Polymers in drilling fluids tend to adhere to the inside surfaces of metal pipes, improving the lubricity characteristics of the fluid. The present study evaluated the adsorption of polymers from their aqueous solutions on metal surfaces by means of visual observation and contact angle measurements. The polymers tested were xanthan gum, starch, and partially hydrolyzed polyacrylamide (PHPA). The contact angle measurements were carried out to enable calculating the adhesion and adsorption energy. The visual observation, although not furnishing quantitative data, agreed with the results of the contact angle measurements. The results show that the tendency of these polymers to be adsorbed on metal surfaces varies as follows: starch > PHPA > xanthan gum. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Summary: This work describes a method to evaluate, in reduced scale, the performance of polymer samples as drag reduction agents in aqueous solutions. To measure the pressure drop in a turbulent regime, a specially adapted capillary viscosimeter was used, with reduced dimensions adapted to produce the desired regime and adequate pressure measurement points. To verify the technique's reliability, samples of polyacrylamide were synthesized with different molar masses, by varying the quantity of the polymerization initiator. The molar masses obtained were determined by size exclusion chromatography (SEC). The efficiency of the polymer as a drag reducer, as expected, increased as the molar mass increased, which validates the use of this method to study the drag reduction properties of polymer materials in aqueous solutions.

TX 75083-3836 U.S.A., fax 1.972.952.9435. AbstractFast and non-progressive drilling fluid gelation is desired to prevent drilled solids sedimentation during pumps-off, while avoiding excessive pressure peaks when circulation is resumed. Gelation tendencies are normally higher at low temperatures typical of deepwater risers. Excessive pressure peaks can cause detrimental effects when fracture pressure is reached.Besides gelation issues, excessive pressures and/or difficulties to resume circulation have been observed during drilling operations in water depths greater than 1.800 m. The problem happened especially with the fluid volume filling the control lines, at the time of circulation restart. Two field cases of fluid freezing in choke and kill lines have been reported which led to riser and BOP removal to unplug the lines, with significant non productive time and high costs.The paper shows the results of an experimental study carried out to evaluate the rheological behavior and gelation properties of non aqueous drilling muds under low temperatures (bellow 4 o C) and high pressures (up to 5.000 psi). The study aimed to quantify pressure effects on freezing temperatures and to develop representative methodologies for the evaluation of thyxotropic properties of such fluids. Experiments included steady state and transient shear and oscillatory tests at cone-plate geometries. The final goals are to design additives and drilling fluid formulations with flow point lower than 0 o C at pressures higher than 2.500 psi and taylor made gelation profiles. Additionally modeling work was carried on to represent the time dependent behavior of relevant rheological properties at different temperatures and pressures. Such models were used to predict pressure peaks and compare them with real PWD data from ultra deepwater wells.

Sand control is a major issue for offshore unconsolidated sandstone reservoirs, where any workover or production interruption event is associated with high costs. Horizontal well openhole gravel packs proved to be a very reliable strategy to prevent sand production in the prolific offshore Brazil fields. Over 250 operations were successfully performed in different critical scenarios, such as ultra deepwater wells, long horizontals, in the presence of shale interlayers, etc. Pushed by the present fluctuations in oil production revenues and aware of the expressive costs related to gravel pumping operations, PETROBRAS started a broad R&D and field test strategy to reduce operational times and costs. This article details both aspects of the development, as follows: An unique flow loop test program developed as a technical cooperation agreement with HALLIBURTON, including real scale 8.5 in open hole and 12.25 in rat hole sections. Such tests allowed the validation of novel technology, pumping procedures and products including limit flow rates which avoid premature rat hole screen outs, low cost conventional and lightweight propants and high concentration slurry pumping.2. The learning curve of new pumping design strategies, and their associated cost reduction, in different offshore fields including Marlim Sul, Albacora Leste, Marlim Leste, Roncador, Jubarte and Golfinho fields. New strategies contemplate multiple alpha waves, multiple propants and high concentration slurry designs.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractLong horizontal section wells are economical requirements for heavy oil fields in deepwater environments. This article discusses the operational limits for drilling and completing such kind of wells, considering the well extension and low fracture gradients encountered in deepwater reservoirs. Among the operational issues related to hydraulics, the following are critical: ECD restrictions, drilled cuttings transport, fluid substitution while running the screen and gravel pack placement (if this is the adopted sand control technique). A parametric study on the variables governing each of the three operations indicates that careful hydraulic design and detailed operational procedures can guarantee proper well construction.