Wells often require being drilled through and cemented across salt formations. In many parts of the world, salt sections consist of multiple salt types. This analysis shows that intercalated salts subject cement sheaths to a series of tensile and compressive loads whose magnitude depends on the size and relative position of different salts. The salt/salt-interface effects dominate the general tenet of increasing creep rate with increasing depth. This work demonstrates cement design that includes evaluating cement-sheath mechanical integrity in intercalated salts.
Drilling and cementing challenges associated with salt formations are well-known. One of the more significant of these is the plastic deformation of salt attributed to the existence of deviatoric (shear) stress. This deformation is known as creep.
To determine the role of creep in the mechanical integrity of a cement sheath, it is necessary to analyze the thermostructural model of the well-construction process using the creep constitutive relationship. The outcome of the analysis is the stresses experienced by the cement sheath. It is possible to quantify the risk posed by salt creep and other operational loads to the cement-sheath integrity by comparing these stresses to the failure properties of the cement. To provide an accurate quantification of the risk, it is necessary to verify the creep constitutive relationship with data from experimental creep tests.
Design Procedure for Cementing Intercalated Salt Zones
10 April 2016