An experimental study has been conducted to evaluate the effects of solids on the drag reduction characteristics of polymeric drilling fluids, loaded with solids, through straight and coiled tubing. Polymers investigated were PHPA and XCD. These polymers were dissolved in brines which were prepared by mixing potassium chloride (KCl) and sodium formate (Na-formate) in water. Various concentrations of polysaccharide gum (XCD) and partially hydrolyzed polyacrylamide (PHPA) polymers were dissolved in the KCl and Na-formate solutions. These fluids were pumped through straight pipes. Based on the results it was established that PHPA/KCl solution exhibited better drag reduction than PHPA/Na-formate, XCD/KCl, and XCD/Na-formate solutions in straight pipes. Thus PHPA/KCl solution was selected for further study.
This polymer solution was then loaded with barite and bentonite to simulate solid cuttings. The fluid system was pumped through different size coiled tubing and straight pipes. Correlation in terms of Fanning friction factor and generalized Reynolds number was developed and percentage drag reduction was calculated. It was observed that when clear polymeric solutions were loaded with solids, drag reduction decreases drastically. Finally, the effect of curvature on the flow of solid-laden fluids was studied. It was observed that frictional losses in coiled tubing were almost twice those of frictional losses in straight tubing for solid-laden polymeric fluids under investigation.
The oil and gas industry is experiencing a period of rapid change. Cost reductions are intense and environmental issues are becoming more dominant. These conditions are forcing the operating companies to reevaluate their present business practices. In several cases, radical changes to the former status quo are being made. This is having an effect on almost every sector of the oil industry. Therefore, it is necessary to reduce energy waste as much as possible during various operations. One of the fluids through pipes. Whether it is crude oil transportation or drilling or hydraulic fracturing or even gas injection, energy is wasted due to frictional resistance between the fluids and pipe wall. This is seen in the form of pressure drop along the pipe. To help reduce pressure losses, polymers are added to the fluid stream. Polymer additions efficiency can dramatically reduce the overall operation cost for drilling, hydraulic fracturing, and crude oil transportation.
In the past various studies have been conducted on the flow of clean Newtonian and non-Newtonian fluids through straight pipes in turbulent flow. For flow of Newtonian fluids through smooth pipes von Karman1, Nikuradse2, and Prandtl3 suggested correlations but the most commonly used correlation was proposed by Drew et al4. Their correlation is valid for Reynolds number between 3,000 and 3,000,000. Similarly for Newtonian fluids flowing through rough pipes in turbulent flow regime,- Moody5, Nikuradse2, Churchill6, and Chen7 developed correlations. Among these, Chen's correlation is the most widely used in the industry as Chen's correlation is explicit for Fanning friction factor and correlates the Fanning friction factor, pipe roughness, pipe diameter, and Reynolds number.
