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Collaborating Authors
Shahbazi, K.
Abstract Oil and synthetic-based drilling fluids are the drilling muds of choice in high pressure and high temperature wells. The hot drilling fluid is returned to the surface and is exposed to air in the mud tanks. Since the base liquids of these drilling fluid systems are expensive, they are used in many wells before disposal. The long exposure of the oil to air can result in a substantial oxidation of the oil; especially in hot reservoirs in summer temperatures. To simulate the oxidation of these drilling fluids, an experimental study was conducted in which 20 oil-based and synthetic-based drilling fluid systems which are used in Western Canada, were examined. The drilling fluid systems were aged in stationary reactors in the presence of one charge of air for 52 hours at 150 ºC and 13.5 MPa initial pressure. While rapid heat releases or explosions in the synthetic-based drilling fluids were observed, oil-based systems were safe under the conditions tested. The rheological properties of the drilling fluid samples after aging were compared with the original (before aging) samples. The results at an ultra low shear rate range of 0.0 – 0.2 s and a high shear rate range of 0 – 4,000 s are presented. It is shown that the aged drilling fluid systems exhibited a tremendous increase in viscosity at ultra-low shear rates. Furthermore, relatively low increases in viscosity at medium and high shear rates were observed. Introduction Demand for energy sources is increasing throughout the world at a rapid rate due to industrial development and population growth. The search for new sources of oil and gas on land and offshore, and also developing current resources, has intensified due to this increasing demand. Oil production involves two main phases of drilling operations; namely, exploration and development. The exploration phase operations determine the potential hydrocarbon reserves and include drilling of exploratory wells, whereas, the development phase operations include drilling of production wells once a hydrocarbon reserve has already been discovered. Drilling fluids are one of the essential components of the drilling operation. Inappropriate design of a drilling fluid system can lead to numerous problems such as stuck pipe, lost circulation, wellbore instability, gellation, insufficient hole cleaning, bit balling, barite sag, excessive torque and drag, corrosion, H2S contamination and plugging due to gas hydrates. Due to some underbalanced drilling applications that employ gasified liquids, oxidation of oil and synthetic-based drilling fluids has recently received some attention. Historically, in situ combustion and high pressure air injection (HPAI) are two major areas in thermal enhanced oil recovery techniques where the oxidation of oils are of special importance. In these processes, it is of vital importance to know what effects the oxidation has on rheological properties of the oil, because it affects the mobility of the oil and, therefore, the recovery factor. In drilling fluids, in addition to changes in rheological properties, safety considerations and explosion potential require investigation. In the first phase of this research, the oxidation of different base oils was investigated.
- Geology > Mineral > Sulfate > Barite (0.65)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (0.46)
- Geology > Geological Subdiscipline > Geochemistry (0.46)
Abstract Oil and synthetic-based drilling fluids are the drilling muds of choice in high pressure and high temperature wells. The hot drilling fluid is returned to the surface tanks and is exposed to air in mud tanks. Since the base liquids of these drilling fluid systems are expensive, they are used in many wells before disposal. The long exposure of the oil with air can result in substantial oxidation of the oil, especially in hot reservoirs in summer temperatures. To simulate the oxidation of these drilling fluids, an experimental study was conducted in which 20 oil-based and synthetic-based drilling fluid systems, which are used in Western Canada, were examined. The drilling fluid systems were aged in stationary reactors in the presence of one charge of air for 52 hours at 150 °C and 13.5 MPa initial pressure. While rapid heat releases or explosions in the synthetic-based drilling fluids were observed, oil-based systems were safe under the conditions tested. The rheological properties of the drilling fluid samples after aging were compared with the original (before aging) samples. The results at an ultra low shear rate range of 0.0–0.2 s and a high shear rate range of 0–4,000 s are presented. It is shown that the aged drilling fluid systems exhibited a tremendous increase in viscosity at ultralow shear rates. Furthermore, relatively low increases in viscosity at medium and high shear rates were observed. Introduction Demand for energy sources is increasing throughout the world at a rapid rate due to industrial development and population growth. The search for new sources of oil and gas on land and offshore and also developing the current resources has been increased due to this increasing demand. Oil production involves two main phases of drilling operations, namely exploration and development. The exploration phase operations determine the potential hydrocarbon reserves and include drilling of exploratory wells, whereas the development phase operations include drilling of production wells, once a hydrocarbon reserve has already been discovered. Drilling fluids are one of the essential components of the drilling operation. Inappropriate design of a drilling fluid system can lead to numerous problems such as stuck pipe, lost circulation, wellbore instability, gellation, insufficient hole cleaning, bit balling, barite sag, excessive torque and drag, corrosion, H2S contamination, and plugging due to gas hydrates. Due to some underbalanced drilling applications that employ gasified liquids, oxidation of oil and synthetic-based drilling fluids has recently received some attention. Historically, in-situ combustion and high pressure air injection (HPAI) are two major areas in thermal enhanced oil recovery techniques that oxidation of oils are of special importance. In these processes it is of vital importance to know what effects the oxidation has on rheological properties of the oil, because it affects the mobility of the oil and therefore the recovery factor. In drilling fluids, in addition to changes in rheological properties, safety considerations and explosion potential require investigation. The current research, which has been conducted by the In Situ Combustion Research Group at University of Calgary benefits their vast experience in the oxidation of bitumen, heavy oils, and light oils.
