Abstract
Deviated well sections are common in modern well construction. In mature areas like the North Sea region, practically all producers or injector wells will have highly deviated sections. These wells must be completed in an optimal manner especially with respect to annular barrier integrity. The zonal isolation is important through all stages of the well’s life cycle. Since all wells must be permanently plugged before abandonment it is vital to ensure that annular barriers are designed with a long-term perspective and not only to minimize construction time and cost. Controlled laboratory environments with various fluid compositions and flow parameters are important to develop, validate and improve models and practices. Laboratory testing may often require significant simplifications to fit available resources, premises etc. and will not always be optimally designed to match relevant practical operations. Cement displacement is the objective for many such studies, while due to selection of fluids, in reality casing cleaning operations are investigated.
Most laboratory-scale experiments are conducted with water-based fluids for both the displaced and the displacing fluid. However, during cementing and clean-out operations the fluids are commonly immiscible, i.e. one fluid is water-based and the other fluid is oil-based. As a consequence, effects like immiscibility and wettability are important and will play a role for the displacement process.
We present results from displacement experiments where oil-based fluids are displaced by water-based fluids. Four experiment series were conducted. In the first series a commercial base oil was displaced by tap water with 3% NaCl. In the other three experiment series a real oil-based drilling fluid was displaced with three different brines with different viscosities and densities.
The experiments have been performed in a flow loop that consists of a 10 meters long test section with 5″ OD transparent pipe inside a 6,5″ transparent pipe. We investigate the effects of flow rate, string rotation speed, wellbore inclination, wellbore eccentricity and fluid properties on the displacement process. The displacement front is tracked using video recordings and electrical conductivity probes. Differential pressure and temperature transient measurements provide data which give additional information about the displacement process. The data can be used for validation of simulators as well as for designing cementing and wellbore cleanout operations.
Most laboratory-scale experiments are conducted with water-based fluids for both the displaced and the displacing fluid. However, during cementing and clean-out operations the fluids are commonly immiscible, i.e. one fluid is water-based and the other fluid is oil-based. As a consequence, effects like immiscibility and wettability are important and will play a role for the displacement process.
We present results from displacement experiments where oil-based fluids are displaced by water-based fluids. Four experiment series were conducted. In the first series a commercial base oil was displaced by tap water with 3% NaCl. In the other three experiment series a real oil-based drilling fluid was displaced with three different brines with different viscosities and densities.
The experiments have been performed in a flow loop that consists of a 10 meters long test section with 5″ OD transparent pipe inside a 6,5″ transparent pipe. We investigate the effects of flow rate, string rotation speed, wellbore inclination, wellbore eccentricity and fluid properties on the displacement process. The displacement front is tracked using video recordings and electrical conductivity probes. Differential pressure and temperature transient measurements provide data which give additional information about the displacement process. The data can be used for validation of simulators as well as for designing cementing and wellbore cleanout operations.
