The Effect of Rheology on Rate of Penetration
- F.E. Beck (Arco Alaska Inc.) | J.W. Powell (M-I Drilling Fluids) | Mario Zamora (M-I Drilling Fluids)
- Document ID
- Society of Petroleum Engineers
- SPE/IADC Drilling Conference, 28 February-2 March, Amsterdam, Netherlands
- Publication Date
- Document Type
- Conference Paper
- 1995. SPE/IADC Drilling Conference
- 1.6.6 Directional Drilling, 7.2.3 Decision-making Processes, 1.11.4 Solids Control, 1.12.6 Drilling Data Management and Standards, 1.11 Drilling Fluids and Materials, 4.1.2 Separation and Treating, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.6 Drilling Operations, 1.5.4 Bit hydraulics, 1.7.7 Cuttings Transport, 2.2.3 Fluid Loss Control
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Field data have been collected and analyzed to 1) identify the characteristics of a drilling fluid that enhance rate of penetration, and 2) quantify the impact of particular fluid properties on rate of penetration. The information is being used to evaluate the economics of a fluid treatment program in order to deliver optimal drilling performance and minimum drilling cost, rather than minimum fluid cost. Additionally, it is demonstrated how bit hydraulics can be improved through rheological modification without adjusting flow rate or nozzle size.
It has long been known that drilling fluid properties can dramatically impact drilling rate. This fact was established early in the drilling literature, and confirmed by numerous laboratory studies. Several early studies focused directly on mud properties, clearly demonstrating the effect of kinematic viscosity at bit conditions on drilling rate. In laboratory conditions, penetration rates can be affected by as much as a factor of three by altering fluid viscosity. It can be concluded from the early literature that drilling rate is not directly dependent on the type or amount of solids in the fluid, but on the impact of those solids on fluid properties, particularly on the viscosity of the fluid as it flows through bit nozzles. This conclusion indicates that drilling rates should be directly correlative to fluid properties which reflect the viscosity of the fluid at bit shear rate conditions, such as the plastic viscosity. Secondary fluid properties reflecting solids content in the fluid should also provide a means of correlating to rate of penetration, as the solids will impact the viscosity of the fluid.
As the technical literature began to focus on the effect of different types and concentrations of solids, the industry began to turn its attention to the removal of those solids, but with little regard for the resulting viscosity of the fluid. Industry also began to recognize the wellbore stability benefits gained from low fluid loss muds, but once again ignored the effect that polymers and bridging solids added to the fluid to gain filtration control had on rheology, particularly high shear rate rheology. Low shear-rate rheology is often modified to provide for cuttings transport, which often raises the high shear-rate rheology as well, with potential detrimental effects on rate of penetration.
|File Size||635 KB||Number of Pages||9|