INTEGRATED APPROACH FOR SUCCESSFULLY CEMENTING SALTY FORMATIONS. OPERATING PROCEDURES AND NEW LAB TESTING METHODOLOGIES

摘要

This paper presents the results of an investigative case study to determine, solve and prevent the causes of the unsatisfactory Leak Off Test results obtained below 20' casing shoe, resulting in a request of multiple cement squeezes prior to proceed drilling the 17 1/2' section. The slurries currently used so far on some Eni wells are not fully saturated and the lab test results carried on in Eni HQ laboratories highlighted the slurry tendency to dissolve salty formation and therefore get contaminated compromising the mechanical properties and increase the wash out phenomena. In literatures and reference standards there are no test methodologies that have the purpose of evaluating the variation of the properties of the cement slurry, due to contamination with the salty formation drilled; about that, Eni HQ laboratories developed a test methodology to evaluate the possible dissolution of the salty formation during the passage and the contact of the cement slurry with it. The methodology developed is based on the times and surfaces of contact of the slurry with the formation that passes through the displacement, and its final aim is to evaluate the amount of dissolved formation in the mixing water and the variation of the times and resistances characteristic of the slurry. The article lastly reports the entire methodology of the tests designed, the changes made to the slurry formulation used in the past and the description of the operational steps during the cement job, both carried out in collaboration with the service contractor.