Correlations of Mud Rheological Properties With Cuttings-Transport Performance in Directional Drilling

Abstract

SPE J 9535Summa..,. An experimental study comparing the effects of mud rheological parameters on annular drill-cuttings buildup was conducted in a large-scale flow section. Rheological parameters examined were mud yield point (YP); plastic viscosity (PV); YP/PV ratio; power-law exponent; consistency index; Fann™ V-G Meter dial readings at 600,300,200, 100,6, and 3 rev/min; effective viscosity (calculated by the power-law derivation); and initial and 100minute gel strengths. Fifteen bentonite/polymer water-based muds were used, ranging from water to a mud with yP and PV values of 20 Ibf/l00 ft2 and 40 cp [19.6 Pa and 0.04 Pa's], respectively. For each mud, flow tests were run at annular velocities from 120 to 240 ftlmin [37 to 73 m/min] and hole angles from 30 to 90° from vertical. The effective drilling rate for all tests was 50 ftIhr [15 mIh]. Altogether, 180 tests are analyzed.When data were correlated with annular cuttings volume in steady-state flow, the best fit was obtained with low-shear-rate parameters. These parameters include the 6-and 3-rev/min dial readings and initial gel strength. Correlation coefficients for these were often from 0.9 to 0.95. For hole angles ::s45° (from vertical), increasing values of these parameters improved cuttings removal (Le., reduced cuttings volume). The same was observed at angles near horizontal, but only in the laminar flow regime. Cuttings volumes were always smaller in the turbulent regime during near-horizontal flow. IntroductionAdequate cuttings removal from a well during rotary drilling is critical for cost-effective drilling. High annular cuttings buildup is often responsible for stuck drillpipe and other impediments to standard drilling and completion procedures. Increasing hole inclination from vertical aggravates the tendency for annular cuttings accumulation, intensifying the need for mud hydraulics aimed at acceptable hole cleaning.Many factors affect cuttings transport, 1 but the options available for effective transport are few. Such influential parameters as mud density and hole angle are predetermined for reasons ranging from rock and fluid in-situ characteristics to overall well-planning strategy. Other variables, such as drill-cutting physical properties, are uncontrollable. The windows of opportunity for ensuring adequate hole cleaning during drilling lie, to a considerable extent, with mud flow rate and mud rheology.While mud rheology does not (during high-angle drilling) affect annular cuttings flow as strongly as such factors as mud flow rate, mud density, and hole angle,l-6 its effect is significant. Furthermore, its effect depends appreciably on interactions with mud annular velocity and hole angle. 2The complex viscous nature of drilling muds has led to many proposed means of varying sophistication to characterize mud rheology. In tum, questions are (or should be) raised concerning the appropriate rheological parameters best suited for particular hydrodynamic applications. This study entertains the applicability of various parameters to annular s...

A Practical Approach to Drilling-Fluid Surveillance and Management

“…P-f is used to approximate the mud viscosity and thus the mud's ability to transport cuttings moving up the annulus at relatively low shear rate. Becker et al 6 presented experimental evidence that the 6rev/min reading from the Fann V-G meter provides the best indicator of cuttings-carTying capacity. While this may be the best value to use, its field application is limited because many mud engineers only have two-speed (300-and 6OO-rev/min) rheometers.…”

Applicability of petroleum horizontal drilling technology to hazardous waste site characterization and remediation

“…This pipe reduces bending stresses caused by rotation through the curved section of the hole (Schuh, 1991a and1991b) and has been shown to reduce rotary and axial torque, reduce the tendency for differential sticking and allow increased weight transfer to the bit. viscosity and yield point should be maintained to insure cuttings removal (Okrajni and Azar, 1986;Becker et al, 1991). Cutting transport models have been developed to describe the process (Gavignet and So bey, 1989).…”

Hole Cleaning Performance of Light-Weight Drilling Fluids During Horizontal Underbalanced Drilling

“…Tomren et al (4) investigated the effects of pipe rotation and hole inclination angle, eccentricity and flow regimes on cuttings transport performance. Becker et al (8) conducted an experimental study comparing the effects of fluid rheological parameters [fluid yield point (YP), plastic viscosity (PV), YP/PV ratio, power law exponent, consistency index, etc.] on annular hole cleaning, using a large scale flow loop.…”