A Rationale for Routine Laboratory Probe Permeametry
Andrew Hurst: Aberdeen University, United Kingdom, Christian Halvorsen
and Erling Siring, Statoil, Stavanger, Norway
Abstract: Laboratory steady-state probe permeametry provides accurate, nondestructive permeability data over a range of investigation comparable to Hassler-sleeve measurements on core plugs. Automated systems allow cost-effective acquisition of data that are comparable to conventional core plug data. Images of permeability contrast resolve similar features to geological descriptions and CT-scan images. This article addresses typical criticisms of probe permeameter data and gives examples of the advantages of acquiring and applying probe permeameter data.
Measurement and Interpretation of Centrifuge Capillary Pressure Curves—The
SCA Survey Data
Douglas W. Ruth and Zhigang Andy Chen: University of Manitoba
Abstract: A survey on centrifuge capillary pressure measurements was conducted by the Society of Core Analysts to determine the experimental procedures and data-analysis techniques used in the petroleum industry. Many problems were found in the experimental reports. In this article, the authors attempt, in light of the SCA survey, to present some guidelines for designing and interpreting a centrifuge experiment. Emphasis is placed on controllable factors affecting raw data quality. Existing interpretation techniques are also discussed.
Spontaneous Potential: Laboratory Experimentsand Modeling Results
M. R. Taherian, T. M. Habashy, R. J. Schroeder, D. R. Mariani, and M-Y.
Chen: Schlumberger-Doll Research
Abstract: The complex distribution of electrochemical sources in the borehole environment has historically limited the quantitative interpretation of spontaneous potential (SP) logs. In addition, SP models based on characterizations of these sources have been poorly validated because of the difficulty of generating realistic SP signals in controlled environments. In this article, we report on our SP experiments and models to address these problems. We describe a novel experimental technique for simulating SP signals in the laboratory. By placing synthetic, ion-selective membranes between aqueous saline solutions of different concentrations, we created source distributions that approximated those encountered by borehole logging tools in oilfield formations. Configurations of cation- selective and anion-selective membranes simulated cases of piston-like invasion, sawtooth-shaped invasion, and no invasion of a sand zone flanked by two shale layers. We used these data to validate a forward model that represents SP sources as electrical double layers. Also, we devised an inversion scheme to estimate the transference numbers of the membranes (and hence their strengths as SP sources), assuming that their geometric distribution is known. Results from both the forward and inverse models agree with the experimental data. This suggests that these simple models could be successfully adapted to the analysis of SP field logs.
Scale-Model Response of Fracture Zones to a Coplanar Induction Tool
in a Borehole
Nelson Paiva Raulino de Souza and Om Prakash Verma: Centro de Geociˆncias,
Universidade Federal do Par , Brazil
Abstract: Through reduced scale-model experiments in the laboratory,
we studied the suitability of using a coplanar induction two-coil system
in a borehole to detect a fracture zone. The scale factor chosen was 10
and field conductivities were simulated by ammonium chloride solutions.
The geologic model consisted of a homogeneous resistive rock with fractured
and nonfractured parts. The field resistivities were 4 ohm-m in the fractured
zone and 200 ohm-m in the nonfractured zone. Two types of fracture were
studied: vertical, at varying distances from the borehole wall, and those
crossing the well dipping at 0ø, 45ø, and 60ø. The
majority of the laboratory measurements were performed at a frequency of
100 kHz. The results, presented in the form of anomaly profiles (secondary
field/primary field), show the measurements are sensitive to coil orientations,
thickness of fractures, their distance from the borehole wall, and, to
some extent, their dip.
Since we did not obtain information about all the formation around the
coils with the coplanar system, we suggest the use of a new coil system.
The seminull double coupling (SNDC) system provides a quick-look technique
to estimate the dip of the fracture zone qualitatively, and this article
presents various logs recorded with this new system.