Paper Number
PO125
Session
Poster Session
Title
Innovative rheology method for barite sagging prediction
Presentation Date and Time
October 17, 2018 (Wednesday) 6:30
Track / Room
Poster Session / Woodway II/III
Authors
- Gao, Yan (Schlumberger)
- Chen, Yiyan (Schlumberger)
- Karoum, Reda (Schlumberger)
Author and Affiliation Lines
Yan Gao1, Yiyan Chen2, and Reda Karoum2
1Schlumberger, Sugar Land, TX; 2Schlumberger, Houston, TX
Speaker / Presenter
Gao, Yan
Text of Abstract
In the past, drilling fluids engineers relied on viscosity at low shear rate or gel strength measured by conventional API methods as an indication for barite sag tendency. However, a significant number of studies have shown that the near-static sag behavior is not well correlated to rheology parameters (yield point, plastic viscosity, gel strength) measured this way. An in-depth investigation, studying the rheological properties of various drilling fluids utilizing both flow ramp and oscillation tests was conducted. This resulted in one rheological parameter of 16-hour heat aged samples showing a high linear correlation to the density differences measured after 7-day aging. As drilling technology has advanced, the use of extended reach drilling has become a norm in achieving economic success during development drilling. There is a desire to develop standard practices to minimize drilling risk, in particular that related to narrow pressure margins. One of the challenges faced is the potential for barite sagging due to drilling fluid instability created by long circulation periods without high shear. If barite sagging occurs, the density gradient of fluid form along the wellbore. The resulting pressure differential can lead to loss of circulation, wellbore collapse or well control problems. In this context, engineers need to design drilling fluids with the ability to fully suspend barite particles at elevated temperature under static conditions for extended reach, deep water, or HPHT wells. Drilling fluids are currently designed based on specific chemical selection guidelines and are refined via laboratory testings directed towards wellsite performance prediction. Among these tests, static sag analysis requires a 7-day aging period of the fluid. It is one of the most crucial tests and can also be a bottle neck for formulation optimization. Until recently, there has been no rapid method that can accurately predict the long term, near static, sag behavior of the fluid formulations.