Study of Formation and Stability Conditions of Gas Hydrates in Drilling Fluids

• Main Author: Kharrat, Mamdouh
• Other Authors: Génie des Procédés (GDP), Unité de Chimie et Procédés (UCP), École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-École Nationale Supérieure de Techniques Avancées (ENSTA Paris), École Nationale Supérieure des Mines de Paris, Walter FÜrst
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2004
• Subjects: Natural gas; Drilling fluids; Thermodynamics; Hydrate; Clathrate; Méthane; Gaz naturel; Fluides de fora ge; émulsion; Dsc; Thermodynamique; [SPI]Engineering Sciences [physics]; [CHIM]Chemical Sciences; Methane hydrate
• Online Access: https://pastel.archives-ouvertes.fr/pastel-00001073; https://pastel.archives-ouvertes.fr/pastel-00001073/document; https://pastel.archives-ouvertes.fr/pastel-00001073/file/pre-these.pdf

Drilling fluids are complex media, in which solid particles are in suspension in a water-in-oil emulsion. The formation of gas hydrates in these fluids during off shore drilling operations has been suspected to be the cause of serious accidents. The purpose of this thesis is the study of the formation conditions as well as the stability of gas hydrates in complex fluids containing water-in-oil emulsions. The technique of high-pressure differential scanning calorimetry was used to characterise the conditions of hydrates formation and dissociation. Special attention has first been given to the validation of thermodynamic measurements in homogeneous solutions, in the pressure range 4 to 12 Mpa; the results were found to be in good agreement with literature data, as well as with modelling results. The method was then applied to water-in-oil emulsion, used as a model for real drilling fluids. It was proven that thermodynamics of hydrate stability are not significantly influenced by the state of dispersion of the water phase. On the other hand, the kinetics of formation and the amount of hydrates formed are highly increased by the dispersion. Applying the technique to real drilling fluids confirmed the results obtained in emulsions. Results interpretation allowed giving a representation of the process of hydrate formation in emulsion. Empirical modelling was developed to compute the stability limits of methane hydrate in the presence of various inhibitors, at pressures ranging from ambient to 70 MPa. Isobaric phase diagrams were constructed, that allow predicting the inhibiting efficiency of sodium chloride and calcium chloride at constant pressure, from 0,25 to 70 MPa. Les fluides employés lors du forage pétrolier pour la lubrification de l'outil de forage, l'évacuation des déblais et le maintien de la pression hydrostatique dans le puits sont composés de solides en suspension dans une huile minérale, qui contiennent également une solution aqueuse en émulsion. La formation d'hydrates de gaz dans ces fluides, rendue ...