Abstract
Brazilian pre-salt reservoir is mainly composed of carbonate rocks which are naturally fractured and where severe loss of circulation has often occurred.
Loss of circulation during drilling or cementing is a serious issue that usually leads to nonproductive time, increase of well construction costs, and impairment of cement sheath quality, which may lead to deficient zonal isolation in the future and compromise well integrity in long term.
Data analysis from studies developed by operators around the world show that approximately 12% of all nonproductive time accumulated in a certain period is due to loss of circulation occurrence. In Brazil, an analysis performed by an operator in 2014, pointed that more than 100 days were lost in pre-salt wells in operations to cure or minimize loss of circulation. This same analysis concluded that more than 170 000 barrels of drilling fluid were consumed due to this scenario of losses. It is also important to emphasize the cases where a remedial cementing job was necessary due to failure of zonal isolation achievement through primary cementing, resulting in additional costs and nonproductive time.
Said that, it was important to develop and implement a new technology capable of mitigate losses during cementing operations and minimize the risk of a remedial cementing need. Since January 2017, Fibrous Loss Circulation Material has been used in the cementing jobs for production casings in the pre-salt wells successfully. Up to now, six wells were cemented using this technology; no remedial job necessary and the cementing logging evaluation showed excellent results.
