OIl well cement . This cement is usee for cementing oil wells

Oil wells are very deep . ordinary cement if used at sucvh depths will harden before it could reach its place of use . Oil well cement should be capable of being pumped for about 3 hours when subjected to high pressure and temperature . Thus cement to be used for this purpose should have the property of slow setting and must harden quickly after settting . This is accomplished by adjustingthe compound composition of cement or by adding retarders to the ordinary cement . This is possible by adjusting the proportion of iron oxide so that all the alumina is converted to Tetra calcium alumino ferrite ( C4AF) . The proportion of tri-calcium aluminate ( C3A) formed is , therefore , very small and setting time of cement is increased .

  The function of cement in oil well is to fill the space between the steel lining tube and wall of the well and also to grout porous strata to prevent water or gas from gaining access to the oil bearing strata . Oil well cements besides prventing water from infilterating the oil bearing strata also protect the oil well casing from corrosion , help support the oil well casing , and thus reduce the tension in steel pipe .