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (0.68)
- Geology > Mineral > Sulfate > Barite (0.65)
Abstract True downhole rheological properties affect equivalent circulating density, hole cleaning, barite sag, surge/swab pressures during tripping, pump pressure, and bit hydraulics. Gelation and excessive viscosity are major concerns at high temperatures. When using oil-based drilling fluids lightened by an injection of de-oxygenated air (containing small amounts of oxygen, usually around five per cent) in underbalanced drilling (UBD) operations, there is a need to be able to predict the effect of oxidation on the viscosity of the oil-based muds as a function of temperature and pressure. This paper presents the results of an experimental investigation that was aimed at establishing the effect of oxidation on the viscosity of an oil-based drilling fluid. The drilling fluid was aged for 2.5 days and for 7 days in the presence of air at temperatures ranging from 100 to 150 °C and at pressures ranging from 14 to 44 MPa. The viscosity of the drilling fluid samples after aging is compared with the corresponding fresh samples (before aging). The results show that oxidation causes an increase in viscosity. The amount of the increase depends on the amount of oxygen reacted, which is a function of temperature, pressure, and time. The higher temperatures of the reactors lead to the higher increases in viscosity. Furthermore, at higher temperatures, solid (mostly coke) formation was observed. Introduction Underbalanced drilling (UBD), in which drilling fluid pressure is lower than reservoir pore pressure, has been studied by many researchers since the late 1980s. This method can improve the financial returns on drilling a well by reducing formation damage (especially in horizontal wells and depleted reservoirs), minimizing lost circulation (especially in fractured reservoirs and depleted reservoirs), increasing the penetration rate of drilling, increasing bit life, minimizing differential sticking, reducing stimulation, and improving formation evaluation. The underbalanced condition is created by using different drilling fluids such as dry air, nitrogen, natural gas, mist, stable foam, stiff foam, gasified liquids, glass bubbles, and liquids. In gasified liquids, a gas is injected into the liquid to reduce the density of the drilling fluid. In these mixtures, since the pressure difference between the formation and the wellbore is relatively low (1.72 - 3.45 MPa), these drilling fluids have fewer UBD related problems such as wellbore instability and formation fluid inflows(1). These specifications have made them the most appropriate drilling fluid in UBD. The unique performance of oils makes them preferable to water as the liquid phase in gasified liquids. Oils prevent clay swelling and they are resistant to contaminants. Their rheological properties are stable at high pressures and temperatures. Also, they are highly lubricious and non-corrosive. On the other hand, to prevent downhole fires, de-oxygenated air from membrane units with maximum five per cent oxygen is usually used as the gas phase in gasified liquids. The presence of oxygen causes the oil in the gasified liquid to be oxidized. In this paper, the effect of oxidation on the viscosity of the gasified liquids is investigated.
- Europe (0.46)
- North America > Canada > Alberta (0.32)
- Asia > Middle East > Iran (0.28)
- Research Report > New Finding (0.34)
- Research Report > Experimental Study (0.34)
- Geology > Geological Subdiscipline > Geomechanics (0.68)
- Geology > Mineral (0.54)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (0.31)
Abstract Diesels and distillates are used as the base liquid for the majority of oil-based drilling fluids in conventional drilling and as the liquid phase in gasified liquids in some underbalanced drilling operations. They are also used as the friction reducing agents in situations such as freeing stuck pipe. Understanding the true downhole rheological properties is crucial as they affect equivalent circulating density, hole cleaning, barite sag, surge/swab pressures during tripping, pump pressure and bit hydraulics. Moreover, gelation and excessively high viscosity are major concerns, especially at high temperatures. This paper presents the results of an experimental investigation which was aimed at establishing the effect of oxidation on some base liquids for oil-based and synthetic based drilling fluids at high pressures and high temperatures. Base liquids were aged at 150 °C and 14 MPa initial pressure in the presence of air for 60 hours. Characterization of gas and liquid phases and measurements of solid phase has beencarried out. Viscosity measurements at temperatures and pressures ranging from 20 to 152 °C and atmospheric to 103.4MPa, respectively, have been performed. The viscosity of the liquid samples after aging is compared with that of corresponding fresh samples. The results show that the degree of oxidation plays an important role in increasing the sample viscosity. This increase in viscosity is a function of temperature, and is more significant at low temperatures. Furthermore, agitation of samples during aging with air resulted in increased amounts of solid precipitation while lowering the viscosity of the liquid phase. Introduction Historically, in-situ combustion and high pressure air injection (HPAI) are two major areas in thermal enhanced oil recovery techniques that oxidation of oils are of special importance. In these processes it is of vital importance to know what effects the oxidation has on rheological properties of the oil, because it affects the mobility of the oil and therefore the recovery factor. Another area that in which oxidation of oils can be an issue is drilling a well. Generally a well can be drilled either by conventional drilling or underbalanced drilling (UBD) techniques. In conventional drilling employing oil-based drilling fluids in hot wells, the hot oil is returned to the surfacetanks and is exposed to air. Since the base liquids in oil-based drilling fluids are expensive, they are used in many wells before disposal. Therefore, even if the rate of oxidation is low, the long time of exposure can result in substantial oxidation of the oil.On the other hand, in underbalanced drilling a variety of different drilling fluids such as dry air, nitrogen, natural gas, mist, stable foam, stiff foam, gasified liquids (aerated muds), glass bubbles and liquids are used. In some gasified liquids (aerated muds), the liquid phase is primarily light oils (diesels, distillates,...). Deoxygenated air from membrane units (air with about 5 percent oxygen content) is used as the gas phase. In this case, oxidation is more severe, because deoxygenated air is continuously exposed to oil downhole at higher temperature and pressure conditions.
- Geology > Geological Subdiscipline (0.46)
- Geology > Petroleum Play Type > Unconventional Play > Heavy Oil Play (0.31)