fax 01-972-952-9435. AbstractIn drilling directional and horizontal wells, the oil and synthetic-based drilling fluids are required to exhibit high viscosity at low shear rates to properly suspend the weighting materials and drilling cuttings and to prevent sag and settling of weighting materials. This can be achieved by employing different rheology modifiers such as dimeric and trimeric fatty acids, imidazolines, amides, and synthetic polymers. Moreover, the safety of the drilling operation has been one of the main concerns of drilling companies.Since oil and synthetic-based drilling muds are widely used in high pressure high temperature wells, a set of drilling fluids commonly used in Western Canada were examined to study the effect of long exposure of the drilling mud with air. They consist of three oil base liquids (Diesel, Drillsol, and Distillate) and one synthetic base liquid (Envirodrill) together with water scavengers, viscosifiers, wetting materials, fluid loss controllers, and weighting materials. The drilling fluids were aged in stationary reactors in the presence of one charge of air for 52 hours at 150 o C and 13.5 MPa initial pressure. This paper presents the results related to changes in rheological properties and occurrence of explosion in the drilling fluids employed. The results at different shear rates, ranging from ultra low shear rates to high shear rates, are presented. It is shown that the aged drilling fluid systems exhibited a tremendous increase in viscosity at ultra-low shear rates and relatively low increases at medium and high shear rates. Furthermore, the amounts of solids precipitated in the base liquids were correlated with the mononuclear aromatics content. While rapid heat releases or explosions in the synthetic-based drilling fluids were observed with 0.5 -1.6 hours induction delay times with gradual increase in liquid phase temperature, oil-based systems were safe under the conditions tested.These experimental results imply that oxidation serves as a rheology modifier and induction delay time can be used as a warning parameter for an impeding explosion. Moreover, the impact of each chemical on the extent of increasing the viscosity and the occurrence of explosion is given.
fax 01-972-952-9435. AbstractThe development of mature fields has led operators to use underbalanced drilling to benefit from advantages such as reducing formation damage and increasing penetration rate. In gasified liquids, a light oil can be used as the liquid phase and nitrogen with almost 5 percent oxygen as the gas phase. Due to the simultaneous presence of oil and oxygen in the drillstring, safety considerations are a major concern in these operations.To study and simulate the occurrence of explosions, oil base liquids were aged at 150 o C and 14 MPa initial pressure in rocking and stationary reactors for 2.5 and 5 days in the presence of a gas with different concentrations of oxygen. The presence of drilling cuttings was simulated by addition of calcium carbonate to the base liquids. To cover the real penetration rates encountered in the drilling industry, volume percentages of 0.3, 0.6, 1.2, 2.4, and 4.8 of calcite were employed.The experimental results of the samples that experienced explosions show that a delay time of approximately 0.5 hours was observed. In the period leading up to an explosion, the vapor phase temperature remained relatively constant while the liquid phase temperature first increased gradually and then more rapidly. At the time of the explosion, a rapid rise in the vapor phase temperature accompanied by a sudden increase in the reactor pressure was observed. This behavior indicates that the explosion was triggered by liquid phase oxidation reactions but that the sudden energy release event was associated with combustion reactions in the vapor phase.This study signifies the important impact of the liquid phase temperature on explosion occurrence. The liquid phase acts as an initiator or an ignition source for explosions. Furthermore, it can be used as a parameter to warn of an impending explosion.
In this paper, an improved characterization of three-phase flow under HPAI conditions was achieved based on experimental results and numerical reservoir simulation.A three-phase coreflood experiment was conducted at reservoir conditions, using 37˚API stock tank oil, 84% nitrogen -16% carbon dioxide flue gas mixture, and 3% KCl brine. The aim of the test was to evaluate the effects that the highly liquid-saturated front produced by the thermal reactions has on the mobility of each phase. Departing from connate water saturation and reservoir pressure and temperature, sequential injection of water, gas and oil was carried out, followed by a final gas flood to residual liquid saturation. Other twoand three-phase tests performed on this rock specimen were published elsewhere. Numerical history matching was employed to determine oil-water and liquid-gas relative permeability (k r ) curves for both imbibition and drainage cases. A Combustion Tube (CT) test was simulated using both conventional k r curves and a set including hysteresis. The degree of hysteresis observed during the coreflood test was maintained for the CT simulation.History matching of the coreflood showed that k r to the gas phase is much smaller during liquid re-imbibition than during drainage. The use of gas phase hysteresis for the CT test allows for a better matching of liquid volumes and pressure drop. Analysis of the simulated data suggests that the reduction in gas phase mobility encourages an early increase in the oil rate, which is more consistent with experimental data than that predicted by a model with conventional k r . It also reveals that water distilled below the saturated steam temperature plays an important role on the increase of liquid saturation and oil mobilization.The improved characterization on relative permeability considering gas phase hysteresis for simulating HPAI enhances the predictive capability of the available commercial simulators, providing a more certain method to evaluate the technical and economical feasibility of a project. The ability to predict an early increase in oil rate, consistent with experimental observations, results in improved economics for the project.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.