Drilling the Marlim field at the Campos Basin has shown quite a challenge in the last few years. The field is located 110 km from Sao Tome cape at the north coast of Rio de Janeiro State, at the Campos Basin, have started commercial exploration for in 1991 and with water depths varying between 600 to 1000 m. The reservoir is composed of sandstone formation and just recently, an exploratory campaign at the field surroundings.
The project of the well in the Marlim field was always complex with eight phases predicted. For the phase 4, due to the narrow fracture and pore pressure window, and also the high number of potential flow zones to be isolated, the client has decided to run a 13 5/8" stage collar in order to isolate all sandstone formations and cement the combined 14" × 13 5/8" Intermediate Casing. The idea of using the stage collar was to isolate the water holder formation, Carapebus Lambrusco sandstone, located just at the stage collar depth and then open the stage collar and cement the remaining sandstone all the way to the last water holder formation, Carapebus Marlim sandstone. The other objective of this job was to provide enough integrity to the shoe, set at the salt formation, in order to allow drilling the subsequent 14 ¾"open hole all the way to the carbonate formation.
After drilled the 16 1/2" open hole of an offshore well, the intermediate casing had to be cemented with a two stage collar with sub sea release plug set, to bring the top of cement higher and isolate upper formation. Due to operational issues, there was a failure in the first stage cement job, which was confirmed with a failed formation integrity test - necessary 13.0 lb/gal to drill ahead the subsequent 14 3/4" phase.
To solve the issue, to achieve formation integrity test of 13 lb/gal, it was necessary to perform a Casing Shoe Squeeze Cement job. The problem is that historically those intervals experience very narrow gaps, which means low injectivity. After several failed attempts with conventional cement, a novel technology was used combining microcement with a strong fluid loss control that could enable the cement to be injected into narrow gaps. The use of microcement alone provides rapid compressive strength development, very low rheology and combining with a fluid loss additive enables to provide the system with very high injectivity