Before this phenomenon can be well understood and modelled, the solubility of natural gases in a wide variety of oil-base drilling fluids must be known as a function of temperature and pressure. This danger is the greatest when bottom hole conditions are such that the gas will completely dissolve into the drilling fluid and rapidly evolve as the gas cut drilling fluid is circulated up the well. Furthermore, the model matches data that had not been previously matched by other models.read more read lessĪbstract: Gas contamination of an oil-base drilling fluid during drilling operations, whether it be by the uncontrolled flow of formation gas into the well bore (gas kick) or by the drilling of gas bearing formations (drilled gas), poses a potential hazard to the drilling equipment, environment, and personnel. Data matches have been made for both water- and oil-based muds in both shallow and deep wells. Comparisons between the model and field data demonstrate good agreement. This paper presents a dynamic surge/swab model that extends existing technology with the following features: (1) pipe and annulus pressures are coupled through the pipe elasticity (2) longitudinal pipe elasticity and fluid viscous forces determine pipe displacement (3) fluid properties vary as a function of temperature and pressure and (4) formation elasticity pipe elasticity, and cement elasticity are all used to determine the composite elastic response of the wellbore. For these wells, the drilling engineer needs the best possible method of calculating surge pressures to drill wells with a minimum of trouble. The prediction of pressure surges is of economic importance in wells where the pressure must be examined within narrow limits to prevent lost circulation and formation-fluid influx. Abstract: It is generally accepted that the pulling and running of pipe causes pressure surges.
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