Impact of Suspended Cuttings on Drilling Fluid Rheology and Hole Cleaning Capacity in Horizontal Directional Drilling

• Author / Creator

  Su, Yi

• Trenchless technologies are a family of techniques to install or rehabilitate conduits under the ground without conventional open excavation processes. Among them, horizontal directional drilling (HDD) is one of the most popular methods for installation of pipelines under surface obstacles, due to its exceptional performance in reducing the social, environmental and economical costs. However, the transportation of drilled cuttings out of the borehole annular space has always been a challenge for the HDD operations, and proper hole cleaning performance is vital for a successful HDD project. Some of the potential consequences of poor hole cleaning jobs include stuck pipes, excessive torque, elevated annular pressure and hydrofracture, or undesirable fluid return to the surface. These risks induce significant uncertainties in HDD design and project control, and hydrofracture is also one of the major concerns for the permitting and regulatory agencies.
  The current research and understanding of cutting transportation in HDD annular spaces is still limited, especially for the horizontal and build sections. Furthermore, the practical limit of the maximum allowable pressure of the geological formations also places additional constraints on the options for improving hole cleaning performances. For example, the drilling fluids’ annular flow rate should be carefully controlled to prevent excessive frictional pressure loss, because this could drastically increase the risks of hydrofracture incidents.
  A comprehensive review was conducted to improve the understanding of cutting transport processes in HDD operations, as well as the established hole cleaning performance indicators for evaluating the drilling fluids. The rheological properties of drilling fluids was found to be the most important and readily controllable variable for enhanced hole cleaning performances, considering the fact that the fluid flow rate was limited by the formation’s maximum allowable pressure.
  In addition, it was found that the drilling fluids’ hole cleaning performance can be evaluated from 2 aspects: the cutting carrying capacity and the sweeping capacity. The annular plug width, which is a parameter indicating the annular fluid velocity profile, was found to be a desirable indicator of the drilling fluids’ cutting carrying capacity, while the annular friction pressure loss and the ratio of yield point and plastic viscosity was found to be suitable indicators for the drilling fluids’ sweeping capacity.
  Effects of suspended drilled cuttings, in this case sand particles, have been investigated by carefully measuring the fluid samples’ shear stress-shear rate responses, and it was found that the solid volumetric fractions have significant impacts on the drilling fluids’ rheological properties, and this effect is more profound once the solid volumetric fractions exceed 30-35%. Both the Herschel-Bulkley and the Bingham Plastic rheology models were applied to analyze the rheological parameters of the drilling fluid samples, and other parameters, including the annular plug width, friction pressure loss and the ratio of yield point and plastic viscosity were calculated. It was found that increasing solid volumetric fractions negatively impact these hole cleaning performance indicators. Considering the degree of impact and the maximum allowable pressure of the geological formations, it is recommended to keep the solid volumetric fractions as low as possible in the drilling fluid, and it should not exceed 30-35% overall. This value is consistent with the commonly accepted fluid-to-soil ratio of 2:1 to 3:1 for HDD operation within fine sands.

• Subjects / Keywords

  • Borehole Pressure
  • Cutting
  • Rheology
  • HDD
  • Horizontal Directional Drilling
  • Drilling Fluid
  • Hole Cleaning

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-c1b1-7591

• License

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