Abstract
In the recent years horizontal drilling (HD) has become increasingly important in oil and gas exploration because it can increase the production per well and can effectively rework old and marginal vertical wells. The key element of successful HD is accurate navigation of the drill bit with advanced measurement-while-drilling (MWD) tools. The size of the MWD tools is not significantly restricted in vertical wells because there is enough space for their installation in traditional well drilling, but the diameter of devices for HD must be restricted to less than 30 mm for some applications, such as lateral drilling from existing horizontal wells. Therefore, it is essential to design miniature devices for lateral HD applications. Additionally, magnetometers in traditional MWD devices are easily susceptible to complex downhole interferences, and gyroscopes have been previously suggested as the best avenue to replace magnetometers for azimuth measurements. The aim of this paper is to propose a miniature gyroscope-based MWD system which is referred to as miniature gyroscope-based while drilling (MGWD) system. A prototype of such MGWD system is proposed. The device consists of a two-axis gyroscope and a three-axis accelerometer. Miniaturization design approaches for MGWD are proposed. In addition, MGWD data collection software is designed to provide real-time data display and navigation algorithm verification. A fourth-order autoregressive (AR) model is introduced for stochastic noise modeling of the gyroscope and the accelerometer data. Zero velocity and position are injected into a Kalman filter as a system reference to update system states, which can effectively improve the state observability of the MGWD system and decrease estimation errors. Nevertheless, the azimuth of the proposed MGWD system is not observable in the Kalman filter, and reliable azimuth estimation remains a problem.
Highlights
Horizontal directional wells offer large contact areas with oil- or gas-layered reservoirs, so horizontal directional drilling (HDD) can enhance the production and exploration rate of oil or gas
The susceptibility of micro-electro-mechanical system (MEMS) gyroscopes to shocks and vibrations was successfully tested in harsh downhole environments and a wavelet-denoising method was used to enhance the azimuth accuracy of the BHA [19]
This paper presents the design and algorithm verification of a miniature gyroscope-based while drilling (MGWD) device for lateral HDD applications
Summary
Horizontal directional wells offer large contact areas with oil- or gas-layered reservoirs, so horizontal directional drilling (HDD) can enhance the production and exploration rate of oil or gas. The susceptibility of MEMS gyroscopes to shocks and vibrations was successfully tested in harsh downhole environments and a wavelet-denoising method was used to enhance the azimuth accuracy of the BHA [19]. In-drilling Alignment (IDA) was proposed to constrain the azimuth error which was estimated to be 25 times smaller than the error restriction in traditional magnetometer-based surveying [24,25]. Rotary-In-Drilling Alignment (R-IDA), a reduced version of the IDA, was recently proposed to minimize INS dynamic position and azimuth errors. The alignment method of the MGWD device utilized zero velocity together with zero position update and accurate Kalman filter state space equation was. BBooddyy ffrraammee iiss aann oorrtthhooggoonnaall aaxxiiss aalliiggnneedd wwiitthh rroollll,, ppiittcchh,, aanndd aazziimmuutthh ooff tthhee oobbjjeeccttss [[2277]].
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