Applications Of NMR Mud Logging Technology In China

Wang, Zhizhan (Department of Geology, Northwest University ) | Martinez, Yardenia (KMS Technologies ) | Strack, Kurt (KMS Technologies ) | Yu, Gang (KMS Technologies )

OnePetro 

ABSTRACT

Nuclear Magnetic Resonance (NMR) mud logging technology has been widely used in Chinese oilfields and successfully solved many critical problems such as low SNR from small cuttings, well site reservoir characterization, rapid formation evaluation, and long sample preparation time for conventional core measurement. This technology realizes the transformation of reservoir petrophysical analysis from laboratory to drilling site, and extends the analysis samples from conventional cores to small fresh cuttings, sidewall cores and formation fluids. The formation petrophysical properties of small cuttings measured by NMR mud logging system include total porosity, effective porosity, absolute permeability, probable minimum and maximum permeability, irreducible water (liquid) saturation Swirr free water (fluid) saturation, oil saturation, etc. When used in the laboratory, it can deliver the most standard NMR petrophysical parameters. In addition, mud logging NMR has many advantages such as small sample quantity, short analysis time, low cost, nondestructive, multiple parameters from a single sample, high accuracy, excellent repeatability, measurement and analysis while drilling. It is a low-cost alternative for log calibration and even a replacement when it is difficult to obtain NMR logs from a wireline tool.

With NMR mud logging we can effectively evaluate the formation petrophysical properties, reserve and capacity of interstitial liquid by rapidly and accurately analyzing petrophysical parameters, such as porosity, permeability, FFI, BVI, oil saturation, etc., from cuttings, core plugs and sidewall cores on the drilling site, and then provide valuable and critical information for onsite decision-making of drilling and well completion. In recent years, a few thousands of cuttings and core samples have been measured by the NMR mud logging system and excellent application results of this technology have been achieved in such aspects as petrophysics evaluation, pore structure evaluation, pore fluid features evaluation, testing layer determination, and geopressure evaluation. The technology has been incorporated in the mud logging industry in six Chinese oilfields.

INTRODUCTION

Oil and gas reservoirs are the formation of interest in exploration and production (E&P) activities; its properties controls hydrocarbon reserves, output and production capacities (Fang et al., 2003). Reservoir evaluation is very important in the course of E&P. With the rapid development of E&P technologies and the improvements of drilling techniques, the drilling rate is getting faster. At the same time, drilling cost (especially offshore) is increasing. Therefore, we must improve the reliability and authenticity of well evaluation results, as well as turn-around time.

Often, reservoir evaluation data comes from core analysis done in the laboratory or from well log interpretation. Limited by the availability of cores, the data volume of conventional core analysis is very small, and the analysis turn-around is slow. Especially, clay bound water and capillary bound water of core samples could not be measured by conventional core analysis techniques (Wang et al., 2005). Well logging is only conducted after the well has been drilled and completed, the timelines and accuracy cannot meet the demands of E&P. Although some models have been developed to quantitative evaluate the reservoir formation at the well site, one model is only for one parameter such as porosity or permeability.