Physics-Based Observers for Measurement-While-Drilling System in Down-the-Hole Drills

Abstract

Measurement While Drilling (MWD) is a technology for assessing rock mass conditions by collecting and analyzing data of mechanical drilling variables while the system operates. Nowadays, typical MWD systems rely on physical sensors directly installed on the drill rig. Sensors used in this context must be designed and conditioned for operating in harsh conditions, imposing trade-offs between the complexity, cost, and reliability of the measurement system. This paper presents a methodology for integrating physics-based observers into an MWD system as an alternative to complement or replace traditional physical sensors. The proposed observers leverage mathematical models of the drill’s electrical motor and its interaction with dynamic loads to estimate the bit speed and torque in a Down-the-Hole rig using current and voltage measurements taken from the motor power line. Experiments using data collected from four test samples with different rock strengths show a consistent correlation between the rate of penetration and specific energy derived from the observed drilling variables with the ones obtained from standardized tests of uniaxial compressive strength. The simplicity of the setup and results validate the feasibility of the proposed approach to be evaluated as an alternative to reduce the complexity and increase the reliability of MWD systems.

Identification of Impact Frequency for Down-the-Hole Drills Using Motor Current Signature Analysis

“…The rated speed of the drilling tool bit is 90 rpm. For detailed technical specifications about these components, see [16]. Figure 2 shows the main components of the experimental setup and their interconnections, where the yellow arrows indicate the air pressure lines, the green arrows indicate the location of a pressure sensor for direct measurement of operating pressure, and the light blue arrows indicate the location of the power line outputs of the VFD and power lines on the drill motor connection box.…”

“…The pressure and current sensor data analyzed in this paper are captured at a fixed sample frequency of 50 kHz, while the drilling machine rotates at rated speed. The setup extends the one described in [16] with additional sensors. Additionally, a Sony HDR-XR500V video camera recorder (not shown in the figures) is used to capture the environmental sound signal during the operation of the drilling rig with a sample rate of 48 kHz.…”

“…The adequate operation ranges for the impact frequency vary depending on the mechanic properties of the drilling surface, drilling angle, and hammer type [12][13][14][15]. According to [16], DTH hammers usually operate with impact frequencies ranging from 10 to 28 Hz, generating high-frequency torsional impacts, which produce highly dynamic variations in the magnitude of bit torque. The work in [17] shows that as the hammer vertical deviation angle increases from 0°(vertical) to 90°(horizontal), the impact frequency of the pneumatic hammer decreases from 10.8 to 10 Hz, resulting in a reduction of the effective energy per blow of 22.5%.…”

“…Figure 2. Descriptions of the DTH drilling setup, including the main components and their interconnections.The setup extends the one described in[16] with additional sensors.…”

A Developed Robust Model and Artificial Intelligence Techniques to Predict Drilling Fluid Density and Equivalent Circulation Density in Real Time

“…This information helps operators optimize drilling parameters, such as drilling speed and bit rotation, ensuring efficient hole cleaning and minimizing the risk of bit damage or stuck pipe. The logging-while-drilling (LWD) sensor provides real-time measurements of formation properties, such as resistivity, porosity, and density [ 46 ]. These data are used to evaluate the reservoir, optimize drilling parameters, and monitor hole-cleaning efficiency.…”