Oxidation as a Rheology Modifier and a Potential Cause of Explosions in Oil and Synthetic-Based Drilling Fluids

Abstract

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.

Combined Effect of Pressure and Temperature on the Viscous Behaviour of All-Oil Drilling Fluids

“…However, knowledge of the flow behaviour of clay-based drilling fluid, as function of temperature and pressure, is decisive in order to deal with different important issues, such as excessive torque, gelation, hole cleaning or barite sag (Shahbazi et al, 2007). In this sense, one of the objectives of this study was to define the temperature-pressure-shear stress relationship for two organoclays suspensions, aiming to support a physical interpretation of the rheological behaviour obtained.…”

Investigation of Explosion Occurrence in Underbalanced Drilling

“…In in situ combustion applications, the main concerns are to stabilize a burning front and to characterize the impacts of the oxidation on the rheological properties of the oil. 13,16 Due to high pressure air injection 17,18 applications which are performed in light oils, some data on the oxidation of light oils have been published in the open literature. Phillips and Hsieh 19 analyzed the CO and CO 2 formation in the post-test gases and suggested that CO is not further oxidized to CO 2 .…”

Lipophilic rheology modifier and its application in oil‐based drilling fluids

“…These rheology modifiers can be classified into three types: organoclay, [10][11][12][13] gel polymers, [14][15][16][17] and polycarboxylic acid derivatives. [18][19][20][21][22] The organoclay contribute to fine solids which are detrimental to rheological properties as well as contributes to formation damage especially while drilling oil-producing zone. 23,24 Meanwhile, the temperature limitations and the unpredictable performance of drilling fluids such as the progressive gels and yields make it difficult to be used in drilling operations.…”

“…To control the rheological property of oil‐based drilling fluids, domestic and foreign scholars have developed a series of rheology modifiers. These rheology modifiers can be classified into three types: organoclay, 10–13 gel polymers, 14–17 and polycarboxylic acid derivatives 18–22 . The organoclay contribute to fine solids which are detrimental to rheological properties as well as contributes to formation damage especially while drilling oil‐producing zone 23,24 .…”