Weight on bit (WOB) and differential pressure (DIFP) are two essential parameters derived from surface sensors during the drilling process. However, there can be significant errors in these measurements due to improper zeroing of these traces. Regular zeroing of WOB is important to ensure that it is calibrated for additional stands that have been added to the drillstring. Similarly, regular zeroing of DIFP is important to ensure that added hydrostatic pressure, which increases with depth, is taken into account, and to ensure that DIFP has been calibrated to the correct pump rate. In this paper, we quantify the errors due to forgotten and incorrect zeroing, and discuss an algorithm that was developed to automatically zero WOB and DIFP to eliminate these errors.

This study has two main sections. In the first section, the current practice of zeroing WOB (prior to rotary drilling) is analyzed in 40 onshore wells. It is found for 86% of all stands that WOB is either zeroed incorrectly or not at all. An algorithm is developed to determine the appropriate time to perform the zero WOB operation. Using this algorithm, it is found that the average WOB error per stand due to improper zeroing is 16.8 and 17.6% in the vertical and lateral wellbore sections, respectively. Further, it was found that repeated forgotten zeroes could result in large errors, particularly in the vertical where 8% of stands have WOB inaccuracies of more than 30%. In the second section, the analysis is repeated for DIFP and it is found that zeroing DIFP is forgotten in 51% of all stands, resulting in errors of 17.5 and 8.9% in the vertical and lateral, respectively. In the vertical, 9.9% of stands have DIFP inaccuracies of more than 30% due to forgotten zeroing. Applying these algorithms to historic data can eliminate these errors, and improve the effectiveness of data-based drilling optimization and analytics. Further, these algorithms could be implemented in an electronic drilling recorder (EDR) to improve the quality of real-time data at the rig.

钻压（WOB）和压差（DIFP）是钻井过程中从地面传感器得出的两个基本参数。但是，由于这些迹线的不正确归零，在这些测量中可能会存在重大误差。定期对WOB进行调零对于确保已针对已添加至钻柱的其他机架进行校准非常重要。同样，定期对DIFP进行调零很重要，以确保考虑到随深度增加的静水压力，并确保DIFP已校准至正确的泵速。在本文中，我们将量化由于遗忘和不正确的归零所引起的误差，并讨论一种算法，该算法可以自动将WOB和DIFP归零以消除这些误差。

这项研究有两个主要部分。在第一部分中，在40座陆上井中分析了WOB归零（旋转钻井之前）的当前做法。对于86％的展位，发现WOB归零错误或根本不归零。开发了一种算法来确定执行零WOB操作的适当时间。使用该算法，发现由于垂直归零和不垂直归零导致的每站平均WOB误差分别为16.8和17.6％。此外，发现重复的被遗忘的零可能导致较大的误差，特别是在垂直的情况下，其中8％的机架的WOB误差大于30％。在第二部分中，对DIFP进行了重复分析，发现在51％的机架中忘记了对DIFP的调零，结果误差为17.5和8。纵向和横向分别为9％。在垂直行业中，由于忘记了调零，9.9％的展台DIFP误差超过30％。将这些算法应用于历史数据可以消除这些错误，并提高基于数据的钻探优化和分析的效率。此外，可以在电子钻井记录仪（EDR）中实现这些算法，以提高钻机处实时数据的质量。