Physical Properties of Drilling Fluids at High Temperatures and Pressures
- J.V. Fisk (Baroid Drilling Fluids) | D.E. Jamison (Baroid Drilling Fluids)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling Engineering
- Publication Date
- December 1989
- Document Type
- Journal Paper
- 341 - 346
- 1989. Society of Petroleum Engineers
- 1.6 Drilling Operations, 1.11 Drilling Fluids and Materials, 5.1 Reservoir Characterisation, 5.9.2 Geothermal Resources, 1.6.9 Coring, Fishing, 5.3.1 Flow in Porous Media, 4.2.3 Materials and Corrosion
- 1 in the last 30 days
- 1,264 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 5.00|
|SPE Non-Member Price:||USD 35.00|
Rheological and dynamic filtration properties are presented for water- and oil-based drilling fluids. The physical properties were obtained by use of the DYNAMIC HPHT- test system at test temperatures to 400F [478 K], system pressures to 15,000 psi [103 MPa], and differential pressures to 600 psi [4.1 MPa]. The data indicated that the de Guzman-Andrade law can be used to describe the temperature effects on the viscosity of oil muds. We also observed that dynamic filtration rates of drilling fluids are greatly affected by solids plugging the pore space in the formation. Temperature and pressure affect dynamic, filtration by changing the dispersion of the solids in the fluid.
Drilling fluids are heterogeneous fluids containing approximately 10 chemical compounds that must remain stable at high temperatures and pressures. Many researchers have developed equations that predict temperature and pressure effects on the physical properties of drilling fluids. The goal of this investigation was to examine, with data from the DYNAMIC HPHT test system, existing theories and prediction equations for viscosity and dynamic filtration. Three fluid types (mineral oil, diesel oil, and water) were considered at temperatures to 400F [478 K], system pressures to 15,000 psi [103 MPa], and differential pressures to 600 psi [4.1 Mpa]. The de Guzman-Andrade and Houwen equations, which predict the effects of temperature on fluid viscosity, were examined. Filtration equations developed by Williams, Outmans, Tiller, and Peters and Timmerhaus were also reviewed. Williams performed filtration tests with a circulating loop system that allowed for radial filtration through a core in a flow loop. The design of the filter in the DYNAMIC HPHT test system is different. In this system, filtrate flows radially through a core, and shear is applied to the core surface by a concentric rotating shaft rather am by a circulating fluid. Outmans and Tiller stressed compressibility of the filter cake during filtration. By use of consolidometer tests at room temperature, they derive compressibility coefficients for different filter cakes. This investigation addresses those compressibility parameters and the temperature and pressure effects on them.
DYNAMIC HPHT Test System. This system is capable of operating at pressures to 20,000 psi [140 MPa] and maximum temperatures to 650F [616 K]. The system provides for measurements of rheology, density, corrosion rates (water-based systems), and dynamic filtration rates. The salient feature is the capability of this system to perform these measurements concurrently on the same fluid sample. Testing requires 6 gal [0.02 m ] of sample fluid. During testing, the sample is agitated continuously with an impeller mixer to minimize temperature gradients and maintain solids suspension. This system features a coaxial cylinder rheometer geometrically identical to standard oilfield rheometers. Shear rates of 5 to 1,750 seconds are possible. Density measurements are achieved by computing density changes of the fluid from the weight changes of a bob with known mass and volume suspended in the sample. Fluids are filtered radially through cylindrical cores with dimensions of 1.5-in. OD x 1.0-in. ID x 0.75-in. length [3.8 x 2.54 x 1.91 cm]. The core is placed in a core holder (Fig. 1) and suspended in the drilling fluid. The inner surface of the core is exposed to the fluid, while the outer surface is sealed from the fluid. The filtrate flows radially from the inner surface through the core to a collection cylinder. The filtrate volume is determined by measuring the linear displacement of a piston within a collection cylinder. Coaxial to the core is a shaft that is rotated to apply shear at the fluid/core inter-face. The system is designed to maintain a maximum of 1,000-psi [7-MPa] differential pressure across the core. Water is forced through the core and all lines to saturate the system completely before testing. Three cores were used: natural limestone with a 1-md permeability, ceramic with an average pore diameter of 60, 40m and a permeability of 600 md, and ceramic with an average pore diameter of 10 Am and a permeability of 86 md.
Laboratory Dynamic Filtration Device. The high-temperature, low-pressure data presented were obtained with a laboratory version of the dynamic filter in the DYNAMIC HPHT. The system is identical to that in the DYNAMIC HPHT, except for its temperature and pressure limits of 400F and 1,000 psi [478 K and 7 MPa].
Rheological Properties of Drilling Fluids at High Temperatures and Pressures
Background. The observed physical properties of drilling fluids are controlled by the use of additives that adsorb liquid and disperse into the liquid phase of the mud. The ensuing solid/solid and solid/liquid interactions form the gels and filter cakes that are needed to suspend solids, to control fluid invasion into the formation, and to clean and stabilize the borehole. Water-based drilling fluids often contain bentonite clay, either added to the fluid or acquired by drilling through clay-bearing formations. Thermal instability is associated with bentonite-based fluids. Grim and Gray and Darley attribute these changes in physical properties at high temperatures to changes in the orientation of the adsorbed water layer of the bentonite clay with increasing temperature. Oil-based fluids often contain organic clay complexes that disperse and swell in diesel and mineral oils to form gels. The organophilic clays do not experience the large changes in physical properties with increasing temperature observed with bentonite-based fluids. Grim states that quaternary amine/bentonite complexes expand in organic liquids when the fluids are heated to 338F [443 K]. This expansion is followed by slow decomposition of the clay complex and collapse of the clay/liquid (gel) structure at temperatures above 338F [443 K]. Houwen showed that the temperature effects on the viscosity of oil-based fluids can be predicted by the same logarithmic equation used to predict temperature effects on the viscosity of pure liquids. The general equation cited for describing the temperature effects on the viscosity of pure liquids is the de Guzman-Andrade equation:
The constants C and C are characteristic to each particular fluid and are obtained from plots of log 40 vs. 1/T from viscosity and temperature data collected for the different fluids. For Eq. 1 to produce linear plots of log u vs. 1/T , solid/liquid interaction in the fluid must be minimized at high temperatures. Houwen developed a similar equation for predicting temperature and pressure effects on the plastic viscosity:
With data obtained by the DYNAMIC HPHT system, a modified de Guzman-Andrade equation was developed for oil-based fluids;
|File Size||459 KB||Number of Pages||6|