LWD Quality Control: Standard Procedure

Logging while drilling (LWD) offers opportunities to improve horizontal well drilling efficiency without extending the well construction period. Still, the quality of the data obtained should always be taken into account. There are no standard procedures for LWD data quality control and data package. Nevertheless, top oil and gas companies are currently developing their own solutions in this area. This paper presents LWD quality control standard procedures accepted in Rosneft Oil Company. First, we need to consider the difference of data quality control in case of LWD in horizontal wells and wireline logging in vertical or deviated wells. LWD in horizontal wells has such features: downhole to surface data transmission restrictions, extreme logging conditions, frequent absence of reference horizons, vertical anisotropy, etc. LWD quality control should be performed by both directional drilling contractors and well logging interpreters. Directional drilling contractors must perform the following LWD quality control procedures: valid LWD tool calibrations; LWD tool checks before run in hole; log quality control (LQC) plots monitoring; LWD repeat pass; standard form logging report. The LQC plot is a log plot with special tool technical status curves (LQC curves) and flags (Status Words, LQC flags): currents and voltages, raw sensor readings and count rates, etc. Well logging interpreters must perform the following procedures: specially designed checklist filling; crossplots and histograms of LWD data analysis; petrophysical modelling as an additional tool. Crossplots are recommended in case of pure mineral rocks penetration, while histograms are useful when reference horizons or reference wells are available. The above quality control procedures and tools allow improving the LWD quality and its credibility – both in real time and in record mode in the end of drilling. Rosneft Oil Company has developed and accepted local regulations on LWD quality control based on the above-mentioned procedure, along with an online LWD quality control checklist.