Prediction and Evaluation of Annular Pressure in Horizontal Directional Drilling

• Author / Creator

  Rostami, Ali

• Horizontal directional drilling (HDD) is a crossing technique for the oil and gas, utilities, and infrastructure sectors for pipeline installations in different situations under natural or manmade obstacles. Annular pressure (plan pressure) and maximum allowable pressure predictions are critical issues for annular pressure management. During HDD operation, annular pressure must not exceed the maximum allowable pressure to minimize the risk of hydraulic fracturing, which leads to loss of drilling fluid and increase in overall project risk. This study aims to identify the shortcomings of common industrial methods in current HDD practices due to poor annular pressure management. Furthermore, this study intends to propose a scheme for better annular pressure management. To achieve this objective, the plan pressure and maximum allowable pressure during HDD operations must be estimated; however, the methods presently utilized by industry are not accurate. In the case of plan pressure estimation, the Bingham plastic model is commonly used in HDD operations to estimate the annular pressure. However, the Bingham plastic model overestimates the annular pressure, leading to incorrect bore path design and erroneous information from down-hole conditions. In the case of estimating the maximum allowable pressure of the drilling fluid, the Delft’s cavity expansion method is commonly used. The Delft’s method significantly overestimates the maximum allowable pressure of the drilling fluid due to its simplified assumptions and can lead to hydraulic fracture of the ground during HDD operations. This study introduces two methods extracted from the American Petroleum Institute (API) to estimate the plan pressure according to the power-law and Bingham plastic models, which are adjusted and modified for HDD operation during pilot boring. Prior to calculating the annular pressure, it is assumed that the borehole is under an ideal condition in which the borehole radius is not changed and the pressure loss and infiltration of drilling fluid are negligible. To understand the infiltration of drilling fluid into the adjacent soil, a series of experimental tests on the sandy soil have been conducted to show the formation of cake around the wellbore during HDD operation. The formation of the cake in high permeable soils such as sand prevents drilling fluid from infiltrating into the ground; however, the infiltration of the drilling fluid into the low permeable soil (e.g., clay) is negligible. To estimate the maximum allowable pressure of the drilling fluid during HDD operation in non-cohesive soil, a new approach has been introduced to overcome the improper estimations based on Delft’s method. This study has attempted to illustrate the lack of correlation between the allowable plastic radius and the failure pressure. This correlation has been applied in industry to the Delft’s cavity expansion method and Yu and Houlsby’s (1991) large strain cavity expansion method and has resulted in an overestimation of the failure pressure. The new approach is formulated based on the calculation of limit pressure using Yu and Houlsby’s (1991) large-strain cavity expansion method. The suggested limit pressure approach has been advanced further to obtain a practical and useful solution to estimate the failure pressure in different geotechnical conditions by providing a coefficient of limit pressure following the Yu and Houlsby’s (1991) method. To achieve this objective, the commercial finite element program ABAQUS has been used to estimate the failure pressure based on the limit pressure approach and correlates it with Yu and Houlsbly’s (1991) failure pressure. The coefficient of limit pressure is determined as a function of model and soil parameters (overburden depth, friction angle, and elastic modulus), and the significance of these parameters have been identified based on a parametric study. In the current study, several graphs have been generated to calculate the coefficient of limit pressure to estimate the failure pressure properly. The new approach on annular pressure management enables engineers to better predict and monitor the annular pressure in the borehole during the HDD operation. This allows engineers to diagnose and prevent any upcoming issues during drilling and estimate the maximum allowable pressure of the drilling fluid to mitigate the risks associated with high annular pressure in the borehole during HDD operation.

• Subjects / Keywords

  • Annular Pressure Management
  • Horizontal Directional Drilling
  • Hydraulic Fracture
  • Cavity Expansion Method

• Graduation date

  Fall 2017

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3804XZ9X

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.