Gilson Campos

A Joint Industry Project To Assess Circulating Temperatures in Deepwater Wells

Drilling oil wells offshore in water depths exceeding 1000 m is not uncommon in many parts of the world. These conditions present a number of challenges for successfully drilling and completing these wells. A major challenge is predicting the temperature of various fluids, such as drilling muds and cements, when they are circulated or placed in the well and during static periods. What sounds like an easy task for the majority of land or offshore wells with shallow water depths turns out to be much more difficult for deepwater wells. Tills is particularly caused by inverse temperature gradients across the sea and convective thermal exchanges between the sea and the fluids in the riser and/or drillpipe. To better understand the phenomena involved, a series of temperature measureless was made as part of a joint industry project (JIP). The primary objective of these measurements as specifically to monitor the cooling effect of the sea by measuring the fluid temperature at the mudline depth. All temperature data were measured by a sensor deployed inside the bottomhole assembly (BHA) while circulating or drilling. Data were collected in the Gulf of -exico, Brazil, Indonesia, and west Africa in an average water depth of 1200 m. A summary of the temperature measurements is presented, and comparison is also made with the predictions of a numerical simulator. Detailed interpretation of the data gathered pinpoints the importance of correctly accounting for the exact temperature profile in the sea as well as the velocity of sea currents vs. depth.

Dynamic Aspects Governing Cement-Plug Placement in Deepwater Wells

Plug cementing is still considered to be a critical operation and cases of failure eventually happen. Large annular gap and eccentricity, typical of these operations, are factors which may promote unstable flows resulting in cement slurry contamination. Deepwater conditions enhance chances of free fall, and consequently, low displacement velocities can occur in the annulus[1]. This article presents a parametric study in the role of rheological properties of fluids (drilling fluid, spacers and cements slurries), string rotation, flow rates (including free-fall effects, where due the differences between density of the fluids the injection flow rate is different of return flow rate) in the displacement quality of cement plugs. Analyses are based on 2 different simulation tools. Conventional cement pumping softwares define flow rate profiles at annulus entrance, accounting for free fall effects and CFD simulation to define interface propagation and contamination levels. The main issues addressed by the simulations are how to optimize density and rheology hierarchy which minimizes contamination and avoids channeling The compilation of simulation results in useful guidelines and procedures for displacing cement plugs in vertical inclined and horizontal offshore wells.