Abstract
Mud losses are one of the most severe problems encountered in drilling. This is commonly known as lost circulation. It can occur in naturally fractured formations and also can be induced in formations through drilling. Mud losses while drilling leading to cost overruns and HSE concerns, primary cement job failure due to not getting the cement up to the desired height resulting in subsequent sustained casing pressure and corrosion, not able to perform work over activity on certain wells due to losses. The objective of this paper is to explain extreme lost circulation problem and introduce cement plug formulation to cure or mitigate this problem. In addition, the cement plug has certain compressive strength that this is proper for use to control lost circulation in field. And finally, the application of a cement plug is described in one well of the Gas Field (National Iranian Oil Company).
Highlights
IntroductionLost circulation is an undesirable situation. Lost circulation is defined as partial or total loss of circulation mud [1]
During drilling operation, lost circulation is an undesirable situation
China started to study some critical lost circulation materials and only one single material is used during lost circulation
Summary
Lost circulation is an undesirable situation. Lost circulation is defined as partial or total loss of circulation mud [1]. Exploratory wells currently drilled by Petrobras in Brazil present average depths around 5500 m and in extreme situations can reach around 7000 m In this scenario, geological characteristics such as faults, natural fractures, high permeability zones and formations with vugular features are responsible for increased lost circulation events. One of the most commonly used methods is to place bridging materials into the leakage zone [17]-[23] These materials act to bridge or seal the cracks, crevices, fissures, or other porous or faulty formations into where the drilling fluid is lost, thereby forming a barrier for preventing further loss of the drilling fluid. The main idea of this study is to investigate and evaluate cement plug technology used in the oil industry with the aim of reducing and minimizing lost circulation event during drilling operations And the application of a cement plug is studied in one well of the exploration Gas Field (National Iranian Oil Company) and the reasons of successful of this cement plug are examined
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