Dale F. Brost

Optical Methods for Monitoring Treating Chemicals in Oilfield Water Systems

Abstract Spectroscopic methods of analysis have been developed for the determination of treating chemicals in oilfield water systems. Part 1 describes a xenon flash photometer (XFP) that was designed for on-line measurements under harsh, oilfield conditions. The instrumentation is capable of absorption and fluorescence measurements in the ultraviolet and visible spectral ranges. Chemicals are determined by virtue of their ability to absorb or emit light at characteristic wavelengths. Light signals are carried between a central photometric console and remote analysis sites by fiber optic cables, eliminating the need for troublesome flow-through cells. Aspects of instrument design, drift compensation, and calibration methodology are discussed. Laboratory and field data are presented. Part 2 describes the potential of short-wave ultraviolet spectroscopy for the simultaneous determination of multiple treating chemicals in supply water. Absorption measurements at wavelengths between 190 and 250 nm are shown to yield part-per-million sensitivity for a wide range of chemical products. The severe spectral overlap, which has previously limited the analytical utility of this portion of the spectrum, is overcome by multivariate calibration. Using this technique, a scale and corrosion inhibitor were simultaneously determined from a single spectrum with approximately 2% relative error.

Determination of Oil Saturation Distributions in Field Cores By Microwave Spectroscopy

Two microwave adsorption spectrometers have been developed for routine monitoring of oil saturation (S/sub o/) distributions during laboratory flooding experiments in field core material. Operating frequencies are 10.525 and 24.125 GHz. A core sample cell has been designed which permits S/sub o/ distributions to be determined in narrow rectangular and cylindrical cores. An indirect calibration technique has been developed. Details of the instrumentation are presented with a theoretical description of instrumental response. The practical utility of this instrumentation for the a priori detection of core defects and quantitative determination of porosity distributions is demonstrated. 20 refs.

Characterization of Surfactants Using a Scaling Law Interpretation of Coreflood Residual Oil Saturation Profiles

The characterization of surfactant candidates for a given reservoir can be improved by the use of linear coreflood residual-oil-saturation profiles measured along the core after chemical flooding. A surfactant formulations functional relation of oil recovery to slug size can be calculated from a single coreflood with the assumption of a relaxed scaling law. A volumetric linear scaling approach is developed from laboratory coreflood data. Residual-oil-saturation profiles measured in reservoir material with a microwave absorption instrument support this approximate scaling relation. Analysis of 32 linear surfactant-slug corefloods is presented as additional verification. The limits of this scaling law are defined, with emphasis on the role of mixing and dispersion. The procedure for using saturation profiles to calculate oil recovery as a function of slug size is developed and a test case is presented. A recovery relation derived from a single coreflood saturation profile is compared with that determined by multiple conventional corefloods.