Mud losses/gains have been a major problem in the drilling industry and the detection of this problem is still a crucial issue because of the cost of the non-productive time. Minor but continuous losses occur while circulating and fluid lost to the isolated fracture network is regained when the pumps are off.This phenomena is known as borehole ballooning/breathing.The major problem with borehole ballooning is to identify the problem correctly and not to mix it with any other loss circulation events and drilling troubles. If borehole ballooning is correctly identified, it can be easily dealt with by reducing the mud weight,lowering the flow rates, reducing the rate of penetration (ROP),or using a thinner drilling fluid [1]. However, during the pumps off period, mud returns are very often misdiagnosed as a kick caused by an influx of the formation fluids (gas, liquid hydrocarbon or water) [2].
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