In ultra deep offshore operations, one of the major problems during both well planning and drilling is that pore pressure and fracture pressure gradients are very close. As these gradients come closer, possibility of having losses while drilling increases. One of the important problems of Black Sea offshore operations was losses in which TPAO has one partnership and two operatorships. The mud weights that was considered as sufficient with respect to the expected pressure values exceeded the fracture pressure gradients, which led to revision on previous hydraulic programs. In order to stop those losses, as common in the industry, loss prevention chemicals were used. Moreover, the casing depths were changed after the real time pressure measurements. At first, losses were tired to be cured by monitoring the drilling parameters such as equivalent circulating density (ECD) and penetration rate (ROP) , which are fairly less easy and reduced in cost. Using synthetic or oil based mud in Black Sea should also be considered after experiencing the water based mud. In this study, mud losses; which is one of the major problems in Black Sea ultra deep water operations, will be presented by analyzing the drilling parameters, mud and formation properties.


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