Assessment of Drilling Fluid Hole Cleaning Capacity in Horizontal Directional Drilling – A Parametric Study of the Effects of Drilling Fluid Additives

• Author / Creator

  Deng, Sai

• Horizontal directional drilling (HDD) as one of the most popular trenchless technology has seen a rapid growth during the past decades. Hole cleaning has been one of the most challenging problems of the directional well drilling in the oil and gas industry. As an outgrowth of the directional drilling technique from the petroleum industry, HDD faces the similar challenges. Transporting drilled solids (i.e. cuttings) out of the borehole is more difficult in HDD due to its unique features such as large borehole diameter and associated low fluid velocity (i.e. laminar flow regime). Insufficient hole cleaning will lead to various costly operational problems such as high torque and drag, slow drilling rate and stuck pipe as well as environmental issues. To improve the understanding of cuttings transport in HDD annulus, a comprehensive review of the hole cleaning related researches in directional drilling of oil and gas wells (including limited studies in HDD industry,) has been conducted. The review focused on the factors affecting hole cleaning performance with relatively high effectiveness and controllability to provide guidelines for future research and field applications. Annular flow velocity, drilling fluid rheological properties and drill pipe rotation were found to be the most influential factors. The annular velocity profile, which is dependent on the annular flow velocity as well as the rheological properties of drilling fluid plays an important role in cuttings transport in laminar flow regime. Effect of drilling fluid rheological properties on its hole cleaning capacity was chosen as the major focus of interest in this study. A new evaluation method of drilling fluid hole cleaning capacity for Herschel-Bulkley (yield-power-law) type fluids is proposed for HDD applications and compared with conventional hole cleaning indicators. Hole cleaning capacity of the drilling fluid was divided into two components: suspension capacity and sweeping capacity. The high value of yield stress (τy) and the width of plug flow velocity profile (plug width, h) were used to indicate better suspension capacity while low frictional pressure loss (ΔP) caused by the viscosity of the drilling fluid was used to indicate better sweeping capacity. Effect of different additives (bentonite and biopolymer) on the rheological properties of water-based drilling fluids and the hydraulic behaviors, as well as the hole cleaning capacity indicators, were investigated. The commonly used rotational viscometer was used to test the rheological properties of the drilling fluids. And Herschel-Bulkley model was applied to calculate the rheological parameters as well as the hydraulic parameters following the API standards. The experimental results showed that adding more bentonite or biopolymer will both increase the τy and ΔP which indicates higher suspension and lower sweeping capacity. Selection of the right concentration should depend on the real conditions like the velocity level, pump capacity, and allowable annular pressure. Samples with higher bentonite concentration and lower biopolymer concentration usually showed better hole cleaning capacity (higher τy and lower ΔP). Since lower ΔP not only can enhance the sweeping capacity and widen the plug width but also reduces the risk of hydrofracture and allows higher flow velocity. Considering the huge price difference between the bentonite and biopolymer, the bentonite used in this study is more economical effective in improving hole cleaning capacity of the drilling fluid.

• Subjects / Keywords

  • HDD hole cleaning

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3CN6ZF9V

• License

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