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Abstract Lost circulation while cementing is always one of the main causes of poor zonal isolation and well integrity problems which can lead to costly consequences such as reduced safety, corrosion, sustained casing pressure, formation damage, loss of production rate, costly remedial operations and loss of an oil or gas well. Lost circulation usually occurred in vugular or cavernous formations and high permeability zones. However most frequently, the zones are depleted, highly fractured (induced or natural), or loosely consolidated that are hydraulically parted at relatively low hydrostatic pressures. In Gulf of Thailand (GoT), the field is characterized by shallow-water wells with ultra-high temperature (UHT) gas reservoirs with low fracture gradients, ballooning, and depleted formations. Lost circulation poses the main challenge while drilling and impacts the success of cementing operations. Historically, lost circulation usually occurs while drilling and/or cementing in the reservoir section. When Lost Circulation Materials (LCM) are utilized for curing losses in reservoir sections, it is desirable that the LCM maintain its stability for sufficient time to allow well completion but eventually self-degrade to leave undamaged formation prior putting the well into production. This paper will describe the successful implementation of an engineered self-Degradable Lost-Circulation Fiber Spacer (DFS) system which has been developed to address lost circulation situations while cementing in naturally fractured reservoirs. Two field case histories from numerous jobs will be discussed with cement post-job evaluation via playback simulations to validate the concept of innovative technology.
Thanasarnpisut et al. (Tue,) studied this question.