curing | ||||
| i) At 38 0C, Atmospheric Pressure | psi | 300 (min) (2.1 Mpa) | Only at 3,7 & 28 Days Strengths are specified based on Grades | |
| ii) At 60 0C, Atmospheric Pressure | psi | 1500 (min) (10.5 Mpa) | ||
| Thickening Time at 52 0C, 5160 psi raised in 28 minutes |
minutes | 90 (min) - 120 (max) | Not Applicable. Initial (30 Min) - Final (600 max) |
|
| Maximum Consistency (15 to 30 min. stirring period) |
Bc | 30 (Bc is a measure of consistency of cement slurry) |
Not Applicable | |
| Chemical Requirements | Class G Requirements | OPC/ PPC | ||
| Magnesium Oxide (MgO) | % | 6.0 (maximum) | 6.0 ( Maximum) | |
| Sulphur Trioxide (SO3) | % | 3.0 (maximum) | 3.5% ( Maximum) | |
| Iron Oxide (Fe2O3) | % | - | Alumina to Iron ratio 0.66 Min for OPC |
|
| Aluminium Oxide (Al2O3) | % | - | ||
| Loss on Ignition | % | 3.0 (maximum) | 4-5% depending on Grade | |
| Insoluble Residue | % | 0.75 (maximum) | 4-5% depending on OPC Grade. For PPC based on Fly ash Content |
|
| Tricalcium Silicate (3CaO.SiO2) | % | 48 – 65 | No Specification | |
| Tricalcium Aluminate (3CaO.Al2O3) |
% | 3.0 (maximum) | Specified only for Sulfate Resistant cement as<5% |
|
| Tetracalcium Aluminoferrite (4CaO.Al2O3.Fe2O3) + Twice the Tricalcium Aluminate (3CaO.Al2O3) |
% | 24.0 (maximum) | Specified only for Sulfate Resistant cement as 25% max |
|
| Total Alkali content expressed as Sodium Oxide (Na2O) Equivalent |
% | 0.75 (maximum) | Optional requirement. (0.6%) | |
| Additives | % | No additive other than Clinker & gypsum permitted | 5 % addition of other components in OPC | |
*American Petroleum Institute Specification – 10 A for Class- G- High Sulfate Resistant (HSR)
