Lost circulation occurs when drilling fluids pumped downhole to control formation pressure exits the wellbore into a fractured, highly permeable, or underpressure formation. If not remediated quickly, these fluid losses can jeopardize well control if the reduced fluid volume results in a hydrostatic pressure that is less than the pore pressure of an exposed formation. In a worst-case scenario, the wellbore may be lost.
Treatments for lost circulation typically involve adding solids—lost circulation material—to the drilling fluids. When the solids-laden fluids are drawn into the lost circulation zone, they form a barrier on the borehole wall or create a plug in the fracture, preventing more fluid from exiting the wellbore.
Conventional lost circulation treatments are typically time-consuming and ineffective, particularly when wide fractures require sealing. A system that uses natural cellulose fiber as a lost-circulation-material base is one solution to this challenge. Schlumberger fiber-based solutions include the Losseal family of reinforced composite mat pills, CemNET advanced fiber technology, and PressureNET fiber- and solids-based lost circulation solution.
An article in the Autumn issue of Oilfield Review, “Sealing Fractures: Advances in Lost Circulation Control Treatments,” describes lost circulation management through the implementation of best drilling practices and the predrill selection of drilling fluid, wellbore strengthening materials, and lost circulation materials. Case histories from the Middle East, the North Sea, and Indonesia are presented to illustrate the use of these fiber-based treatments for drilling and cementing operations.
Baggini Almagro, S.P., Frates, C., Garand, J. and Meyer A: “Sealing Fractures: Advances in Lost Circulation Control Treatments,” Oilfield Review (Autumn 2014): 26, No. 3, 4–13.