Verification of the OOC Mud and Produced Water Discharge Model using lab-scale plume behaviour experiments
Abstract This paper describes comparisons of predictions by the Offshore Operators Committee (OOC) Mud and Produced Water Discharge Model with published data on experimental laboratory-scale observations of plume behavior in flumes, towing tanks, and wind tunnels. The ability of the OOC Model to predict the plume characteristics observed in numerous individual tests of plume behavior covering a wide range of discharge conditions was examined. Data are provided summarizing the predictive ability of the model for all tests. The dimensionless parameters describing the physical characteristics of the plumes were within the range expected for typical Gulf of Mexico produced water and drilling fluid discharges for most of the comparisons. The model was in good to excellent agreement with measurements of plume behavior under most discharge conditions. The model was less accurate for those experimental cases where extreme plume bending occurred. It is believed that turbulence caused by the discharge pipe itself influenced the behavior of these extreme-bending plumes. The predicted density of solids accumulation on the bottom of a towing tank, a lab-scale analogy of the seabed accumulation of drilling solids, was within a factor of two of experimental observations. Excluding the three simulations of extreme bending plumes, the model showed no systematic trend towards either under- or over-estimation of any parameter examined. This suggests that experimental errors or biases may have contributed to observed differences between predictions and observations. The results of the validation testing described in this report increases confidence in the use of OOC Model predictions as an alternative to the difficult and expensive process of performing field measurements for every practical discharge situation.
Evaluation of modeling as a tool to determine the potential impacts related to drilling wastes in the Brazilian offshore
Numerical models that predict the fate of drilling discharges at sea constitute a valuable tool for both the oil industry and regulatory agencies. In order to provide reliable estimates, models must be validated through the comparison of predictions with field or laboratory observations. In this paper, we used the Offshore Operators Committee Model to simulate the discharges from two wells drilled at Campos Basin, offshore SE Brazil, and compared the results with field observations obtained 3 months after drilling. The comparison showed that the model provided reasonable predictions, considering that data about currents were reconstructed and theoretical data were used to characterize the classes of solids. The model proved to be a valuable tool to determine the degree of potential impact associated to drilling activities. However, since the accuracy of the model is directly dependent on the quality of input data, different possible scenarios should be considered when used for forecast modeling.
Wakes in Stratified Fluids
In this article we review research activities concerning wakes generated by moving bodies in stratified fluids. A wake is defined to be the non­ propagating disturbance produced by a moving body, and thus research activities concerning internal waves generated by a moving body are not included. Wakes have been of interest to many fluid dynamicists and engineers because they are a basic flow phenomenon associated with fluid flowing over an obstacle or with the movement of a natural or man-made body. The wake flow depends strongly on the Reynolds number RD == VoDjv, which is defined as the ratio of the inertia force to the viscous force. Here U 0 is the body speed, D is the characteristic length, e.g. the diameter of a cylinder or a sphere, and v is the kinematic viscosity of the fluid. For small Reynolds numbers, the viscous force dominates the inertia force and the wake is laminar. As the Reynolds number increases, the wake becomes unstable and a regular flow pattern, such as Karman's vortex street in the wake of a cylinder, can be observed. At still higher Reynolds numbers, the flow pattern becomes irregular and a turbulent flow is formed. Books written by Townsend (1956), Hinze (1959), and Schlichting ( 1960) can be referred to for further information about wakes. When the fluid is stratified thermally or with foreign additives, such as salt, a gravitational force, in addition to inertia and viscous forces, is exerted on the flow. A stratified fluid occurs very commonly in the